548a2ec49b
This adds the PT_GETREGSET and PT_SETREGSET ptrace types. These can be used to access all the registers from a specified core dump note type. The NT_PRSTATUS and NT_FPREGSET notes are initially supported. Other machine-dependant types are expected to be added in the future. The ptrace addr points to a struct iovec pointing at memory to hold the registers along with its length. On success the length in the iovec is updated to tell userspace the actual length the kernel wrote or, if the base address is NULL, the length the kernel would have written. Because the data field is an int the arguments are backwards when compared to the Linux PTRACE_GETREGSET call. Reviewed by: kib Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D19831
1355 lines
34 KiB
Groff
1355 lines
34 KiB
Groff
.\" $FreeBSD$
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.\" $NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $
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.\"
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.\" This file is in the public domain.
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.Dd January 27, 2022
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.Dt PTRACE 2
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.Os
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.Sh NAME
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.Nm ptrace
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.Nd process tracing and debugging
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/ptrace.h
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.Ft int
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.Fn ptrace "int request" "pid_t pid" "caddr_t addr" "int data"
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.Sh DESCRIPTION
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The
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.Fn ptrace
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system call
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provides tracing and debugging facilities.
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It allows one process
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(the
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.Em tracing
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process)
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to control another
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(the
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.Em traced
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process).
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The tracing process must first attach to the traced process, and then
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issue a series of
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.Fn ptrace
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system calls to control the execution of the process, as well as access
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process memory and register state.
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For the duration of the tracing session, the traced process will be
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.Dq re-parented ,
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with its parent process ID (and resulting behavior)
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changed to the tracing process.
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It is permissible for a tracing process to attach to more than one
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other process at a time.
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When the tracing process has completed its work, it must detach the
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traced process; if a tracing process exits without first detaching all
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processes it has attached, those processes will be killed.
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.Pp
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Most of the time, the traced process runs normally, but when it
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receives a signal
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(see
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.Xr sigaction 2 ) ,
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it stops.
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The tracing process is expected to notice this via
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.Xr wait 2
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or the delivery of a
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.Dv SIGCHLD
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signal, examine the state of the stopped process, and cause it to
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terminate or continue as appropriate.
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The signal may be a normal process signal, generated as a result of
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traced process behavior, or use of the
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.Xr kill 2
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system call; alternatively, it may be generated by the tracing facility
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as a result of attaching, stepping by the tracing
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process,
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or an event in the traced process.
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The tracing process may choose to intercept the signal, using it to
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observe process behavior (such as
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.Dv SIGTRAP ) ,
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or forward the signal to the process if appropriate.
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The
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.Fn ptrace
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system call
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is the mechanism by which all this happens.
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.Pp
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A traced process may report additional signal stops corresponding to
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events in the traced process.
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These additional signal stops are reported as
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.Dv SIGTRAP
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or
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.Dv SIGSTOP
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signals.
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The tracing process can use the
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.Dv PT_LWPINFO
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request to determine which events are associated with a
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.Dv SIGTRAP
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or
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.Dv SIGSTOP
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signal.
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Note that multiple events may be associated with a single signal.
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For example, events indicated by the
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.Dv PL_FLAG_BORN ,
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.Dv PL_FLAG_FORKED ,
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and
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.Dv PL_FLAG_EXEC
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flags are also reported as a system call exit event
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.Pq Dv PL_FLAG_SCX .
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The signal stop for a new child process enabled via
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.Dv PTRACE_FORK
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will report a
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.Dv SIGSTOP
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signal.
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All other additional signal stops use
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.Dv SIGTRAP .
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.Sh DETACH AND TERMINATION
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.Pp
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Normally, exiting tracing process should wait for all pending
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debugging events and then detach from all alive traced processes
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before exiting using
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.Dv PT_DETACH
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request.
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If tracing process exits without detaching, for instance due to abnormal
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termination, the destiny of the traced children processes is determined
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by the
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.Dv kern.kill_on_debugger_exit
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sysctl control.
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.Pp
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If the control is set to the default value 1, such traced processes
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are terminated.
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If set to zero, kernel implicitly detaches traced processes.
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Traced processes are un-stopped if needed, and then continue the execution
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without tracing.
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Kernel drops any
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.Dv SIGTRAP
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signals queued to the traced children, which could be either generated by
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not yet consumed debug events, or sent by other means, the later should
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not be done anyway.
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.Sh DISABLING PTRACE
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The
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.Nm
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subsystem provides rich facilities to manipulate other processes state.
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Sometimes it may be desirable to disallow it either completely, or limit
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its scope.
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The following controls are provided for this:
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.Bl -tag -width security.bsd.unprivileged_proc_debug
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.It Dv security.bsd.allow_ptrace
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Setting this sysctl to zero value makes
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.Xr ptrace 2
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return
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.Er ENOSYS
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always as if the syscall is not implemented by the kernel.
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.It Dv security.bsd.unprivileged_proc_debug
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Setting this sysctl to zero disallows use of
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.Fn ptrace
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by unprivileged processes.
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.It Dv security.bsd.see_other_uids
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Setting this sysctl to zero value disallows
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.Fn ptrace
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requests from targeting processes with the real user identifier different
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from the real user identifier of the caller.
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The requests return
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.Er ESRCH
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if policy is not met.
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.It Dv security.bsd.see_other_gids
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Setting this sysctl to zero value disallows
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.Fn ptrace
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requests from process belonging to a group that is not also one of
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the group of the target process.
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The requests return
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.Er ESRCH
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if policy is not met.
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.It Dv securelevel and init
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The
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.Xr init 1
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process can only be traced with
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.Nm
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if securelevel is zero.
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.It Dv procctl(2) PROC_TRACE_CTL
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Process can deny attempts to trace itself with
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.Xr procctl 2
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.Dv PROC_TRACE_CTL
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request.
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In this case requests return
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.Xr EPERM
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error.
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.El
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.Sh TRACING EVENTS
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.Pp
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Each traced process has a tracing event mask.
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An event in the traced process only reports a
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signal stop if the corresponding flag is set in the tracing event mask.
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The current set of tracing event flags include:
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.Bl -tag -width "Dv PTRACE_SYSCALL"
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.It Dv PTRACE_EXEC
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Report a stop for a successful invocation of
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.Xr execve 2 .
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This event is indicated by the
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.Dv PL_FLAG_EXEC
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flag in the
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.Va pl_flags
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member of
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.Vt "struct ptrace_lwpinfo" .
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.It Dv PTRACE_SCE
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Report a stop on each system call entry.
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This event is indicated by the
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.Dv PL_FLAG_SCE
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flag in the
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.Va pl_flags
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member of
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.Vt "struct ptrace_lwpinfo" .
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.It Dv PTRACE_SCX
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Report a stop on each system call exit.
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This event is indicated by the
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.Dv PL_FLAG_SCX
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flag in the
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.Va pl_flags
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member of
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.Vt "struct ptrace_lwpinfo" .
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.It Dv PTRACE_SYSCALL
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Report stops for both system call entry and exit.
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.It Dv PTRACE_FORK
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This event flag controls tracing for new child processes of a traced process.
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.Pp
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When this event flag is enabled,
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new child processes will enable tracing and stop before executing their
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first instruction.
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The new child process will include the
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.Dv PL_FLAG_CHILD
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flag in the
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.Va pl_flags
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member of
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.Vt "struct ptrace_lwpinfo" .
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The traced process will report a stop that includes the
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.Dv PL_FLAG_FORKED
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flag.
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The process ID of the new child process will also be present in the
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.Va pl_child_pid
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member of
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.Vt "struct ptrace_lwpinfo" .
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If the new child process was created via
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.Xr vfork 2 ,
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the traced process's stop will also include the
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.Dv PL_FLAG_VFORKED
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flag.
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Note that new child processes will be attached with the default
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tracing event mask;
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they do not inherit the event mask of the traced process.
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.Pp
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When this event flag is not enabled,
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new child processes will execute without tracing enabled.
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.It Dv PTRACE_LWP
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This event flag controls tracing of LWP
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.Pq kernel thread
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creation and destruction.
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When this event is enabled,
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new LWPs will stop and report an event with
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.Dv PL_FLAG_BORN
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set before executing their first instruction,
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and exiting LWPs will stop and report an event with
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.Dv PL_FLAG_EXITED
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set before completing their termination.
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.Pp
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Note that new processes do not report an event for the creation of their
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initial thread,
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and exiting processes do not report an event for the termination of the
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last thread.
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.It Dv PTRACE_VFORK
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Report a stop event when a parent process resumes after a
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.Xr vfork 2 .
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.Pp
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When a thread in the traced process creates a new child process via
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.Xr vfork 2 ,
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the stop that reports
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.Dv PL_FLAG_FORKED
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and
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.Dv PL_FLAG_SCX
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occurs just after the child process is created,
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but before the thread waits for the child process to stop sharing process
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memory.
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If a debugger is not tracing the new child process,
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it must ensure that no breakpoints are enabled in the shared process
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memory before detaching from the new child process.
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This means that no breakpoints are enabled in the parent process either.
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.Pp
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The
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.Dv PTRACE_VFORK
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flag enables a new stop that indicates when the new child process stops
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sharing the process memory of the parent process.
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A debugger can reinsert breakpoints in the parent process and resume it
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in response to this event.
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This event is indicated by setting the
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.Dv PL_FLAG_VFORK_DONE
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flag.
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.El
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.Pp
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The default tracing event mask when attaching to a process via
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.Dv PT_ATTACH ,
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.Dv PT_TRACE_ME ,
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or
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.Dv PTRACE_FORK
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includes only
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.Dv PTRACE_EXEC
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events.
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All other event flags are disabled.
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.Sh PTRACE REQUESTS
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.Pp
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The
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.Fa request
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argument specifies what operation is being performed; the meaning of
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the rest of the arguments depends on the operation, but except for one
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special case noted below, all
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.Fn ptrace
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calls are made by the tracing process, and the
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.Fa pid
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argument specifies the process ID of the traced process
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or a corresponding thread ID.
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The
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.Fa request
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argument
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can be:
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.Bl -tag -width "Dv PT_GET_EVENT_MASK"
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.It Dv PT_TRACE_ME
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This request is the only one used by the traced process; it declares
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that the process expects to be traced by its parent.
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All the other arguments are ignored.
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(If the parent process does not expect to trace the child, it will
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probably be rather confused by the results; once the traced process
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stops, it cannot be made to continue except via
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.Fn ptrace . )
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When a process has used this request and calls
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.Xr execve 2
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or any of the routines built on it
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(such as
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.Xr execv 3 ) ,
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it will stop before executing the first instruction of the new image.
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Also, any setuid or setgid bits on the executable being executed will
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be ignored.
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If the child was created by
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.Xr vfork 2
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system call or
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.Xr rfork 2
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call with the
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.Dv RFMEM
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flag specified, the debugging events are reported to the parent
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only after the
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.Xr execve 2
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|
is executed.
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.It Dv PT_READ_I , Dv PT_READ_D
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|
These requests read a single
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.Vt int
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of data from the traced process's address space.
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Traditionally,
|
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.Fn ptrace
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has allowed for machines with distinct address spaces for instruction
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and data, which is why there are two requests: conceptually,
|
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.Dv PT_READ_I
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reads from the instruction space and
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.Dv PT_READ_D
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reads from the data space.
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In the current
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.Fx
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implementation, these two requests are completely identical.
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The
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.Fa addr
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argument specifies the address
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(in the traced process's virtual address space)
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at which the read is to be done.
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This address does not have to meet any alignment constraints.
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The value read is returned as the return value from
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.Fn ptrace .
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.It Dv PT_WRITE_I , Dv PT_WRITE_D
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These requests parallel
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.Dv PT_READ_I
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and
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.Dv PT_READ_D ,
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except that they write rather than read.
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The
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.Fa data
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argument supplies the value to be written.
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.It Dv PT_IO
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This request allows reading and writing arbitrary amounts of data in
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the traced process's address space.
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The
|
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.Fa addr
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argument specifies a pointer to a
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.Vt "struct ptrace_io_desc" ,
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which is defined as follows:
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.Bd -literal
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struct ptrace_io_desc {
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int piod_op; /* I/O operation */
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void *piod_offs; /* child offset */
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void *piod_addr; /* parent offset */
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size_t piod_len; /* request length */
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};
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/*
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* Operations in piod_op.
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*/
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#define PIOD_READ_D 1 /* Read from D space */
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#define PIOD_WRITE_D 2 /* Write to D space */
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#define PIOD_READ_I 3 /* Read from I space */
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#define PIOD_WRITE_I 4 /* Write to I space */
|
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.Ed
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.Pp
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The
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.Fa data
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argument is ignored.
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The actual number of bytes read or written is stored in
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.Va piod_len
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upon return.
|
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.It Dv PT_CONTINUE
|
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The traced process continues execution.
|
|
The
|
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.Fa addr
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argument
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is an address specifying the place where execution is to be resumed
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(a new value for the program counter),
|
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or
|
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.Po Vt caddr_t Pc Ns 1
|
|
to indicate that execution is to pick up where it left off.
|
|
The
|
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.Fa data
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argument
|
|
provides a signal number to be delivered to the traced process as it
|
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resumes execution, or 0 if no signal is to be sent.
|
|
.It Dv PT_STEP
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The traced process is single stepped one instruction.
|
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The
|
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.Fa addr
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argument
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should be passed
|
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.Po Vt caddr_t Pc Ns 1 .
|
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The
|
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.Fa data
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argument
|
|
provides a signal number to be delivered to the traced process as it
|
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resumes execution, or 0 if no signal is to be sent.
|
|
.It Dv PT_KILL
|
|
The traced process terminates, as if
|
|
.Dv PT_CONTINUE
|
|
had been used with
|
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.Dv SIGKILL
|
|
given as the signal to be delivered.
|
|
.It Dv PT_ATTACH
|
|
This request allows a process to gain control of an otherwise
|
|
unrelated process and begin tracing it.
|
|
It does not need any cooperation from the to-be-traced process.
|
|
In
|
|
this case,
|
|
.Fa pid
|
|
specifies the process ID of the to-be-traced process, and the other
|
|
two arguments are ignored.
|
|
This request requires that the target process must have the same real
|
|
UID as the tracing process, and that it must not be executing a setuid
|
|
or setgid executable.
|
|
(If the tracing process is running as root, these restrictions do not
|
|
apply.)
|
|
The tracing process will see the newly-traced process stop and may
|
|
then control it as if it had been traced all along.
|
|
.It Dv PT_DETACH
|
|
This request is like PT_CONTINUE, except that it does not allow
|
|
specifying an alternate place to continue execution, and after it
|
|
succeeds, the traced process is no longer traced and continues
|
|
execution normally.
|
|
.It Dv PT_GETREGS
|
|
This request reads the traced process's machine registers into the
|
|
.Do
|
|
.Vt "struct reg"
|
|
.Dc
|
|
(defined in
|
|
.In machine/reg.h )
|
|
pointed to by
|
|
.Fa addr .
|
|
.It Dv PT_SETREGS
|
|
This request is the converse of
|
|
.Dv PT_GETREGS ;
|
|
it loads the traced process's machine registers from the
|
|
.Do
|
|
.Vt "struct reg"
|
|
.Dc
|
|
(defined in
|
|
.In machine/reg.h )
|
|
pointed to by
|
|
.Fa addr .
|
|
.It Dv PT_GETFPREGS
|
|
This request reads the traced process's floating-point registers into
|
|
the
|
|
.Do
|
|
.Vt "struct fpreg"
|
|
.Dc
|
|
(defined in
|
|
.In machine/reg.h )
|
|
pointed to by
|
|
.Fa addr .
|
|
.It Dv PT_SETFPREGS
|
|
This request is the converse of
|
|
.Dv PT_GETFPREGS ;
|
|
it loads the traced process's floating-point registers from the
|
|
.Do
|
|
.Vt "struct fpreg"
|
|
.Dc
|
|
(defined in
|
|
.In machine/reg.h )
|
|
pointed to by
|
|
.Fa addr .
|
|
.It Dv PT_GETDBREGS
|
|
This request reads the traced process's debug registers into
|
|
the
|
|
.Do
|
|
.Vt "struct dbreg"
|
|
.Dc
|
|
(defined in
|
|
.In machine/reg.h )
|
|
pointed to by
|
|
.Fa addr .
|
|
.It Dv PT_SETDBREGS
|
|
This request is the converse of
|
|
.Dv PT_GETDBREGS ;
|
|
it loads the traced process's debug registers from the
|
|
.Do
|
|
.Vt "struct dbreg"
|
|
.Dc
|
|
(defined in
|
|
.In machine/reg.h )
|
|
pointed to by
|
|
.Fa addr .
|
|
.It Dv PT_GETREGSET
|
|
This request reads the registers from the traced process.
|
|
The
|
|
.Fa data
|
|
argument specifies the register set to read, with the
|
|
.Fa addr
|
|
argument pointing at a
|
|
.Vt "struct iovec"
|
|
where the
|
|
.Va iov_base
|
|
field points to a register set specific structure to hold the registers,
|
|
and the
|
|
.Va iov_len
|
|
field holds the length of the structure.
|
|
.It Dv PT_SETREGSET
|
|
This request writes to the registers of the traced process.
|
|
The
|
|
.Fa data
|
|
argument specifies the register set to write to, with the
|
|
.Fa addr
|
|
argument pointing at a
|
|
.Vt "struct iovec"
|
|
where the
|
|
.Va iov_base
|
|
field points to a register set specific structure to hold the registers,
|
|
and the
|
|
.Va iov_len
|
|
field holds the length of the structure.
|
|
If
|
|
.Va iov_base
|
|
is NULL the kernel will return the expected length of the register set
|
|
specific structure in the
|
|
.Va iov_len
|
|
field and not change the target register set.
|
|
.It Dv PT_LWPINFO
|
|
This request can be used to obtain information about the kernel thread,
|
|
also known as light-weight process, that caused the traced process to stop.
|
|
The
|
|
.Fa addr
|
|
argument specifies a pointer to a
|
|
.Vt "struct ptrace_lwpinfo" ,
|
|
which is defined as follows:
|
|
.Bd -literal
|
|
struct ptrace_lwpinfo {
|
|
lwpid_t pl_lwpid;
|
|
int pl_event;
|
|
int pl_flags;
|
|
sigset_t pl_sigmask;
|
|
sigset_t pl_siglist;
|
|
siginfo_t pl_siginfo;
|
|
char pl_tdname[MAXCOMLEN + 1];
|
|
pid_t pl_child_pid;
|
|
u_int pl_syscall_code;
|
|
u_int pl_syscall_narg;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is to be set to the size of the structure known to the caller.
|
|
This allows the structure to grow without affecting older programs.
|
|
.Pp
|
|
The fields in the
|
|
.Vt "struct ptrace_lwpinfo"
|
|
have the following meaning:
|
|
.Bl -tag -width indent -compact
|
|
.It Va pl_lwpid
|
|
LWP id of the thread
|
|
.It Va pl_event
|
|
Event that caused the stop.
|
|
Currently defined events are:
|
|
.Bl -tag -width "Dv PL_EVENT_SIGNAL" -compact
|
|
.It Dv PL_EVENT_NONE
|
|
No reason given
|
|
.It Dv PL_EVENT_SIGNAL
|
|
Thread stopped due to the pending signal
|
|
.El
|
|
.It Va pl_flags
|
|
Flags that specify additional details about observed stop.
|
|
Currently defined flags are:
|
|
.Bl -tag -width indent -compact
|
|
.It Dv PL_FLAG_SCE
|
|
The thread stopped due to system call entry, right after the kernel is entered.
|
|
The debugger may examine syscall arguments that are stored in memory and
|
|
registers according to the ABI of the current process, and modify them,
|
|
if needed.
|
|
.It Dv PL_FLAG_SCX
|
|
The thread is stopped immediately before syscall is returning to the usermode.
|
|
The debugger may examine system call return values in the ABI-defined registers
|
|
and/or memory.
|
|
.It Dv PL_FLAG_EXEC
|
|
When
|
|
.Dv PL_FLAG_SCX
|
|
is set, this flag may be additionally specified to inform that the
|
|
program being executed by debuggee process has been changed by successful
|
|
execution of a system call from the
|
|
.Fn execve 2
|
|
family.
|
|
.It Dv PL_FLAG_SI
|
|
Indicates that
|
|
.Va pl_siginfo
|
|
member of
|
|
.Vt "struct ptrace_lwpinfo"
|
|
contains valid information.
|
|
.It Dv PL_FLAG_FORKED
|
|
Indicates that the process is returning from a call to
|
|
.Fn fork 2
|
|
that created a new child process.
|
|
The process identifier of the new process is available in the
|
|
.Va pl_child_pid
|
|
member of
|
|
.Vt "struct ptrace_lwpinfo" .
|
|
.It Dv PL_FLAG_CHILD
|
|
The flag is set for first event reported from a new child which is
|
|
automatically attached when
|
|
.Dv PTRACE_FORK
|
|
is enabled.
|
|
.It Dv PL_FLAG_BORN
|
|
This flag is set for the first event reported from a new LWP when
|
|
.Dv PTRACE_LWP
|
|
is enabled.
|
|
It is reported along with
|
|
.Dv PL_FLAG_SCX .
|
|
.It Dv PL_FLAG_EXITED
|
|
This flag is set for the last event reported by an exiting LWP when
|
|
.Dv PTRACE_LWP
|
|
is enabled.
|
|
Note that this event is not reported when the last LWP in a process exits.
|
|
The termination of the last thread is reported via a normal process exit
|
|
event.
|
|
.It Dv PL_FLAG_VFORKED
|
|
Indicates that the thread is returning from a call to
|
|
.Xr vfork 2
|
|
that created a new child process.
|
|
This flag is set in addition to
|
|
.Dv PL_FLAG_FORKED .
|
|
.It Dv PL_FLAG_VFORK_DONE
|
|
Indicates that the thread has resumed after a child process created via
|
|
.Xr vfork 2
|
|
has stopped sharing its address space with the traced process.
|
|
.El
|
|
.It Va pl_sigmask
|
|
The current signal mask of the LWP
|
|
.It Va pl_siglist
|
|
The current pending set of signals for the LWP.
|
|
Note that signals that are delivered to the process would not appear
|
|
on an LWP siglist until the thread is selected for delivery.
|
|
.It Va pl_siginfo
|
|
The siginfo that accompanies the signal pending.
|
|
Only valid for
|
|
.Dv PL_EVENT_SIGNAL
|
|
stop when
|
|
.Dv PL_FLAG_SI
|
|
is set in
|
|
.Va pl_flags .
|
|
.It Va pl_tdname
|
|
The name of the thread.
|
|
.It Va pl_child_pid
|
|
The process identifier of the new child process.
|
|
Only valid for a
|
|
.Dv PL_EVENT_SIGNAL
|
|
stop when
|
|
.Dv PL_FLAG_FORKED
|
|
is set in
|
|
.Va pl_flags .
|
|
.It Va pl_syscall_code
|
|
The ABI-specific identifier of the current system call.
|
|
Note that for indirect system calls this field reports the indirected
|
|
system call.
|
|
Only valid when
|
|
.Dv PL_FLAG_SCE
|
|
or
|
|
.Dv PL_FLAG_SCX
|
|
is set in
|
|
.Va pl_flags .
|
|
.It Va pl_syscall_narg
|
|
The number of arguments passed to the current system call not counting
|
|
the system call identifier.
|
|
Note that for indirect system calls this field reports the arguments
|
|
passed to the indirected system call.
|
|
Only valid when
|
|
.Dv PL_FLAG_SCE
|
|
or
|
|
.Dv PL_FLAG_SCX
|
|
is set in
|
|
.Va pl_flags .
|
|
.El
|
|
.It Dv PT_GETNUMLWPS
|
|
This request returns the number of kernel threads associated with the
|
|
traced process.
|
|
.It Dv PT_GETLWPLIST
|
|
This request can be used to get the current thread list.
|
|
A pointer to an array of type
|
|
.Vt lwpid_t
|
|
should be passed in
|
|
.Fa addr ,
|
|
with the array size specified by
|
|
.Fa data .
|
|
The return value from
|
|
.Fn ptrace
|
|
is the count of array entries filled in.
|
|
.It Dv PT_SETSTEP
|
|
This request will turn on single stepping of the specified process.
|
|
Stepping is automatically disabled when a single step trap is caught.
|
|
.It Dv PT_CLEARSTEP
|
|
This request will turn off single stepping of the specified process.
|
|
.It Dv PT_SUSPEND
|
|
This request will suspend the specified thread.
|
|
.It Dv PT_RESUME
|
|
This request will resume the specified thread.
|
|
.It Dv PT_TO_SCE
|
|
This request will set the
|
|
.Dv PTRACE_SCE
|
|
event flag to trace all future system call entries and continue the process.
|
|
The
|
|
.Fa addr
|
|
and
|
|
.Fa data
|
|
arguments are used the same as for
|
|
.Dv PT_CONTINUE .
|
|
.It Dv PT_TO_SCX
|
|
This request will set the
|
|
.Dv PTRACE_SCX
|
|
event flag to trace all future system call exits and continue the process.
|
|
The
|
|
.Fa addr
|
|
and
|
|
.Fa data
|
|
arguments are used the same as for
|
|
.Dv PT_CONTINUE .
|
|
.It Dv PT_SYSCALL
|
|
This request will set the
|
|
.Dv PTRACE_SYSCALL
|
|
event flag to trace all future system call entries and exits and continue
|
|
the process.
|
|
The
|
|
.Fa addr
|
|
and
|
|
.Fa data
|
|
arguments are used the same as for
|
|
.Dv PT_CONTINUE .
|
|
.It Dv PT_GET_SC_ARGS
|
|
For the thread which is stopped in either
|
|
.Dv PL_FLAG_SCE
|
|
or
|
|
.Dv PL_FLAG_SCX
|
|
state, that is, on entry or exit to a syscall,
|
|
this request fetches the syscall arguments.
|
|
.Pp
|
|
The arguments are copied out into the buffer pointed to by the
|
|
.Fa addr
|
|
pointer, sequentially.
|
|
Each syscall argument is stored as the machine word.
|
|
Kernel copies out as many arguments as the syscall accepts,
|
|
see the
|
|
.Va pl_syscall_narg
|
|
member of the
|
|
.Vt struct ptrace_lwpinfo ,
|
|
but not more than the
|
|
.Fa data
|
|
bytes in total are copied.
|
|
.It Dv PT_GET_SC_RET
|
|
Fetch the system call return values on exit from a syscall.
|
|
This request is only valid for threads stopped in a syscall
|
|
exit (the
|
|
.Dv PL_FLAG_SCX
|
|
state).
|
|
The
|
|
.Fa addr
|
|
argument specifies a pointer to a
|
|
.Vt "struct ptrace_sc_ret" ,
|
|
which is defined as follows:
|
|
.Bd -literal
|
|
struct ptrace_sc_ret {
|
|
register_t sr_retval[2];
|
|
int sr_error;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is set to the size of the structure.
|
|
.Pp
|
|
If the system call completed successfully,
|
|
.Va sr_error
|
|
is set to zero and the return values of the system call are saved in
|
|
.Va sr_retval .
|
|
If the system call failed to execute,
|
|
.Va sr_error
|
|
field is set to a positive
|
|
.Xr errno 2
|
|
value.
|
|
If the system call completed in an unusual fashion,
|
|
.Va sr_error
|
|
is set to a negative value:
|
|
.Bl -tag -width Dv EJUSTRETURN -compact
|
|
.It Dv ERESTART
|
|
System call will be restarted.
|
|
.It Dv EJUSTRETURN
|
|
System call completed sucessfully but did not set a return value
|
|
.Po for example,
|
|
.Xr setcontext 2
|
|
and
|
|
.Xr sigreturn 2
|
|
.Pc .
|
|
.El
|
|
.It Dv PT_FOLLOW_FORK
|
|
This request controls tracing for new child processes of a traced process.
|
|
If
|
|
.Fa data
|
|
is non-zero,
|
|
.Dv PTRACE_FORK
|
|
is set in the traced process's event tracing mask.
|
|
If
|
|
.Fa data
|
|
is zero,
|
|
.Dv PTRACE_FORK
|
|
is cleared from the traced process's event tracing mask.
|
|
.It Dv PT_LWP_EVENTS
|
|
This request controls tracing of LWP creation and destruction.
|
|
If
|
|
.Fa data
|
|
is non-zero,
|
|
.Dv PTRACE_LWP
|
|
is set in the traced process's event tracing mask.
|
|
If
|
|
.Fa data
|
|
is zero,
|
|
.Dv PTRACE_LWP
|
|
is cleared from the traced process's event tracing mask.
|
|
.It Dv PT_GET_EVENT_MASK
|
|
This request reads the traced process's event tracing mask into the
|
|
integer pointed to by
|
|
.Fa addr .
|
|
The size of the integer must be passed in
|
|
.Fa data .
|
|
.It Dv PT_SET_EVENT_MASK
|
|
This request sets the traced process's event tracing mask from the
|
|
integer pointed to by
|
|
.Fa addr .
|
|
The size of the integer must be passed in
|
|
.Fa data .
|
|
.It Dv PT_VM_TIMESTAMP
|
|
This request returns the generation number or timestamp of the memory map of
|
|
the traced process as the return value from
|
|
.Fn ptrace .
|
|
This provides a low-cost way for the tracing process to determine if the
|
|
VM map changed since the last time this request was made.
|
|
.It Dv PT_VM_ENTRY
|
|
This request is used to iterate over the entries of the VM map of the traced
|
|
process.
|
|
The
|
|
.Fa addr
|
|
argument specifies a pointer to a
|
|
.Vt "struct ptrace_vm_entry" ,
|
|
which is defined as follows:
|
|
.Bd -literal
|
|
struct ptrace_vm_entry {
|
|
int pve_entry;
|
|
int pve_timestamp;
|
|
u_long pve_start;
|
|
u_long pve_end;
|
|
u_long pve_offset;
|
|
u_int pve_prot;
|
|
u_int pve_pathlen;
|
|
long pve_fileid;
|
|
uint32_t pve_fsid;
|
|
char *pve_path;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The first entry is returned by setting
|
|
.Va pve_entry
|
|
to zero.
|
|
Subsequent entries are returned by leaving
|
|
.Va pve_entry
|
|
unmodified from the value returned by previous requests.
|
|
The
|
|
.Va pve_timestamp
|
|
field can be used to detect changes to the VM map while iterating over the
|
|
entries.
|
|
The tracing process can then take appropriate action, such as restarting.
|
|
By setting
|
|
.Va pve_pathlen
|
|
to a non-zero value on entry, the pathname of the backing object is returned
|
|
in the buffer pointed to by
|
|
.Va pve_path ,
|
|
provided the entry is backed by a vnode.
|
|
The
|
|
.Va pve_pathlen
|
|
field is updated with the actual length of the pathname (including the
|
|
terminating null character).
|
|
The
|
|
.Va pve_offset
|
|
field is the offset within the backing object at which the range starts.
|
|
The range is located in the VM space at
|
|
.Va pve_start
|
|
and extends up to
|
|
.Va pve_end
|
|
(inclusive).
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_COREDUMP
|
|
This request creates a coredump for the stopped program.
|
|
The
|
|
.Fa addr
|
|
argument specifies a pointer to a
|
|
.Vt "struct ptrace_coredump" ,
|
|
which is defined as follows:
|
|
.Bd -literal
|
|
struct ptrace_coredump {
|
|
int pc_fd;
|
|
uint32_t pc_flags;
|
|
off_t pc_limit;
|
|
};
|
|
.Ed
|
|
The fields of the structure are:
|
|
.Bl -tag -width pc_flags
|
|
.It Dv pc_fd
|
|
File descriptor to write the dump to.
|
|
It must refer to a regular file, opened for writing.
|
|
.It Dv pc_flags
|
|
Flags.
|
|
The following flags are defined:
|
|
.Bl -tag -width PC_COMPRESS
|
|
.It Dv PC_COMPRESS
|
|
Request compression of the dump.
|
|
.It Dv PC_ALL
|
|
Include non-dumpable entries into the dump.
|
|
The dumper ignores
|
|
.Dv MAP_NOCORE
|
|
flag of the process map entry, but device mappings are not dumped even with
|
|
.Dv PC_ALL
|
|
set.
|
|
.El
|
|
.It Dv pc_limit
|
|
Maximum size of the coredump.
|
|
Specify zero for no limit.
|
|
.El
|
|
.Pp
|
|
The size of
|
|
.Vt "struct ptrace_coredump"
|
|
must be passed in
|
|
.Fa data .
|
|
.Pp
|
|
The process must be stopped before dumping core.
|
|
A single thread in the target process is temporarily unsuspended
|
|
in kernel to write the dump.
|
|
If the
|
|
.Nm
|
|
call fails before a thread is unsuspended, there is no event to
|
|
.Xr waitpid 2
|
|
for.
|
|
If a thread was unsuspended, it will stop again before the
|
|
.Nm
|
|
call returns, and the process must be waited upon using
|
|
.Xr waitpid 2
|
|
to consume the new stop event.
|
|
Since it is hard to deduce whether a thread was unsuspended before
|
|
an error occurred, it is recommended to unconditionally perform
|
|
.Xr waitpid 2
|
|
with
|
|
.Dv WNOHANG
|
|
flag after
|
|
.Dv PT_COREDUMP ,
|
|
and silently accept zero result from it.
|
|
.El
|
|
.Sh ARM MACHINE-SPECIFIC REQUESTS
|
|
.Bl -tag -width "Dv PT_SETVFPREGS"
|
|
.It Dv PT_GETVFPREGS
|
|
Return the thread's
|
|
.Dv VFP
|
|
machine state in the buffer pointed to by
|
|
.Fa addr .
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_SETVFPREGS
|
|
Set the thread's
|
|
.Dv VFP
|
|
machine state from the buffer pointed to by
|
|
.Fa addr .
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.El
|
|
.Sh x86 MACHINE-SPECIFIC REQUESTS
|
|
.Bl -tag -width "Dv PT_GETXSTATE_INFO"
|
|
.It Dv PT_GETXMMREGS
|
|
Copy the XMM FPU state into the buffer pointed to by the
|
|
argument
|
|
.Fa addr .
|
|
The buffer has the same layout as the 32-bit save buffer for the
|
|
machine instruction
|
|
.Dv FXSAVE .
|
|
.Pp
|
|
This request is only valid for i386 programs, both on native 32-bit
|
|
systems and on amd64 kernels.
|
|
For 64-bit amd64 programs, the XMM state is reported as part of
|
|
the FPU state returned by the
|
|
.Dv PT_GETFPREGS
|
|
request.
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_SETXMMREGS
|
|
Load the XMM FPU state for the thread from the buffer pointed to
|
|
by the argument
|
|
.Fa addr .
|
|
The buffer has the same layout as the 32-bit load buffer for the
|
|
machine instruction
|
|
.Dv FXRSTOR .
|
|
.Pp
|
|
As with
|
|
.Dv PT_GETXMMREGS ,
|
|
this request is only valid for i386 programs.
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_GETXSTATE_INFO
|
|
Report which XSAVE FPU extensions are supported by the CPU
|
|
and allowed in userspace programs.
|
|
The
|
|
.Fa addr
|
|
argument must point to a variable of type
|
|
.Vt struct ptrace_xstate_info ,
|
|
which contains the information on the request return.
|
|
.Vt struct ptrace_xstate_info
|
|
is defined as follows:
|
|
.Bd -literal
|
|
struct ptrace_xstate_info {
|
|
uint64_t xsave_mask;
|
|
uint32_t xsave_len;
|
|
};
|
|
.Ed
|
|
The
|
|
.Dv xsave_mask
|
|
field is a bitmask of the currently enabled extensions.
|
|
The meaning of the bits is defined in the Intel and AMD
|
|
processor documentation.
|
|
The
|
|
.Dv xsave_len
|
|
field reports the length of the XSAVE area for storing the hardware
|
|
state for currently enabled extensions in the format defined by the x86
|
|
.Dv XSAVE
|
|
machine instruction.
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument value must be equal to the size of the
|
|
.Vt struct ptrace_xstate_info .
|
|
.It Dv PT_GETXSTATE
|
|
Return the content of the XSAVE area for the thread.
|
|
The
|
|
.Fa addr
|
|
argument points to the buffer where the content is copied, and the
|
|
.Fa data
|
|
argument specifies the size of the buffer.
|
|
The kernel copies out as much content as allowed by the buffer size.
|
|
The buffer layout is specified by the layout of the save area for the
|
|
.Dv XSAVE
|
|
machine instruction.
|
|
.It Dv PT_SETXSTATE
|
|
Load the XSAVE state for the thread from the buffer specified by the
|
|
.Fa addr
|
|
pointer.
|
|
The buffer size is passed in the
|
|
.Fa data
|
|
argument.
|
|
The buffer must be at least as large as the
|
|
.Vt struct savefpu
|
|
(defined in
|
|
.Pa x86/fpu.h )
|
|
to allow the complete x87 FPU and XMM state load.
|
|
It must not be larger than the XSAVE state length, as reported by the
|
|
.Dv xsave_len
|
|
field from the
|
|
.Vt struct ptrace_xstate_info
|
|
of the
|
|
.Dv PT_GETXSTATE_INFO
|
|
request.
|
|
Layout of the buffer is identical to the layout of the load area for the
|
|
.Dv XRSTOR
|
|
machine instruction.
|
|
.It Dv PT_GETFSBASE
|
|
Return the value of the base used when doing segmented
|
|
memory addressing using the %fs segment register.
|
|
The
|
|
.Fa addr
|
|
argument points to an
|
|
.Vt unsigned long
|
|
variable where the base value is stored.
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_GETGSBASE
|
|
Like the
|
|
.Dv PT_GETFSBASE
|
|
request, but returns the base for the %gs segment register.
|
|
.It Dv PT_SETFSBASE
|
|
Set the base for the %fs segment register to the value pointed to
|
|
by the
|
|
.Fa addr
|
|
argument.
|
|
.Fa addr
|
|
must point to the
|
|
.Vt unsigned long
|
|
variable containing the new base.
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_SETGSBASE
|
|
Like the
|
|
.Dv PT_SETFSBASE
|
|
request, but sets the base for the %gs segment register.
|
|
.El
|
|
.Sh PowerPC MACHINE-SPECIFIC REQUESTS
|
|
.Bl -tag -width "Dv PT_SETVRREGS"
|
|
.It Dv PT_GETVRREGS
|
|
Return the thread's
|
|
.Dv ALTIVEC
|
|
machine state in the buffer pointed to by
|
|
.Fa addr .
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_SETVRREGS
|
|
Set the thread's
|
|
.Dv ALTIVEC
|
|
machine state from the buffer pointed to by
|
|
.Fa addr .
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_GETVSRREGS
|
|
Return doubleword 1 of the thread's
|
|
.Dv VSX
|
|
registers VSR0-VSR31 in the buffer pointed to by
|
|
.Fa addr .
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.It Dv PT_SETVSRREGS
|
|
Set doubleword 1 of the thread's
|
|
.Dv VSX
|
|
registers VSR0-VSR31 from the buffer pointed to by
|
|
.Fa addr .
|
|
.Pp
|
|
The
|
|
.Fa data
|
|
argument is ignored.
|
|
.El
|
|
.Pp
|
|
Additionally, other machine-specific requests can exist.
|
|
.Sh RETURN VALUES
|
|
Most requests return 0 on success and \-1 on error.
|
|
Some requests can cause
|
|
.Fn ptrace
|
|
to return
|
|
\-1
|
|
as a non-error value, among them are
|
|
.Dv PT_READ_I
|
|
and
|
|
.Dv PT_READ_D ,
|
|
which return the value read from the process memory on success.
|
|
To disambiguate,
|
|
.Va errno
|
|
can be set to 0 before the call and checked afterwards.
|
|
.Pp
|
|
The current
|
|
.Fn ptrace
|
|
implementation always sets
|
|
.Va errno
|
|
to 0 before calling into the kernel, both for historic reasons and for
|
|
consistency with other operating systems.
|
|
It is recommended to assign zero to
|
|
.Va errno
|
|
explicitly for forward compatibility.
|
|
.Sh ERRORS
|
|
The
|
|
.Fn ptrace
|
|
system call may fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ESRCH
|
|
.Bl -bullet -compact
|
|
.It
|
|
No process having the specified process ID exists.
|
|
.El
|
|
.It Bq Er EINVAL
|
|
.Bl -bullet -compact
|
|
.It
|
|
A process attempted to use
|
|
.Dv PT_ATTACH
|
|
on itself.
|
|
.It
|
|
The
|
|
.Fa request
|
|
argument
|
|
was not one of the legal requests.
|
|
.It
|
|
The signal number
|
|
(in
|
|
.Fa data )
|
|
to
|
|
.Dv PT_CONTINUE
|
|
was neither 0 nor a legal signal number.
|
|
.It
|
|
.Dv PT_GETREGS ,
|
|
.Dv PT_SETREGS ,
|
|
.Dv PT_GETFPREGS ,
|
|
.Dv PT_SETFPREGS ,
|
|
.Dv PT_GETDBREGS ,
|
|
or
|
|
.Dv PT_SETDBREGS
|
|
was attempted on a process with no valid register set.
|
|
(This is normally true only of system processes.)
|
|
.It
|
|
.Dv PT_VM_ENTRY
|
|
was given an invalid value for
|
|
.Fa pve_entry .
|
|
This can also be caused by changes to the VM map of the process.
|
|
.It
|
|
The size (in
|
|
.Fa data )
|
|
provided to
|
|
.Dv PT_LWPINFO
|
|
was less than or equal to zero, or larger than the
|
|
.Vt ptrace_lwpinfo
|
|
structure known to the kernel.
|
|
.It
|
|
The size (in
|
|
.Fa data )
|
|
provided to the x86-specific
|
|
.Dv PT_GETXSTATE_INFO
|
|
request was not equal to the size of the
|
|
.Vt struct ptrace_xstate_info .
|
|
.It
|
|
The size (in
|
|
.Fa data )
|
|
provided to the x86-specific
|
|
.Dv PT_SETXSTATE
|
|
request was less than the size of the x87 plus the XMM save area.
|
|
.It
|
|
The size (in
|
|
.Fa data )
|
|
provided to the x86-specific
|
|
.Dv PT_SETXSTATE
|
|
request was larger than returned in the
|
|
.Dv xsave_len
|
|
member of the
|
|
.Vt struct ptrace_xstate_info
|
|
from the
|
|
.Dv PT_GETXSTATE_INFO
|
|
request.
|
|
.It
|
|
The base value, provided to the amd64-specific requests
|
|
.Dv PT_SETFSBASE
|
|
or
|
|
.Dv PT_SETGSBASE ,
|
|
pointed outside of the valid user address space.
|
|
This error will not occur in 32-bit programs.
|
|
.El
|
|
.It Bq Er EBUSY
|
|
.Bl -bullet -compact
|
|
.It
|
|
.Dv PT_ATTACH
|
|
was attempted on a process that was already being traced.
|
|
.It
|
|
A request attempted to manipulate a process that was being traced by
|
|
some process other than the one making the request.
|
|
.It
|
|
A request
|
|
(other than
|
|
.Dv PT_ATTACH )
|
|
specified a process that was not stopped.
|
|
.El
|
|
.It Bq Er EPERM
|
|
.Bl -bullet -compact
|
|
.It
|
|
A request
|
|
(other than
|
|
.Dv PT_ATTACH )
|
|
attempted to manipulate a process that was not being traced at all.
|
|
.It
|
|
An attempt was made to use
|
|
.Dv PT_ATTACH
|
|
on a process in violation of the requirements listed under
|
|
.Dv PT_ATTACH
|
|
above.
|
|
.El
|
|
.It Bq Er ENOENT
|
|
.Bl -bullet -compact
|
|
.It
|
|
.Dv PT_VM_ENTRY
|
|
previously returned the last entry of the memory map.
|
|
No more entries exist.
|
|
.El
|
|
.It Bq Er ENOMEM
|
|
.Bl -bullet -compact
|
|
.It
|
|
A
|
|
.Dv PT_READ_I,
|
|
.Dv PT_READ_D,
|
|
.Dv PT_WRITE_I, or
|
|
.Dv PT_WRITE_D
|
|
request attempted to access an invalid address, or a memory allocation failure
|
|
occurred when accessing process memory.
|
|
.El
|
|
.It Bq Er ENAMETOOLONG
|
|
.Bl -bullet -compact
|
|
.It
|
|
.Dv PT_VM_ENTRY
|
|
cannot return the pathname of the backing object because the buffer is not big
|
|
enough.
|
|
.Fa pve_pathlen
|
|
holds the minimum buffer size required on return.
|
|
.El
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr execve 2 ,
|
|
.Xr sigaction 2 ,
|
|
.Xr wait 2 ,
|
|
.Xr execv 3 ,
|
|
.Xr i386_clr_watch 3 ,
|
|
.Xr i386_set_watch 3
|
|
.Sh HISTORY
|
|
The
|
|
.Fn ptrace
|
|
function appeared in
|
|
.At v6 .
|