The process is reparented to the debugger while it is attached.
B B
/ ----> |
A A D
Every time when the process is reparented, it is added to the orphan list
of the previous parent:
A->orphan = B
D->orphan = NULL
When the A process will close the process descriptor to the B process,
the B process will be reparented to the init process.
B B - init
| ---->
A D A D
A->orphan = B
D->orphan = B
In this scenario, the B process is in the orphan list of A and D.
When the last process descriptor is closed instead of reparenting
it to the reaper let it stay with the debugger process and set
our previews parent to the reaper.
Add test case for this situation.
Notice that without this patch the kernel will crash with this test case:
panic: orphan 0xfffff8000e990530 of 0xfffff8000e990000 has unexpected oppid 1
Reviewed by: markj, kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D20361
This ptrace operation returns a structure containing the error and
return values from the current system call. It is only valid when a
thread is stopped during a system call exit (PL_FLAG_SCX is set).
The sr_error member holds the error value from the system call. Note
that this error value is the native FreeBSD error value that has _not_
been translated to an ABI-specific error value similar to the values
logged to ktrace.
If sr_error is zero, then the return values of the system call will be
set in sr_retval[0] and sr_retval[1].
Reviewed by: kib
MFC after: 1 month
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D20901
Such processes will be reparented to the reaper when the current
parent is done with them (i.e., ptrace detached), so p_oppid must be
updated accordingly.
Add a regression test to exercise this code path. Previously it
would not be possible to reap an orphan with a stale oppid.
Reviewed by: kib, mjg
Tested by: pho
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D19825
Once a signal's siginfo was copied to 'td_si' as part of the signal
exchange in issignal(), it was never cleared. This caused future
thread events that are reported as SIGTRAP events without signal
information to report the stale siginfo in 'td_si'. For example, if a
debugger created a new process and used SIGSTOP to stop it after
PT_ATTACH, future system call entry / exit events would set PL_FLAG_SI
with the SIGSTOP siginfo in pl_siginfo. This broke 'catch syscall' in
current versions of gdb as it assumed PL_FLAG_SI with SIGTRAP
indicates a breakpoint or single step trap.
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D18487
FreeBSD's mkstemp sets the temporary file's permissions to 600, and has ever
since mkstemp was added in 1987. Coverity's warning is still relevant for
portable programs since OpenGroup does not require that behavior, and POSIX
didn't until 2008. But none of these programs are portable.
umask(2) should always be used prior to mkstemp(3) so the temporary file
won't be created with insecure permissions.
Reported by: Coverity
CID: 1331605 1347173 1375366 1339800 1331604 1296056 1296060
CID: 1296057 1296062
MFC after: 2 weeks
- ptrace__breakpoint_siginfo tests that a SIGTRAP for a software breakpoint
in userland triggers a SIGTRAP with a signal code of TRAP_BRKPT.
- ptrace__step_siginfo tests that a SIGTRAP reported for a step after
stepping via PT_STEP or PT_SETSTEP has a signal code of TRAP_TRACE.
- Use a single list of platforms to define HAVE_BREAKPOINT for platforms
that expose a functional breakpoint() inline to userland. Replace
existing lists of platform tests with HAVE_BREAKPOINT instead.
- Add support for advancing PC past a breakpoint inserted via breakpoint()
to support the existing ptrace__PT_CONTINUE_different_thread test on
non-x86 platforms (x86 advances the PC past the breakpoint instruction,
but other platforms do not). This is implemented by defining a new
SKIP_BREAK macro which accepts a pointer to a 'struct reg' as its sole
argument and modifies the contents to advance the PC. The intention is
to use it in between PT_GETREGS and PT_SETREGS.
Tested on: amd64, i386, mips (after adding a breakpoint() to mips)
MFC after: 1 month
Some of the ptrace tests need to wait for a child process to become a
zombie before preceding. The parent process polls the child process
via the kern.proc.pid sysctl to wait for it to become a zombie.
Previously the code polled until the sysctl failed with ESRCH. Now it
will poll until either the sysctl fails with ESRCH (for compatiblity
with older kernels) or returns a kinfo_proc structure with the ki_stat
field set to SZOMB.
Reported by: Jenkins
Tested by: markj
Discussed with: mjg
MFC after: 1 week
When multiple threads wish to report a tracing event to a debugger,
both threads call ptracestop() and one thread will win the race to be
the reporting thread (p->p_xthread). The debugger uses PT_LWPINFO
with the process ID to determine which thread / LWP is reporting an
event and the details of that event. This event is cleared as a side
effect of the subsequent ptrace event that resumed the process
(PT_CONTINUE, PT_STEP, etc.). However, ptrace() was clearing the
event identified by the LWP ID passed to the resume request even if
that wasn't the 'p_xthread'. This could result in clearing an event
that had not yet been observed by the debugger and leaving the
existing event for 'p_thread' pending so that it was reported a second
time.
Specifically, if the debugger stopped due to a software breakpoint in
one thread, but then switched to another thread that was used to
resume (e.g. if the user switched to a different thread and issued a
step), the resume request (PT_STEP) cleared a pending event (if any)
for the thread being stepped. However, the process immediately
stopped and the first thread reported it's breakpoint event a second
time. The debugger decremented the PC for "both" breakpoint events
which resulted in the PC now pointing into the middle of an
instruction (on x86) and a SIGILL fault when the process was resumed a
second time.
To fix, always clear the pending event for 'p_xthread' when resuming a
process. ptrace() still honors the requested LWP ID when enabling
single-stepping (PT_STEP) or setting a different PC (PT_CONTINUE).
Reported by: GDB testsuite (gdb.threads/continue-pending-status.exp)
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D12794
A couple of the ptrace tests make assumptions about which thread in a
multithreaded process will run after a halt. This makes the tests less
portable across branches, and susceptible to future breakage. Instead,
twiddle thread scheduling and priorities to match the tests'
expectation.
X-MFC with: r313992
Sponsored by: Dell EMC
The ptrace() user has the option of discarding the signal. In such a
case, p_ptevents should not be modified. If the ptrace() user decides to
send a SIGKILL, ptevents will be cleared in ptracestop(). procfs events
do not have the capability to discard the signal, so continue to clear
the mask in that case.
Reviewed by: jhb (initial revision)
MFC after: 1 week
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D9939
Suppose a traced process is stopped in ptracestop() due to receipt of a
SIGSTOP signal, and is awaiting orders from the tracing process on how
to handle the signal. Before sending any such orders, the tracing
process exits. This should kill the traced process. But suppose a second
thread handles the SIGKILL and proceeds to exit1(), calling
thread_single(). The first thread will now awaken and will have a chance
to check once more if it should go to sleep due to the SIGSTOP. It must
not sleep after P_SINGLE_EXIT has been set; this would prevent the
SIGKILL from taking effect, leaving a stopped orphan behind after the
tracing process dies.
Also add new tests for this condition.
Reviewed by: kib
MFC after: 2 weeks
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D9890
When a thread is stopped in ptracestop(), the ptrace(2) user may request
a signal be delivered upon resumption of the thread. Heretofore, those signals
were discarded unless ptracestop()'s caller was issignal(). Fix this by
modifying ptracestop() to queue up signals requested by the ptrace user that
will be delivered when possible. Take special care when the signal is SIGKILL
(usually generated from a PT_KILL request); no new stop events should be
triggered after a PT_KILL.
Add a number of tests for the new functionality. Several tests were authored
by jhb.
PR: 212607
Reviewed by: kib
Approved by: kib (mentor)
MFC after: 2 weeks
Sponsored by: Dell EMC
In collaboration with: jhb
Differential Revision: https://reviews.freebsd.org/D9260
First, PL_FLAG_FORKED events now also set a PL_FLAG_VFORKED flag when
the new child was created via vfork() rather than fork(). Second, a
new PL_FLAG_VFORK_DONE event can now be enabled via the PTRACE_VFORK
event mask. This new stop is reported after the vfork parent resumes
due to the child calling exit or exec. Debuggers can use this stop to
reinsert breakpoints in the vfork parent process before it resumes.
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D7045
ptrace() now stores a mask of optional events in p_ptevents. Currently
this mask is a single integer, but it can be expanded into an array of
integers in the future.
Two new ptrace requests can be used to manipulate the event mask:
PT_GET_EVENT_MASK fetches the current event mask and PT_SET_EVENT_MASK
sets the current event mask.
The current set of events include:
- PTRACE_EXEC: trace calls to execve().
- PTRACE_SCE: trace system call entries.
- PTRACE_SCX: trace syscam call exits.
- PTRACE_FORK: trace forks and auto-attach to new child processes.
- PTRACE_LWP: trace LWP events.
The S_PT_SCX and S_PT_SCE events in the procfs p_stops flags have
been replaced by PTRACE_SCE and PTRACE_SCX. PTRACE_FORK replaces
P_FOLLOW_FORK and PTRACE_LWP replaces P2_LWP_EVENTS.
The PT_FOLLOW_FORK and PT_LWP_EVENTS ptrace requests remain for
compatibility but now simply toggle corresponding flags in the
event mask.
While here, document that PT_SYSCALL, PT_TO_SCE, and PT_TO_SCX both
modify the event mask and continue the traced process.
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D7044
Add two new LWPINFO flags: PL_FLAG_BORN and PL_FLAG_EXITED for reporting
thread creation and destruction. Newly created threads will stop to report
PL_FLAG_BORN before returning to userland and exiting threads will stop to
report PL_FLAG_EXIT before exiting completely. Both of these events are
only enabled and reported if PT_LWP_EVENTS is enabled on a process.
- Always set td_dbg_sc_* when P_TRACED is set on system call entry
even if the debugger is not tracing system call entries. This
ensures the fields are valid when reporting other stops that
occur at system call boundaries such as for PT_FOLLOW_FORKS or
when only tracing system call exits.
- Set TDB_SCX when reporting the stop for a new child process in
fork_return(). This causes the event to be reported as a system
call exit.
- Report a system call exit event in fork_return() for new threads in
a traced process.
- Copy td_dbg_sc_* to new threads instead of zeroing. This ensures
that td_dbg_sc_code in particular will report the system call that
created the new thread or process when it reports a system call
exit event in fork_return().
- Add new ptrace tests to verify that new child processes and threads
report system call exit events with a valid pl_syscall_code via
PT_LWPINFO.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D3822
getppid() after a debugger process that is not the parent has attached.
Reviewed by: kib (earlier version)
Differential Revision: https://reviews.freebsd.org/D3615
original parent. Otherwise the debugee will be set as an orphan of
the debugger.
Add tests for tracing forks via PT_FOLLOW_FORK.
Reviewed by: kib
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D2809
