092a543ec3
Suggested by: Mina Galić <freebsd@igalic.co> Reviewed by: christos Differential Revision: https://reviews.freebsd.org/D38823
94 lines
3.4 KiB
Groff
94 lines
3.4 KiB
Groff
.\" Copyright (c) 2022 Christos Margiolis <christos@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 27, 2023
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.Dt DTRACE_KINST 4
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.Os
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.Sh NAME
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.Nm dtrace_kinst
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.Nd a DTrace provider for tracing arbitrary instructions in a given kernel function
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.Sh SYNOPSIS
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kinst::<function>:<instruction>
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.Sh DESCRIPTION
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The DTrace
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.Nm kinst
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provider allows the user to trace any instruction in a given kernel function.
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<function> corresponds to the function to be traced, and <instruction> is the
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offset to the specific instruction, and can be obtained from the function's
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disassembly using kgdb from the gdb package.
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.Pp
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.Nm kinst
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creates probes on-demand, meaning it searches for and parses the function's
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instructions each time
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.Xr dtrace 1
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is run, and not at module load time.
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This is in contrast to FBT's load-time parsing, since
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.Nm kinst
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can potentially create thousands of probes for just a single function, instead
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of up to two (entry and return) in the case of FBT.
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A result of this is that
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.Cm dtrace -l -P kinst
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will not match any probes.
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.Sh IMPLEMENTATION NOTES
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The provider is currently implemented only for amd64.
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.Sh EXAMPLES
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Find the offset corresponding to the third instruction in
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.Fn vm_fault
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and trace it, printing the contents of the RSI register:
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.Bd -literal -offset indent
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# kgdb
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(kgdb) disas /r vm_fault
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Dump of assembler code for function vm_fault:
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0xffffffff80876df0 <+0>: 55 push %rbp
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0xffffffff80876df1 <+1>: 48 89 e5 mov %rsp,%rbp
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0xffffffff80876df4 <+4>: 41 57 push %r15
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# dtrace -n 'kinst::vm_fault:4 {printf("%#x", regs[R_RSI]);}'
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2 81500 vm_fault:4 0x827c56000
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2 81500 vm_fault:4 0x827878000
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2 81500 vm_fault:4 0x1fab9bef0000
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2 81500 vm_fault:4 0xe16cf749000
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0 81500 vm_fault:4 0x13587c366000
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...
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.Ed
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.Pp
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Trace all instructions in
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.Fn amd64_syscall :
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.Bd -literal -offset indent
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# dtrace -n 'kinst::amd64_syscall:'
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.Ed
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.Sh SEE ALSO
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.Xr dtrace 1
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.Sh HISTORY
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The
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.Nm kinst
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provider first appeared in
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.Fx
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14.0.
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.Sh AUTHORS
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This manual page was written by
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.An Christos Margiolis Aq Mt christos@FreeBSD.org .
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