1.\" Copyright (c) 2022 Christos Margiolis <christos@FreeBSD.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd October 01, 2022 28.Dt DTRACE_KINST 4 29.Os 30.Sh NAME 31.Nm dtrace_kinst 32.Nd a DTrace provider for tracing arbitrary instructions in a given kernel 33function. 34.Sh SYNOPSIS 35kinst::<function>:<instruction> 36.Sh DESCRIPTION 37.Pp 38The DTrace 39.Nm kinst 40provider allows the user to trace any instruction in a given kernel function. 41<function> corresponds to the function to be traced, and <instruction> is the 42offset to the specific instruction, and can be obtained from the function's 43disassembly using 44.Xr kgdb 1 . 45.Pp 46.Nm kinst 47creates probes on-demand, meaning it searches for and parses the function's 48instructions each time 49.Xr dtrace 1 50is run, and not at module load time. This is in contrast to FBT's load-time 51parsing, since 52.Nm kinst 53can potentially create thousands of probes for just a single function, instead 54of up to two (entry and return) in the case of FBT. 55.Sh EXAMPLES 56.Pp 57Find the offset to the third instruction in 58.Fn vm_fault 59and trace it: 60.Bd -literal -offset indent 61# kgdb 62(kgdb) disas /r vm_fault 63Dump of assembler code for function vm_fault: 64 0xffffffff80876df0 <+0>: 55 push %rbp 65 0xffffffff80876df1 <+1>: 48 89 e5 mov %rsp,%rbp 66 0xffffffff80876df4 <+4>: 41 57 push %r15 67 68# dtrace -n 'kinst::vm_fault:4' 69.Ed 70.Pp 71Trace all instructions in 72.Fn amd64_syscall : 73.Bd -literal -offset indent 74# dtrace -n 'kinst::amd64_syscall:' 75.Ed 76.Sh IMPLEMENTATION NOTES 77The provider is currently implemented only for amd64. 78.Sh SEE ALSO 79.Xr dtrace 1 , 80.Xr kgdb 1 81.Sh HISTORY 82The 83.Nm kinst 84provider first appeared in 85.Fx 8614.0. 87.Sh AUTHORS 88This manual page was written by 89.An Christos Margiolis Aq Mt christos@FreeBSD.org . 90