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diff --git a/share/man/man4/dtrace_kinst.4 b/share/man/man4/dtrace_kinst.4 new file mode 100644 index 000000000000..9debbc1bd106 --- /dev/null +++ b/share/man/man4/dtrace_kinst.4 @@ -0,0 +1,91 @@ +.\" Copyright (c) 2022 Christos Margiolis <christos@FreeBSD.org> +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.Dd February 27, 2023 +.Dt DTRACE_KINST 4 +.Os +.Sh NAME +.Nm dtrace_kinst +.Nd a DTrace provider for tracing arbitrary instructions in a given kernel function +.Sh SYNOPSIS +kinst::<function>:<instruction> +.Sh DESCRIPTION +The DTrace +.Nm kinst +provider allows the user to trace any instruction in a given kernel function. +<function> corresponds to the function to be traced, and <instruction> is the +offset to the specific instruction, and can be obtained from the function's +disassembly using kgdb from the gdb package. +.Pp +.Nm kinst +creates probes on-demand, meaning it searches for and parses the function's +instructions each time +.Xr dtrace 1 +is run, and not at module load time. +This is in contrast to FBT's load-time parsing, since +.Nm kinst +can potentially create thousands of probes for just a single function, instead +of up to two (entry and return) in the case of FBT. +A result of this is that +.Cm dtrace -l -P kinst +will not match any probes. +.Sh IMPLEMENTATION NOTES +The provider is currently implemented only for amd64. +.Sh EXAMPLES +Find the offset corresponding to the third instruction in +.Fn vm_fault +and trace it, printing the contents of the RSI register: +.Bd -literal -offset indent +# kgdb +(kgdb) disas /r vm_fault +Dump of assembler code for function vm_fault: + 0xffffffff80876df0 <+0>: 55 push %rbp + 0xffffffff80876df1 <+1>: 48 89 e5 mov %rsp,%rbp + 0xffffffff80876df4 <+4>: 41 57 push %r15 + +# dtrace -n 'kinst::vm_fault:4 {printf("%#x", regs[R_RSI]);}' + 2 81500 vm_fault:4 0x827c56000 + 2 81500 vm_fault:4 0x827878000 + 2 81500 vm_fault:4 0x1fab9bef0000 + 2 81500 vm_fault:4 0xe16cf749000 + 0 81500 vm_fault:4 0x13587c366000 + ... +.Ed +.Pp +Trace all instructions in +.Fn amd64_syscall : +.Bd -literal -offset indent +# dtrace -n 'kinst::amd64_syscall:' +.Ed +.Sh SEE ALSO +.Xr dtrace 1 +.Sh HISTORY +The +.Nm kinst +provider first appeared in +.Fx +14.0. +.Sh AUTHORS +This manual page was written by +.An Christos Margiolis Aq Mt christos@FreeBSD.org . |