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DTRACE_KINST(4)		    Kernel Interfaces Manual	       DTRACE_KINST(4)

NAME
       dtrace_kinst -- a DTrace	provider for tracing arbitrary instructions in
       a given kernel function

SYNOPSIS
       kinst::<function>:<instruction>

DESCRIPTION
       The DTrace 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.

       kinst  creates probes on-demand,	meaning	it searches for	and parses the
       function's instructions each time dtrace(1) is run, and not  at	module
       load  time.   This is in	contrast to dtrace_fbt(4)'s load-time parsing,
       since kinst can potentially create thousands of probes for just a  sin-
       gle  function,  instead	of up to two (entry and	return)	in the case of
       dtrace_fbt(4).  A result	of this	is that	dtrace -l -P  kinst  will  not
       match any probes.

IMPLEMENTATION NOTES
       The provider is currently implemented only for amd64.

EXAMPLES
       Find  the  offset  corresponding	to the third instruction in vm_fault()
       and trace it, printing the contents of the RSI register:

	     # 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
	       ...

       Trace all instructions in amd64_syscall():

	     # dtrace -n 'kinst::amd64_syscall:'

SEE ALSO
       dtrace(1), dtrace_fbt(4)

HISTORY
       The kinst provider first	appeared in FreeBSD 14.0.

AUTHORS
       This    manual	 page	 was	written	   by	 Christos    Margiolis
       <christos@FreeBSD.org>.

FreeBSD	15.0			 July 16, 2025		       DTRACE_KINST(4)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=dtrace_kinst&sektion=4&manpath=FreeBSD+15.0-RELEASE+and+Ports>

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