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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 FBT's	load-time parsing, since 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 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)

HISTORY
       The kinst provider first	appeared in FreeBSD 14.0.

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

FreeBSD	13.2		       February	27, 2023	       DTRACE_KINST(4)
NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS

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