Commit fc06b852 authored Sep 10, 2009 by Steven Rostedt Committed by Steven Rostedt Sep 10, 2009

x86/tracing: comment need for atomic nop



The dynamic function tracer relys on the macro P6_NOP5 always being
an atomic NOP. If for some reason it is changed to be two operations
(like a nop2 nop3) it can faults within the kernel when the function
tracer modifies the code.

This patch adds a comment to note that the P6_NOPs are expected to
be atomic. This will hopefully prevent anyone from changing that.

Reported-by: Mathieu Desnoyer <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent 197e2eab

arch/x86/include/asm/nops.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -65,6 +65,8 @@
		6: osp nopl 0x00(%eax,%eax,1)
		7: nopl 0x00000000(%eax)
		8: nopl 0x00000000(%eax,%eax,1)
		Note: All the above are assumed to be a single instruction.
		There is kernel code that depends on this.
		*/
		#define P6_NOP1 GENERIC_NOP1
		#define P6_NOP2 ".byte 0x66,0x90\n"