Commit 01be50a3 authored Nov 27, 2009 by Jan Beulich Committed by Ingo Molnar Dec 02, 2009

x86/alternatives: Check replacementlen <= instrlen at build time



Having run into the run-(boot-)time check a couple of times lately,
I finally took time to find a build-time check so that one doesn't
need to analyze the register/stack dump and resolve this (through
manual lookup in vmlinux) to the offending construct.

The assembler will emit a message like "Error: value of <num> too
large for field of 1 bytes at <offset>", which while not pointing
out the source location still makes analysis quite a bit easier.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <4B0FF8AA0200007800022703@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 8ec6993d

arch/x86/include/asm/alternative.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -84,6 +84,7 @@ static inline void alternatives_smp_switch(int smp) {}
		" .byte " __stringify(feature) "\n" /* feature bit */ \
		" .byte 662b-661b\n" /* sourcelen */ \
		" .byte 664f-663f\n" /* replacementlen */ \
		" .byte 0xff + (664f-663f) - (662b-661b)\n" /* rlen <= slen */ \
		".previous\n" \
		".section .altinstr_replacement, \"ax\"\n" \
		"663:\n\t" newinstr "\n664:\n" /* replacement */ \