From 1b1d9258181bae199dc940f4bd0298126b9a73d9 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 18 Dec 2009 16:12:56 +0000 Subject: x86-64: Modify copy_user_generic() alternatives mechanism In order to avoid unnecessary chains of branches, rather than implementing copy_user_generic() as a function consisting of just a single (possibly patched) branch, instead properly deal with patching call instructions in the alternative instructions framework, and move the patching into the callers. As a follow-on, one could also introduce something like __EXPORT_SYMBOL_ALT() to avoid patching call sites in modules. Signed-off-by: Jan Beulich Cc: Nick Piggin Cc: Linus Torvalds Cc: Andrew Morton LKML-Reference: <4B2BB8180200007800026AE7@vpn.id2.novell.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/alternative.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel/alternative.c') diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index de7353c0ce9c..2589ea4c60ce 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -205,7 +205,7 @@ void __init_or_module apply_alternatives(struct alt_instr *start, struct alt_instr *end) { struct alt_instr *a; - char insnbuf[MAX_PATCH_LEN]; + u8 insnbuf[MAX_PATCH_LEN]; DPRINTK("%s: alt table %p -> %p\n", __func__, start, end); for (a = start; a < end; a++) { @@ -223,6 +223,8 @@ void __init_or_module apply_alternatives(struct alt_instr *start, } #endif memcpy(insnbuf, a->replacement, a->replacementlen); + if (*insnbuf == 0xe8 && a->replacementlen == 5) + *(s32 *)(insnbuf + 1) += a->replacement - a->instr; add_nops(insnbuf + a->replacementlen, a->instrlen - a->replacementlen); text_poke_early(instr, insnbuf, a->instrlen); -- cgit v1.2.3