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x86-64: Modify copy_user_generic() alternatives mechanism

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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 <jbeulich@novell.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4B2BB8180200007800026AE7@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jan Beulich
2009-12-18 16:12:56 +00:00
committed by Ingo Molnar
parent 499a5f1efa
commit 1b1d925818
5 changed files with 31 additions and 10 deletions
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4
arch/x86/kernel/alternative.c
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@@ -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);