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kprobes-x86-fix-kprobes-to-skip-prefixes-correctly.patch (#610941)

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Chuck Ebbert 2010-08-27 02:07:13 -04:00
parent b30c150da1
commit 8f132e348c
2 changed files with 104 additions and 0 deletions
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6
kernel.spec
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@ -710,6 +710,8 @@ Patch12050: direct-io-move-aio_complete-into-end_io.patch
Patch12060: ext4-move-aio-completion-after-unwritten-extent-conversion.patch
Patch12070: xfs-move-aio-completion-after-unwritten-extent-conversion.patch
Patch12080: kprobes-x86-fix-kprobes-to-skip-prefixes-correctly.patch
%endif
BuildRoot: %{_tmppath}/kernel-%{KVERREL}-root
@ -1305,6 +1307,9 @@ ApplyPatch direct-io-move-aio_complete-into-end_io.patch
ApplyPatch ext4-move-aio-completion-after-unwritten-extent-conversion.patch
ApplyPatch xfs-move-aio-completion-after-unwritten-extent-conversion.patch
# bz 610941
ApplyPatch kprobes-x86-fix-kprobes-to-skip-prefixes-correctly.patch
# END OF PATCH APPLICATIONS
%endif
@ -1893,6 +1898,7 @@ fi
%changelog
* Fri Aug 27 2010 Chuck Ebbert <cebbert@redhat.com> 2.6.35.4-12
- Linux 2.6.35.4
- kprobes-x86-fix-kprobes-to-skip-prefixes-correctly.patch (#610941)
* Wed Aug 25 2010 Chuck Ebbert <cebbert@redhat.com> 2.6.35.4-11.rc1
- Linux 2.6.35.4-rc1

98
kprobes-x86-fix-kprobes-to-skip-prefixes-correctly.patch Normal file
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@ -0,0 +1,98 @@
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Date: Tue, 29 Jun 2010 05:53:50 +0000 (+0900)
Subject: kprobes/x86: Fix kprobes to skip prefixes correctly
X-Git-Tag: v2.6.36-rc1~41^2~53
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=567a9fd86735ccdc897768ed2dacdd5e83a13509
kprobes/x86: Fix kprobes to skip prefixes correctly
Fix resume_execution() and is_IF_modifier() to skip x86
instruction prefixes correctly by using x86 instruction
attribute.
Without this fix, resume_execution() can't handle instructions
which have non-REX prefixes (REX prefixes are skipped). This
will cause unexpected kernel panic by hitting bad address when a
kprobe hits on two-byte ret (e.g. "repz ret" generated for
Athlon/K8 optimization), because it just checks "repz" and can't
recognize the "ret" instruction.
These prefixes can be found easily with x86 instruction
attribute. This patch introduces skip_prefixes() and uses it in
resume_execution() and is_IF_modifier() to skip prefixes.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
LKML-Reference: <4C298A6E.8070609@hitachi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 345a4b1..175f85c 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -126,16 +126,22 @@ static void __kprobes synthesize_reljump(void *from, void *to)
}
/*
- * Check for the REX prefix which can only exist on X86_64
- * X86_32 always returns 0
+ * Skip the prefixes of the instruction.
*/
-static int __kprobes is_REX_prefix(kprobe_opcode_t *insn)
+static kprobe_opcode_t *__kprobes skip_prefixes(kprobe_opcode_t *insn)
{
+ insn_attr_t attr;
+
+ attr = inat_get_opcode_attribute((insn_byte_t)*insn);
+ while (inat_is_legacy_prefix(attr)) {
+ insn++;
+ attr = inat_get_opcode_attribute((insn_byte_t)*insn);
+ }
#ifdef CONFIG_X86_64
- if ((*insn & 0xf0) == 0x40)
- return 1;
+ if (inat_is_rex_prefix(attr))
+ insn++;
#endif
- return 0;
+ return insn;
}
/*
@@ -272,6 +278,9 @@ static int __kprobes can_probe(unsigned long paddr)
*/
static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
{
+ /* Skip prefixes */
+ insn = skip_prefixes(insn);
+
switch (*insn) {
case 0xfa: /* cli */
case 0xfb: /* sti */
@@ -280,13 +289,6 @@ static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
return 1;
}
- /*
- * on X86_64, 0x40-0x4f are REX prefixes so we need to look
- * at the next byte instead.. but of course not recurse infinitely
- */
- if (is_REX_prefix(insn))
- return is_IF_modifier(++insn);
-
return 0;
}
@@ -803,9 +805,8 @@ static void __kprobes resume_execution(struct kprobe *p,
unsigned long orig_ip = (unsigned long)p->addr;
kprobe_opcode_t *insn = p->ainsn.insn;
- /*skip the REX prefix*/
- if (is_REX_prefix(insn))
- insn++;
+ /* Skip prefixes */
+ insn = skip_prefixes(insn);
regs->flags &= ~X86_EFLAGS_TF;
switch (*insn) {