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