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[PATCH] kprobe: kprobe-2byte-booster
- From: Masami Hiramatsu <hiramatu at sdl dot hitachi dot co dot jp>
- To: Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Prasanna S Panchamukhi <prasanna at in dot ibm dot com>, "Keshavamurthy, Anil S" <anil dot s dot keshavamurthy at intel dot com>, SystemTAP <systemtap at sources dot redhat dot com>
- Cc: Yumiko Sugita <sugita at sdl dot hitachi dot co dot jp>, Satoshi Oshima <soshima at redhat dot com>, Hideo Aoki <haoki at redhat dot com>
- Date: Wed, 12 Apr 2006 19:10:30 +0900
- Subject: [PATCH] kprobe: kprobe-2byte-booster
Hi,
Here is a patch of kprobe-booster enhancement on i386
This patch can be applied to 2.6.17-rc1.
Previous kprobe-booster patch has not handled any 2byte opcodes
and prefixes. I checked whole IA32 opcode map and classified it.
This patch enables kprobe to boost those 2byte opcodes and prefixes.
Best regards,
--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: hiramatu@sdl.hitachi.co.jp
kprobes.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 50 insertions(+), 13 deletions(-)
diff -Narup a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
--- a/arch/i386/kernel/kprobes.c 2006-04-03 18:30:59.000000000 +0900
+++ b/arch/i386/kernel/kprobes.c 2006-04-03 19:41:54.000000000 +0900
@@ -55,32 +55,69 @@ static inline void set_jmp_op(void *from
}
/*
+ * Undefined/reserved opcodes, conditional jump, Opcode Extension Groups,
+ * and some special opcodes can not be boost.
+ */
+static char boostable_2nd_opcode[256] = {
+0,0,1,1,0,0,1,0,1,1,0,0,0,0,0,0,
+0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,
+0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+1,1,1,1,1,1,1,1,1,1,1,1,0,0,1,1,
+0,0,0,0,1,1,1,1,0,0,0,0,0,0,1,1,
+0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+1,1,0,1,1,1,0,0,1,1,0,1,1,1,0,1,
+1,1,1,1,1,1,1,1,0,0,0,1,1,1,1,1,
+1,1,0,0,0,0,0,0,1,1,1,1,1,1,1,1,
+0,1,1,1,0,1,0,0,1,1,0,1,1,1,0,1,
+0,1,1,0,0,1,0,0,1,1,0,1,1,1,0,1,
+0,1,1,1,0,1,0,0,1,1,1,0,1,1,1,0
+};
+
+/*
* returns non-zero if opcodes can be boosted.
*/
-static inline int can_boost(kprobe_opcode_t opcode)
+static inline int can_boost(kprobe_opcode_t *opcodes)
{
- switch (opcode & 0xf0 ) {
+ kprobe_opcode_t opcode;
+ kprobe_opcode_t *orig_opcodes = opcodes;
+retry:
+ if (opcodes - orig_opcodes > MAX_INSN_SIZE) return 0;
+ opcode = *(opcodes++);
+ /* 2nd-byte opcode */
+ if (opcode == 0x0f)
+ return boostable_2nd_opcode[*opcodes];
+
+ switch (opcode & 0xf0) {
+ case 0x60:
+ if (0x63 < opcode && opcode < 0x67)
+ goto retry; /* prefixes */
+ /* can't boost Address-size override and bound */
+ return (opcode != 0x62 && opcode != 0x67);
case 0x70:
return 0; /* can't boost conditional jump */
- case 0x90:
- /* can't boost call and pushf */
- return opcode != 0x9a && opcode != 0x9c;
case 0xc0:
- /* can't boost undefined opcodes and soft-interruptions */
- return (0xc1 < opcode && opcode < 0xc6) ||
- (0xc7 < opcode && opcode < 0xcc) || opcode == 0xcf;
+ /* can't boost software-interruptions */
+ return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
case 0xd0:
/* can boost AA* and XLAT */
return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
case 0xe0:
- /* can boost in/out and (may be) jmps */
- return (0xe3 < opcode && opcode != 0xe8);
+ /* can boost in/out and absolute jmps */
+ return ((opcode & 0x04) || opcode == 0xea);
case 0xf0:
+ if ((opcode & 0x0c) == 0 && opcode != 0xf1)
+ goto retry; /* lock/rep(ne) prefix */
/* clear and set flags can be boost */
return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
default:
- /* currently, can't boost 2 bytes opcodes */
- return opcode != 0x0f;
+ if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e)
+ goto retry; /* prefixes */
+ /* can't boost CS override and call */
+ return (opcode != 0x2e && opcode != 0x9a);
}
}
@@ -109,7 +146,7 @@ int __kprobes arch_prepare_kprobe(struct
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
p->opcode = *p->addr;
- if (can_boost(p->opcode)) {
+ if (can_boost(p->addr)) {
p->ainsn.boostable = 0;
} else {
p->ainsn.boostable = -1;