[PATCH] kprobe: boost 2byte-opcodes on i386

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.

Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Yumiko Sugita <sugita@sdl.hitachi.co.jp>
Cc: Satoshi Oshima <soshima@redhat.com>
Cc: Hideo Aoki <haoki@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 395a9a6..37f8623 100644 (file)
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -57,34 +57,85 @@ static __always_inline void set_jmp_op(void *from, void *to)
 /*
  * returns non-zero if opcodes can be boosted.
  */
-static __always_inline int can_boost(kprobe_opcode_t opcode)
+static __always_inline int can_boost(kprobe_opcode_t *opcodes)
 {
-       switch (opcode & 0xf0 ) {
+#define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf)               \
+       (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
+         (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
+         (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
+         (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
+        << (row % 32))
+       /*
+        * Undefined/reserved opcodes, conditional jump, Opcode Extension
+        * Groups, and some special opcodes can not be boost.
+        */
+       static const unsigned long twobyte_is_boostable[256 / 32] = {
+               /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
+               /*      -------------------------------         */
+               W(0x00, 0,0,1,1,0,0,1,0,1,1,0,0,0,0,0,0)| /* 00 */
+               W(0x10, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 10 */
+               W(0x20, 1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0)| /* 20 */
+               W(0x30, 0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 30 */
+               W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 40 */
+               W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 50 */
+               W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,0,0,1,1)| /* 60 */
+               W(0x70, 0,0,0,0,1,1,1,1,0,0,0,0,0,0,1,1), /* 70 */
+               W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 80 */
+               W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1), /* 90 */
+               W(0xa0, 1,1,0,1,1,1,0,0,1,1,0,1,1,1,0,1)| /* a0 */
+               W(0xb0, 1,1,1,1,1,1,1,1,0,0,0,1,1,1,1,1), /* b0 */
+               W(0xc0, 1,1,0,0,0,0,0,0,1,1,1,1,1,1,1,1)| /* c0 */
+               W(0xd0, 0,1,1,1,0,1,0,0,1,1,0,1,1,1,0,1), /* d0 */
+               W(0xe0, 0,1,1,0,0,1,0,0,1,1,0,1,1,1,0,1)| /* e0 */
+               W(0xf0, 0,1,1,1,0,1,0,0,1,1,1,0,1,1,1,0)  /* f0 */
+               /*      -------------------------------         */
+               /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
+       };
+#undef W
+       kprobe_opcode_t opcode;
+       kprobe_opcode_t *orig_opcodes = opcodes;
+retry:
+       if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
+               return 0;
+       opcode = *(opcodes++);
+
+       /* 2nd-byte opcode */
+       if (opcode == 0x0f) {
+               if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
+                       return 0;
+               return test_bit(*opcodes, twobyte_is_boostable);
+       }
+
+       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);
        }
 }
 
-
 /*
  * returns non-zero if opcode modifies the interrupt flag.
  */
@@ -109,7 +160,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 
        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;