[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>

1 files changed, 65 insertions, 14 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 395a9a6dff88..37f86234bdd7 100644
--- 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;