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Commit 585deaca authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Linus Torvalds
Browse files

[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: default avatarMasami 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: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6ae7440e

arch/i386/kernel/kprobes.c

+65 −14
Original line number Diff line number Diff line
@@ -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)

{

#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;