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Commit 888be254 authored by Ben Dooks's avatar Ben Dooks Committed by Taras Kondratiuk
Browse files

ARM: probes: fix instruction fetch order with <asm/opcodes.h> 



If we are running BE8, the data and instruction endianness do not
match, so use <asm/opcodes.h> to correctly translate memory accesses
into ARM instructions.

Acked-by: default avatarJon Medhurst <tixy@linaro.org>
Signed-off-by: default avatarBen Dooks <ben.dooks@codethink.co.uk>
[taras.kondratiuk@linaro.org: fixed Thumb instruction fetch order]
Signed-off-by: default avatarTaras Kondratiuk <taras.kondratiuk@linaro.org>
parent c7edc9e3

arch/arm/kernel/kprobes-common.c

+3 −1
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 


#include <linux/kernel.h>

#include <linux/kprobes.h>

#include <asm/opcodes.h>



#include "kprobes.h"
@@ -153,7 +154,8 @@ kprobe_decode_ldmstm(probes_opcode_t insn, struct arch_probes_insn *asi, 


	if (handler) {

		/* We can emulate the instruction in (possibly) modified form */

		asi->insn[0] = (insn & 0xfff00000) | (rn << 16) | reglist;

		asi->insn[0] = __opcode_to_mem_arm((insn & 0xfff00000) |

						   (rn << 16) | reglist);

		asi->insn_handler = handler;

		return INSN_GOOD;

	}

arch/arm/kernel/kprobes-thumb.c

+12 −8
Original line number Diff line number Diff line
@@ -149,9 +149,9 @@ t32_decode_ldmstm(probes_opcode_t insn, struct arch_probes_insn *asi, 
	enum probes_insn ret = kprobe_decode_ldmstm(insn, asi, d);



	/* Fixup modified instruction to have halfwords in correct order...*/

	insn = asi->insn[0];

	((u16 *)asi->insn)[0] = insn >> 16;

	((u16 *)asi->insn)[1] = insn & 0xffff;

	insn = __mem_to_opcode_arm(asi->insn[0]);

	((u16 *)asi->insn)[0] = __opcode_to_mem_thumb16(insn >> 16);

	((u16 *)asi->insn)[1] = __opcode_to_mem_thumb16(insn & 0xffff);



	return ret;

}
@@ -516,7 +516,7 @@ t16_decode_hiregs(probes_opcode_t insn, struct arch_probes_insn *asi, 
{

	insn &= ~0x00ff;

	insn |= 0x001; /* Set Rdn = R1 and Rm = R0 */

	((u16 *)asi->insn)[0] = insn;

	((u16 *)asi->insn)[0] = __opcode_to_mem_thumb16(insn);

	asi->insn_handler = t16_emulate_hiregs;

	return INSN_GOOD;

}
@@ -547,8 +547,10 @@ t16_decode_push(probes_opcode_t insn, struct arch_probes_insn *asi, 
	 * and call it with R9=SP and LR in the register list represented

	 * by R8.

	 */

	((u16 *)asi->insn)[0] = 0xe929;		/* 1st half STMDB R9!,{} */

	((u16 *)asi->insn)[1] = insn & 0x1ff;	/* 2nd half (register list) */

	/* 1st half STMDB R9!,{} */

	((u16 *)asi->insn)[0] = __opcode_to_mem_thumb16(0xe929);

	/* 2nd half (register list) */

	((u16 *)asi->insn)[1] = __opcode_to_mem_thumb16(insn & 0x1ff);

	asi->insn_handler = t16_emulate_push;

	return INSN_GOOD;

}
@@ -600,8 +602,10 @@ t16_decode_pop(probes_opcode_t insn, struct arch_probes_insn *asi, 
	 * and call it with R9=SP and PC in the register list represented

	 * by R8.

	 */

	((u16 *)asi->insn)[0] = 0xe8b9;		/* 1st half LDMIA R9!,{} */

	((u16 *)asi->insn)[1] = insn & 0x1ff;	/* 2nd half (register list) */

	/* 1st half LDMIA R9!,{} */

	((u16 *)asi->insn)[0] = __opcode_to_mem_thumb16(0xe8b9);

	/* 2nd half (register list) */

	((u16 *)asi->insn)[1] = __opcode_to_mem_thumb16(insn & 0x1ff);

	asi->insn_handler = insn & 0x100 ? t16_emulate_pop_pc

					 : t16_emulate_pop_nopc;

	return INSN_GOOD;

arch/arm/kernel/kprobes.c

+5 −4
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#include <linux/stop_machine.h>

#include <linux/stringify.h>

#include <asm/traps.h>

#include <asm/opcodes.h>

#include <asm/cacheflush.h>

#include <linux/percpu.h>

#include <linux/bug.h>
@@ -67,10 +68,10 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) 
#ifdef CONFIG_THUMB2_KERNEL

	thumb = true;

	addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */

	insn = ((u16 *)addr)[0];

	insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);

	if (is_wide_instruction(insn)) {

		insn <<= 16;

		insn |= ((u16 *)addr)[1];

		u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);

		insn = __opcode_thumb32_compose(insn, inst2);

		decode_insn = thumb32_probes_decode_insn;

		actions = kprobes_t32_actions;

	} else {
@@ -81,7 +82,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) 
	thumb = false;

	if (addr & 0x3)

		return -EINVAL;

	insn = *p->addr;

	insn = __mem_to_opcode_arm(*p->addr);

	decode_insn = arm_probes_decode_insn;

	actions = kprobes_arm_actions;

#endif

arch/arm/kernel/probes.c

+8 −7
Original line number Diff line number Diff line
@@ -202,13 +202,14 @@ prepare_emulated_insn(probes_opcode_t insn, struct arch_probes_insn *asi, 
#ifdef CONFIG_THUMB2_KERNEL

	if (thumb) {

		u16 *thumb_insn = (u16 *)asi->insn;

		thumb_insn[1] = 0x4770; /* Thumb bx lr */

		thumb_insn[2] = 0x4770; /* Thumb bx lr */

		/* Thumb bx lr */

		thumb_insn[1] = __opcode_to_mem_thumb16(0x4770);

		thumb_insn[2] = __opcode_to_mem_thumb16(0x4770);

		return insn;

	}

	asi->insn[1] = 0xe12fff1e; /* ARM bx lr */

	asi->insn[1] = __opcode_to_mem_arm(0xe12fff1e); /* ARM bx lr */

#else

	asi->insn[1] = 0xe1a0f00e; /* mov pc, lr */

	asi->insn[1] = __opcode_to_mem_arm(0xe1a0f00e); /* mov pc, lr */

#endif

	/* Make an ARM instruction unconditional */

	if (insn < 0xe0000000)
@@ -228,12 +229,12 @@ set_emulated_insn(probes_opcode_t insn, struct arch_probes_insn *asi, 
	if (thumb) {

		u16 *ip = (u16 *)asi->insn;

		if (is_wide_instruction(insn))

			*ip++ = insn >> 16;

		*ip++ = insn;

			*ip++ = __opcode_to_mem_thumb16(insn >> 16);

		*ip++ = __opcode_to_mem_thumb16(insn);

		return;

	}

#endif

	asi->insn[0] = insn;

	asi->insn[0] = __opcode_to_mem_arm(insn);

}



/*