On Wed, Jul 31, 2013 at 08:43:07PM +0100, Ben Dooks wrote:

On 29/07/13 09:01, Jon Medhurst (Tixy) wrote:

quoted

On Thu, 2013-07-25 at 22:08 +0100, Ben Dooks wrote:

quoted

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

Signed-off-by: Ben Dooks<redacted>y
---
 arch/arm/kernel/kprobes-common.c |   14 ++++++++------
 arch/arm/kernel/kprobes.c        |    9 +++++----
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/arch/arm/kernel/kprobes-common.c b/arch/arm/kernel/kprobes-common.c
index 18a7628..c0b202e 100644
--- a/arch/arm/kernel/kprobes-common.c
+++ b/arch/arm/kernel/kprobes-common.c

@@ -14,6 +14,7 @@
 #include<linux/kernel.h>
 #include<linux/kprobes.h>
 #include<asm/system_info.h>
+#include<asm/opcodes.h>

 #include "kprobes.h"

@@ -305,7 +306,8 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_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;
 	}

@@ -338,9 +340,9 @@ prepare_emulated_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi,
 		thumb_insn[2] = 0x4770; /* Thumb bx lr */

The line above and the one before it not in this diff also need fixing
by changing to __opcode_to_mem_thumb16(0x4770).

IIRC, these are then fixed by the set_emulated instruction, which is
also why the insn return is not swapped.

Ah, I see.

I think it would be better to have consistent behaviour between the ARM
and Thumb cases here: in its current form, this patch makes
set_emulated_insn() responsible for the swabbing in the Thumb case and
not in the ARM case.

Doing it in the same place for both cases would be preferable ... or was
there a reason why this doesn't work?

Cheers
---Dave

quoted

quoted

 		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)

@@ -360,12 +362,12 @@ set_emulated_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi,
 	if (thumb) {
 		u16 *ip = (u16 *)asi->insn;
 		if (is_wide_instruction(insn))
-			*ip++ = insn>>  16;
-		*ip++ = insn;
+			*ip++ = ___asm_opcode_to_mem_thumb16(insn>>  16);
+		*ip++ = ___asm_opcode_to_mem_thumb16(insn);

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