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

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.

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);

Should these two ___asm_opcode_thumb32_compose() not be
__opcode_thumb32_compose() ?

I decided to leave this as is.

quoted

  		return;
  	}
  #endif
-	asi->insn[0] = insn;
+	asi->insn[0] = __opcode_to_mem_arm(insn);
  }

  /*

diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 170e9f3..3775af1 100644
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c

@@ -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 "kprobes.h"

@@ -62,10 +63,10 @@ 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 = ___asm_opcode_thumb32_compose(insn, inst2);

Again, __opcode_thumb32_compose instead of
___asm_opcode_thumb32_compose

quoted

  		decode_insn = thumb32_kprobe_decode_insn;
  	} else
  		decode_insn = thumb16_kprobe_decode_insn;

@@ -73,7 +74,7 @@ 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_kprobe_decode_insn;
  #endif

-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius