[PATCH 1/4] ARM: kprobes: fix instruction fetch order with <asm/opcodes.h>

[tixy@linaro.org (Jon Medhurst (Tixy))]

On Thu, 2013-07-25 at 22:08 +0100, Ben Dooks wrote:
> 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 <ben.dooks@codethink.co.uk>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).

>  		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() ?

>  		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

>  		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
>  

-- 
Tixy