[PATCH v3 3/9] powerpc/kprobes/optprobes: Move over to patch_instruction

[Naveen N. Rao]

On 2017/06/06 02:29PM, Balbir Singh wrote:
> With text moving to read-only migrate optprobes to using
> the patch_instruction infrastructure. Without this optprobes
> will fail and complain.
> 
> Signed-off-by: Balbir Singh <bsingharora at gmail.com>
> ---
>  arch/powerpc/kernel/optprobes.c | 58 ++++++++++++++++++++++++++---------------
>  1 file changed, 37 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> index ec60ed0..1c7326c 100644
> --- a/arch/powerpc/kernel/optprobes.c
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -158,12 +158,13 @@ void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
>  void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
>  {
>  	/* addis r4,0,(insn)@h */
> -	*addr++ = PPC_INST_ADDIS | ___PPC_RT(4) |
> -		  ((val >> 16) & 0xffff);
> +	patch_instruction((unsigned int *)addr, PPC_INST_ADDIS | ___PPC_RT(4) |

We can probably get rid of those casts, seeing as we're not using it in 
kprobes.c.

> +					((val >> 16) & 0xffff));
> +	addr++;
> 
>  	/* ori r4,r4,(insn)@l */
> -	*addr = PPC_INST_ORI | ___PPC_RA(4) | ___PPC_RS(4) |
> -		(val & 0xffff);
> +	patch_instruction((unsigned int *)addr, PPC_INST_ORI | ___PPC_RA(4) |
> +					___PPC_RS(4) | (val & 0xffff));
>  }
> 
>  /*
> @@ -173,24 +174,28 @@ void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
>  void patch_imm64_load_insns(unsigned long val, kprobe_opcode_t *addr)
>  {
>  	/* lis r3,(op)@highest */
> -	*addr++ = PPC_INST_ADDIS | ___PPC_RT(3) |
> -		  ((val >> 48) & 0xffff);
> +	patch_instruction((unsigned int *)addr, PPC_INST_ADDIS | ___PPC_RT(3) |
> +					((val >> 48) & 0xffff));
> +	addr++;
> 
>  	/* ori r3,r3,(op)@higher */
> -	*addr++ = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
> -		  ((val >> 32) & 0xffff);
> +	patch_instruction((unsigned int *)addr, PPC_INST_ORI | ___PPC_RA(3) |
> +				___PPC_RS(3) | ((val >> 32) & 0xffff));
> +	addr++;
> 
>  	/* rldicr r3,r3,32,31 */
> -	*addr++ = PPC_INST_RLDICR | ___PPC_RA(3) | ___PPC_RS(3) |
> -		  __PPC_SH64(32) | __PPC_ME64(31);
> +	patch_instruction((unsigned int *)addr, PPC_INST_RLDICR | ___PPC_RA(3) |
> +				___PPC_RS(3) | __PPC_SH64(32) | __PPC_ME64(31));
> +	addr++;
> 
>  	/* oris r3,r3,(op)@h */
> -	*addr++ = PPC_INST_ORIS | ___PPC_RA(3) | ___PPC_RS(3) |
> -		  ((val >> 16) & 0xffff);
> +	patch_instruction((unsigned int *)addr, PPC_INST_ORIS | ___PPC_RA(3) |
> +					___PPC_RS(3) | ((val >> 16) & 0xffff));
> +	addr++;
> 
>  	/* ori r3,r3,(op)@l */
> -	*addr = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
> -		(val & 0xffff);
> +	patch_instruction((unsigned int *)addr, PPC_INST_ORI | ___PPC_RA(3) |
> +				___PPC_RS(3) | (val & 0xffff));
>  }
> 
>  int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
> @@ -198,7 +203,8 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  	kprobe_opcode_t *buff, branch_op_callback, branch_emulate_step;
>  	kprobe_opcode_t *op_callback_addr, *emulate_step_addr;
>  	long b_offset;
> -	unsigned long nip;
> +	unsigned long nip, size;
> +	int rc, i;
> 
>  	kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
> 
> @@ -231,8 +237,15 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  		goto error;
> 
>  	/* Setup template */
> -	memcpy(buff, optprobe_template_entry,
> -			TMPL_END_IDX * sizeof(kprobe_opcode_t));
> +	/* We can optimize this via patch_instruction_window later */

This probably needs a TODO just so it's clear. I do think this would be 
good to add since we copy many instructions while setting up the 
optprobe, so this is quite slow as it exists today.

> +	size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int);

That's just TMPL_END_IDX.

Thanks,
Naveen

> +	pr_devel("Copying template to %p, size %lu\n", buff, size);
> +	for (i = 0; i < size; i++) {
> +		rc = patch_instruction((unsigned int *)buff + i,
> +			*((unsigned int *)(optprobe_template_entry) + i));
> +		if (rc < 0)
> +			goto error;
> +	}
> 
>  	/*
>  	 * Fixup the template with instructions to:
> @@ -261,8 +274,10 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  	if (!branch_op_callback || !branch_emulate_step)
>  		goto error;
> 
> -	buff[TMPL_CALL_HDLR_IDX] = branch_op_callback;
> -	buff[TMPL_EMULATE_IDX] = branch_emulate_step;
> +	patch_instruction((unsigned int *)buff + TMPL_CALL_HDLR_IDX,
> +				branch_op_callback);
> +	patch_instruction((unsigned int *)buff + TMPL_EMULATE_IDX,
> +				branch_emulate_step);
> 
>  	/*
>  	 * 3. load instruction to be emulated into relevant register, and
> @@ -272,8 +287,9 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  	/*
>  	 * 4. branch back from trampoline
>  	 */
> -	buff[TMPL_RET_IDX] = create_branch((unsigned int *)buff + TMPL_RET_IDX,
> -				(unsigned long)nip, 0);
> +	patch_instruction((unsigned int *)buff + TMPL_RET_IDX,
> +				create_branch((unsigned int *)buff +
> +				TMPL_RET_IDX, (unsigned long)nip, 0));
> 
>  	flush_icache_range((unsigned long)buff,
>  			   (unsigned long)(&buff[TMPL_END_IDX]));
> -- 
> 2.9.4
>