[1/2] powerpc/kprobes: Remove redundant code
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Message ID 642c8b4ca59e658be38d8dde00f994e183790a6a.1581687838.git.christophe.leroy@c-s.fr
State Superseded
Headers show
Series
  • [1/2] powerpc/kprobes: Remove redundant code
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snowpatch_ozlabs/needsstable success Patch has no Fixes tags
snowpatch_ozlabs/checkpatch success total: 0 errors, 0 warnings, 0 checks, 31 lines checked
snowpatch_ozlabs/apply_patch success Successfully applied on branch powerpc/merge (a5bc6e124219546a81ce334dc9b16483d55e9abf)

Commit Message

Christophe Leroy Feb. 14, 2020, 1:44 p.m. UTC
At the time being we have something like

	if (something) {
		p = get();
		if (p) {
			if (something_wrong)
				goto out;
			...
			return;
		} else if (a != b) {
			if (some_error)
				goto out;
			...
		}
		goto out;
	}
	p = get();
	if (!p) {
		if (a != b) {
			if (some_error)
				goto out;
			...
		}
		goto out;
	}

This is similar to

	p = get();
	if (something) {
		if (p) {
			if (something_wrong)
				goto out;
			...
			return;
		}
	}
	if (!p) {
		if (a != b) {
			if (some_error)
				goto out;
			...
		}
		goto out;
	}

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/kprobes.c | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

Comments

Naveen N. Rao Feb. 18, 2020, 2:39 p.m. UTC | #1
Christophe Leroy wrote:
> At the time being we have something like
> 
> 	if (something) {
> 		p = get();
> 		if (p) {
> 			if (something_wrong)
> 				goto out;
> 			...
> 			return;
> 		} else if (a != b) {
> 			if (some_error)
> 				goto out;
> 			...
> 		}
> 		goto out;
> 	}
> 	p = get();
> 	if (!p) {
> 		if (a != b) {
> 			if (some_error)
> 				goto out;
> 			...
> 		}
> 		goto out;
> 	}
> 
> This is similar to
> 
> 	p = get();
> 	if (something) {
> 		if (p) {
> 			if (something_wrong)
> 				goto out;
> 			...
> 			return;
> 		}
> 	}
> 	if (!p) {
> 		if (a != b) {
> 			if (some_error)
> 				goto out;
> 			...
> 		}
> 		goto out;
> 	}
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>  arch/powerpc/kernel/kprobes.c | 15 +--------------
>  1 file changed, 1 insertion(+), 14 deletions(-)

Good cleanup, thanks.

> 
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index f8b848aa65bd..7a925eb76ec0 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -276,8 +276,8 @@ int kprobe_handler(struct pt_regs *regs)
>  	kcb = get_kprobe_ctlblk();
>  
>  	/* Check we're not actually recursing */
> +	p = get_kprobe(addr);
>  	if (kprobe_running()) {
> -		p = get_kprobe(addr);
>  		if (p) {
>  			kprobe_opcode_t insn = *p->ainsn.insn;
>  			if (kcb->kprobe_status == KPROBE_HIT_SS &&
> @@ -308,22 +308,9 @@ int kprobe_handler(struct pt_regs *regs)
>  			}
>  			prepare_singlestep(p, regs);
>  			return 1;
> -		} else if (*addr != BREAKPOINT_INSTRUCTION) {
> -			/* If trap variant, then it belongs not to us */
> -			kprobe_opcode_t cur_insn = *addr;
> -
> -			if (is_trap(cur_insn))
> -				goto no_kprobe;
> -			/* The breakpoint instruction was removed by
> -			 * another cpu right after we hit, no further
> -			 * handling of this interrupt is appropriate
> -			 */
> -			ret = 1;
>  		}
> -		goto no_kprobe;

A minot nit -- removing the above goto makes a slight change to the 
logic. But, see my comments for the next patch.

- Naveen

>  	}
>  
> -	p = get_kprobe(addr);
>  	if (!p) {
>  		if (*addr != BREAKPOINT_INSTRUCTION) {
>  			/*
> -- 
> 2.25.0
> 
>
Christophe Leroy Feb. 19, 2020, 7:48 a.m. UTC | #2
Le 18/02/2020 à 15:39, Naveen N. Rao a écrit :
> Christophe Leroy wrote:
>> At the time being we have something like
>>
>>     if (something) {
>>         p = get();
>>         if (p) {
>>             if (something_wrong)
>>                 goto out;
>>             ...
>>             return;
>>         } else if (a != b) {
>>             if (some_error)
>>                 goto out;
>>             ...
>>         }
>>         goto out;
>>     }
>>     p = get();
>>     if (!p) {
>>         if (a != b) {
>>             if (some_error)
>>                 goto out;
>>             ...
>>         }
>>         goto out;
>>     }
>>
>> This is similar to
>>
>>     p = get();
>>     if (something) {
>>         if (p) {
>>             if (something_wrong)
>>                 goto out;
>>             ...
>>             return;
>>         }
>>     }
>>     if (!p) {
>>         if (a != b) {
>>             if (some_error)
>>                 goto out;
>>             ...
>>         }
>>         goto out;
>>     }
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>  arch/powerpc/kernel/kprobes.c | 15 +--------------
>>  1 file changed, 1 insertion(+), 14 deletions(-)
> 
> Good cleanup, thanks.
> 
>>
>> diff --git a/arch/powerpc/kernel/kprobes.c 
>> b/arch/powerpc/kernel/kprobes.c
>> index f8b848aa65bd..7a925eb76ec0 100644
>> --- a/arch/powerpc/kernel/kprobes.c
>> +++ b/arch/powerpc/kernel/kprobes.c
>> @@ -276,8 +276,8 @@ int kprobe_handler(struct pt_regs *regs)
>>      kcb = get_kprobe_ctlblk();
>>
>>      /* Check we're not actually recursing */
>> +    p = get_kprobe(addr);
>>      if (kprobe_running()) {
>> -        p = get_kprobe(addr);
>>          if (p) {
>>              kprobe_opcode_t insn = *p->ainsn.insn;
>>              if (kcb->kprobe_status == KPROBE_HIT_SS &&
>> @@ -308,22 +308,9 @@ int kprobe_handler(struct pt_regs *regs)
>>              }
>>              prepare_singlestep(p, regs);
>>              return 1;
>> -        } else if (*addr != BREAKPOINT_INSTRUCTION) {
>> -            /* If trap variant, then it belongs not to us */
>> -            kprobe_opcode_t cur_insn = *addr;
>> -
>> -            if (is_trap(cur_insn))
>> -                goto no_kprobe;
>> -            /* The breakpoint instruction was removed by
>> -             * another cpu right after we hit, no further
>> -             * handling of this interrupt is appropriate
>> -             */
>> -            ret = 1;
>>          }
>> -        goto no_kprobe;
> 
> A minot nit -- removing the above goto makes a slight change to the 
> logic. But, see my comments for the next patch.

All legs of the (p) case are have either a return or a goto, so that 
goto no_kprobe is limited to the !p case, we have to fall_through now.

Christophe

Patch
diff mbox series

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index f8b848aa65bd..7a925eb76ec0 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -276,8 +276,8 @@  int kprobe_handler(struct pt_regs *regs)
 	kcb = get_kprobe_ctlblk();
 
 	/* Check we're not actually recursing */
+	p = get_kprobe(addr);
 	if (kprobe_running()) {
-		p = get_kprobe(addr);
 		if (p) {
 			kprobe_opcode_t insn = *p->ainsn.insn;
 			if (kcb->kprobe_status == KPROBE_HIT_SS &&
@@ -308,22 +308,9 @@  int kprobe_handler(struct pt_regs *regs)
 			}
 			prepare_singlestep(p, regs);
 			return 1;
-		} else if (*addr != BREAKPOINT_INSTRUCTION) {
-			/* If trap variant, then it belongs not to us */
-			kprobe_opcode_t cur_insn = *addr;
-
-			if (is_trap(cur_insn))
-				goto no_kprobe;
-			/* The breakpoint instruction was removed by
-			 * another cpu right after we hit, no further
-			 * handling of this interrupt is appropriate
-			 */
-			ret = 1;
 		}
-		goto no_kprobe;
 	}
 
-	p = get_kprobe(addr);
 	if (!p) {
 		if (*addr != BREAKPOINT_INSTRUCTION) {
 			/*