[PATCH] x86/mm: Directly return instead of using local ret variable

[PATCH] x86/mm: Directly return instead of using local ret variable

[Haowen Bai]

fixes coccinelle warning:
./arch/x86/mm/pf_in.c:133:18-20: Unneeded variable: "rv". Return "OTHERS" on line 144

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
---
 arch/x86/mm/pf_in.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/mm/pf_in.c b/arch/x86/mm/pf_in.c
index 3f83e31..4eff3ee 100644
--- a/arch/x86/mm/pf_in.c
+++ b/arch/x86/mm/pf_in.c
@@ -130,7 +130,6 @@ enum reason_type get_ins_type(unsigned long ins_addr)
 	unsigned char *p;
 	struct prefix_bits prf;
 	int i;
-	enum reason_type rv = OTHERS;
 
 	p = (unsigned char *)ins_addr;
 	p += skip_prefix(p, &prf);
@@ -141,7 +140,7 @@ enum reason_type get_ins_type(unsigned long ins_addr)
 	CHECK_OP_TYPE(opcode, imm_wop, IMM_WRITE);
 
 exit:
-	return rv;
+	return OTHERS;
 }
 #undef CHECK_OP_TYPE
 
-- 
2.7.4

Re: [PATCH] x86/mm: Directly return instead of using local ret variable

[Dave Hansen]

On 3/27/22 19:12, Haowen Bai wrote:
> 
> diff --git a/arch/x86/mm/pf_in.c b/arch/x86/mm/pf_in.c
> index 3f83e31..4eff3ee 100644
> --- a/arch/x86/mm/pf_in.c
> +++ b/arch/x86/mm/pf_in.c
> @@ -130,7 +130,6 @@ enum reason_type get_ins_type(unsigned long ins_addr)
>  	unsigned char *p;
>  	struct prefix_bits prf;
>  	int i;
> -	enum reason_type rv = OTHERS;
>  
>  	p = (unsigned char *)ins_addr;
>  	p += skip_prefix(p, &prf);
> @@ -141,7 +140,7 @@ enum reason_type get_ins_type(unsigned long ins_addr)
>  	CHECK_OP_TYPE(opcode, imm_wop, IMM_WRITE);
>  
>  exit:
> -	return rv;
> +	return OTHERS;
>  }
>  #undef CHECK_OP_TYPE
>  

Does this even compile?  Take a look at this macro:

> #define CHECK_OP_TYPE(opcode, array, type) \
>         for (i = 0; i < ARRAY_SIZE(array); i++) { \
>                 if (array[i] == opcode) { \
>                         rv = type; \
>                         goto exit; \
>                 } \

It uses 'rv'.

答复: [PATCH] x86/mm: Directly return instead of using local ret variable

[白浩文]

Thank you for pointing my mistaken.
________________________________________
发件人: Dave Hansen <dave.hansen@intel.com>
发送时间: 2022年3月28日 10:49:19
收件人: 白浩文; dave.hansen@linux.intel.com; luto@kernel.org; peterz@infradead.org
抄送: linux-kernel@vger.kernel.org
主题: Re: [PATCH] x86/mm: Directly return instead of using local ret variable

On 3/27/22 19:12, Haowen Bai wrote:
>
> diff --git a/arch/x86/mm/pf_in.c b/arch/x86/mm/pf_in.c
> index 3f83e31..4eff3ee 100644
> --- a/arch/x86/mm/pf_in.c
> +++ b/arch/x86/mm/pf_in.c
> @@ -130,7 +130,6 @@ enum reason_type get_ins_type(unsigned long ins_addr)
>       unsigned char *p;
>       struct prefix_bits prf;
>       int i;
> -     enum reason_type rv = OTHERS;
>
>       p = (unsigned char *)ins_addr;
>       p += skip_prefix(p, &prf);
> @@ -141,7 +140,7 @@ enum reason_type get_ins_type(unsigned long ins_addr)
>       CHECK_OP_TYPE(opcode, imm_wop, IMM_WRITE);
>
>  exit:
> -     return rv;
> +     return OTHERS;
>  }
>  #undef CHECK_OP_TYPE
>

Does this even compile?  Take a look at this macro:

> #define CHECK_OP_TYPE(opcode, array, type) \
>         for (i = 0; i < ARRAY_SIZE(array); i++) { \
>                 if (array[i] == opcode) { \
>                         rv = type; \
>                         goto exit; \
>                 } \

It uses 'rv'.

Re: [PATCH] x86/mm: Directly return instead of using local ret variable

[kernel test robot]

Hi Haowen,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tip/x86/mm]
[also build test ERROR on v5.17 next-20220325]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Haowen-Bai/x86-mm-Directly-return-instead-of-using-local-ret-variable/20220328-101514
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git b64dfcde1ca9cb82e38e573753f0c0db8fb841c2
config: i386-randconfig-a014-20220328 (https://download.01.org/0day-ci/archive/20220328/202203281559.hHXuSFrA-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 0f6d9501cf49ce02937099350d08f20c4af86f3d)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/852ab1aec48033b3a4df180698ab9c29aca0b248
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Haowen-Bai/x86-mm-Directly-return-instead-of-using-local-ret-variable/20220328-101514
        git checkout 852ab1aec48033b3a4df180698ab9c29aca0b248
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> arch/x86/mm/pf_in.c:138:2: error: use of undeclared identifier 'rv'
           CHECK_OP_TYPE(opcode, reg_rop, REG_READ);
           ^
   arch/x86/mm/pf_in.c:122:4: note: expanded from macro 'CHECK_OP_TYPE'
                           rv = type; \
                           ^
   arch/x86/mm/pf_in.c:139:2: error: use of undeclared identifier 'rv'
           CHECK_OP_TYPE(opcode, reg_wop, REG_WRITE);
           ^
   arch/x86/mm/pf_in.c:122:4: note: expanded from macro 'CHECK_OP_TYPE'
                           rv = type; \
                           ^
   arch/x86/mm/pf_in.c:140:2: error: use of undeclared identifier 'rv'
           CHECK_OP_TYPE(opcode, imm_wop, IMM_WRITE);
           ^
   arch/x86/mm/pf_in.c:122:4: note: expanded from macro 'CHECK_OP_TYPE'
                           rv = type; \
                           ^
   3 errors generated.


vim +/rv +138 arch/x86/mm/pf_in.c

8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  118  
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  119  #define CHECK_OP_TYPE(opcode, array, type) \
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  120  	for (i = 0; i < ARRAY_SIZE(array); i++) { \
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  121  		if (array[i] == opcode) { \
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  122  			rv = type; \
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  123  			goto exit; \
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  124  		} \
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  125  	}
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  126  
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  127  enum reason_type get_ins_type(unsigned long ins_addr)
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  128  {
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  129  	unsigned int opcode;
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  130  	unsigned char *p;
611b1597680dd4a arch/x86/mm/pf_in.c               Pekka Paalanen 2008-07-21  131  	struct prefix_bits prf;
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  132  	int i;
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  133  
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  134  	p = (unsigned char *)ins_addr;
611b1597680dd4a arch/x86/mm/pf_in.c               Pekka Paalanen 2008-07-21  135  	p += skip_prefix(p, &prf);
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  136  	p += get_opcode(p, &opcode);
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  137  
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12 @138  	CHECK_OP_TYPE(opcode, reg_rop, REG_READ);
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  139  	CHECK_OP_TYPE(opcode, reg_wop, REG_WRITE);
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  140  	CHECK_OP_TYPE(opcode, imm_wop, IMM_WRITE);
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  141  
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  142  exit:
852ab1aec48033b arch/x86/mm/pf_in.c               Haowen Bai     2022-03-28  143  	return OTHERS;
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  144  }
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  145  #undef CHECK_OP_TYPE
8b7d89d02ef3c6a arch/x86/kernel/mmiotrace/pf_in.c Pekka Paalanen 2008-05-12  146  

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