objtool: Use value of intended enum to compile with clang

objtool: Use value of intended enum to compile with clang

[Lukas Bulwahn]

Hi,

Please include this patch in tools/objtool to properly compile with clang-5.0.

I successfully compiled this patch (make defconfig && make) on top of tag
next-20171208 from linux-next with clang-5.0.0 and gcc (Debian 7.2.0-16) 7.2.0,
but I did not test anything further than that.

Exact compiler version of clang-5.0.0 is:

  clang version 5.0.0-+rc2-1 (tags/RELEASE_500/rc2)
  Target: x86_64-pc-linux-gnu
  Thread model: posix
  InstalledDir: /usr/bin

This is my first kernel contribution, so please apologize any kernel newbie
mistakes.

Lukas

[PATCH] objtool: Use value of intended enum to compile with clang

[Lukas Bulwahn]

Just use the right value and avoid an implicit conversion between the two
enumeration types that just happened to work in this case. It seems that
this must have just been overlooked in the new implementation of objtool
in commit baa41469a7b9 ("objtool: Implement stack validation 2.0").

I found this when compiling the kernel with clang-5.0, i.e., executing

  make HOSTCC=clang-5.0 CC=clang-5.0 defconfig && \
  make HOSTCC=clang-5.0 CC=clang-5.0

fails with:

```
arch/x86/decode.c:141:20: error: implicit conversion from enumeration type 'enum op_src_type' to different enumeration type 'enum op_dest_type' [-Werror,-Wenum-conversion]
                        op->dest.type = OP_SRC_REG;
                                      ~ ^~~~~~~~~~
1 error generated.
```

Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
---
 tools/objtool/arch/x86/decode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 8acfc47..540a209 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -138,7 +138,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			*type = INSN_STACK;
 			op->src.type = OP_SRC_ADD;
 			op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
-			op->dest.type = OP_SRC_REG;
+			op->dest.type = OP_DEST_REG;
 			op->dest.reg = CFI_SP;
 		}
 		break;
-- 
2.7.4

Re: [SIL2review] [PATCH] objtool: Use value of intended enum to compile with clang

[Nicholas Mc Guire]

On Sun, Dec 10, 2017 at 07:35:00PM +0100, Lukas Bulwahn wrote:
> Just use the right value and avoid an implicit conversion between the two
> enumeration types that just happened to work in this case. It seems that
> this must have just been overlooked in the new implementation of objtool
> in commit baa41469a7b9 ("objtool: Implement stack validation 2.0").
> 
> I found this when compiling the kernel with clang-5.0, i.e., executing
> 
>   make HOSTCC=clang-5.0 CC=clang-5.0 defconfig && \
>   make HOSTCC=clang-5.0 CC=clang-5.0
> 
> fails with:
> 
> ```
> arch/x86/decode.c:141:20: error: implicit conversion from enumeration type 'enum op_src_type' to different enumeration type 'enum op_dest_type' [-Werror,-Wenum-conversion]
>                         op->dest.type = OP_SRC_REG;
>                                       ~ ^~~~~~~~~~
> 1 error generated.
> ```

given the declaration in tools/objtool/arch.h
enum op_dest_type {
        OP_DEST_REG,
        ...

enum op_src_type {
        OP_SRC_REG,
        ...

the change seems correct and it is clear why it worked with the wrong type

> 
> Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Nicholas Mc Guire <der.herr@hofr.at>

> ---
>  tools/objtool/arch/x86/decode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
> index 8acfc47..540a209 100644
> --- a/tools/objtool/arch/x86/decode.c
> +++ b/tools/objtool/arch/x86/decode.c
> @@ -138,7 +138,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
>  			*type = INSN_STACK;
>  			op->src.type = OP_SRC_ADD;
>  			op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> -			op->dest.type = OP_SRC_REG;
> +			op->dest.type = OP_DEST_REG;
>  			op->dest.reg = CFI_SP;
>  		}
>  		break;
> -- 
> 2.7.4
> 
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