[PATCH] /target/i386: fix gdbstub k_gs_base issue

[PATCH] /target/i386: fix gdbstub k_gs_base issue

[Marek Dolata - mkdolata@us.ibm.com]

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Fixes: corrects clobbering of registers appearing after k_gs_base
Buglink: https://bugs.launchpad.net/qemu/+bug/1857640

Signed-off-by: Marek Dolata <mkdolata@us.ibm.com>
---
target/i386/gdbstub.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/target/i386/gdbstub.c b/target/i386/gdbstub.c
index aef25b70f1..7228d20674 100644
--- a/target/i386/gdbstub.c
+++ b/target/i386/gdbstub.c
@@ -350,14 +350,16 @@ int x86_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
             env->segs[R_GS].base = ldl_p(mem_buf);
             return 4;
-#ifdef TARGET_X86_64
         case IDX_SEG_REGS + 8:
+#ifdef TARGET_X86_64
             if (env->hflags & HF_CS64_MASK) {
                 env->kernelgsbase = ldq_p(mem_buf);
                 return 8;
             }
             env->kernelgsbase = ldl_p(mem_buf);
             return 4;
+#else
+            return 4;
#endif
         case IDX_FP_REGS + 8:
--
2.21.0



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Re: [PATCH] /target/i386: fix gdbstub k_gs_base issue

[Philippe Mathieu-Daudé]

Hi Marek,

If you look at the other patches, you'll notice no leading slash is 
used, so please remove it when resending.

Maybe you can use "target/i386: Fix handling of k_gs_base register in 
32-bit mode in gdbstub" as patch subject.

Please Cc the maintainers. See:
https://wiki.qemu.org/Contribute/SubmitAPatch#CC_the_relevant_maintainer
Doing it for you now (adding Richard and Eduardo).

On 12/27/19 3:41 AM, Marek Dolata - mkdolata@us.ibm.com wrote:
> Fixes: corrects clobbering of registers appearing after k_gs_base
> 
> Buglink: https://bugs.launchpad.net/qemu/+bug/1857640
> 
> Signed-off-by: Marek Dolata <mkdolata@us.ibm.com>
> 
> ---
> 
> target/i386/gdbstub.c | 4 +++-
> 
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/gdbstub.c b/target/i386/gdbstub.c
> 
> index aef25b70f1..7228d20674 100644
> 
> --- a/target/i386/gdbstub.c
> 
> +++ b/target/i386/gdbstub.c

I am having troubles trying to apply your patch:

Applying: /target/i386: fix gdbstub k_gs_base issue
error: corrupt patch at line 23
Patch failed at 0001 /target/i386: fix gdbstub k_gs_base issue
hint: Use 'git am --show-current-patch' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

The information on the wiki might help you to use proper format:
https://wiki.qemu.org/Contribute/SubmitAPatch#Use_git_format-patch

> 
> @@ -350,14 +350,16 @@ int x86_cpu_gdb_write_register(CPUState *cs, 
> uint8_t *mem_buf, int n)
> 
>               env->segs[R_GS].base = ldl_p(mem_buf);
> 
>               return 4;
> 
> -#ifdef TARGET_X86_64
> 
>           case IDX_SEG_REGS + 8:
> 
> +#ifdef TARGET_X86_64
> 
>               if (env->hflags & HF_CS64_MASK) {
> 
>                   env->kernelgsbase = ldq_p(mem_buf);
> 
>                   return 8;
> 
>               }
> 
>               env->kernelgsbase = ldl_p(mem_buf);

You can add here the

#endif

> 
>               return 4;

and remove the '#else return 4; #endif' lines.

> 
> +#else
> 
> +            return 4;
> 
> #endif
> 
>           case IDX_FP_REGS + 8:
> 
> -- 
> 
> 2.21.0
> 

Regards,

Phil.