merged.

Bruce

In message: [linux-yocto][v6.12/standard/x86 & 
v6.12/standard/preempt-rt/x86][PATCH]  x86/elf: Fix core dump truncation on 
CPUs with no extended xfeatures
on 16/12/2025 [email protected] wrote:

> From: Yongxin Liu <[email protected]>
> 
> Zero can be a valid value of num_records. For example, on Intel Atom x6425RE,
> only x87 and SSE are supported (features 0, 1), and fpu_user_cfg.max_features
> is 3. The for_each_extended_xfeature() loop only iterates feature 2, which is
> not enabled, so num_records = 0. This is valid and should not cause core dump
> failure.
> 
> The issue is that dump_xsave_layout_desc() returns 0 for both genuine errors
> (dump_emit() failure) and valid cases (no extended features). Use negative
> return values for errors and only abort on genuine failures.
> 
> Fixes: ba386777a30b ("x86/elf: Add a new FPU buffer layout info to x86 core 
> files")
> Link: 
> https://patch.msgid.link/[email protected]
> Signed-off-by: Yongxin Liu <[email protected]>
> ---
>  arch/x86/kernel/fpu/xstate.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index 22abb5ee0cf2..aacb59c4a35c 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -1879,7 +1879,7 @@ static int dump_xsave_layout_desc(struct 
> coredump_params *cprm)
>               };
>  
>               if (!dump_emit(cprm, &xc, sizeof(xc)))
> -                     return 0;
> +                     return -1;
>  
>               num_records++;
>       }
> @@ -1917,7 +1917,7 @@ int elf_coredump_extra_notes_write(struct 
> coredump_params *cprm)
>               return 1;
>  
>       num_records = dump_xsave_layout_desc(cprm);
> -     if (!num_records)
> +     if (num_records < 0)
>               return 1;
>  
>       /* Total size should be equal to the number of records */
> -- 
> 2.46.2
> 
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