Re: [PATCH 1/3] x86: Use pt_regs pointer in do_device_not_available()

[Tejun Heo <tj@kernel.org>]

Hello, Brian.

Brian Gerst wrote:
> The generic exception handler (error_code) passes in the pt_regs
> pointer and the error code (unused in this case).  The commit
> "x86: fix math_emu register frame access" changed this to pass by
> value, which doesn't work correctly with stack protector enabled.
> Change it back to use the pt_regs pointer.
> 
> Signed-off-by: Brian Gerst <brgerst@gmail.com>
> ---
>  arch/x86/include/asm/traps.h |    2 +-
>  arch/x86/kernel/traps.c      |    9 +++++----
>  2 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
> index cf3bb05..0d53425 100644
> --- a/arch/x86/include/asm/traps.h
> +++ b/arch/x86/include/asm/traps.h
> @@ -41,7 +41,7 @@ dotraplinkage void do_int3(struct pt_regs *, long);
>  dotraplinkage void do_overflow(struct pt_regs *, long);
>  dotraplinkage void do_bounds(struct pt_regs *, long);
>  dotraplinkage void do_invalid_op(struct pt_regs *, long);
> -dotraplinkage void do_device_not_available(struct pt_regs);
> +dotraplinkage void do_device_not_available(struct pt_regs *, long);
>  dotraplinkage void do_coprocessor_segment_overrun(struct pt_regs *, long);
>  dotraplinkage void do_invalid_TSS(struct pt_regs *, long);
>  dotraplinkage void do_segment_not_present(struct pt_regs *, long);
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index 3b7b2e1..71a8f87 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -905,19 +905,20 @@ void math_emulate(struct math_emu_info *info)
>  }
>  #endif /* CONFIG_MATH_EMULATION */
>  
> -dotraplinkage void __kprobes do_device_not_available(struct pt_regs regs)
> +dotraplinkage void __kprobes
> +do_device_not_available(struct pt_regs *regs, long error_code)

What do you think about just taking pt_regs and accessing
regs->orig_eax instead of having separate call convention for pt_regs
ones and trap ones?  Too much work without enough benefit?

Thanks.

-- 
tejun