[Request for help] issue when add relative extable support to riscv64

[Jisheng Zhang]

On Sat, 18 Sep 2021 09:23:48 +0800
Kefeng Wang <wangkefeng.wang at huawei.com> wrote:

> On 2021/9/18 0:26, Jisheng Zhang wrote:
> > On Fri, 17 Sep 2021 23:57:33 +0800 Jisheng Zhang wrote:
> >  
> >> Hi,
> >>
> >> Now the extable entry contains 16bytes for riscv64 -- 8bytes for the insn and
> >> another 8bytes for the fixup. This wastes mem a bit. I think we can add
> >> the relative extable support. A draft patch put at the end of this mail. But
> >> I met abnormal build errors:
> >>
> >> FATAL: modpost: The relocation at __ex_table+0x0 references
> >> section "__ex_table" which is not executable, IOW
> >> it is not possible for the kernel to fault
> >> at that address.  Something is seriously wrong
> >> and should be fixed.  
> 
> I try this before, and meet the same issue,  and add norelax to the label,
> 
> but it won't fix the error. seems that we con't find the lable from the 
> text?

I also tried adding --no-relax to LDFLAGS and -mno-relax to AFLAGS and CFLAGS
but still met the error. This is an insteresting issue.

Thanks

> 
> 
>   82 index 1b00badb9f87..cb1aca8e8a23 100644
>   83 --- a/arch/riscv/include/asm/futex.h
>   84 +++ b/arch/riscv/include/asm/futex.h
>   85 @@ -23,17 +23,18 @@
>   86         uintptr_t tmp; \
>   87         __enable_user_access(); \
>   88         __asm__ __volatile__ ( \
>   89 +       "       .option push                            \n" \
>   90 +       "       .option norelax                         \n" \
>   91 +       "       .option norvc                           \n" \
>   92         "1:     " insn "                                \n" \
>   93 +       "       .option pop                             \n" \
>   94         "2:                                             \n" \
> 
> 
>