Re: [PATCH -next] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION

[liuyuntao (F)]

On 2024/2/27 16:06, liuyuntao (F) wrote:
> On 2024/2/23 0:04, Arnd Bergmann wrote:
> > On Thu, Feb 22, 2024, at 12:24, liuyuntao (F) wrote:
> > > The position of the caret has been moved below the right brace
> > > of { KEEP(*(.vectors.bhb.loop8)) }, indicating that lld is treating
> > > the entire `KEEP(*(.vectors))` as a file name. This could potentially be
> > > a bug in lld. Perhaps we can temporarily
> > > enable the DCE option only when option LD_IS_LLD is disabled,
> > > like risc-v:
> > >
> > > `select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if !LD_IS_LLD`.
> >
> > I would really like to see this working with lld if at all
> > possible, as it allows the combination of gc-sections with
> > lto and CONFIG_TRIM_UNUSED_KSYMS.
Another way to preserve .vector sections without using KEEP annotation.
It boots well. How do you feel about this approach? and, could I submit 
a v2 patch?

1: Define ARM_VECTORS_TEXT to explicitly preserve .vectors section.

> --- a/arch/arm/include/asm/vmlinux.lds.h
> +++ b/arch/arm/include/asm/vmlinux.lds.h
> @@ -87,6 +87,13 @@
>                 *(.vfp11_veneer)                                \
>                 *(.v4_bx)
>
> +#define ARM_VECTORS_TEXT                                       \
> +       .vectors.text : {                                       \
> +               KEEP(*(.vectors))                               \
> +               KEEP(*(.vectors.bhb.loop8))                     \
> +               KEEP(*(.vectors.bhb.bpiall))                    \
> +       }
> +
>  #define ARM_TEXT                                               \
>                 IDMAP_TEXT                                      \
>                 __entry_text_start = .;                         \

2: Ref ARM_VECTORS_TEXT if config HAVE_LD_DEAD_CODE_DATA_ELIMINATION is 
enabled, and the same to arch/arm/kernel/vmlinux.lds.S

> --- a/arch/arm/kernel/vmlinux-xip.lds.S 

> +++ b/arch/arm/kernel/vmlinux-xip.lds.S 

> @@ -135,6 +135,10 @@ SECTIONS 

>         ARM_TCM 

>  #endif 

> 

> +#ifdef HAVE_LD_DEAD_CODE_DATA_ELIMINATION 

> +       ARM_VECTORS_TEXT 

> +#endif 

> + 

>         /* 

>          * End of copied data. We need a dummy section to get its 
LMA.
>          * Also located before final ALIGN() as trailing padding is
> not stored