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SubjectRe: [PATCH v1 10/14] DCE/DSE: riscv: make every ex_table's name unique
On Fri, Nov 3, 2023 at 9:02 AM Yuan Tan <tanyuan@tinylab.org> wrote:
>
> gc-sections require section names to be unique.

This is not precise, since a monolithic section can be garbage
collected as well.

https://maskray.me/blog/2021-02-28-linker-garbage-collection

"Without the options, the compiler tends to produce monolithic text
and data sections. The large sections make the GC coarse-grained and
they will likely be retained as a whole. ld --gc-sections can still
discard some sections, but the effect is likely very poor."


> Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
> Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> ---
> arch/riscv/include/asm/asm-extable.h | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/asm-extable.h b/arch/riscv/include/asm/asm-extable.h
> index 00a96e7a9664..d0be5a838242 100644
> --- a/arch/riscv/include/asm/asm-extable.h
> +++ b/arch/riscv/include/asm/asm-extable.h
> @@ -9,10 +9,12 @@
>
> #ifdef CONFIG_MMU
>
> +#include <linux/compiler.h>
> +
> #ifdef __ASSEMBLY__
>
> #define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
> - .pushsection __ex_table, "a"; \
> + .pushsection __SECTION_NAME(__ex_table), "a"; \
> .balign 4; \
> .long ((insn) - .); \
> .long ((fixup) - .); \
> @@ -31,7 +33,7 @@
> #include <asm/gpr-num.h>

__SECTION_NAME is probably added by a previous patch.
An alternative is to use the .section directive's `unique` feature
(binutils>=2.35).

> #define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
> - ".pushsection __ex_table, \"a\"\n" \
> + ".pushsection " __SECTION_NAME(__ex_table) ", \"a\"\n" \
> ".balign 4\n" \
> ".long ((" insn ") - .)\n" \
> ".long ((" fixup ") - .)\n" \
> --
> 2.34.1
>

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