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SubjectRe: [PATCH] arm64: vmlinux.lds.S: keep .entry.tramp.text section
On Fri, Feb 26, 2021 at 03:03:39PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> When building with CONFIG_LD_DEAD_CODE_DATA_ELIMINATION,
> I sometimes see an assertion
>
> ld.lld: error: Entry trampoline text too big

Heh, "too big" seems a weird report for having it discarded. :)

Any idea on this Fangrui?

( I see this is https://github.com/ClangBuiltLinux/linux/issues/1311 )

>
> This happens when any reference to the trampoline is discarded at link
> time. Marking the section as KEEP() avoids the assertion, but I have
> not figured out whether this is the correct solution for the underlying
> problem.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

As a work-around, it seems fine to me.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
> arch/arm64/kernel/vmlinux.lds.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index 926cdb597a45..c5ee9d5842db 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -96,7 +96,7 @@ jiffies = jiffies_64;
> #define TRAMP_TEXT \
> . = ALIGN(PAGE_SIZE); \
> __entry_tramp_text_start = .; \
> - *(.entry.tramp.text) \
> + KEEP(*(.entry.tramp.text)) \
> . = ALIGN(PAGE_SIZE); \
> __entry_tramp_text_end = .;
> #else
> --
> 2.29.2
>

--
Kees Cook

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