linux-kernel - Re: [PATCH v2] firmware_loader: Align .builtin

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Date:   Tue, 5 Jan 2021 09:44:48 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Fangrui Song <maskray@...gle.com>, Arnd Bergmann <arnd@...db.de>
Cc:     linux-arch@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] firmware_loader: Align .builtin_fw to 8

Hi,

On Mon, Dec 7, 2020 at 9:49 PM Fangrui Song <maskray@...gle.com> wrote:
>
> arm64 references the start address of .builtin_fw (__start_builtin_fw)
> with a pair of R_AARCH64_ADR_PREL_PG_HI21/R_AARCH64_LDST64_ABS_LO12_NC
> relocations. The compiler is allowed to emit the
> R_AARCH64_LDST64_ABS_LO12_NC relocation because struct builtin_fw in
> include/linux/firmware.h is 8-byte aligned.
>
> The R_AARCH64_LDST64_ABS_LO12_NC relocation requires the address to be a
> multiple of 8, which may not be the case if .builtin_fw is empty.
> Unconditionally align .builtin_fw to fix the linker error. 32-bit
> architectures could use ALIGN(4) but that would add unnecessary
> complexity, so just use ALIGN(8).
>
> Fixes: 5658c76 ("firmware: allow firmware files to be built into kernel image")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1204
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Fangrui Song <maskray@...gle.com>
> Acked-by: Arnd Bergmann <arnd@...db.de>
>
> ---
> Change in v2:
> * Use output section alignment instead of inappropriate ALIGN_FUNCTION()
> ---
>  include/asm-generic/vmlinux.lds.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Tested-by: Douglas Anderson <dianders@...omium.org>

For whatever reason this is hitting developers on Chrome OS a whole
lot suddenly.  Any chance it could be landed?  Which tree should it go
through?

-Doug