linux-kernel - Re: [PATCH] kbuild: Use --strip-unneeded with INSTALL_MOD

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Message-ID: <20250131035245.GA47826@ax162>
Date: Thu, 30 Jan 2025 20:52:45 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Charlie Jenkins <charlie@...osinc.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP

On Wed, Jan 22, 2025 at 07:17:26PM -0800, Charlie Jenkins wrote:
> On riscv, kernel modules end up with a significant number of local
> symbols. This becomes apparent when compiling modules with debug symbols
> enabled. Using amdgpu.ko as an example of a large module, on riscv the
> size is 754MB (no stripping), 53MB (--strip-debug), and 21MB
> (--strip-unneeded). ON x86, amdgpu.ko is 482MB (no stripping), 21MB
> (--strip-debug), and 20MB (--strip-unneeded).
> 
> Use --strip-unneeded instead of --strip-debug to strip modules so
> decrease the size of the resulting modules. This is particularly
> relevant for riscv, but also marginally aids other architectures.
> 
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>

Is there any sort of regression risk with this patch? If so, another
option may be to give another level to INSTALL_MOD_STRIP like 2 so that
INSTALL_MOD_STRIP=1 continues to behave as before but people can easily
opt into this option. No strong opinion because I am not sure but was
not sure if it was considered.

Regardless:

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  scripts/Makefile.modinst | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/Makefile.modinst b/scripts/Makefile.modinst
> index f97c9926ed31b2b14601ff7773a2ea48b225628b..c22f35f6b9db3cac3923b9e787b219f752570642 100644
> --- a/scripts/Makefile.modinst
> +++ b/scripts/Makefile.modinst
> @@ -80,7 +80,7 @@ quiet_cmd_install = INSTALL $@
>  ifdef INSTALL_MOD_STRIP
>  
>  ifeq ($(INSTALL_MOD_STRIP),1)
> -strip-option := --strip-debug
> +strip-option := --strip-unneeded
>  else
>  strip-option := $(INSTALL_MOD_STRIP)
>  endif
> 
> ---
> base-commit: ffd294d346d185b70e28b1a28abe367bbfe53c04
> change-id: 20250122-strip_unneeded-cab729310056
> -- 
> - Charlie
>