linux-kernel - Re: [PATCH 2/2] x86/purgatory: remove -nostdlib compiler flag

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Message-ID: <CAKwvOdmCaXAMvouD7bsWqmgOUxQ9vpdt3LY7qWpzTVm-2gddEw@mail.gmail.com>
Date:   Mon, 8 Nov 2021 15:52:35 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        Fangrui Song <maskray@...gle.com>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        clang-built-linux@...glegroups.com,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH 2/2] x86/purgatory: remove -nostdlib compiler flag

On Sun, Nov 7, 2021 at 8:27 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> The -nostdlib option requests the compiler to not use the standard
> system startup files or libraries when linking. It is effective only
> when $(CC) is used as a linker driver.

Is that right? ld.lld recognizes --nostdlib and has --help text for it.

>
> $(LD) is directly used for linking purgatory.{ro,chk} here, hence
> -nostdlib is unneeded.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  arch/x86/purgatory/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> index 95ea17a9d20c..ae53d54d7959 100644
> --- a/arch/x86/purgatory/Makefile
> +++ b/arch/x86/purgatory/Makefile
> @@ -16,7 +16,7 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
>
>  # When linking purgatory.ro with -r unresolved symbols are not checked,
>  # also link a purgatory.chk binary without -r to check for unresolved symbols.
> -PURGATORY_LDFLAGS := -e purgatory_start -nostdlib -z nodefaultlib
> +PURGATORY_LDFLAGS := -e purgatory_start -z nodefaultlib
>  LDFLAGS_purgatory.ro := -r $(PURGATORY_LDFLAGS)
>  LDFLAGS_purgatory.chk := $(PURGATORY_LDFLAGS)
>  targets += purgatory.ro purgatory.chk
> --
> 2.30.2

-- 
Thanks,
~Nick Desaulniers