All of lore.kernel.org
 help / color / mirror / Atom feed
From: Kees Cook <keescook@chromium.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Ard Biesheuvel <ardb@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	David Brazdil <dbrazdil@google.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Fangrui Song <maskray@google.com>
Subject: Re: [PATCH] arm64: vmlinux.lds.S: keep .entry.tramp.text section
Date: Fri, 26 Feb 2021 12:59:17 -0800	[thread overview]
Message-ID: <202102261256.AF256702@keescook> (raw)
In-Reply-To: <20210226140352.3477860-1-arnd@kernel.org>

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

WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Fangrui Song <maskray@google.com>, Arnd Bergmann <arnd@arndb.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-kernel@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	David Brazdil <dbrazdil@google.com>,
	Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: vmlinux.lds.S: keep .entry.tramp.text section
Date: Fri, 26 Feb 2021 12:59:17 -0800	[thread overview]
Message-ID: <202102261256.AF256702@keescook> (raw)
In-Reply-To: <20210226140352.3477860-1-arnd@kernel.org>

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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-02-26 21:00 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-26 14:03 [PATCH] arm64: vmlinux.lds.S: keep .entry.tramp.text section Arnd Bergmann
2021-02-26 14:03 ` Arnd Bergmann
2021-02-26 20:59 ` Kees Cook [this message]
2021-02-26 20:59   ` Kees Cook
2021-02-27  4:32   ` Fangrui Song
2021-02-27  4:32     ` Fangrui Song
2021-03-16 10:45     ` Catalin Marinas
2021-03-16 10:45       ` Catalin Marinas
2021-03-16 16:27       ` Catalin Marinas
2021-03-16 16:27         ` Catalin Marinas
2021-03-16 16:39         ` Arnd Bergmann
2021-03-16 16:39           ` Arnd Bergmann
2021-03-16 19:09           ` Catalin Marinas
2021-03-16 19:09             ` Catalin Marinas
2021-06-02 19:32             ` Kees Cook
2021-06-02 19:32               ` Kees Cook
2021-06-03 12:07               ` Catalin Marinas
2021-06-03 12:07                 ` Catalin Marinas

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=202102261256.AF256702@keescook \
    --to=keescook@chromium.org \
    --cc=ardb@kernel.org \
    --cc=arnd@arndb.de \
    --cc=arnd@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=dbrazdil@google.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=maskray@google.com \
    --cc=maz@kernel.org \
    --cc=will@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.