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From: Johannes Hirte <johannes.hirte@datenkhaos.de>
To: Kees Cook <keescook@chromium.org>
Cc: Borislav Petkov <bp@suse.de>,
	Sami Tolvanen <samitolvanen@google.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] x86/build: Move _etext to actual end of .text
Date: Tue, 14 May 2019 14:04:21 +0200	[thread overview]
Message-ID: <20190514120416.GA11736@probook> (raw)
In-Reply-To: <20190423183827.GA4012@beast>

On 2019 Apr 23, Kees Cook wrote:
> When building x86 with Clang LTO and CFI, CFI jump regions are
> automatically added to the end of the .text section late in linking. As a
> result, the _etext position was being labelled before the appended jump
> regions, causing confusion about where the boundaries of the executable
> region actually are in the running kernel, and broke at least the fault
> injection code. This moves the _etext mark to outside (and immediately
> after) the .text area, as it already the case on other architectures
> (e.g. arm64, arm).
> 
> Reported-and-tested-by: Sami Tolvanen <samitolvanen@google.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/x86/kernel/vmlinux.lds.S | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index bad8c51fee6e..de94da2366e7 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -141,11 +141,11 @@ SECTIONS
>  		*(.text.__x86.indirect_thunk)
>  		__indirect_thunk_end = .;
>  #endif
> -
> -		/* End of text section */
> -		_etext = .;
>  	} :text = 0x9090
>  
> +	/* End of text section */
> +	_etext = .;
> +
>  	NOTES :text :note
>  
>  	EXCEPTION_TABLE(16) :text = 0x9090
> -- 
> 2.17.1

This breaks the build on my system:

  RELOCS  arch/x86/boot/compressed/vmlinux.relocs
  CC      arch/x86/boot/compressed/early_serial_console.o
  CC      arch/x86/boot/compressed/kaslr.o
  AS      arch/x86/boot/compressed/mem_encrypt.o
  CC      arch/x86/boot/compressed/kaslr_64.o
Invalid absolute R_X86_64_32S relocation: _etext
make[2]: *** [arch/x86/boot/compressed/Makefile:130: arch/x86/boot/compressed/vmlinux.relocs] Error 1
make[2]: *** Deleting file 'arch/x86/boot/compressed/vmlinux.relocs'
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [arch/x86/boot/Makefile:112: arch/x86/boot/compressed/vmlinux] Error 2
make: *** [arch/x86/Makefile:283: bzImage] Error 2



-- 
Regards,
  Johannes


  parent reply	other threads:[~2019-05-14 12:14 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-23 18:38 Kees Cook
2019-04-24 11:12 ` [tip:x86/mm] " tip-bot for Kees Cook
2019-05-14 12:04 ` Johannes Hirte [this message]
2019-05-14 15:43   ` [PATCH] " Kees Cook
2019-05-14 16:10     ` Johannes Hirte
2019-05-15 18:54       ` Kees Cook
2019-05-16 13:56         ` Johannes Hirte
2019-05-16 17:51           ` Kees Cook
2019-06-01  8:51 Klaus Kusche
2019-06-05 16:08 Alec Ari
2019-06-05 18:16 ` Kees Cook
2019-06-05 18:43   ` Greg KH
2019-06-09  9:35 Klaus Kusche
2019-06-09 18:40 ` Johannes Hirte
2019-06-19 18:37   ` Ross Zwisler
2019-06-20 17:58     ` Kees Cook

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