From: Arvind Sankar <nivedita@alum.mit.edu>
To: Fangrui Song <maskray@google.com>
Cc: x86@kernel.org, Arvind Sankar <nivedita@alum.mit.edu>,
linux-efi@vger.kernel.org, clang-built-linux@googlegroups.com,
Nick Desaulniers <ndesaulniers@google.com>,
Ard Biesheuvel <ardb@kernel.org>,
kbuild test robot <lkp@intel.com>
Subject: Re: [PATCH] x86/boot: Discard .discard.unreachable for arch/x86/boot/compressed/vmlinux
Date: Wed, 20 May 2020 15:19:40 -0400 [thread overview]
Message-ID: <20200520191940.GA3450657@rani.riverdale.lan> (raw)
In-Reply-To: <20200520182010.242489-1-maskray@google.com>
On Wed, May 20, 2020 at 11:20:10AM -0700, Fangrui Song wrote:
> In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b
> "efi/printf: Add 64-bit and 8-bit integer support",
> arch/x86/boot/compressed/vmlinux may have an undesired
> .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o
>
> .discard.unreachable contains an R_X86_64_PC32 relocation, which will be
> warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not
> part of the memory image, thus conceptually the distance between a
> non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at
> link time.
>
> % ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux
> ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''
>
> Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable
>
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Fangrui Song <maskray@google.com>
> ---
> arch/x86/boot/compressed/vmlinux.lds.S | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> index 0dc5c2b9614b..8f1025d1f681 100644
> --- a/arch/x86/boot/compressed/vmlinux.lds.S
> +++ b/arch/x86/boot/compressed/vmlinux.lds.S
> @@ -74,4 +74,6 @@ SECTIONS
> #endif
> . = ALIGN(PAGE_SIZE); /* keep ZO size page aligned */
> _end = .;
> +
> + DISCARDS
> }
> --
> 2.26.2.761.g0e0b3e54be-goog
>
Thanks! Maybe add a note in the commit message that the section is
generated from unreachable() annotations when CONFIG_STACK_VALIDATION is
enabled.
Tested-by: Arvind Sankar <nivedita@alum.mit.edu>
next prev parent reply other threads:[~2020-05-20 19:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 18:20 [PATCH] x86/boot: Discard .discard.unreachable for arch/x86/boot/compressed/vmlinux Fangrui Song
2020-05-20 19:19 ` Arvind Sankar [this message]
2020-05-22 2:42 ` Kees Cook
2020-05-22 6:51 ` Sedat Dilek
2020-05-22 15:54 ` Ard Biesheuvel
2020-05-22 15:57 ` Sedat Dilek
2020-05-22 15:59 ` Ard Biesheuvel
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