linux-kernel - [tip: x86/boot] x86/boot: Discard .eh

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Date:   Sat, 14 Dec 2019 07:12:55 -0000
From:   "tip-bot2 for Ilie Halip" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Borislav Petkov <bp@...en8.de>, Ilie Halip <ilie.halip@...il.com>,
        Borislav Petkov <bp@...e.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        clang-built-linux@...glegroups.com,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "x86-ml" <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/boot] x86/boot: Discard .eh_frame sections

The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     163159aad74d3763b350861b879b41e8f64121fc
Gitweb:        https://git.kernel.org/tip/163159aad74d3763b350861b879b41e8f64121fc
Author:        Ilie Halip <ilie.halip@...il.com>
AuthorDate:    Tue, 26 Nov 2019 16:45:44 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Fri, 13 Dec 2019 11:45:59 +01:00

x86/boot: Discard .eh_frame sections

When using GCC as compiler and LLVM's lld as linker, linking setup.elf
fails:

   LD      arch/x86/boot/setup.elf
  ld.lld: error: init sections too big!

This happens because GCC generates .eh_frame sections for most of the
files in that directory, then ld.lld places the merged section before
__end_init, triggering an assert in the linker script.

Fix this by discarding the .eh_frame sections, as suggested by Boris.
The kernel proper linker script discards them too.

 [ bp: Going back in history, 64-bit kernel proper has been discarding
   .eh_frame since 2002:

    commit acca80acefe20420e69561cf55be64f16c34ea97
    Author: Andi Kleen <ak@....de>
    Date:   Tue Oct 29 23:54:35 2002 -0800

      [PATCH] x86-64 updates for 2.5.44

      ...

    - Remove the .eh_frame on linking. This saves several hundred KB in the
      bzImage
 ]

Suggested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Ilie Halip <ilie.halip@...il.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com
Cc: Andy Lutomirski <luto@...nel.org>
Cc: clang-built-linux@...glegroups.com
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86-ml <x86@...nel.org>
Link: https://lore.kernel.org/lkml/20191118175223.GM6363@zn.tnic/
Link: https://github.com/ClangBuiltLinux/linux/issues/760
Link: https://lkml.kernel.org/r/20191126144545.19354-1-ilie.halip@gmail.com
---
 arch/x86/boot/setup.ld | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
index 0149e41..3da1c37 100644
--- a/arch/x86/boot/setup.ld
+++ b/arch/x86/boot/setup.ld
@@ -51,7 +51,10 @@ SECTIONS
 	. = ALIGN(16);
 	_end = .;
 
-	/DISCARD/ : { *(.note*) }
+	/DISCARD/	: {
+		*(.eh_frame)
+		*(.note*)
+	}
 
 	/*
 	 * The ASSERT() sink to . is intentional, for binutils 2.14 compatibility: