linux-kernel - [PATCH v3] x86/boot: discard .eh

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Message-Id: <20191126144545.19354-1-ilie.halip@gmail.com>
Date:   Tue, 26 Nov 2019 16:45:44 +0200
From:   Ilie Halip <ilie.halip@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>, Andy <luto@...nel.org>,
        Ilie Halip <ilie.halip@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH v3] 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.

Signed-off-by: Ilie Halip <ilie.halip@...il.com>
Link: https://lore.kernel.org/lkml/20191118175223.GM6363@zn.tnic/
Link: https://github.com/ClangBuiltLinux/linux/issues/760
Suggested-by: Borislav Petkov <bp@...en8.de>
---

Changes in V3:
 * discard .eh_frame instead of placing it after .rodata

Changes in V2:
 * removed wildcard for input sections (.eh_frame* -> .eh_frame)

 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 0149e41d42c2..3da1c37c6dd5 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:
-- 
2.17.1