linux-kernel - [PATCH 6.1 fix build id for arm64 1/5] arch: fix broken BuildID for arm64 and riscv

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Message-Id: <e9fea9abe5fc908a95d2289a2cc8e61cadc8dee1.1674876902.git.tom.saeger@oracle.com>
Date:   Fri, 27 Jan 2023 21:10:18 -0700
From:   Tom Saeger <tom.saeger@...cle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Rich Felker <dalias@...c.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Dennis Gilmore <dennis@...il.us>,
        Jisheng Zhang <jszhang@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tom Saeger <tom.saeger@...cle.com>, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org
Subject: [PATCH 6.1 fix build id for arm64 1/5] arch: fix broken BuildID for arm64 and riscv

From: Masahiro Yamada <masahiroy@...nel.org>

commit 99cb0d917ffa1ab628bb67364ca9b162c07699b1 upstream.

Dennis Gilmore reports that the BuildID is missing in the arm64 vmlinux
since commit 994b7ac1697b ("arm64: remove special treatment for the
link order of head.o").

The issue is that the type of .notes section, which contains the BuildID,
changed from NOTES to PROGBITS.

Ard Biesheuvel figured out that whichever object gets linked first gets
to decide the type of a section. The PROGBITS type is the result of the
compiler emitting .note.GNU-stack as PROGBITS rather than NOTE.

While Ard provided a fix for arm64, I want to fix this globally because
the same issue is happening on riscv since commit 2348e6bf4421 ("riscv:
remove special treatment for the link order of head.o"). This problem
will happen in general for other architectures if they start to drop
unneeded entries from scripts/head-object-list.txt.

Discard .note.GNU-stack in include/asm-generic/vmlinux.lds.h.

Link: https://lore.kernel.org/lkml/CAABkxwuQoz1CTbyb57n0ZX65eSYiTonFCU8-LCQc=74D=xE=rA@mail.gmail.com/
Fixes: 994b7ac1697b ("arm64: remove special treatment for the link order of head.o")
Fixes: 2348e6bf4421 ("riscv: remove special treatment for the link order of head.o")
Reported-by: Dennis Gilmore <dennis@...il.us>
Suggested-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Acked-by: Palmer Dabbelt <palmer@...osinc.com>
Signed-off-by: Tom Saeger <tom.saeger@...cle.com>
---
 include/asm-generic/vmlinux.lds.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 3dc5824141cd..7ad6f51b3d91 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -929,7 +929,12 @@
 #define PRINTK_INDEX
 #endif
 
+/*
+ * Discard .note.GNU-stack, which is emitted as PROGBITS by the compiler.
+ * Otherwise, the type of .notes section would become PROGBITS instead of NOTES.
+ */
 #define NOTES								\
+	/DISCARD/ : { *(.note.GNU-stack) }				\
 	.notes : AT(ADDR(.notes) - LOAD_OFFSET) {			\
 		__start_notes = .;					\
 		KEEP(*(.note.*))					\
-- 
2.39.1