linux-kernel - [PATCH] firmware_loader: Align .builtin

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Message-Id: <20201203170529.1029105-1-maskray@google.com>
Date:   Thu,  3 Dec 2020 09:05:29 -0800
From:   Fangrui Song <maskray@...gle.com>
To:     Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Fangrui Song <maskray@...gle.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] firmware_loader: Align .builtin_fw to 8

arm64 references the start address of .builtin_fw (__start_builtin_fw)
with a pair of R_AARCH64_ADR_PREL_PG_HI21/R_AARCH64_LDST64_ABS_LO12_NC
relocations. The compiler is allowed to emit the
R_AARCH64_LDST64_ABS_LO12_NC relocation because struct builtin_fw in
include/linux/firmware.h is 8-byte aligned.

The R_AARCH64_LDST64_ABS_LO12_NC relocation requires the address to be a
multiple of 8, which may not be the case if .builtin_fw is empty.
Unconditionally align .builtin_fw to fix the linker error.

Fixes: 5658c76 ("firmware: allow firmware files to be built into kernel image")
Link: https://github.com/ClangBuiltLinux/linux/issues/1204
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Fangrui Song <maskray@...gle.com>
---
 include/asm-generic/vmlinux.lds.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b2b3d81b1535..3cd4bd1193ab 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -459,6 +459,7 @@
 	}								\
 									\
 	/* Built-in firmware blobs */					\
+	ALIGN_FUNCTION();						\
 	.builtin_fw        : AT(ADDR(.builtin_fw) - LOAD_OFFSET) {	\
 		__start_builtin_fw = .;					\
 		KEEP(*(.builtin_fw))					\
-- 
2.29.2.576.ga3fc446d84-goog