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From: Fangrui Song <maskray@google.com>
To: Arnd Bergmann <arnd@arndb.de>, linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
	Nathan Chancellor <natechancellor@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Fangrui Song <maskray@google.com>,
	kernel test robot <lkp@intel.com>
Subject: [PATCH v2] firmware_loader: Align .builtin_fw to 8
Date: Mon,  7 Dec 2020 21:46:46 -0800	[thread overview]
Message-ID: <20201208054646.2913063-1-maskray@google.com> (raw)
In-Reply-To: <20201203202737.7c4wrifqafszyd5y@google.com>

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. 32-bit
architectures could use ALIGN(4) but that would add unnecessary
complexity, so just use ALIGN(8).

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@intel.com>
Signed-off-by: Fangrui Song <maskray@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

---
Change in v2:
* Use output section alignment instead of inappropriate ALIGN_FUNCTION()
---
 include/asm-generic/vmlinux.lds.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b2b3d81b1535..b97c628ad91f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -459,7 +459,7 @@
 	}								\
 									\
 	/* Built-in firmware blobs */					\
-	.builtin_fw        : AT(ADDR(.builtin_fw) - LOAD_OFFSET) {	\
+	.builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) ALIGN(8) {	\
 		__start_builtin_fw = .;					\
 		KEEP(*(.builtin_fw))					\
 		__end_builtin_fw = .;					\
-- 
2.29.2.576.ga3fc446d84-goog


  reply	other threads:[~2020-12-08  5:47 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-03 17:05 [PATCH] firmware_loader: Align .builtin_fw to 8 Fangrui Song
2020-12-03 18:00 ` Arnd Bergmann
2020-12-03 19:04 ` Nick Desaulniers
2020-12-03 20:27   ` Fangrui Song
2020-12-08  5:46     ` Fangrui Song [this message]
2020-12-08 17:59       ` [PATCH v2] " Nick Desaulniers
2021-01-05 17:44       ` Doug Anderson
2021-01-05 19:20         ` Nick Desaulniers
2021-01-22 19:04           ` Doug Anderson
2021-02-05 17:19             ` Doug Anderson
2021-02-05 19:08       ` Nathan Chancellor

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