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From: Fangrui Song <maskray@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,  Ard Biesheuvel <ardb@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Cc: Nathan Chancellor <nathan@kernel.org>,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
	 Fangrui Song <maskray@google.com>
Subject: [PATCH] arm64 module: remove (NOLOAD)
Date: Fri, 18 Feb 2022 00:12:09 -0800	[thread overview]
Message-ID: <20220218081209.354383-1-maskray@google.com> (raw)

On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
inappropriate for .plt and .text.* sections which are always
SHT_PROGBITS.

In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
and (NOLOAD) will be essentially ignored. In ld.lld, since
https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
customize the output section type"), ld.lld will report a `section type
mismatch` error. Just remove (NOLOAD) to fix the error.

[1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
section should be marked as not loadable" on
https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
outdated for ELF.
---
 arch/arm64/include/asm/module.lds.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
index a11ccadd47d2..094701ec5500 100644
--- a/arch/arm64/include/asm/module.lds.h
+++ b/arch/arm64/include/asm/module.lds.h
@@ -1,8 +1,8 @@
 SECTIONS {
 #ifdef CONFIG_ARM64_MODULE_PLTS
-	.plt 0 (NOLOAD) : { BYTE(0) }
-	.init.plt 0 (NOLOAD) : { BYTE(0) }
-	.text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
+	.plt 0 : { BYTE(0) }
+	.init.plt 0 : { BYTE(0) }
+	.text.ftrace_trampoline 0 : { BYTE(0) }
 #endif
 
 #ifdef CONFIG_KASAN_SW_TAGS
-- 
2.35.1.265.g69c8d7142f-goog


WARNING: multiple messages have this Message-ID (diff)
From: Fangrui Song <maskray@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,  Ard Biesheuvel <ardb@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Cc: Nathan Chancellor <nathan@kernel.org>,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
	Fangrui Song <maskray@google.com>
Subject: [PATCH] arm64 module: remove (NOLOAD)
Date: Fri, 18 Feb 2022 00:12:09 -0800	[thread overview]
Message-ID: <20220218081209.354383-1-maskray@google.com> (raw)

On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
inappropriate for .plt and .text.* sections which are always
SHT_PROGBITS.

In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
and (NOLOAD) will be essentially ignored. In ld.lld, since
https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
customize the output section type"), ld.lld will report a `section type
mismatch` error. Just remove (NOLOAD) to fix the error.

[1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
section should be marked as not loadable" on
https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
outdated for ELF.
---
 arch/arm64/include/asm/module.lds.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
index a11ccadd47d2..094701ec5500 100644
--- a/arch/arm64/include/asm/module.lds.h
+++ b/arch/arm64/include/asm/module.lds.h
@@ -1,8 +1,8 @@
 SECTIONS {
 #ifdef CONFIG_ARM64_MODULE_PLTS
-	.plt 0 (NOLOAD) : { BYTE(0) }
-	.init.plt 0 (NOLOAD) : { BYTE(0) }
-	.text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
+	.plt 0 : { BYTE(0) }
+	.init.plt 0 : { BYTE(0) }
+	.text.ftrace_trampoline 0 : { BYTE(0) }
 #endif
 
 #ifdef CONFIG_KASAN_SW_TAGS
-- 
2.35.1.265.g69c8d7142f-goog


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             reply	other threads:[~2022-02-18  8:12 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-18  8:12 Fangrui Song [this message]
2022-02-18  8:12 ` [PATCH] arm64 module: remove (NOLOAD) Fangrui Song
2022-02-18  8:17 ` Ard Biesheuvel
2022-02-18  8:17   ` Ard Biesheuvel
2022-02-18  8:50   ` Fangrui Song
2022-02-18  8:50     ` Fangrui Song
2022-02-18 16:34     ` Nathan Chancellor
2022-02-18 16:34       ` Nathan Chancellor
2022-02-18 19:08       ` Ard Biesheuvel
2022-02-18 19:08         ` Ard Biesheuvel
2022-02-25 15:50 ` Will Deacon
2022-02-25 15:50   ` Will Deacon
2022-03-09  7:55 ` [tip: x86/core] arm64: module: remove (NOLOAD) from linker script tip-bot2 for Fangrui Song

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