Re: [PATCH] arm64 module: remove (NOLOAD)
From: Ard Biesheuvel <ardb@kernel.org>
Date: 2022-02-18 19:09:01
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On Fri, 18 Feb 2022 at 17:34, Nathan Chancellor [off-list ref] wrote:
On Fri, Feb 18, 2022 at 12:50:16AM -0800, Fangrui Song wrote:quoted
On 2022-02-18, Ard Biesheuvel wrote:quoted
On Fri, 18 Feb 2022 at 09:12, Fangrui Song [off-list ref] wrote:quoted
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"The section should be marked as not loadable" on https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is outdated for ELF.This patch lacks a SOB line. With one added, Acked-by: Ard Biesheuvel <ardb@kernel.org>Ah, yes. Sorry, I haven't sent a kernel patch for a while... Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Fangrui Song <redacted> Acked-by: Ard Biesheuvel <ardb@kernel.org>I am assuming this patch is the solution we want, as opposed to Ard's suggestion of renaming these sections at https://reviews.llvm.org/D118840 (unless that was a tangential suggestion).
Renaming will not make the problem go away. It will only clear up the confusion regarding the contents of these sections, which are not in fact linker emitted PLT entries, but branching veneers emitted by the kernel's module loader.
I have verified that modules still load. Additionally, this needs to go to stable so that groups who upgrade their toolchain to a revision that include the LLD patch don't get broken as well. Cc: stable@vger.kernel.org Tested-by: Nathan Chancellor <nathan@kernel.org>quoted
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--- 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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