Message-ID: <86186254-b2c6-4818-af0a-4eb67d90e501@csgroup.eu>
Date: Thu, 14 Aug 2025 15:43:09 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
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Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 llvm@...ts.linux.dev, linux-mm@...ck.org, linux-um@...ts.infradead.org,
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 Arnaldo Carvalho de Melo <acme@...hat.com>,
 Alexandre Ghiti <alexghiti@...osinc.com>
Subject: Re: [PATCH v4 00/24] vdso: Reject absolute relocations during build



Le 12/08/2025 à 07:44, Thomas Weißschuh a écrit :
> The compiler can emit absolute relocations in vDSO code,
> which are invalid in vDSO code.
> Detect them at compile-time.

I'm a bit puzzled with this series.

If I understand correctly, the check will be done only when you have 
RUST available ?

I wouldn't expect having RUST to build a C kernel.

By the way, aren't relocations already detected by command 
cmd_vdso_check in lib/vdso/Makefile.include , using readelf ? Why is a 
new tool needed and why does it have to be written in RUST langage ?

Thanks
Christophe

> 
> libc elf.h is missing some of the relocation constants,
> so make user of the kernels own UAPI headers instead.
> 
> Kbuild and Rust folks: This contains custom definitions of hostprog
> bindgen and rust library commands.
> These are currently only defined inside the subsystem directory.
> Let me know if they should go into scripts/Makefile.host.
> 
> This will conflict with my SPARC64 generic vDSO patches [0].
> If both end up being applied at the same time, please leave out commit
> 'vdso/vdsocheck: Drop the transitional kconfig option' from this series.
> 
> [0] https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flkml%2F20250724-vdso-sparc64-generic-2-v1-0-e376a3bd24d1%40linutronix.de%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C3f03f6747325451ee98808ddd9634f27%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638905742749561064%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=HacF%2FvlUoxA9P6fTiN1ytw49gwayX1wNE7IxfEkFutE%3D&reserved=0
> 
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> ---
> Changes in v4:
> - Replace the inline shell logic with a dedicated build-time tool
> - Link to v3: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fr%2F20250611-vdso-absolute-reloc-v3-0-47897d73784b%40linutronix.de&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C3f03f6747325451ee98808ddd9634f27%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638905742749584369%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=7NxAhutk6IXl%2B3fe1kkZEzhZz6CWye%2FVAcFO%2BgtS4uo%3D&reserved=0
> 
> Changes in v3:
> - Drop already applied bugfix for arm64
> - Disable LTO for the riscv vDSO, as it is incompatible
> - Link to v2: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fr%2F20250430-vdso-absolute-reloc-v2-0-5efcc3bc4b26%40linutronix.de&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C3f03f6747325451ee98808ddd9634f27%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638905742749600546%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=uv0qMS5qq0DovLHtxfRvT42atbJEkztylpOS8zt6bJ4%3D&reserved=0
> 
> Changes in v2:
> - Link to openend (invalid) GCC bug containing more explanations
> - Refine commit messages
> - Don't fail on commit absolute relocations in debug info
> - Link to v1: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fr%2F20250429-vdso-absolute-reloc-v1-0-987a0afd10b5%40linutronix.de&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C3f03f6747325451ee98808ddd9634f27%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638905742749616057%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=K5iwoz0Xqc8kheotWEc4M2KrZ7UVMDObOyFfCPj4N8Q%3D&reserved=0
> 
> ---
> Thomas Weißschuh (24):
>        elf, uapi: Add a header for relocation constants
>        x86/elf, um/x86/elf: Move relocation constants to UAPI
>        ARM: elf: Move relocation constants to UAPI
>        arm64: elf: Move relocation constants to UAPI
>        powerpc/elf: Move relocation constants to UAPI
>        riscv: elf: Move relocation constants to UAPI
>        LoongArch: Move relocation constants to UAPI
>        s390/elf: Move relocation constants to UAPI
>        MIPS: ELF: Move relocation constants to UAPI
>        tools headers UAPI: Sync ELF headers with the kernel sources
>        vdso: Add the vdsocheck tool
>        x86/vdso: Enable the vdsocheck tool
>        ARM: vdso: Enable the vdsocheck tool
>        arm64: vdso: Enable the vdsocheck tool
>        powerpc/elf: Add 32-bit REL16 relocation definitions
>        powerpc/vdso: Enable the vdsocheck tool
>        riscv: vdso: Deduplicate CFLAGS_REMOVE_* variables
>        riscv: vdso: Disable LTO for the vDSO
>        riscv: vdso: Enable the vdsocheck tool
>        LoongArch: vDSO: Enable the vdsocheck tool
>        s390/vdso: Enable the vdsocheck tool
>        MIPS: ELF: Add more PC-relative relocation definitions
>        MIPS: vdso: Enable the vdsocheck tool
>        vdso/vdsocheck: Drop the transitional kconfig option
> 
>   arch/arm/include/asm/elf.h          |  24 --
>   arch/arm/vdso/Makefile              |   4 +-
>   arch/arm64/include/asm/elf.h        |  55 ----
>   arch/arm64/kernel/vdso/Makefile     |   4 +-
>   arch/loongarch/include/asm/elf.h    | 100 ------
>   arch/loongarch/vdso/Makefile        |   4 +-
>   arch/mips/include/asm/elf.h         |  53 ---
>   arch/mips/vdso/Makefile             |   8 +-
>   arch/powerpc/include/uapi/asm/elf.h | 201 ------------
>   arch/powerpc/kernel/vdso/Makefile   |   4 +-
>   arch/riscv/include/uapi/asm/elf.h   |  66 ----
>   arch/riscv/kernel/vdso/Makefile     |  11 +-
>   arch/s390/include/asm/elf.h         |  83 -----
>   arch/s390/kernel/vdso32/Makefile    |   4 +-
>   arch/s390/kernel/vdso64/Makefile    |   4 +-
>   arch/x86/entry/vdso/Makefile        |   6 +-
>   arch/x86/include/asm/elf.h          |  34 --
>   arch/x86/um/asm/elf.h               |  33 --
>   include/uapi/linux/elf-r.h          | 631 ++++++++++++++++++++++++++++++++++++
>   include/uapi/linux/elf.h            |   1 +
>   lib/vdso/Makefile                   |   2 +
>   lib/vdso/Makefile.include           |  17 +
>   lib/vdso/check/.gitignore           |   3 +
>   lib/vdso/check/Makefile             |  28 ++
>   lib/vdso/check/elf.rs               | 488 ++++++++++++++++++++++++++++
>   lib/vdso/check/vdsocheck.rs         | 279 ++++++++++++++++
>   tools/include/uapi/linux/elf-em.h   |  71 ++++
>   tools/include/uapi/linux/elf-r.h    | 631 ++++++++++++++++++++++++++++++++++++
>   tools/include/uapi/linux/elf.h      | 112 ++++++-
>   29 files changed, 2277 insertions(+), 684 deletions(-)
> ---
> base-commit: 5180c6526acc9f1cb58f8b11fba67583c22e0854
> change-id: 20250428-vdso-absolute-reloc-a226293c1761
> 
> Best regards,

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