linux-kernel - Re: [PATCH v2] vdso: Improve cmd_vdso_check to check all dynamic relocations

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Date:   Thu, 29 Dec 2022 08:22:24 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     maskray@...gle.com
CC:     christophe.leroy@...roup.eu, luto@...nel.org, tglx@...utronix.de,
        vincenzo.frascino@....com, Arnd Bergmann <arnd@...db.de>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-csky@...r.kernel.org, linux-mips@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-riscv@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org
Subject:     Re: [PATCH v2] vdso: Improve cmd_vdso_check to check all dynamic relocations

On Wed, 21 Dec 2022 15:51:47 PST (-0800), maskray@...gle.com wrote:
> The actual intention is that no dynamic relocation exists. However, some
> GNU ld ports produce unneeded R_*_NONE. (If a port fails to determine
> the exact .rel[a].dyn size, the trailing zeros become R_*_NONE
> relocations. E.g. ld's powerpc port recently fixed
> https://sourceware.org/bugzilla/show_bug.cgi?id=29540) R_*_NONE are
> generally no-op in the dynamic loaders. So just ignore them.
>
> With the change, we can remove ARCH_REL_TYPE_ABS. ARCH_REL_TYPE_ABS is a
> bit misnomer as ports may check RELAVETIVE/GLOB_DAT/JUMP_SLOT which are
> not called "absolute relocations". (The patch is motivated by the arm64
> port missing R_AARCH64_RELATIVE.)
>
> Signed-off-by: Fangrui Song <maskray@...gle.com>
> Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
> Change from v1:
> * rebase after 8ac3b5cd3e0521d92f9755e90d140382fc292510 (lib/vdso: use "grep -E" instead of "egrep")
> * change the commit message to mention an example GNU ld bug; no longer say the patch fixes a deprecated egrep use
> ---
>   arch/arm/vdso/Makefile            |  3 ---
>   arch/arm64/kernel/vdso/Makefile   |  3 ---
>   arch/arm64/kernel/vdso32/Makefile |  3 ---
>   arch/csky/kernel/vdso/Makefile    |  3 ---
>   arch/loongarch/vdso/Makefile      |  3 ---
>   arch/mips/vdso/Makefile           |  3 ---
>   arch/powerpc/kernel/vdso/Makefile |  1 -
>   arch/riscv/kernel/vdso/Makefile   |  3 ---
>   arch/s390/kernel/vdso32/Makefile  |  2 --
>   arch/s390/kernel/vdso64/Makefile  |  2 --
>   arch/x86/entry/vdso/Makefile      |  4 ----
>   lib/vdso/Makefile                 | 13 ++++---------
>   12 files changed, 4 insertions(+), 39 deletions(-)

[snip]

> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index 06e6b27f3bcc..d85c37e11b21 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -1,9 +1,6 @@
>   # SPDX-License-Identifier: GPL-2.0-only
>   # Copied from arch/tile/kernel/vdso/Makefile
>
> -# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
> -# the inclusion of generic Makefile.
> -ARCH_REL_TYPE_ABS := R_RISCV_32|R_RISCV_64|R_RISCV_JUMP_SLOT
>   include $(srctree)/lib/vdso/Makefile
>   # Symbols present in the vdso
>   vdso-syms  = rt_sigreturn

Acked-by: Palmer Dabbelt <palmer@...osinc.com> # RISC-V

Thanks!