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

Palmer Dabbelt
2022-12-29T16:23:22Z

On Wed, 21 Dec 2022 15:51:47 PST (-0800), maskray@google.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@google.com>
> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.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@rivosinc.com> # RISC-V

Thanks!