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

[Fangrui Song <maskray@google.com>]

On Thu, Dec 29, 2022 at 11:22 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> 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!

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