Messages in this thread | | | Date | Mon, 14 Nov 2022 16:46:25 -0800 | From | Fangrui Song <> | Subject | Re: [PATCH] vdso: Improve cmd_vdso_check to check all dynamic relocations |
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On 2022-11-14, Christophe Leroy wrote: > > >Le 28/09/2022 à 07:25, Fangrui Song a écrit : >> On Sat, Sep 10, 2022 at 12:53 AM Fangrui Song <maskray@google.com> wrote: >>> >>> On 2022-08-30, Fangrui Song wrote: >>>> The actual intention is that no dynamic relocation exists. However, some >>>> GNU ld ports produce unneeded R_*_NONE. (If a port is not care enough to >>>> determine the exact .rel[a].dyn size, the trailing zeros become R_*_NONE >>>> relocations. E.g. powerpc64le ld as of 2.38 has the issue with >>>> defconfig.) 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.) >>>> >>>> While here, replace "egrep" with "grep" as "egrep" is deprecated in GNU >>>> grep 3.7. >>>> >>>> Signed-off-by: Fangrui Song <maskray@google.com> >>>> --- >>>> [...] >>>> >>> >>> Ping. >> >> Ping^2 :) > >Can you explain which ARCH_REL_TYPE_ABS can be removed with this change ? >How is the verification done if ARCH_REL_TYPE_ABS is removed ?
All ARCH_REL_TYPE_ABS relocation types can be removed. As explained, the real intention is to check no dynamic relocation, and this is done by the new
cmd_vdso_check = if $(READELF) -rW $@ | grep -v _NONE | grep -q "R_\w*_"; \
in this patch.
grep -v _NONE is to work around some GNU ld ports (and likely older releases of some ports even if their latest versions are fixed) which produce unneeded R_*_NONE dynamic relocations.
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