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* vdso function descriptors (VDS64_HAS_DESCRIPTORS)?
@ 2020-02-17 16:08 Joe Lawrence
  2020-02-23  0:07 ` Segher Boessenkool
  0 siblings, 1 reply; 8+ messages in thread
From: Joe Lawrence @ 2020-02-17 16:08 UTC (permalink / raw)
  To: linuxppc-dev

I was wondering if there was history behind VDS64_HAS_DESCRIPTORS and in
what cases would one want to turn them on?  (Note, I'm assuming they are
an implementation of Function Descriptors. [1])

arch/powerpc/include/asm/vdso.h unsets the macro:

  /* Define if 64 bits VDSO has procedure descriptors */
  #undef VDS64_HAS_DESCRIPTORS

so I don't believe they are ever used by default -- in this case
V_FUNCTION_BEGIN doesn't add to the .opd section with .name, .TOC base,
etc.

Manually setting VDS64_HAS_DESCRIPTORS results in a vdso64.so in which
binutils tools like readelf properly report functions with symbol type
FUNC instead of NOTYPE.

Are there pieces of the build/etc toolchain unprepared for function
descriptors?  I'm just trying to figure out why the code defaults to
unsetting them.

Thanks,

-- Joe


[1] http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html#FUNC-DES


^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2020-03-17 13:37 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-02-17 16:08 vdso function descriptors (VDS64_HAS_DESCRIPTORS)? Joe Lawrence
2020-02-23  0:07 ` Segher Boessenkool
2020-02-24 10:17   ` Benjamin Herrenschmidt
2020-02-24 15:20     ` Joe Lawrence
2020-02-24 15:34       ` Benjamin Herrenschmidt
2020-02-24 21:18         ` [PATCH] powerpc/vdso: remove deprecated VDS64_HAS_DESCRIPTORS references Joe Lawrence
2020-02-24 23:37           ` Michael Ellerman
2020-03-17 13:14           ` Michael Ellerman

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