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From: "i at maskray dot me" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug dynamic-link/27924] ld.so: Support DT_RELR relative relocation
 format
Date: Thu, 27 May 2021 19:01:46 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27924

--- Comment #1 from Fangrui Song <i at maskray dot me> ---
It is probably well-known that position independent executables have many
relative relocations.

If the Distribution adopts -Bsymbolic-non-weak-functions (safer alternative
-Bsymbolic-functions which respects pointer equality for C++ vague linkage
definitions), shared objects can benefit a lot as well
https://sourceware.org/bugzilla/show_bug.cgi?id=3D27871

Here is an example of libLLVM-13git.so

# -Bsymbolic-functions (-Bsymbolic-non-weak-functions is similar since
-fvisibility-inlines-hidden is already used)
% llvm-readelf -WS symbolic.so | egrep 'Nr|\.rel[ar]'
  [Nr] Name              Type            Address          Off    Size   ES =
Flg
Lk Inf Al
  [ 8] .rela.dyn         RELA            00000000003c8d60 3c8d60 27d368 18 =
  A=20
1   0  8
  [ 9] .rela.plt         RELA            00000000006460c8 6460c8 0020a0 18 =
 AI=20
1  25  8

# -Bsymbolic-functions --pack-dyn-relocs=3Drelr
% llvm-readelf -WS relr.so | egrep 'Nr|\.rel[ar]'=20=20=20=20
  [Nr] Name              Type            Address          Off    Size   ES =
Flg
Lk Inf Al
  [ 8] .rela.dyn         RELA            00000000003c8d60 3c8d60 016bd8 18 =
  A=20
1   0  8
  [ 9] .relr.dyn         RELR            00000000003df938 3df938 007ba8 08 =
  A=20
0   0  8
  [10] .rela.plt         RELA            00000000003e74e0 3e74e0 0020a0 18 =
 AI=20
1  26  8

--=20
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