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x86-64: Add GLIBC_ABI_DT_X86_64_PLT [BZ #33212] 

When the linker -z mark-plt option is used to add DT_X86_64_PLT,
DT_X86_64_PLTSZ and DT_X86_64_PLTENT, the r_addend field of the
R_X86_64_JUMP_SLOT relocation stores the offset of the indirect
branch instruction.  However, glibc versions without the commit:

commit f8587a6189
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Fri May 20 19:21:48 2022 -0700

    x86-64: Ignore r_addend for R_X86_64_GLOB_DAT/R_X86_64_JUMP_SLOT

    According to x86-64 psABI, r_addend should be ignored for R_X86_64_GLOB_DAT
    and R_X86_64_JUMP_SLOT.  Since linkers always set their r_addends to 0, we
    can ignore their r_addends.

    Reviewed-by: Fangrui Song <maskray@google.com>

won't ignore the r_addend value in the R_X86_64_JUMP_SLOT relocation.
Such programs and shared libraries will fail at run-time randomly.

Add GLIBC_ABI_DT_X86_64_PLT version to indicate that glibc is compatible
with DT_X86_64_PLT.

The linker can add the glibc GLIBC_ABI_DT_X86_64_PLT version dependency
whenever -z mark-plt is passed to the linker.  The resulting programs and
shared libraries will fail to load at run-time against libc.so without the
GLIBC_ABI_DT_X86_64_PLT version, instead of fail randomly.

This fixes BZ #33212.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
This commit is contained in:
H.J. Lu 2025-08-14 07:03:20 -07:00
parent ed1b7a5a48
commit 399384e0c8
2 changed files with 14 additions and 0 deletions
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9
sysdeps/x86_64/Makefile
View File

@ -214,6 +214,15 @@ LDFLAGS-tst-plt-rewritemod2.so = -Wl,-z,now,-z,undefs
tst-plt-rewrite2-ENV = GLIBC_TUNABLES=glibc.cpu.plt_rewrite=2
$(objpfx)tst-plt-rewrite2: $(objpfx)tst-plt-rewritemod2.so
tests-special += $(objpfx)check-dt-x86-64-plt.out
$(objpfx)check-dt-x86-64-plt.out: $(common-objpfx)libc.so
LC_ALL=C $(READELF) -V -W $< \
| sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \
| grep GLIBC_ABI_DT_X86_64_PLT > $@; \
$(evaluate-test)
generated += check-dt-x86-64-plt.out
tests-special += $(objpfx)check-gnu2-tls.out
$(objpfx)check-gnu2-tls.out: $(common-objpfx)libc.so

5
sysdeps/x86_64/Versions
View File

@ -10,6 +10,11 @@ libc {
# by scripts/versions.awk.
__placeholder_only_for_empty_version_map;
}
GLIBC_ABI_DT_X86_64_PLT {
# This symbol is used only for empty version map and will be removed
# by scripts/versions.awk.
__placeholder_only_for_empty_version_map;
}
}
libm {
GLIBC_2.1 {