From: H.J. Lu <hjl.tools@gmail.com>
Date: Thu, 14 Aug 2025 14:03:20 +0000 (-0700)
Subject: x86-64: Add GLIBC_ABI_DT_X86_64_PLT [BZ #33212]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fheads%2Frelease%2F2.38%2Fmaster;p=thirdparty%2Fglibc.git

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 f8587a61892cbafd98ce599131bf4f103466f084
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>
(cherry picked from commit 399384e0c8193e31aea014220ccfa24300ae5938)
---

diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
index 00120ca9ca..105a9a431e 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -175,6 +175,15 @@ ifeq (no,$(build-hardcoded-path-in-tests))
 tests-container += tst-glibc-hwcaps-cache
 endif
 
+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
+
 endif # $(subdir) == elf
 
 ifeq ($(subdir),csu)
diff --git a/sysdeps/x86_64/Versions b/sysdeps/x86_64/Versions
index e94758b236..6a989ad3b3 100644
--- a/sysdeps/x86_64/Versions
+++ b/sysdeps/x86_64/Versions
@@ -5,6 +5,11 @@ libc {
   GLIBC_2.13 {
     __fentry__;
   }
+  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 {