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%2F2.41%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 21f1ff1167..15fb72a952 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -212,6 +212,15 @@ 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
diff --git a/sysdeps/x86_64/Versions b/sysdeps/x86_64/Versions
index a63c11bcb2..0a759029e5 100644
--- a/sysdeps/x86_64/Versions
+++ b/sysdeps/x86_64/Versions
@@ -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 {