Bug#1122107: dpkg-shlibdeps: please consider symbol versions from '.gnu.version_r' section

Guillem Jover <[email protected]> Mon, 8 Dec 2025 01:45:28 +0100

Newsgroups	gmane.linux.debian.devel.dpkg.bugs
Message-ID	<aTYfqOyiNgK0152D__46792.4584330589$1765154848$gmane$org@thunder.hadrons.org>

Hi!

On Sun, 2025-12-07 at 12:04:40 +0100, Aurelien Jarno wrote:
> Package: dpkg-dev
> Version: 1.22.21
> Severity: wishlist
> Control: block 1122038 by -1

> When symbol versioning is in use, the '.gnu.version_r' section records
> all symbol version requirements declared by the binary for each of its
> shared library dependencies. At runtime, ld.so checks that all symbol
> versions are provided by the target library and refuse to run if a
> required symbol version is missing. 
> 
> On its side, dpkg-shlibdeps computes versioned dependencies only from
> the versions used by the symbols (from the '.dynsym' section).  This
> works fine as long as every symbol version required by the binary is
> also reference by at least one symbol.
> 
> Unfortunately, recent binutils and glibc versions started to use the
> symbol version requirements from section '.gnu.version_r' as ABI flags,
> meaning they do not have symbols associated with them. For instance the
> 'GLIBC_ABI_GNU_TLS' symbol on i386, which triggered the issue in bug
> #1122038. It is not seen by dpkg-shlibdeps, causing the generated
> dependency on libc6 to be lower than what is actually need at runtime,
> and the binary fails to start with older glibc.
> 
> Would it be possible for dpkg-shlibdeps to handle the requirements found
> in the '.gnu.version_r' section? In the above case it means that an
> entry for GLIBC_ABI_GNU_TLS in the '.gnu.version_r' section would match
> the ' GLIBC_ABI_GNU_TLS@GLIBC_ABI_GNU_TLS 2.42' in the symbols file.

Ah, hmm, that's unfortunate. The attached patch seems to fix this for
me (once I removed the workaround from the libc6:i386.symbols file
from the chroot. I've queued the patch for my next push, which will be
part of the 1.23.0 release.

Thanks,
Guillem

0001-Dpkg-Shlibs-Objdump-Object-Add-support-for-Version-R.patch (text/x-diff, 2.5 KB)

From ae5057e32f399759ea13f715e79e305747226fe2 Mon Sep 17 00:00:00 2001
From: Guillem Jover <[email protected]>
Date: Mon, 8 Dec 2025 01:23:23 +0100
Subject: [PATCH] Dpkg::Shlibs::Objdump::Object: Add support for "Version
 References" symbols

New binutils can emit dependencies on specific versions via the
DT_VERNEED tags in the .gnu.version_r section. But these dependencies
are not exposed in the Dynamic Symbol Table.

Inject those dependencies as if they were normal undefined symbols into
the object metadata.

Closes: #1122107
---
 scripts/Dpkg/Shlibs/Objdump/Object.pm | 36 +++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/scripts/Dpkg/Shlibs/Objdump/Object.pm b/scripts/Dpkg/Shlibs/Objdump/Object.pm
index cc635a24e..63e944ffd 100644
--- a/scripts/Dpkg/Shlibs/Objdump/Object.pm
+++ b/scripts/Dpkg/Shlibs/Objdump/Object.pm
@@ -109,6 +109,7 @@ sub parse_objdump_output {
     my ($self, $fh) = @_;
 
     my $section = 'none';
+    my $verneed_lib = undef;
     while (<$fh>) {
         s/\s*$//;
         next if length == 0;
@@ -164,6 +165,12 @@ sub parse_objdump_output {
                     $self->{RPATH} = [ split /:/, $rpath ];
                 }
             }
+        } elsif ($section eq 'verref') {
+            if (/^\s*required from ([^:]*):/) {
+                $verneed_lib = $1;
+            } elsif (/^\s*0x[[:xdigit:]]*\s*0x[[:xdigit:]]*\s*\d*\s*(.*)/) {
+                $self->add_verneed_symbol($verneed_lib, $1);
+            }
         } elsif ($section eq 'program') {
             if (/^\s*INTERP\s+/) {
                 $self->{INTERP} = 1;
@@ -307,6 +314,35 @@ sub apply_relocations {
     }
 }
 
+# Inject the version reference dependency as an undefined symbol into the
+# dynamic symbol information.
+#
+# We do not currently use the $solib name, which would denote a stronger
+# tighter dependency on a specific shared object, but for now this should
+# suffice.
+sub add_verneed_symbol($self, $solib, $name)
+{
+    my $symbol = {
+        name => $name,
+        version => $name,
+        section => '*UND*',
+        dynamic => 1,
+        debug => 0,
+        type => 'O',
+        weak => 0,
+        local => 0,
+        global => 1,
+        visibility => '',
+        hidden => '',
+        defined => 0,
+    };
+
+    # Register artificial symbol.
+    $self->add_dynamic_symbol($symbol);
+
+    return;
+}
+
 sub add_dynamic_symbol {
     my ($self, $symbol) = @_;
     $symbol->{objid} = $symbol->{soname} = $self->get_id();
-- 
2.51.0