Preserve some symbols in libc.so.6's symtab (#1965374)

glibc.spec

@@ -97,7 +97,7 @@
 Summary: The GNU libc libraries
 Name: glibc
 Version: %{glibcversion}
-Release: 15%{?dist}
+Release: 16%{?dist}
 
 # In general, GPLv2+ is used by programs, LGPLv2+ is used for
 # libraries.
@@ -2186,6 +2186,9 @@ fi
 %files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
 
 %changelog
+* Tue Jun 15 2021 Florian Weimer <fweimer@redhat.com> - 2.33.9000-16
+- Preserve some symbols in libc.so.6's symtab (#1965374)
+
 * Tue Jun 15 2021 Florian Weimer <fweimer@redhat.com> - 2.33.9000-15
 - Install shared objects under their ABI names, avoiding symlinks (#1652867)
 

wrap-find-debuginfo.sh

@@ -9,10 +9,14 @@
 # LDSO-PATH file, followed by note merging and DWZ compression.
 # As a result, ld.so has (mostly) unchanged debuginfo even
 # after debuginfo extraction.
+#
+# For libc.so.6, a set of strategic symbols is preserved in .symtab
+# that are frequently used in valgrind suppressions.
 
 set -ex
 
 ldso_tmp="$(mktemp)"
+libc_tmp="$(mktemp)"
 
 # Prefer a separately installed debugedit over the RPM-integrated one.
 if command -v debugedit >/dev/null ; then
@@ -22,7 +26,7 @@ else
 fi
 
 cleanup () {
-    rm -f "$ldso_tmp"
+    rm -f "$ldso_tmp" "$libc_tmp"
 }
 trap cleanup 0
 
@@ -43,21 +47,50 @@ for ldso_candidate in `find "$sysroot_path" -regextype posix-extended \
     fi
 done
 
-# Preserve the original file.
+# libc.so.6 always uses this name, so it is simpler to locate.
+libc_path=
+for libc_candidate in `find "$sysroot_path" -name libc.so.6`; do
+    if test -z "$libc_path" ; then
+	libc_path="$libc_candidate"
+    else
+	echo "error: multiple libc.so.6 candidates: $libc_path, $libc_candidate"
+	exit 1
+    fi
+done
+
+
+# Preserve the original files.
 cp "$ldso_path" "$ldso_tmp"
+cp "$libc_path" "$libc_tmp"
 
 # Run the debuginfo extraction.
 "$script_path" "$@"
 
-# Restore the original file.
+# Restore the original files.
 cp "$ldso_tmp" "$ldso_path"
+cp "$libc_tmp" "$libc_path"
 
 # Reduce the size of notes.  Primarily for annobin.
 objcopy --merge-notes "$ldso_path"
+objcopy --merge-notes "$libc_path"
 
-# Rewrite the source file paths to match the extracted locations.
-# First compute the arguments for invoking debugedit.  See
-# find-debuginfo.sh.
+# libc.so.6: Reduce to strategic symbols needed by valgrind.
+# (Debuginfo is gone after this, so no need to optimize it.)
+strip -w \
+      -K '*vfprintf*' \
+      -K '__bzero*' \
+      -K '__mem*' \
+      -K '__rawmemchr*' \
+      -K '__stp*' \
+      -K '__str*' \
+      -K '__wcs*' \
+      -K '__wmem*' \
+      -K '_nl_make_l10nflist' \
+      "$libc_path"
+
+# ld.so: Rewrite the source file paths to match the extracted
+# locations.  First compute the arguments for invoking debugedit.
+# See find-debuginfo.sh.
 debug_dest_name="/usr/src/debug"
 last_arg=
 while true ; do