elf: Add -z unique-symbol to avoid duplicated local symbol names

The symbol string table in the .symtab section is optional and cosmetic.
The contents of the .symtab section have no impact on run-time execution.
The symbol names in the symbol string table help distinguish addresses at
different locations.  Add a linker option, -z unique-symbol, to avoid
duplicated local symbol names in the symbol string table.

This feature was well received by the livepatch maintainers.  It not only
solves the duplicated local symbol name problem, but also would allow
livepatch to more precisely locate duplicate symbols in general for
patching.

bfd/

	PR ld/26391
	* elflink.c (elf_final_link_info): Add local_hash_table.
	(local_hash_entry): New.
	(local_hash_newfunc): Likewise.
	(elf_link_output_symstrtab): Append ".COUNT" to duplicated local
	symbols.
	(bfd_elf_final_link): Initialize and free local_hash_table for
	"-z unique-symbol".

include/

	PR ld/26391
	* bfdlink.h (bfd_link_info): Add unique_symbol.

ld/

	PR ld/26391
	* NEWS: Mention "-z unique-symbol".
	* emultempl/elf.em (gld${EMULATION_NAME}_handle_option): Handle
	"-z unique-symbol" and "-z nounique-symbol".
	* ld.texi: Document "-z unique-symbol" and "-z nounique-symbol".
	* lexsup.c (elf_static_list_options): Add "-z unique-symbol" and
	"-z nounique-symbol".
	* testsuite/ld-elf/elf.exp: Add PR ld/26391 tests.
	* testsuite/ld-elf/pr26391.nd: New file.
	* testsuite/ld-elf/pr26391.out: Likewise.
	* testsuite/ld-elf/pr26391a.c: Likewise.
	* testsuite/ld-elf/pr26391b.c: Likewise.
	* testsuite/ld-elf/pr26391c.c: Likewise.
	* testsuite/ld-elf/pr26391d.c: Likewise.

7 files changed, 188 insertions, 0 deletions

diff --git a/ld/testsuite/ld-elf/elf.exp b/ld/testsuite/ld-elf/elf.exp
index c0d67d8..f2ff039 100644
--- a/ld/testsuite/ld-elf/elf.exp
+++ b/ld/testsuite/ld-elf/elf.exp
@@ -359,4 +359,125 @@ if { [istarget *-*-linux*]
 
 run_ld_link_exec_tests $array_tests_static $xfails
 
+run_cc_link_tests [list \
+    [list \
+	"Build pr26391-1" \
+	"-Wl,-z,unique-symbol" \
+	"-fno-function-sections" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	{{nm "" pr26391.nd}} \
+	"pr26391-1" \
+    ] \
+    [list \
+	"Build pr26391-2" \
+	"-Wl,-z,unique-symbol" \
+	"-ffunction-sections" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	{{nm "" pr26391.nd}} \
+	"pr26391-2" \
+    ] \
+    [list \
+	"Build pr26391-3" \
+	"-Wl,-z,unique-symbol,--emit-relocs" \
+	"-fno-function-sections" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	{{nm "" pr26391.nd}} \
+	"pr26391-3" \
+    ] \
+    [list \
+	"Build pr26391-4" \
+	"-Wl,-z,unique-symbol,--emit-relocs" \
+	"-ffunction-sections" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	{{nm "" pr26391.nd}} \
+	"pr26391-4" \
+    ] \
+]
+
+run_ld_link_tests [list \
+    [list \
+	"Build pr26391-5.o" \
+	"-z unique-symbol -r" \
+	"" \
+	"" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	{{nm "" pr26391.nd}} \
+	"pr26391-5.o" \
+	"-fno-function-sections" \
+    ] \
+    [list \
+	"Build pr26391-6.o" \
+	"-z unique-symbol -r" \
+	"" \
+	"" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	{{nm "" pr26391.nd}} \
+	"pr26391-6.o" \
+	"-ffunction-sections" \
+    ] \
+]
+
+run_ld_link_exec_tests [list \
+    [list \
+	"Run pr26391-1" \
+	"-Wl,-z,unique-symbol" \
+	"" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	"pr26391-1" \
+	"pr26391.out" \
+	"-fno-function-sections" \
+    ] \
+    [list \
+	"Run pr26391-2" \
+	"-Wl,-z,unique-symbol" \
+	"" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	"pr26391-2" \
+	"pr26391.out" \
+	"-ffunction-sections" \
+    ] \
+    [list \
+	"Run pr26391-3" \
+	"-Wl,-z,unique-symbol,--emit-relocs" \
+	"" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	"pr26391-3" \
+	"pr26391.out" \
+	"-fno-function-sections" \
+    ] \
+    [list \
+	"Run pr26391-4" \
+	"-Wl,-z,unique-symbol,--emit-relocs" \
+	"" \
+	{pr26391a.c pr26391b.c pr26391c.c pr26391d.c} \
+	"pr26391-4" \
+	"pr26391.out" \
+	"-ffunction-sections" \
+    ] \
+    [list \
+	"Run pr26391-5" \
+	"-Wl,-z,unique-symbol" \
+	"" \
+	{dummy.c} \
+	"pr26391-5" \
+	"pr26391.out" \
+	"" \
+	"c" \
+	"" \
+	"tmpdir/pr26391-5.o" \
+    ] \
+    [list \
+	"Run pr26391-6" \
+	"-Wl,-z,unique-symbol" \
+	"" \
+	{dummy.c} \
+	"pr26391-6" \
+	"pr26391.out" \
+	"" \
+	"c" \
+	"" \
+	"tmpdir/pr26391-6.o" \
+    ] \
+]
+
 catch "exec rm -f tmpdir/preinit tmpdir/init tmpdir/fini tmpdir/init-mixed" status
diff --git a/ld/testsuite/ld-elf/pr26391.nd b/ld/testsuite/ld-elf/pr26391.nd
new file mode 100644
index 0000000..8dd48d9
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr26391.nd
@@ -0,0 +1,7 @@
+#...
+[0-9a-z]+ t _?bar
+#...
+[0-9a-z]+ t _?bar.1
+#...
+[0-9a-z]+ t _?bar.2
+#pass
diff --git a/ld/testsuite/ld-elf/pr26391.out b/ld/testsuite/ld-elf/pr26391.out
new file mode 100644
index 0000000..73654ee
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr26391.out
@@ -0,0 +1,3 @@
+bar 1
+bar 2
+bar 3
diff --git a/ld/testsuite/ld-elf/pr26391a.c b/ld/testsuite/ld-elf/pr26391a.c
new file mode 100644
index 0000000..7356d9d
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr26391a.c
@@ -0,0 +1,18 @@
+typedef void (*func_p) (void);
+
+extern func_p bar1_p (void);
+extern func_p bar2_p (void);
+extern func_p bar3_p (void);
+
+int
+main ()
+{
+  func_p f;
+  f = bar1_p ();
+  f ();
+  f = bar2_p ();
+  f ();
+  f = bar3_p ();
+  f ();
+  return 0;
+}
diff --git a/ld/testsuite/ld-elf/pr26391b.c b/ld/testsuite/ld-elf/pr26391b.c
new file mode 100644
index 0000000..8f716a5
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr26391b.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+static void
+bar (void)
+{
+  printf ("bar 1\n");
+}
+
+void *
+bar1_p (void)
+{
+  return bar;
+}
diff --git a/ld/testsuite/ld-elf/pr26391c.c b/ld/testsuite/ld-elf/pr26391c.c
new file mode 100644
index 0000000..e5bf1c1
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr26391c.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+static void
+bar (void)
+{
+  printf ("bar 2\n");
+}
+
+void *
+bar2_p (void)
+{
+  return bar;
+}
diff --git a/ld/testsuite/ld-elf/pr26391d.c b/ld/testsuite/ld-elf/pr26391d.c
new file mode 100644
index 0000000..6e388f8
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr26391d.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+static void
+bar (void)
+{
+  printf ("bar 3\n");
+}
+
+void *
+bar3_p (void)
+{
+  return bar;
+}