elf: Discard input .note.gnu.build-id sections

1. Discard input .note.gnu.build-id sections.
2. Clear the build ID field before writing.
3. Use bfd_make_section_anyway_with_flags to create the output
.note.gnu.build-id section.

	PR ld/28639
	* ldelf.c (ldelf_after_open): Discard input .note.gnu.build-id
	sections, excluding the first one.
	(write_build_id): Clear the build ID field before writing.
	(ldelf_setup_build_id): Use bfd_make_section_anyway_with_flags
	to create the output .note.gnu.build-id section.
	* testsuite/ld-elf/build-id.exp: New file.
	* testsuite/ld-elf/pr28639a.rd: Likewise.
	* testsuite/ld-elf/pr28639b.rd: Likewise.
	* testsuite/ld-elf/pr28639c.rd: Likewise.
	* testsuite/ld-elf/pr28639d.rd: Likewise.

5 files changed, 103 insertions, 0 deletions

diff --git a/ld/testsuite/ld-elf/build-id.exp b/ld/testsuite/ld-elf/build-id.exp
new file mode 100644
index 0000000..19c22a7
--- /dev/null
+++ b/ld/testsuite/ld-elf/build-id.exp
@@ -0,0 +1,77 @@
+# Expect script for --build-id tests.
+#   Copyright (C) 2021 Free Software Foundation, Inc.
+#
+# This file is part of the GNU Binutils.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+# MA 02110-1301, USA.
+#
+
+# Exclude non-ELF targets.
+
+if ![is_elf_format] {
+    return
+}
+
+if { [istarget frv-*-*] || [istarget lm32-*-*] } {
+    return
+}
+
+if { !([istarget *-*-linux*]
+       || [istarget arm*-*-uclinuxfdpiceabi]
+       || [istarget *-*-nacl*]
+       || [istarget *-*-gnu*]) } then {
+    return
+}
+
+run_ld_link_tests [list \
+    [list \
+	"pr28639a.o" \
+	"-r --build-id=md5" \
+	"" \
+	"" \
+	{start.s} \
+	{{readelf {--notes} pr28639a.rd}} \
+	"pr28639a.o" \
+    ] \
+    [list \
+	"pr28639a.o" \
+	"-r --build-id" \
+	"" \
+	"" \
+	{dummy.s} \
+	{{readelf {--notes} pr28639b.rd}} \
+	"pr28639b.o" \
+    ] \
+    [list \
+	"pr28639a" \
+	"--build-id tmpdir/pr28639a.o tmpdir/pr28639b.o" \
+	"" \
+	"" \
+	{dummy.s} \
+	{{readelf {--notes} pr28639b.rd}  \
+	 {readelf {--notes} pr28639c.rd}} \
+	"pr28639a" \
+    ] \
+    [list \
+	"pr28639b" \
+	"--build-id=none tmpdir/pr28639a.o tmpdir/pr28639b.o" \
+	"" \
+	"" \
+	{dummy.s} \
+	{{readelf {--notes} pr28639d.rd}} \
+	"pr28639b" \
+    ] \
+]
diff --git a/ld/testsuite/ld-elf/pr28639a.rd b/ld/testsuite/ld-elf/pr28639a.rd
new file mode 100644
index 0000000..e850870
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr28639a.rd
@@ -0,0 +1,6 @@
+#...
+Displaying notes found in: \.note\.gnu\.build-id
+  Owner                Data size 	Description
+  GNU                  0x00000010	NT_GNU_BUILD_ID \(unique build ID bitstring\)
+    Build ID: [0-9a-f]+
+#pass
diff --git a/ld/testsuite/ld-elf/pr28639b.rd b/ld/testsuite/ld-elf/pr28639b.rd
new file mode 100644
index 0000000..04dcb04
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr28639b.rd
@@ -0,0 +1,6 @@
+#...
+Displaying notes found in: \.note\.gnu\.build-id
+  Owner                Data size 	Description
+  GNU                  0x00000014	NT_GNU_BUILD_ID \(unique build ID bitstring\)
+    Build ID: [0-9a-f]+
+#pass
diff --git a/ld/testsuite/ld-elf/pr28639c.rd b/ld/testsuite/ld-elf/pr28639c.rd
new file mode 100644
index 0000000..64221e5
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr28639c.rd
@@ -0,0 +1,10 @@
+#failif
+#...
+Displaying notes found in: \.note\.gnu\.build-id
+  Owner                Data size 	Description
+  GNU                  0x[0-9a-f]+	NT_GNU_BUILD_ID \(unique build ID bitstring\)
+    Build ID: [0-9a-f]+
+  Owner                Data size 	Description
+  GNU                  0x[0-9a-f]+	NT_GNU_BUILD_ID \(unique build ID bitstring\)
+    Build ID: [0-9a-f]+
+#...
diff --git a/ld/testsuite/ld-elf/pr28639d.rd b/ld/testsuite/ld-elf/pr28639d.rd
new file mode 100644
index 0000000..897c849
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr28639d.rd
@@ -0,0 +1,4 @@
+#failif
+#...
+Displaying notes found in: \.note\.gnu\.build-id
+#...