ld: Issue an error for GC on __patchable_function_entries section

__patchable_function_entries section is generated by a compiler with
-fpatchable-function-entry=XX.  The assembly code looks like this:

---
	.text
	.globl	_start
	.type	_start, %function
_start:
	.section __patchable_function_entries,"aw",%progbits
	.dc.a	.LPFE1
	.text
.LPFE1:
	.byte 0
---

But --gc-sections will silently remove __patchable_function_entries
section and generate corrupt result.  This patch disallows garbage
collection on __patchable_function_entries section without linked-to
section.

bfd/

	PR ld/25490
	* elflink.c (_bfd_elf_gc_mark_extra_sections): Issue an error
	for garbage collection on __patchable_function_entries section
	without linked-to section.

ld/

	PR ld/25490
	* testsuite/ld-elf/pr25490-1.d: New file.
	* testsuite/ld-elf/pr25490-1.s: Likewise.

2 files changed, 12 insertions, 0 deletions

diff --git a/ld/testsuite/ld-elf/pr25490-1.d b/ld/testsuite/ld-elf/pr25490-1.d
new file mode 100644
index 0000000..3f58264
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr25490-1.d
@@ -0,0 +1,3 @@
+#ld: --gc-sections -e _start
+#target: [check_gc_sections_available]
+#error: .*\(__patchable_function_entries\): error: need linked-to section for --gc-sections
diff --git a/ld/testsuite/ld-elf/pr25490-1.s b/ld/testsuite/ld-elf/pr25490-1.s
new file mode 100644
index 0000000..51ba1ea
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr25490-1.s
@@ -0,0 +1,9 @@
+	.text
+	.globl	_start
+	.type	_start, %function
+_start:
+	.section	__patchable_function_entries,"aw",%progbits
+	.dc.a	.LPFE1
+	.text
+.LPFE1:
+	.byte 0