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.

1 files changed, 7 insertions, 0 deletions

diff --git a/bfd/elflink.c b/bfd/elflink.c
index 30a572d..3add9f1 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -13365,6 +13365,13 @@ _bfd_elf_gc_mark_extra_sections (struct bfd_link_info *info,
 	      && (isec->flags & SEC_DEBUGGING)
 	      && CONST_STRNEQ (isec->name, ".debug_line."))
 	    debug_frag_seen = TRUE;
+	  else if (strcmp (bfd_section_name (isec),
+			   "__patchable_function_entries") == 0
+		   && elf_linked_to_section (isec) == NULL)
+	      info->callbacks->einfo (_("%F%P: %pB(%pA): error: "
+					"need linked-to section "
+					"for --gc-sections\n"),
+				      isec->owner, isec);
 	}
 
       /* If no non-note alloc section in this file will be kept, then