[binutils-gdb] Arm64/ELF: accept relocations against STN_UNDEF

[binutils-gdb] Arm64/ELF: accept relocations against STN_UNDEF

[Jan Beulich]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=af9eb2ee1b10caa89e1c603cd484bc025e71f4fd

commit af9eb2ee1b10caa89e1c603cd484bc025e71f4fd
Author: Jan Beulich <jbeulich@suse.com>
Date:   Fri Mar 31 08:15:53 2023 +0200

    Arm64/ELF: accept relocations against STN_UNDEF
    
    While only a secondary issue there, the testcase of PR gas/27212 exposes
    an oversight in relocation handling: Just like e.g. Arm32, which has a
    similar comment and a similar check, relocations against STN_UNDEF have
    to be permitted to satisfy the ELF spec.

Diff:
---
 bfd/elfnn-aarch64.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index c4db1e6f168..c23cbd3601a 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -6946,8 +6946,12 @@ elfNN_aarch64_relocate_section (bfd *output_bfd,
 
 	  /* An object file might have a reference to a local
 	     undefined symbol.  This is a daft object file, but we
-	     should at least do something about it.  */
+	     should at least do something about it.  NONE and NULL
+	     relocations do not use the symbol and are explicitly
+	     allowed to use an undefined one, so allow those.
+	     Likewise for relocations against STN_UNDEF.  */
 	  if (r_type != R_AARCH64_NONE && r_type != R_AARCH64_NULL
+	      && r_symndx != STN_UNDEF
 	      && bfd_is_und_section (sec)
 	      && ELF_ST_BIND (sym->st_info) != STB_WEAK)
 	    (*info->callbacks->undefined_symbol)