[binutils-gdb] ld: print branch fixups into the map file for ppc elf targets

[binutils-gdb] ld: print branch fixups into the map file for ppc elf targets

[Cl?ment Chigot]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=fb2908093576cc469c5ee8404070c8521631c019

commit fb2908093576cc469c5ee8404070c8521631c019
Author: Clément Chigot <chigot@adacore.com>
Date:   Mon Nov 6 10:50:23 2023 +0100

    ld: print branch fixups into the map file for ppc elf targets
    
    In a safety context, it could interesting to track the trampolines being
    generated, ensuring there are expected or not.
    
    bfd/ChangeLog:
    
            * elf32-ppc.c (ppc_elf_relax_section): Log branch fixups.
    
    ld/ChangeLog:
    
            * ld.texi (--print-map): Add new item about fixups.

Diff:
---
 bfd/elf32-ppc.c | 12 +++++++++---
 ld/ld.texi      | 11 +++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 5622aaa30c0..bdbd1b4fb36 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -6169,7 +6169,7 @@ ppc_elf_relax_section (bfd *abfd,
 	  asection *tsec;
 	  struct one_branch_fixup *f;
 	  size_t insn_offset = 0;
-	  bfd_vma max_branch_offset = 0, val;
+	  bfd_vma max_branch_offset = 0, val, reladdr;
 	  bfd_byte *hit_addr;
 	  unsigned long t0;
 	  struct elf_link_hash_entry *h;
@@ -6415,6 +6415,7 @@ ppc_elf_relax_section (bfd *abfd,
 	    continue;
 
 	  roff = irel->r_offset;
+	  reladdr = isec->output_section->vma + isec->output_offset + roff;
 
 	  /* Avoid creating a lot of unnecessary fixups when
 	     relocatable if the output section size is such that a
@@ -6433,10 +6434,9 @@ ppc_elf_relax_section (bfd *abfd,
 		     final link, so do not presume they remain in range.  */
 		  || tsec->output_section == isec->output_section))
 	    {
-	      bfd_vma symaddr, reladdr;
+	      bfd_vma symaddr;
 
 	      symaddr = tsec->output_section->vma + tsec->output_offset + toff;
-	      reladdr = isec->output_section->vma + isec->output_offset + roff;
 	      if (symaddr - reladdr + max_branch_offset
 		  < 2 * max_branch_offset)
 		continue;
@@ -6507,6 +6507,12 @@ ppc_elf_relax_section (bfd *abfd,
 	      irel->r_info = ELF32_R_INFO (0, R_PPC_NONE);
 	    }
 
+	  link_info->callbacks->minfo
+	    (_("%pB: Adjusting branch at 0x%V towards \"%s\" in section %s\n"),
+	     abfd, reladdr,
+	     (h && h->root.root.string? h->root.root.string : "<unknown>"),
+	     f->tsec->name);
+
 	  /* Get the section contents.  */
 	  if (contents == NULL)
 	    {
diff --git a/ld/ld.texi b/ld/ld.texi
index f710c02c3d4..1c132561d71 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -920,6 +920,17 @@ Updated property 0xc0010001 (0x1) to merge foo.o (0x1) and bar.o (0x1)
 This indicates that property 0xc0010001 value is updated to 0x1 in output
 when merging properties in  @file{foo.o}, whose 0xc0010001 property value
 is 0x1, and @file{bar.o}, whose 0xc0010001 property value is 0x1.
+
+@item
+On some ELF targets, a list of fixups inserted by @option{--relax}
+
+@smallexample
+foo.o: Adjusting branch at 0x00000008 towards "far" in section .text
+@end smallexample
+
+This indicates that the branch at 0x00000008 in foo.o, targeting
+the symbol "far" in section .text, has been replaced by a trampoline.
+
 @end itemize
 
 @cindex link map discarded