BFD: Fix the bug of R_LARCH_AGLIN caused by discard section

To represent the first and third expression of .align, R_LARCH_ALIGN need to
associate with a symbol. We define a local symbol for R_LARCH_AGLIN.
But if the section of the local symbol is discarded, it may result in
a undefined symbol error.

Instead, we use the section name symbols, and this does not need to
add extra symbols.

During partial linking (ld -r), if the symbol associated with a relocation is
STT_SECTION type, the addend of relocation needs to add the section output
offset. We prevent it for R_LARCH_ALIGN.

The elf_backend_data.rela_normal only can set all relocations of a target to
rela_normal. Add a new function is_rela_normal to elf_backend_data, it can
set part of relocations to rela_normal.

4 files changed, 29 insertions, 1 deletions

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index c5d3254..af507b9 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -1721,6 +1721,10 @@ struct elf_backend_data
      backend relocate_section routine for relocatable linking.  */
   unsigned rela_normal : 1;
 
+  /* Whether a relocation is rela_normal. Compared with rela_normal,
+     is_rela_normal can set part of relocations to rela_normal.  */
+  bool (*is_rela_normal) (Elf_Internal_Rela *);
+
   /* Set if DT_REL/DT_RELA/DT_RELSZ/DT_RELASZ should not include PLT
      relocations.  */
   unsigned dtrel_excludes_plt : 1;
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 24eb30d..5d9b409 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -11692,7 +11692,10 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
 		    {
 		      rel_hash = PTR_ADD (esdo->rela.hashes, esdo->rela.count);
 		      rela_hash_list = rel_hash;
-		      rela_normal = bed->rela_normal;
+		      if (bed->is_rela_normal != NULL)
+			rela_normal = bed->is_rela_normal (irela);
+		      else
+			rela_normal = bed->rela_normal;
 		    }
 
 		  irela->r_offset = _bfd_elf_section_offset (output_bfd,
diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
index c42052f..1679aa5 100644
--- a/bfd/elfnn-loongarch.c
+++ b/bfd/elfnn-loongarch.c
@@ -5454,6 +5454,21 @@ elf_loongarch64_hash_symbol (struct elf_link_hash_entry *h)
   return _bfd_elf_hash_symbol (h);
 }
 
+/* If a relocation is rela_normal and the symbol associated with the
+   relocation is STT_SECTION type, the addend of the relocation would add
+   sec->output_offset when partial linking (ld -r).
+   See elf_backend_data.rela_normal and elf_link_input_bfd().
+   The addend of R_LARCH_ALIGN is used to represent the first and third
+   expression of .align, it should be a constant when linking.  */
+
+static bool
+loongarch_elf_is_rela_normal (Elf_Internal_Rela *rel)
+{
+  if (R_LARCH_ALIGN == ELFNN_R_TYPE (rel->r_info))
+    return false;
+  return true;
+}
+
 #define TARGET_LITTLE_SYM loongarch_elfNN_vec
 #define TARGET_LITTLE_NAME "elfNN-loongarch"
 #define ELF_ARCH bfd_arch_loongarch
@@ -5489,6 +5504,7 @@ elf_loongarch64_hash_symbol (struct elf_link_hash_entry *h)
 #define elf_backend_grok_psinfo loongarch_elf_grok_psinfo
 #define elf_backend_hash_symbol elf_loongarch64_hash_symbol
 #define bfd_elfNN_bfd_relax_section loongarch_elf_relax_section
+#define elf_backend_is_rela_normal loongarch_elf_is_rela_normal
 
 #define elf_backend_dtrel_excludes_plt 1
 
diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h
index 1e6992b..6e2d948 100644
--- a/bfd/elfxx-target.h
+++ b/bfd/elfxx-target.h
@@ -709,6 +709,10 @@
 #define elf_backend_rela_normal 0
 #endif
 
+#ifndef elf_backend_is_rela_normal
+#define elf_backend_is_rela_normal NULL
+#endif
+
 #ifndef elf_backend_dtrel_excludes_plt
 #define elf_backend_dtrel_excludes_plt 0
 #endif
@@ -955,6 +959,7 @@ static const struct elf_backend_data elfNN_bed =
   elf_backend_default_use_rela_p,
   elf_backend_rela_plts_and_copies_p,
   elf_backend_rela_normal,
+  elf_backend_is_rela_normal,
   elf_backend_dtrel_excludes_plt,
   elf_backend_sign_extend_vma,
   elf_backend_want_got_plt,