RISC-V: Fix that IRELATIVE relocs may be inserted to the wrong place.

For the ifunc symbol, which is referenced by GOT rather than PLT relocs,
we should add the dynamic reloc (usually IRELATIVE) into the .rel.iplt
when generating the static executable.  But if we use riscv_elf_append_rela
to add the dynamic relocs into .rela.iplt, this may cause the overwrite
problem.

The reason is that we don't handle the `reloc_index` of .rela.iplt, but
the riscv_elf_append_rela adds the relocs to the place that are calculated
from the reloc_index (in seqential).  Therefore, we may overwrite the
dynamic relocs when the `reloc_index` of .rela.iplt isn't handled correctly.

One solution is that we can add these dynamic relocs (GOT ifunc) from
the last of .rela.iplt section.  But I'm not sure if it is the best way.

	bfd/
	* elfnn-riscv.c (riscv_elf_link_hash_table): Add last_iplt_index.
	(riscv_elf_size_dynamic_sections): Initialize the last_iplt_index.
	(riscv_elf_relocate_section): Use riscv_elf_append_rela.
	(riscv_elf_finish_dynamic_symbol): If the use_elf_append_rela is
	false, then we should add the dynamic relocs from the last of
	the .rela.iplt, and don't use the riscv_elf_append_rela to add.

	ld/
	* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.s: New testcase.
	* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.d: Likewise.
	* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-exe.rd: Likewise.
	* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pic.rd: Likewise.
	* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pie.rd: Likewise.
	* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.

1 files changed, 39 insertions, 7 deletions

diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index a26cd3f..a5b2c8a 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -120,6 +120,9 @@ struct riscv_elf_link_hash_table
   /* Used by local STT_GNU_IFUNC symbols.  */
   htab_t loc_hash_table;
   void * loc_hash_memory;
+
+  /* The index of the last unused .rel.iplt slot.  */
+  bfd_vma last_iplt_index;
 };
 
 
@@ -1424,6 +1427,11 @@ riscv_elf_size_dynamic_sections (bfd *output_bfd, struct bfd_link_info *info)
      local ifunc symbols.  */
   htab_traverse (htab->loc_hash_table, allocate_local_ifunc_dynrelocs, info);
 
+  /* Used to resolve the dynamic relocs overwite problems when
+     generating static executable.  */
+  if (htab->elf.irelplt)
+    htab->last_iplt_index = htab->elf.irelplt->reloc_count - 1;
+
   if (htab->elf.sgotplt)
     {
       struct elf_link_hash_entry *got;
@@ -2904,6 +2912,7 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
       asection *sgot;
       asection *srela;
       Elf_Internal_Rela rela;
+      bfd_boolean use_elf_append_rela = TRUE;
 
       /* This symbol has an entry in the GOT.  Set it up.  */
 
@@ -2920,12 +2929,18 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
 	  if (h->plt.offset == (bfd_vma) -1)
 	    {
 	      /* STT_GNU_IFUNC is referenced without PLT.  */
+
 	      if (htab->elf.splt == NULL)
 		{
-		  /* use .rel[a].iplt section to store .got relocations
+		  /* Use .rela.iplt section to store .got relocations
 		     in static executable.  */
 		  srela = htab->elf.irelplt;
+
+		  /* Do not use riscv_elf_append_rela to add dynamic
+		     relocs.  */
+		  use_elf_append_rela = FALSE;
 		}
+
 	      if (SYMBOL_REFERENCES_LOCAL (info, h))
 		{
 		  info->callbacks->minfo (_("Local IFUNC function `%s' in %pB\n"),
@@ -2973,14 +2988,14 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
 	      return TRUE;
 	    }
 	}
-      /* If this is a local symbol reference, we just want to emit a RELATIVE
-	 reloc.  This can happen if it is a -Bsymbolic link, or a pie link, or
-	 the symbol was forced to be local because of a version file.
-	 The entry in the global offset table will already have been
-	 initialized in the relocate_section function.  */
       else if (bfd_link_pic (info)
 	       && SYMBOL_REFERENCES_LOCAL (info, h))
 	{
+	  /* If this is a local symbol reference, we just want to emit
+	     a RELATIVE reloc.  This can happen if it is a -Bsymbolic link,
+	     or a pie link, or the symbol was forced to be local because
+	     of a version file.  The entry in the global offset table will
+	     already have been initialized in the relocate_section function.  */
 	  BFD_ASSERT((h->got.offset & 1) != 0);
 	  asection *sec = h->root.u.def.section;
 	  rela.r_info = ELFNN_R_INFO (0, R_RISCV_RELATIVE);
@@ -2998,7 +3013,24 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
 
       bfd_put_NN (output_bfd, 0,
 		  sgot->contents + (h->got.offset & ~(bfd_vma) 1));
-      riscv_elf_append_rela (output_bfd, srela, &rela);
+
+      if (use_elf_append_rela)
+	riscv_elf_append_rela (output_bfd, srela, &rela);
+      else
+	{
+	  /* Use riscv_elf_append_rela to add the dynamic relocs into
+	     .rela.iplt may cause the overwrite problems.  Since we insert
+	     the relocs for PLT didn't handle the reloc_index of .rela.iplt,
+	     but the riscv_elf_append_rela adds the relocs to the place
+	     that are calculated from the reloc_index (in seqential).
+
+	     One solution is that add these dynamic relocs (GOT IFUNC)
+	     from the last of .rela.iplt section.  */
+	  bfd_vma iplt_idx = htab->last_iplt_index--;
+	  bfd_byte *loc = srela->contents
+			  + iplt_idx * sizeof (ElfNN_External_Rela);
+	  bed->s->swap_reloca_out (output_bfd, &rela, loc);
+	}
     }
 
   if (h->needs_copy)