Improve handling of ADD and SUB relocations on the RISCV target.

	* elfxx-riscv.c (riscv_elf_add_sub_reloc): New function.
	* (howto_table) [R_RISCV_ADD8]: Use riscv_elf_add_sub_reloc.
	[R_RISCV_ADD16]: Likewise.
	[R_RISCV_ADD32]: Likewise.
	[R_RISCV_ADD64]: Likewise.
	[R_RISCV_SUB6]: Likewise.
	[R_RISCV_SUB8]: Likewise.
	[R_RISCV_SUB16]: Likewise.
	[R_RISCV_SUB32]: Likewise.
	[R_RISCV_SUB64]: Likewise.

2 files changed, 80 insertions, 9 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 9839a3487f..1c0c65b58c 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,16 @@
+2017-07-31  Kuan-Lin Chen  <rufus@andestech.com>
+
+	* elfxx-riscv.c (riscv_elf_add_sub_reloc): New function.
+	* (howto_table) [R_RISCV_ADD8]: Use riscv_elf_add_sub_reloc.
+	[R_RISCV_ADD16]: Likewise.
+	[R_RISCV_ADD32]: Likewise.
+	[R_RISCV_ADD64]: Likewise.
+	[R_RISCV_SUB6]: Likewise.
+	[R_RISCV_SUB8]: Likewise.
+	[R_RISCV_SUB16]: Likewise.
+	[R_RISCV_SUB32]: Likewise.
+	[R_RISCV_SUB64]: Likewise.
+
 2017-07-31  Alan Modra  <amodra@gmail.com>
 
 	* elf64-ppc.c (ppc64_elf_tls_setup): Warn on --plt-localentry
diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index 5fa98f37e9..55db39218e 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -32,6 +32,13 @@
 
 #define MINUS_ONE ((bfd_vma)0 - 1)
 
+/* Special handler for ADD/SUB relocations that allows them to be filled out
+   both in the pre-linked and post-linked file.  This is necessary to make
+   pre-linked debug info work, as due to linker relaxations we need to emit
+   relocations for the debug info.  */
+static bfd_reloc_status_type riscv_elf_add_sub_reloc
+  (bfd *, arelent *, asymbol *, void *, asection *, bfd *, char **);
+
 /* The relocation table used for SHT_RELA sections.  */
 
 static reloc_howto_type howto_table[] =
@@ -480,7 +487,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_ADD8",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -495,7 +502,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_ADD16",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -510,7 +517,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_ADD32",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -525,7 +532,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_ADD64",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -540,7 +547,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_SUB8",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -555,7 +562,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_SUB16",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -570,7 +577,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_SUB32",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -585,7 +592,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_SUB64",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -767,7 +774,7 @@ static reloc_howto_type howto_table[] =
 	 FALSE,				/* pc_relative */
 	 0,				/* bitpos */
 	 complain_overflow_dont,	/* complain_on_overflow */
-	 bfd_elf_generic_reloc,		/* special_function */
+	 riscv_elf_add_sub_reloc,	/* special_function */
 	 "R_RISCV_SUB6",		/* name */
 	 FALSE,				/* partial_inplace */
 	 0,				/* src_mask */
@@ -951,3 +958,54 @@ riscv_elf_rtype_to_howto (unsigned int r_type)
     }
   return &howto_table[r_type];
 }
+
+/* Special_function of RISCV_ADD and RISCV_SUB relocations.  */
+
+static bfd_reloc_status_type
+riscv_elf_add_sub_reloc (bfd *abfd,
+			 arelent *reloc_entry,
+			 asymbol *symbol,
+			 void *data,
+			 asection *input_section,
+			 bfd *output_bfd,
+			 char **error_message ATTRIBUTE_UNUSED)
+{
+  reloc_howto_type *howto = reloc_entry->howto;
+  bfd_vma relocation;
+
+  if (output_bfd != NULL
+      && (symbol->flags & BSF_SECTION_SYM) == 0
+      && (!reloc_entry->howto->partial_inplace || reloc_entry->addend == 0))
+    {
+      reloc_entry->address += input_section->output_offset;
+      return bfd_reloc_ok;
+    }
+
+  if (output_bfd != NULL)
+    return bfd_reloc_continue;
+
+  relocation = symbol->value + symbol->section->output_section->vma
+    + symbol->section->output_offset + reloc_entry->addend;
+  bfd_vma old_value = bfd_get (howto->bitsize, abfd,
+			       data + reloc_entry->address);
+
+  switch (howto->type)
+    {
+    case R_RISCV_ADD8:
+    case R_RISCV_ADD16:
+    case R_RISCV_ADD32:
+    case R_RISCV_ADD64:
+      relocation = old_value + relocation;
+      break;
+    case R_RISCV_SUB6:
+    case R_RISCV_SUB8:
+    case R_RISCV_SUB16:
+    case R_RISCV_SUB32:
+    case R_RISCV_SUB64:
+      relocation = old_value - relocation;
+      break;
+    }
+  bfd_put (howto->bitsize, abfd, relocation, data + reloc_entry->address);
+
+  return bfd_reloc_ok;
+}