RISC-V: Implement support for big endian targets.

RISC-V instruction/code is always little endian, but data might be
big-endian.  Therefore, we can not use the original bfd_get/bfd_put
to get/put the code for big endian targets.  Add new riscv_get_insn
and riscv_put_insn to always get/put code as little endian can resolve
the problem.  Just remember to update them once we have supported
the 48-bit/128-bit instructions in the future patches.

bfd/
    * config.bfd: Added targets riscv64be*-*-*, riscv32be*-*-* and
    riscvbe*-*-*.  Also added riscv_elf[32|64]_be_vec.
    * configure.ac: Handle riscv_elf[32|64]_be_vec.
    * configure: Regenerate.
    * elfnn-riscv.c: Include <limits.h> and define CHAR_BIT for
    riscv_is_insn_reloc.
    (riscv_get_insn): RISC-V instructions are always little endian, but
    bfd_get may be used for big-endian, so add new riscv_get_insn to handle
    the insturctions.
    (riscv_put_insn): Likewsie.
    (riscv_is_insn_reloc): Check if we are relocaing an instruction.
    (perform_relocation): Call riscv_is_insn_reloc to decide if we should
    use riscv_[get|put]_insn or bfd_[get|put].
    (riscv_zero_pcrel_hi_reloc): Use riscv_[get|put]_insn, bfd_[get|put]l32
    or bfd_[get|put]l16 for code.
    (riscv_elf_relocate_section): Likewise.
    (riscv_elf_finish_dynamic_symbol): Likewise.
    (riscv_elf_finish_dynamic_sections): Likewise.
    (_bfd_riscv_relax_call): Likewise.
    (_bfd_riscv_relax_lui): Likewise.
    (_bfd_riscv_relax_align): Likewise.
    (_bfd_riscv_relax_pc): Likewise.
    (riscv_elf_object_p): Handled for big endian.
    (TARGET_BIG_SYM, TARGET_BIG_NAME): Defined.
    * targets.c: Add riscv_elf[32|64]_be_vec.
    (_bfd_target_vector): Likewise.

gas/
    * config/tc-riscv.c (riscv_target_format): Add elf64-bigriscv and
    elf32-bigriscv.
    (install_insn): Always write instructions as little endian.
    (riscv_make_nops): Likewise.
    (md_convert_frag_branch): Likewise.
    (md_number_to_chars): Write data in target endianness.
    (options, md_longopts): Add -mbig-endian and -mlittle-endian options.
    (md_parse_option): Handle the endian options.
    * config/tc-riscv.h: Only define TARGET_BYTES_BIG_ENDIAN if not
    already defined.
    * configure.tgt: Added riscv64be*, riscv32be*, riscvbe*.

ld/
    * configure.tgt: Added riscvbe-*-*, riscv32be*-*-*, riscv64be*-*-*,
    riscv32be*-*-linux*, and riscv64be*-*-linux*.
    * Makefile.am: Added eelf32briscv.c, eelf32briscv_ilp32f.c and
    eelf32briscv_ilp32.c.
    * Makefile.in: Regenerate.
    * emulparams/elf32briscv.sh: Added.
    * emulparams/elf32briscv_ilp32.sh: Likewise.
    * emulparams/elf32briscv_ilp32f.sh: Likewise.
    * emulparams/elf64briscv.sh: Likewise.
    * emulparams/elf64briscv_lp64.sh: Likewise.
    * emulparams/elf64briscv_lp64f.sh: Likewise.

2 files changed, 27 insertions, 7 deletions

diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index e938a88..55d5f1b 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -445,7 +445,10 @@ static char *expr_end;
 const char *
 riscv_target_format (void)
 {
-  return xlen == 64 ? "elf64-littleriscv" : "elf32-littleriscv";
+  if (target_big_endian)
+    return xlen == 64 ? "elf64-bigriscv" : "elf32-bigriscv";
+  else
+    return xlen == 64 ? "elf64-littleriscv" : "elf32-littleriscv";
 }
 
 /* Return the length of instruction INSN.  */
@@ -474,7 +477,7 @@ static void
 install_insn (const struct riscv_cl_insn *insn)
 {
   char *f = insn->frag->fr_literal + insn->where;
-  md_number_to_chars (f, insn->insn_opcode, insn_length (insn));
+  number_to_chars_littleendian (f, insn->insn_opcode, insn_length (insn));
 }
 
 /* Move INSN to offset WHERE in FRAG.  Adjust the fixups accordingly
@@ -2662,7 +2665,10 @@ md_atof (int type, char *litP, int *sizeP)
 void
 md_number_to_chars (char *buf, valueT val, int n)
 {
-  number_to_chars_littleendian (buf, val, n);
+  if (target_big_endian)
+    number_to_chars_bigendian (buf, val, n);
+  else
+    number_to_chars_littleendian (buf, val, n);
 }
 
 const char *md_shortopts = "O::g::G:";
@@ -2681,6 +2687,8 @@ enum options
   OPTION_NO_CSR_CHECK,
   OPTION_MISA_SPEC,
   OPTION_MPRIV_SPEC,
+  OPTION_BIG_ENDIAN,
+  OPTION_LITTLE_ENDIAN,
   OPTION_END_OF_ENUM
 };
 
@@ -2699,6 +2707,8 @@ struct option md_longopts[] =
   {"mno-csr-check", no_argument, NULL, OPTION_NO_CSR_CHECK},
   {"misa-spec", required_argument, NULL, OPTION_MISA_SPEC},
   {"mpriv-spec", required_argument, NULL, OPTION_MPRIV_SPEC},
+  {"mbig-endian", no_argument, NULL, OPTION_BIG_ENDIAN},
+  {"mlittle-endian", no_argument, NULL, OPTION_LITTLE_ENDIAN},
 
   {NULL, no_argument, NULL, 0}
 };
@@ -2777,6 +2787,14 @@ md_parse_option (int c, const char *arg)
     case OPTION_MPRIV_SPEC:
       return riscv_set_default_priv_spec (arg);
 
+    case OPTION_BIG_ENDIAN:
+      target_big_endian = 1;
+      break;
+
+    case OPTION_LITTLE_ENDIAN:
+      target_big_endian = 0;
+      break;
+
     default:
       return 0;
     }
@@ -3258,13 +3276,13 @@ riscv_make_nops (char *buf, bfd_vma bytes)
   /* Use at most one 2-byte NOP.  */
   if ((bytes - i) % 4 == 2)
     {
-      md_number_to_chars (buf + i, RVC_NOP, 2);
+      number_to_chars_littleendian (buf + i, RVC_NOP, 2);
       i += 2;
     }
 
   /* Fill the remainder with 4-byte NOPs.  */
   for ( ; i < bytes; i += 4)
-    md_number_to_chars (buf + i, RISCV_NOP, 4);
+    number_to_chars_littleendian (buf + i, RISCV_NOP, 4);
 }
 
 /* Called from md_do_align.  Used to create an alignment frag in a
@@ -3468,14 +3486,14 @@ md_convert_frag_branch (fragS *fragp)
       insn = bfd_getl32 (buf);
       insn ^= MATCH_BEQ ^ MATCH_BNE;
       insn |= ENCODE_SBTYPE_IMM (8);
-      md_number_to_chars ((char *) buf, insn, 4);
+      bfd_putl32 (insn, buf);
       buf += 4;
 
     jump:
       /* Jump to the target.  */
       fixp = fix_new_exp (fragp, buf - (bfd_byte *)fragp->fr_literal,
 			  4, &exp, FALSE, BFD_RELOC_RISCV_JMP);
-      md_number_to_chars ((char *) buf, MATCH_JAL, 4);
+      bfd_putl32 (MATCH_JAL, buf);
       buf += 4;
       break;
 
diff --git a/gas/config/tc-riscv.h b/gas/config/tc-riscv.h
index a503fc5..6f20288 100644
--- a/gas/config/tc-riscv.h
+++ b/gas/config/tc-riscv.h
@@ -28,7 +28,9 @@
 struct frag;
 struct expressionS;
 
+#ifndef TARGET_BYTES_BIG_ENDIAN
 #define TARGET_BYTES_BIG_ENDIAN 0
+#endif
 
 #define TARGET_ARCH bfd_arch_riscv