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.

Author: zeldin

bfd/ChangeLog

@@ -1,3 +1,32 @@
+2021-01-06  Marcus Comstedt  <[email protected]>
+
+	* 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.
+
 2021-01-05  Alan Modra  <[email protected]>
 
 	* elflink.c (bfd_elf_link_record_dynamic_symbol): Handle no_export

bfd/config.bfd

@@ -1158,14 +1158,24 @@ case "${targ}" in
     ;;
 
 #ifdef BFD64
+  riscvbe-*-* | riscv32be*-*-*)
+    targ_defvec=riscv_elf32_be_vec
+    targ_selvecs="riscv_elf32_vec riscv_elf64_vec riscv_elf32_be_vec riscv_elf64_be_vec"
+    want64=true
+    ;;
   riscv-*-* | riscv32*-*-*)
     targ_defvec=riscv_elf32_vec
-    targ_selvecs="riscv_elf32_vec riscv_elf64_vec"
+    targ_selvecs="riscv_elf32_vec riscv_elf64_vec riscv_elf32_be_vec riscv_elf64_be_vec"
+    want64=true
+    ;;
+  riscv64be*-*-*)
+    targ_defvec=riscv_elf64_be_vec
+    targ_selvecs="riscv_elf32_vec riscv_elf64_vec riscv_elf32_be_vec riscv_elf64_be_vec"
     want64=true
     ;;
   riscv64*-*-*)
     targ_defvec=riscv_elf64_vec
-    targ_selvecs="riscv_elf32_vec riscv_elf64_vec"
+    targ_selvecs="riscv_elf32_vec riscv_elf64_vec riscv_elf32_be_vec riscv_elf64_be_vec"
     want64=true
     ;;
 #endif

bfd/configure

@@ -14919,6 +14919,8 @@ do
     pru_elf32_vec)		 tb="$tb elf32-pru.lo elf32.lo $elf" ;;
     riscv_elf32_vec)		 tb="$tb elf32-riscv.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf" ;;
     riscv_elf64_vec)		 tb="$tb elf64-riscv.lo elf64.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf"; target_size=64 ;;
+    riscv_elf32_be_vec)		 tb="$tb elf32-riscv.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf" ;;
+    riscv_elf64_be_vec)		 tb="$tb elf64-riscv.lo elf64.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf"; target_size=64 ;;
     rl78_elf32_vec)		 tb="$tb elf32-rl78.lo elf32.lo $elf" ;;
     rs6000_xcoff64_vec)		 tb="$tb coff64-rs6000.lo aix5ppc-core.lo $xcoff"; target_size=64 ;;
     rs6000_xcoff64_aix_vec)	 tb="$tb coff64-rs6000.lo aix5ppc-core.lo $xcoff"; target_size=64 ;;

bfd/configure.ac

@@ -625,6 +625,8 @@ do
     pru_elf32_vec)		 tb="$tb elf32-pru.lo elf32.lo $elf" ;;
     riscv_elf32_vec)		 tb="$tb elf32-riscv.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf" ;;
     riscv_elf64_vec)		 tb="$tb elf64-riscv.lo elf64.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf"; target_size=64 ;;
+    riscv_elf32_be_vec)		 tb="$tb elf32-riscv.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf" ;;
+    riscv_elf64_be_vec)		 tb="$tb elf64-riscv.lo elf64.lo elfxx-riscv.lo elf-ifunc.lo elf32.lo $elf"; target_size=64 ;;
     rl78_elf32_vec)		 tb="$tb elf32-rl78.lo elf32.lo $elf" ;;
     rs6000_xcoff64_vec)		 tb="$tb coff64-rs6000.lo aix5ppc-core.lo $xcoff"; target_size=64 ;;
     rs6000_xcoff64_aix_vec)	 tb="$tb coff64-rs6000.lo aix5ppc-core.lo $xcoff"; target_size=64 ;;

bfd/elfnn-riscv.c

@@ -33,6 +33,13 @@
 #include "opcode/riscv.h"
 #include "objalloc.h"
 
+#ifdef HAVE_LIMITS_H
+#include <limits.h>
+#endif
+#ifndef CHAR_BIT
+#define CHAR_BIT 8
+#endif
+
 /* Internal relocations used exclusively by the relaxation pass.  */
 #define R_RISCV_DELETE (R_RISCV_max + 1)
 
@@ -125,6 +132,18 @@ struct riscv_elf_link_hash_table
   bfd_vma last_iplt_index;
 };
 
+/* Instruction access functions. */
+
+#define riscv_get_insn(bits, ptr)		\
+  ((bits) == 16 ? bfd_getl16 (ptr)		\
+   : (bits) == 32 ? bfd_getl32 (ptr)		\
+   : (bits) == 64 ? bfd_getl64 (ptr)		\
+   : (abort (), (bfd_vma) - 1))
+#define riscv_put_insn(bits, val, ptr)		\
+  ((bits) == 16 ? bfd_putl16 (val, ptr)		\
+   : (bits) == 32 ? bfd_putl32 (val, ptr)	\
+   : (bits) == 64 ? bfd_putl64 (val, ptr)	\
+   : (abort (), (void) 0))
 
 /* Get the RISC-V ELF linker hash table from a link_info structure.  */
 #define riscv_elf_hash_table(p) \
@@ -152,6 +171,19 @@ riscv_elf_append_rela (bfd *abfd, asection *s, Elf_Internal_Rela *rel)
   bed->s->swap_reloca_out (abfd, rel, loc);
 }
 
+/* Return true if a relocation is modifying an instruction. */
+
+static bfd_boolean
+riscv_is_insn_reloc (const reloc_howto_type *howto)
+{
+  /* Heuristic: A multibyte destination with a nontrivial mask
+     is an instruction */
+  return (howto->bitsize > 8
+	  && howto->dst_mask != 0
+	  && ~(howto->dst_mask | (howto->bitsize < sizeof(bfd_vma) * CHAR_BIT
+	       ? (MINUS_ONE << howto->bitsize) : (bfd_vma)0)) != 0);
+}
+
 /* PLT/GOT stuff.  */
 
 #define PLT_HEADER_INSNS 8
@@ -1645,10 +1677,10 @@ perform_relocation (const reloc_howto_type *howto,
 	  /* Linker relaxation can convert an address equal to or greater than
 	     0x800 to slightly below 0x800.  C.LUI does not accept zero as a
 	     valid immediate.  We can fix this by converting it to a C.LI.  */
-	  bfd_vma insn = bfd_get (howto->bitsize, input_bfd,
-				  contents + rel->r_offset);
+	  bfd_vma insn = riscv_get_insn (howto->bitsize,
+					 contents + rel->r_offset);
 	  insn = (insn & ~MATCH_C_LUI) | MATCH_C_LI;
-	  bfd_put (howto->bitsize, input_bfd, insn, contents + rel->r_offset);
+	  riscv_put_insn (howto->bitsize, insn, contents + rel->r_offset);
 	  value = ENCODE_RVC_IMM (0);
 	}
       else if (!VALID_RVC_LUI_IMM (RISCV_CONST_HIGH_PART (value)))
@@ -1684,9 +1716,16 @@ perform_relocation (const reloc_howto_type *howto,
       return bfd_reloc_notsupported;
     }
 
-  bfd_vma word = bfd_get (howto->bitsize, input_bfd, contents + rel->r_offset);
+  bfd_vma word;
+  if (riscv_is_insn_reloc (howto))
+    word = riscv_get_insn (howto->bitsize, contents + rel->r_offset);
+  else
+    word = bfd_get (howto->bitsize, input_bfd, contents + rel->r_offset);
   word = (word & ~howto->dst_mask) | (value & howto->dst_mask);
-  bfd_put (howto->bitsize, input_bfd, word, contents + rel->r_offset);
+  if (riscv_is_insn_reloc (howto))
+    riscv_put_insn (howto->bitsize, word, contents + rel->r_offset);
+  else
+    bfd_put (howto->bitsize, input_bfd, word, contents + rel->r_offset);
 
   return bfd_reloc_ok;
 }
@@ -1764,7 +1803,7 @@ riscv_zero_pcrel_hi_reloc (Elf_Internal_Rela *rel,
 			   bfd_vma addr,
 			   bfd_byte *contents,
 			   const reloc_howto_type *howto,
-			   bfd *input_bfd)
+			   bfd *input_bfd ATTRIBUTE_UNUSED)
 {
   /* We may need to reference low addreses in PC-relative modes even when the
    * PC is far away from these addresses.  For example, undefweak references
@@ -1790,9 +1829,9 @@ riscv_zero_pcrel_hi_reloc (Elf_Internal_Rela *rel,
 
   rel->r_info = ELFNN_R_INFO(addr, R_RISCV_HI20);
 
-  bfd_vma insn = bfd_get(howto->bitsize, input_bfd, contents + rel->r_offset);
+  bfd_vma insn = riscv_get_insn(howto->bitsize, contents + rel->r_offset);
   insn = (insn & ~MASK_AUIPC) | MATCH_LUI;
-  bfd_put(howto->bitsize, input_bfd, insn, contents + rel->r_offset);
+  riscv_put_insn(howto->bitsize, insn, contents + rel->r_offset);
   return TRUE;
 }
 
@@ -2380,10 +2419,9 @@ riscv_elf_relocate_section (bfd *output_bfd,
 	      && (!bfd_link_pic (info) || h->plt.offset == MINUS_ONE))
 	    {
 	      /* We can use x0 as the base register.  */
-	      bfd_vma insn = bfd_get_32 (input_bfd,
-					 contents + rel->r_offset + 4);
+	      bfd_vma insn = bfd_getl32 (contents + rel->r_offset + 4);
 	      insn &= ~(OP_MASK_RS1 << OP_SH_RS1);
-	      bfd_put_32 (input_bfd, insn, contents + rel->r_offset + 4);
+	      bfd_putl32 (insn, contents + rel->r_offset + 4);
 	      /* Set the relocation value so that we get 0 after the pc
 		 relative adjustment.  */
 	      relocation = sec_addr (input_section) + rel->r_offset;
@@ -2416,10 +2454,10 @@ riscv_elf_relocate_section (bfd *output_bfd,
 	  if (VALID_ITYPE_IMM (relocation + rel->r_addend))
 	    {
 	      /* We can use tp as the base register.  */
-	      bfd_vma insn = bfd_get_32 (input_bfd, contents + rel->r_offset);
+	      bfd_vma insn = bfd_getl32 (contents + rel->r_offset);
 	      insn &= ~(OP_MASK_RS1 << OP_SH_RS1);
 	      insn |= X_TP << OP_SH_RS1;
-	      bfd_put_32 (input_bfd, insn, contents + rel->r_offset);
+	      bfd_putl32 (insn, contents + rel->r_offset);
 	    }
 	  else
 	    r = bfd_reloc_overflow;
@@ -2433,14 +2471,14 @@ riscv_elf_relocate_section (bfd *output_bfd,
 	    if (x0_base || VALID_ITYPE_IMM (relocation + rel->r_addend - gp))
 	      {
 		/* We can use x0 or gp as the base register.  */
-		bfd_vma insn = bfd_get_32 (input_bfd, contents + rel->r_offset);
+		bfd_vma insn = bfd_getl32 (contents + rel->r_offset);
 		insn &= ~(OP_MASK_RS1 << OP_SH_RS1);
 		if (!x0_base)
 		  {
 		    rel->r_addend -= gp;
 		    insn |= X_GP << OP_SH_RS1;
 		  }
-		bfd_put_32 (input_bfd, insn, contents + rel->r_offset);
+		bfd_putl32 (insn, contents + rel->r_offset);
 	      }
 	    else
 	      r = bfd_reloc_overflow;
@@ -2864,7 +2902,7 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
 	return FALSE;
 
       for (i = 0; i < PLT_ENTRY_INSNS; i++)
-	bfd_put_32 (output_bfd, plt_entry[i], loc + 4*i);
+	bfd_putl32 (plt_entry[i], loc + 4*i);
 
       /* Fill in the initial value of the .got.plt entry.  */
       loc = gotplt->contents + (got_address - sec_addr (gotplt));
@@ -3161,7 +3199,7 @@ riscv_elf_finish_dynamic_sections (bfd *output_bfd,
 	    return ret;
 
 	  for (i = 0; i < PLT_HEADER_INSNS; i++)
-	    bfd_put_32 (output_bfd, plt_header[i], splt->contents + 4*i);
+	    bfd_putl32 (plt_header[i], splt->contents + 4*i);
 
 	  elf_section_data (splt->output_section)->this_hdr.sh_entsize
 	    = PLT_ENTRY_SIZE;
@@ -4118,8 +4156,8 @@ _bfd_riscv_relax_call (bfd *abfd, asection *sec, asection *sym_sec,
   /* Shorten the function call.  */
   BFD_ASSERT (rel->r_offset + 8 <= sec->size);
 
-  auipc = bfd_get_32 (abfd, contents + rel->r_offset);
-  jalr = bfd_get_32 (abfd, contents + rel->r_offset + 4);
+  auipc = bfd_getl32 (contents + rel->r_offset);
+  jalr = bfd_getl32 (contents + rel->r_offset + 4);
   rd = (jalr >> OP_SH_RD) & OP_MASK_RD;
   rvc = rvc && VALID_RVC_J_IMM (foff);
 
@@ -4149,7 +4187,7 @@ _bfd_riscv_relax_call (bfd *abfd, asection *sec, asection *sym_sec,
   /* Replace the R_RISCV_CALL reloc.  */
   rel->r_info = ELFNN_R_INFO (ELFNN_R_SYM (rel->r_info), r_type);
   /* Replace the AUIPC.  */
-  bfd_put (8 * len, abfd, auipc, contents + rel->r_offset);
+  riscv_put_insn (8 * len, auipc, contents + rel->r_offset);
 
   /* Delete unnecessary JALR.  */
   *again = TRUE;
@@ -4223,9 +4261,9 @@ _bfd_riscv_relax_lui (bfd *abfd,
 	  if (undefined_weak)
 	    {
 	      /* Change the RS1 to zero.  */
-	      bfd_vma insn = bfd_get_32 (abfd, contents + rel->r_offset);
+	      bfd_vma insn = bfd_getl32 (contents + rel->r_offset);
 	      insn &= ~(OP_MASK_RS1 << OP_SH_RS1);
-	      bfd_put_32 (abfd, insn, contents + rel->r_offset);
+	      bfd_putl32 (insn, contents + rel->r_offset);
 	    }
 	  else
 	    rel->r_info = ELFNN_R_INFO (sym, R_RISCV_GPREL_I);
@@ -4235,9 +4273,9 @@ _bfd_riscv_relax_lui (bfd *abfd,
 	  if (undefined_weak)
 	    {
 	      /* Change the RS1 to zero.  */
-	      bfd_vma insn = bfd_get_32 (abfd, contents + rel->r_offset);
+	      bfd_vma insn = bfd_getl32 (contents + rel->r_offset);
 	      insn &= ~(OP_MASK_RS1 << OP_SH_RS1);
-	      bfd_put_32 (abfd, insn, contents + rel->r_offset);
+	      bfd_putl32 (insn, contents + rel->r_offset);
 	    }
 	  else
 	    rel->r_info = ELFNN_R_INFO (sym, R_RISCV_GPREL_S);
@@ -4268,13 +4306,13 @@ _bfd_riscv_relax_lui (bfd *abfd,
 			       : ELF_MAXPAGESIZE)))
     {
       /* Replace LUI with C.LUI if legal (i.e., rd != x0 and rd != x2/sp).  */
-      bfd_vma lui = bfd_get_32 (abfd, contents + rel->r_offset);
+      bfd_vma lui = bfd_getl32 (contents + rel->r_offset);
       unsigned rd = ((unsigned)lui >> OP_SH_RD) & OP_MASK_RD;
       if (rd == 0 || rd == X_SP)
 	return TRUE;
 
       lui = (lui & (OP_MASK_RD << OP_SH_RD)) | MATCH_C_LUI;
-      bfd_put_32 (abfd, lui, contents + rel->r_offset);
+      bfd_putl32 (lui, contents + rel->r_offset);
 
       /* Replace the R_RISCV_HI20 reloc.  */
       rel->r_info = ELFNN_R_INFO (ELFNN_R_SYM (rel->r_info), R_RISCV_RVC_LUI);
@@ -4376,11 +4414,11 @@ _bfd_riscv_relax_align (bfd *abfd, asection *sec,
 
   /* Write as many RISC-V NOPs as we need.  */
   for (pos = 0; pos < (nop_bytes & -4); pos += 4)
-    bfd_put_32 (abfd, RISCV_NOP, contents + rel->r_offset + pos);
+    bfd_putl32 (RISCV_NOP, contents + rel->r_offset + pos);
 
   /* Write a final RVC NOP if need be.  */
   if (nop_bytes % 4 != 0)
-    bfd_put_16 (abfd, RVC_NOP, contents + rel->r_offset + pos);
+    bfd_putl16 (RVC_NOP, contents + rel->r_offset + pos);
 
   /* Delete the excess bytes.  */
   return riscv_relax_delete_bytes (abfd, sec, rel->r_offset + nop_bytes,
@@ -4487,9 +4525,9 @@ _bfd_riscv_relax_pc  (bfd *abfd ATTRIBUTE_UNUSED,
 	    {
 	      /* Change the RS1 to zero, and then modify the relocation
 		 type to R_RISCV_LO12_I.  */
-	      bfd_vma insn = bfd_get_32 (abfd, contents + rel->r_offset);
+	      bfd_vma insn = bfd_getl32 (contents + rel->r_offset);
 	      insn &= ~(OP_MASK_RS1 << OP_SH_RS1);
-	      bfd_put_32 (abfd, insn, contents + rel->r_offset);
+	      bfd_putl32 (insn, contents + rel->r_offset);
 	      rel->r_info = ELFNN_R_INFO (sym, R_RISCV_LO12_I);
 	      rel->r_addend = hi_reloc.hi_addend;
 	    }
@@ -4505,9 +4543,9 @@ _bfd_riscv_relax_pc  (bfd *abfd ATTRIBUTE_UNUSED,
 	    {
 	      /* Change the RS1 to zero, and then modify the relocation
 		 type to R_RISCV_LO12_S.  */
-	      bfd_vma insn = bfd_get_32 (abfd, contents + rel->r_offset);
+	      bfd_vma insn = bfd_getl32 (contents + rel->r_offset);
 	      insn &= ~(OP_MASK_RS1 << OP_SH_RS1);
-	      bfd_put_32 (abfd, insn, contents + rel->r_offset);
+	      bfd_putl32 (insn, contents + rel->r_offset);
 	      rel->r_info = ELFNN_R_INFO (sym, R_RISCV_LO12_S);
 	      rel->r_addend = hi_reloc.hi_addend;
 	    }
@@ -4919,7 +4957,8 @@ static bfd_boolean
 riscv_elf_object_p (bfd *abfd)
 {
   /* There are only two mach types in RISCV currently.  */
-  if (strcmp (abfd->xvec->name, "elf32-littleriscv") == 0)
+  if (strcmp (abfd->xvec->name, "elf32-littleriscv") == 0
+      || strcmp (abfd->xvec->name, "elf32-bigriscv") == 0)
     bfd_default_set_arch_mach (abfd, bfd_arch_riscv, bfd_mach_riscv32);
   else
     bfd_default_set_arch_mach (abfd, bfd_arch_riscv, bfd_mach_riscv64);
@@ -4938,6 +4977,8 @@ riscv_elf_obj_attrs_arg_type (int tag)
 
 #define TARGET_LITTLE_SYM		riscv_elfNN_vec
 #define TARGET_LITTLE_NAME		"elfNN-littleriscv"
+#define TARGET_BIG_SYM			riscv_elfNN_be_vec
+#define TARGET_BIG_NAME			"elfNN-bigriscv"
 
 #define elf_backend_reloc_type_class	     riscv_reloc_type_class
 

bfd/targets.c

@@ -843,6 +843,8 @@ extern const bfd_target powerpc_xcoff_vec;
 extern const bfd_target pru_elf32_vec;
 extern const bfd_target riscv_elf32_vec;
 extern const bfd_target riscv_elf64_vec;
+extern const bfd_target riscv_elf32_be_vec;
+extern const bfd_target riscv_elf64_be_vec;
 extern const bfd_target rl78_elf32_vec;
 extern const bfd_target rs6000_xcoff64_vec;
 extern const bfd_target rs6000_xcoff64_aix_vec;
@@ -1237,6 +1239,8 @@ static const bfd_target * const _bfd_target_vector[] =
 #ifdef BFD64
 	&riscv_elf32_vec,
 	&riscv_elf64_vec,
+	&riscv_elf32_be_vec,
+	&riscv_elf64_be_vec,
 #endif
 	&rl78_elf32_vec,
 

gas/ChangeLog

@@ -1,3 +1,17 @@
+2021-01-06  Marcus Comstedt  <[email protected]>
+
+	* 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*.
+
 2021-01-04  H.J. Lu  <[email protected]>
 
 	PR ld/26256