Re: [PATCH] Add support for ARM AAPCS R_ARM_V4BX relocation type

[Khem Raj <kraj at mvista dot com>]

HI Julian

I think the option message should contain 'Rm' instead of 'm'
Rewrite BX Rrn as MOV pc, Rrn for ARMv4\n"
Thanks

-Khem


On Fri, 2005-01-28 at 15:23 +0000, Julian Brown wrote:
> Hi,
> 
> This patch adds support for the R_ARM_V4BX relocation type to bfd and 
> ld. This allows objects compiled for the ARMv4 architecture to be 
> interworking-safe when linked with other objects compiled for ARMv4t, 
> but also allows pure ARMv4 binaries to be built from the same ARMv4 objects.
> 
> In the latter case, the switch "--fix-v4bx" must be passed to the 
> linker, which causes v4t "BX rM" instructions to be rewritten as "MOV 
> PC,rM", since v4 processors do not have a BX instruction.
> 
> In the former case, the switch should not be used, and R_ARM_V4BX 
> relocations are ignored.
> 
> Tested on i686-pc-linux-gnu and arm-none-eabi.
> 
> ChangeLog:
> 
> 	* bfd/bin-in.h (bfd_elf32_arm_set_target_relocs): Update
> 	prototype.
> 	* bfd/bin-in2.h (bfd_elf32_arm_set_target_relocs): Update
> 	prototype.
> 	* bfd/elf32-arm.c (elf32_arm_link_hash_table): Add fix_v4bx
> 	flag.
> 	(bfd_elf32_arm_set_target_relocs): Add formal parameter fix_v4bx
> 	for passing flag value from ld. Set flag value in global hash
> 	table entry.
> 	(elf32_arm_final_link_relocate): Add code to implement
> 	R_ARM_V4BX relocation.
> 	* ld/emultempl/armelf.em (fix_v4bx): New variable.
> 	(arm_elf_create_output_section_statements): Communicate fix_v4bx
> 	flag value to bfd.
> 	(PARSE_AND_LIST_PROLOGUE): Add option token OPTION_FIX_V4BX.
> 	(PARSE_AND_LIST_LONGOPTS): Add option --fix-v4bx.
> 	(PARSE_AND_LIST_OPTIONS): Add option --fix-v4bx.
> 	(PARSE_AND_LIST_ARGS_CASES): Add option OPTION_FIX_V4BX.
> 
> plain text document attachment (binutils-patch-2)
> ? bfd/doc/bfd.info
> ? bfd/doc/bfd.info-1
> ? gas/doc/as.info
> ? gas/doc/as.info-1
> Index: bfd/bfd-in.h
> ===================================================================
> RCS file: /cvs/src/src/bfd/bfd-in.h,v
> retrieving revision 1.90
> diff -c -p -r1.90 bfd-in.h
> *** bfd/bfd-in.h	30 Nov 2004 17:45:53 -0000	1.90
> --- bfd/bfd-in.h	27 Jan 2005 21:24:02 -0000
> *************** extern bfd_boolean bfd_elf32_arm_process
> *** 817,823 ****
>     (bfd *, struct bfd_link_info *, int);
>   
>   void bfd_elf32_arm_set_target_relocs
> !   (struct bfd_link_info *, int, char *);
>   
>   extern bfd_boolean bfd_elf32_arm_get_bfd_for_interworking
>     (bfd *, struct bfd_link_info *);
> --- 817,823 ----
>     (bfd *, struct bfd_link_info *, int);
>   
>   void bfd_elf32_arm_set_target_relocs
> !   (struct bfd_link_info *, int, char *, int);
>   
>   extern bfd_boolean bfd_elf32_arm_get_bfd_for_interworking
>     (bfd *, struct bfd_link_info *);
> Index: bfd/bfd-in2.h
> ===================================================================
> RCS file: /cvs/src/src/bfd/bfd-in2.h,v
> retrieving revision 1.317
> diff -c -p -r1.317 bfd-in2.h
> *** bfd/bfd-in2.h	25 Jan 2005 20:22:20 -0000	1.317
> --- bfd/bfd-in2.h	27 Jan 2005 21:24:06 -0000
> *************** extern bfd_boolean bfd_elf32_arm_process
> *** 824,830 ****
>     (bfd *, struct bfd_link_info *, int);
>   
>   void bfd_elf32_arm_set_target_relocs
> !   (struct bfd_link_info *, int, char *);
>   
>   extern bfd_boolean bfd_elf32_arm_get_bfd_for_interworking
>     (bfd *, struct bfd_link_info *);
> --- 824,830 ----
>     (bfd *, struct bfd_link_info *, int);
>   
>   void bfd_elf32_arm_set_target_relocs
> !   (struct bfd_link_info *, int, char *, int);
>   
>   extern bfd_boolean bfd_elf32_arm_get_bfd_for_interworking
>     (bfd *, struct bfd_link_info *);
> Index: bfd/elf32-arm.c
> ===================================================================
> RCS file: /cvs/src/src/bfd/elf32-arm.c,v
> retrieving revision 1.17
> diff -c -p -r1.17 elf32-arm.c
> *** bfd/elf32-arm.c	26 Jan 2005 06:10:43 -0000	1.17
> --- bfd/elf32-arm.c	27 Jan 2005 21:24:21 -0000
> *************** struct elf32_arm_link_hash_table
> *** 1165,1170 ****
> --- 1165,1173 ----
>       /* The relocation to use for R_ARM_TARGET2 relocations.  */
>       int target2_reloc;
>   
> +     /* Nonzero to fix BX instructions for ARMv4 targets.  */
> +     int fix_v4bx;
> + 
>       /* The number of bytes in the initial entry in the PLT.  */
>       bfd_size_type plt_header_size;
>   
> *************** error_return:
> *** 1931,1937 ****
>   void
>   bfd_elf32_arm_set_target_relocs (struct bfd_link_info *link_info,
>   				 int target1_is_rel,
> ! 				 char * target2_type)
>   {
>     struct elf32_arm_link_hash_table *globals;
>   
> --- 1934,1941 ----
>   void
>   bfd_elf32_arm_set_target_relocs (struct bfd_link_info *link_info,
>   				 int target1_is_rel,
> ! 				 char * target2_type,
> !                                  int fix_v4bx)
>   {
>     struct elf32_arm_link_hash_table *globals;
>   
> *************** bfd_elf32_arm_set_target_relocs (struct 
> *** 1949,1954 ****
> --- 1953,1959 ----
>         _bfd_error_handler (_("Invalid TARGET2 relocation type '%s'."),
>   			  target2_type);
>       }
> +   globals->fix_v4bx = fix_v4bx;
>   }
>   #endif
>   
> *************** elf32_arm_final_link_relocate (reloc_how
> *** 2985,2990 ****
> --- 2990,3011 ----
>       case R_ARM_RBASE:
>         return bfd_reloc_notsupported;
>   
> +     case R_ARM_V4BX:
> +       if (globals->fix_v4bx)
> +         {
> +           bfd_vma insn = bfd_get_32 (input_bfd, hit_data);
> + 
> +           /* Ensure that we have a BX instruction.  */
> +           BFD_ASSERT ((insn & 0x0ffffff0) == 0x012fff10);
> + 
> +           /* Preserve Rm (lowest four bits) and the condition code
> +              (highest four bits). Other bits encode MOV PC,Rm.  */
> +           insn = (insn & 0xf000000f) | 0x01a0f000;
> + 
> +           bfd_put_32 (input_bfd, insn, hit_data);
> +         }
> +       return bfd_reloc_ok;
> + 
>       default:
>         return bfd_reloc_notsupported;
>       }
> Index: ld/emultempl/armelf.em
> ===================================================================
> RCS file: /cvs/src/src/ld/emultempl/armelf.em,v
> retrieving revision 1.42
> diff -c -p -r1.42 armelf.em
> *** ld/emultempl/armelf.em	30 Nov 2004 17:45:54 -0000	1.42
> --- ld/emultempl/armelf.em	27 Jan 2005 21:24:28 -0000
> *************** static bfd *bfd_for_interwork;
> *** 30,35 ****
> --- 30,36 ----
>   static int byteswap_code = 0;
>   static int target1_is_rel = 0${TARGET1_IS_REL};
>   static char *target2_type = "${TARGET2_TYPE}";
> + static int fix_v4bx = 0;
>   
>   static void
>   gld${EMULATION_NAME}_before_parse (void)
> *************** arm_elf_finish (void)
> *** 189,195 ****
>   static void
>   arm_elf_create_output_section_statements (void)
>   {
> !   bfd_elf32_arm_set_target_relocs (&link_info, target1_is_rel, target2_type);
>   }
>   
>   EOF
> --- 190,197 ----
>   static void
>   arm_elf_create_output_section_statements (void)
>   {
> !   bfd_elf32_arm_set_target_relocs (&link_info, target1_is_rel, target2_type,
> !                                    fix_v4bx);
>   }
>   
>   EOF
> *************** PARSE_AND_LIST_PROLOGUE='
> *** 203,208 ****
> --- 205,211 ----
>   #define OPTION_TARGET1_REL		303
>   #define OPTION_TARGET1_ABS		304
>   #define OPTION_TARGET2			305
> + #define OPTION_FIX_V4BX                 306
>   '
>   
>   PARSE_AND_LIST_SHORTOPTS=p
> *************** PARSE_AND_LIST_LONGOPTS='
> *** 214,219 ****
> --- 217,223 ----
>     { "target1-rel", no_argument, NULL, OPTION_TARGET1_REL},
>     { "target1-abs", no_argument, NULL, OPTION_TARGET1_ABS},
>     { "target2", required_argument, NULL, OPTION_TARGET2},
> +   { "fix-v4bx", no_argument, NULL, OPTION_FIX_V4BX},
>   '
>   
>   PARSE_AND_LIST_OPTIONS='
> *************** PARSE_AND_LIST_OPTIONS='
> *** 222,227 ****
> --- 226,232 ----
>     fprintf (file, _("     --target1=rel            Interpret R_ARM_TARGET1 as R_ARM_REL32\n"));
>     fprintf (file, _("     --target1=abs            Interpret R_ARM_TARGET1 as R_ARM_ABS32\n"));
>     fprintf (file, _("     --target2=<type>         Specify definition of R_ARM_TARGET2\n"));
> +   fprintf (file, _("     --fix-v4bx               Rewrite BX rn as MOV pc, rn for ARMv4\n"));
>   '
>   
>   PARSE_AND_LIST_ARGS_CASES='
> *************** PARSE_AND_LIST_ARGS_CASES='
> *** 248,253 ****
> --- 253,262 ----
>       case OPTION_TARGET2:
>         target2_type = optarg;
>         break;
> + 
> +     case OPTION_FIX_V4BX:
> +       fix_v4bx = 1;
> +       break;
>   '
>   
>   # We have our own after_open and before_allocation functions, but they call