| 1 | /* tc-bpf.c -- Assembler for the Linux eBPF. |
| 2 | Copyright (C) 2019-2020 Free Software Foundation, Inc. |
| 3 | Contributed by Oracle, Inc. |
| 4 | |
| 5 | This file is part of GAS, the GNU Assembler. |
| 6 | |
| 7 | GAS is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 3, or (at your option) |
| 10 | any later version. |
| 11 | |
| 12 | GAS is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with GAS; see the file COPYING. If not, write to |
| 19 | the Free Software Foundation, 51 Franklin Street - Fifth Floor, |
| 20 | Boston, MA 02110-1301, USA. */ |
| 21 | |
| 22 | #include "as.h" |
| 23 | #include "subsegs.h" |
| 24 | #include "symcat.h" |
| 25 | #include "opcodes/bpf-desc.h" |
| 26 | #include "opcodes/bpf-opc.h" |
| 27 | #include "cgen.h" |
| 28 | #include "elf/common.h" |
| 29 | #include "elf/bpf.h" |
| 30 | #include "dwarf2dbg.h" |
| 31 | |
| 32 | const char comment_chars[] = ";"; |
| 33 | const char line_comment_chars[] = "#"; |
| 34 | const char line_separator_chars[] = "`"; |
| 35 | const char EXP_CHARS[] = "eE"; |
| 36 | const char FLT_CHARS[] = "fFdD"; |
| 37 | |
| 38 | /* Like s_lcomm_internal in gas/read.c but the alignment string |
| 39 | is allowed to be optional. */ |
| 40 | |
| 41 | static symbolS * |
| 42 | pe_lcomm_internal (int needs_align, symbolS *symbolP, addressT size) |
| 43 | { |
| 44 | addressT align = 0; |
| 45 | |
| 46 | SKIP_WHITESPACE (); |
| 47 | |
| 48 | if (needs_align |
| 49 | && *input_line_pointer == ',') |
| 50 | { |
| 51 | align = parse_align (needs_align - 1); |
| 52 | |
| 53 | if (align == (addressT) -1) |
| 54 | return NULL; |
| 55 | } |
| 56 | else |
| 57 | { |
| 58 | if (size >= 8) |
| 59 | align = 3; |
| 60 | else if (size >= 4) |
| 61 | align = 2; |
| 62 | else if (size >= 2) |
| 63 | align = 1; |
| 64 | else |
| 65 | align = 0; |
| 66 | } |
| 67 | |
| 68 | bss_alloc (symbolP, size, align); |
| 69 | return symbolP; |
| 70 | } |
| 71 | |
| 72 | static void |
| 73 | pe_lcomm (int needs_align) |
| 74 | { |
| 75 | s_comm_internal (needs_align * 2, pe_lcomm_internal); |
| 76 | } |
| 77 | |
| 78 | /* The target specific pseudo-ops which we support. */ |
| 79 | const pseudo_typeS md_pseudo_table[] = |
| 80 | { |
| 81 | { "half", cons, 2 }, |
| 82 | { "word", cons, 4 }, |
| 83 | { "dword", cons, 8 }, |
| 84 | { "lcomm", pe_lcomm, 1 }, |
| 85 | { NULL, NULL, 0 } |
| 86 | }; |
| 87 | |
| 88 | \f |
| 89 | |
| 90 | /* ISA handling. */ |
| 91 | static CGEN_BITSET *bpf_isa; |
| 92 | |
| 93 | \f |
| 94 | |
| 95 | /* Command-line options processing. */ |
| 96 | |
| 97 | enum options |
| 98 | { |
| 99 | OPTION_LITTLE_ENDIAN = OPTION_MD_BASE, |
| 100 | OPTION_BIG_ENDIAN |
| 101 | }; |
| 102 | |
| 103 | struct option md_longopts[] = |
| 104 | { |
| 105 | { "EL", no_argument, NULL, OPTION_LITTLE_ENDIAN }, |
| 106 | { "EB", no_argument, NULL, OPTION_BIG_ENDIAN }, |
| 107 | { NULL, no_argument, NULL, 0 }, |
| 108 | }; |
| 109 | |
| 110 | size_t md_longopts_size = sizeof (md_longopts); |
| 111 | |
| 112 | const char * md_shortopts = ""; |
| 113 | |
| 114 | extern int target_big_endian; |
| 115 | |
| 116 | /* Whether target_big_endian has been set while parsing command-line |
| 117 | arguments. */ |
| 118 | static int set_target_endian = 0; |
| 119 | |
| 120 | int |
| 121 | md_parse_option (int c, const char * arg ATTRIBUTE_UNUSED) |
| 122 | { |
| 123 | switch (c) |
| 124 | { |
| 125 | case OPTION_BIG_ENDIAN: |
| 126 | set_target_endian = 1; |
| 127 | target_big_endian = 1; |
| 128 | break; |
| 129 | case OPTION_LITTLE_ENDIAN: |
| 130 | set_target_endian = 1; |
| 131 | target_big_endian = 0; |
| 132 | break; |
| 133 | default: |
| 134 | return 0; |
| 135 | } |
| 136 | |
| 137 | return 1; |
| 138 | } |
| 139 | |
| 140 | void |
| 141 | md_show_usage (FILE * stream) |
| 142 | { |
| 143 | fprintf (stream, _("\nBPF options:\n")); |
| 144 | fprintf (stream, _("\ |
| 145 | --EL generate code for a little endian machine\n\ |
| 146 | --EB generate code for a big endian machine\n")); |
| 147 | } |
| 148 | |
| 149 | \f |
| 150 | void |
| 151 | md_begin (void) |
| 152 | { |
| 153 | /* Initialize the `cgen' interface. */ |
| 154 | |
| 155 | /* If not specified in the command line, use the host |
| 156 | endianness. */ |
| 157 | if (!set_target_endian) |
| 158 | { |
| 159 | #ifdef WORDS_BIGENDIAN |
| 160 | target_big_endian = 1; |
| 161 | #else |
| 162 | target_big_endian = 0; |
| 163 | #endif |
| 164 | } |
| 165 | |
| 166 | /* Set the ISA, which depends on the target endianness. */ |
| 167 | bpf_isa = cgen_bitset_create (ISA_MAX); |
| 168 | if (target_big_endian) |
| 169 | cgen_bitset_set (bpf_isa, ISA_EBPFBE); |
| 170 | else |
| 171 | cgen_bitset_set (bpf_isa, ISA_EBPFLE); |
| 172 | |
| 173 | /* Set the machine number and endian. */ |
| 174 | gas_cgen_cpu_desc = bpf_cgen_cpu_open (CGEN_CPU_OPEN_ENDIAN, |
| 175 | target_big_endian ? |
| 176 | CGEN_ENDIAN_BIG : CGEN_ENDIAN_LITTLE, |
| 177 | CGEN_CPU_OPEN_ISAS, |
| 178 | bpf_isa, |
| 179 | CGEN_CPU_OPEN_END); |
| 180 | bpf_cgen_init_asm (gas_cgen_cpu_desc); |
| 181 | |
| 182 | /* This is a callback from cgen to gas to parse operands. */ |
| 183 | cgen_set_parse_operand_fn (gas_cgen_cpu_desc, gas_cgen_parse_operand); |
| 184 | |
| 185 | /* Set the machine type. */ |
| 186 | bfd_default_set_arch_mach (stdoutput, bfd_arch_bpf, bfd_mach_bpf); |
| 187 | } |
| 188 | |
| 189 | valueT |
| 190 | md_section_align (segT segment, valueT size) |
| 191 | { |
| 192 | int align = bfd_section_alignment (segment); |
| 193 | |
| 194 | return ((size + (1 << align) - 1) & -(1 << align)); |
| 195 | } |
| 196 | |
| 197 | \f |
| 198 | /* Functions concerning relocs. */ |
| 199 | |
| 200 | /* The location from which a PC relative jump should be calculated, |
| 201 | given a PC relative reloc. */ |
| 202 | |
| 203 | long |
| 204 | md_pcrel_from_section (fixS *fixP, segT sec) |
| 205 | { |
| 206 | if (fixP->fx_addsy != (symbolS *) NULL |
| 207 | && (! S_IS_DEFINED (fixP->fx_addsy) |
| 208 | || (S_GET_SEGMENT (fixP->fx_addsy) != sec) |
| 209 | || S_IS_EXTERNAL (fixP->fx_addsy) |
| 210 | || S_IS_WEAK (fixP->fx_addsy))) |
| 211 | { |
| 212 | /* The symbol is undefined (or is defined but not in this section). |
| 213 | Let the linker figure it out. */ |
| 214 | return 0; |
| 215 | } |
| 216 | |
| 217 | return fixP->fx_where + fixP->fx_frag->fr_address; |
| 218 | } |
| 219 | |
| 220 | /* Write a value out to the object file, using the appropriate endianness. */ |
| 221 | |
| 222 | void |
| 223 | md_number_to_chars (char * buf, valueT val, int n) |
| 224 | { |
| 225 | if (target_big_endian) |
| 226 | number_to_chars_bigendian (buf, val, n); |
| 227 | else |
| 228 | number_to_chars_littleendian (buf, val, n); |
| 229 | } |
| 230 | |
| 231 | arelent * |
| 232 | tc_gen_reloc (asection *sec, fixS *fix) |
| 233 | { |
| 234 | return gas_cgen_tc_gen_reloc (sec, fix); |
| 235 | } |
| 236 | |
| 237 | /* Return the bfd reloc type for OPERAND of INSN at fixup FIXP. This |
| 238 | is called when the operand is an expression that couldn't be fully |
| 239 | resolved. Returns BFD_RELOC_NONE if no reloc type can be found. |
| 240 | *FIXP may be modified if desired. */ |
| 241 | |
| 242 | bfd_reloc_code_real_type |
| 243 | md_cgen_lookup_reloc (const CGEN_INSN *insn ATTRIBUTE_UNUSED, |
| 244 | const CGEN_OPERAND *operand, |
| 245 | fixS *fixP) |
| 246 | { |
| 247 | switch (operand->type) |
| 248 | { |
| 249 | case BPF_OPERAND_OFFSET16: |
| 250 | return BFD_RELOC_BPF_16; |
| 251 | case BPF_OPERAND_IMM32: |
| 252 | return BFD_RELOC_BPF_32; |
| 253 | case BPF_OPERAND_IMM64: |
| 254 | return BFD_RELOC_BPF_64; |
| 255 | case BPF_OPERAND_DISP16: |
| 256 | fixP->fx_pcrel = 1; |
| 257 | return BFD_RELOC_BPF_DISP16; |
| 258 | case BPF_OPERAND_DISP32: |
| 259 | fixP->fx_pcrel = 1; |
| 260 | return BFD_RELOC_BPF_DISP32; |
| 261 | default: |
| 262 | break; |
| 263 | } |
| 264 | return BFD_RELOC_NONE; |
| 265 | } |
| 266 | \f |
| 267 | /* *FRAGP has been relaxed to its final size, and now needs to have |
| 268 | the bytes inside it modified to conform to the new size. |
| 269 | |
| 270 | Called after relaxation is finished. |
| 271 | fragP->fr_type == rs_machine_dependent. |
| 272 | fragP->fr_subtype is the subtype of what the address relaxed to. */ |
| 273 | |
| 274 | void |
| 275 | md_convert_frag (bfd *abfd ATTRIBUTE_UNUSED, |
| 276 | segT sec ATTRIBUTE_UNUSED, |
| 277 | fragS *fragP ATTRIBUTE_UNUSED) |
| 278 | { |
| 279 | as_fatal (_("convert_frag called")); |
| 280 | } |
| 281 | |
| 282 | int |
| 283 | md_estimate_size_before_relax (fragS *fragP ATTRIBUTE_UNUSED, |
| 284 | segT segment ATTRIBUTE_UNUSED) |
| 285 | { |
| 286 | as_fatal (_("estimate_size_before_relax called")); |
| 287 | return 0; |
| 288 | } |
| 289 | |
| 290 | \f |
| 291 | void |
| 292 | md_apply_fix (fixS *fixP, valueT *valP, segT seg) |
| 293 | { |
| 294 | /* Some fixups for instructions require special attention. This is |
| 295 | handled in the code block below. */ |
| 296 | if ((int) fixP->fx_r_type >= (int) BFD_RELOC_UNUSED) |
| 297 | { |
| 298 | int opindex = (int) fixP->fx_r_type - (int) BFD_RELOC_UNUSED; |
| 299 | const CGEN_OPERAND *operand = cgen_operand_lookup_by_num (gas_cgen_cpu_desc, |
| 300 | opindex); |
| 301 | char *where; |
| 302 | |
| 303 | switch (operand->type) |
| 304 | { |
| 305 | case BPF_OPERAND_DISP32: |
| 306 | /* eBPF supports two kind of CALL instructions: the so |
| 307 | called pseudo calls ("bpf to bpf") and external calls |
| 308 | ("bpf to kernel"). |
| 309 | |
| 310 | Both kind of calls use the same instruction (CALL). |
| 311 | However, external calls are constructed by passing a |
| 312 | constant argument to the instruction, whereas pseudo |
| 313 | calls result from expressions involving symbols. In |
| 314 | practice, instructions requiring a fixup are interpreted |
| 315 | as pseudo-calls. If we are executing this code, this is |
| 316 | a pseudo call. |
| 317 | |
| 318 | The kernel expects for pseudo-calls to be annotated by |
| 319 | having BPF_PSEUDO_CALL in the SRC field of the |
| 320 | instruction. But beware the infamous nibble-swapping of |
| 321 | eBPF and take endianness into account here. |
| 322 | |
| 323 | Note that the CALL instruction has only one operand, so |
| 324 | this code is executed only once per instruction. */ |
| 325 | where = fixP->fx_frag->fr_literal + fixP->fx_where; |
| 326 | cgen_put_insn_value (gas_cgen_cpu_desc, (unsigned char *) where + 1, 8, |
| 327 | target_big_endian ? 0x01 : 0x10, |
| 328 | gas_cgen_cpu_desc->endian); |
| 329 | /* Fallthrough. */ |
| 330 | case BPF_OPERAND_DISP16: |
| 331 | /* The PC-relative displacement fields in jump instructions |
| 332 | shouldn't be in bytes. Instead, they hold the number of |
| 333 | 64-bit words to the target, _minus one_. */ |
| 334 | *valP = (((long) (*valP)) - 8) / 8; |
| 335 | break; |
| 336 | default: |
| 337 | break; |
| 338 | } |
| 339 | } |
| 340 | |
| 341 | /* And now invoke CGEN's handler, which will eventually install |
| 342 | *valP into the corresponding operand. */ |
| 343 | gas_cgen_md_apply_fix (fixP, valP, seg); |
| 344 | } |
| 345 | |
| 346 | void |
| 347 | md_assemble (char *str) |
| 348 | { |
| 349 | const CGEN_INSN *insn; |
| 350 | char *errmsg; |
| 351 | CGEN_FIELDS fields; |
| 352 | |
| 353 | #if CGEN_INT_INSN_P |
| 354 | CGEN_INSN_INT buffer[CGEN_MAX_INSN_SIZE / sizeof (CGEN_INT_INSN_P)]; |
| 355 | #else |
| 356 | unsigned char buffer[CGEN_MAX_INSN_SIZE]; |
| 357 | memset (buffer, 0, CGEN_MAX_INSN_SIZE); /* XXX to remove when CGEN |
| 358 | is fixed to handle |
| 359 | opcodes-in-words |
| 360 | properly. */ |
| 361 | #endif |
| 362 | |
| 363 | gas_cgen_init_parse (); |
| 364 | insn = bpf_cgen_assemble_insn (gas_cgen_cpu_desc, str, &fields, |
| 365 | buffer, &errmsg); |
| 366 | |
| 367 | if (insn == NULL) |
| 368 | { |
| 369 | as_bad ("%s", errmsg); |
| 370 | return; |
| 371 | } |
| 372 | |
| 373 | gas_cgen_finish_insn (insn, buffer, CGEN_FIELDS_BITSIZE (&fields), |
| 374 | 0, /* zero to ban relaxable insns. */ |
| 375 | NULL); /* NULL so results not returned here. */ |
| 376 | } |
| 377 | |
| 378 | void |
| 379 | md_operand (expressionS *expressionP) |
| 380 | { |
| 381 | gas_cgen_md_operand (expressionP); |
| 382 | } |
| 383 | |
| 384 | |
| 385 | symbolS * |
| 386 | md_undefined_symbol (char *name ATTRIBUTE_UNUSED) |
| 387 | { |
| 388 | return NULL; |
| 389 | } |
| 390 | |
| 391 | \f |
| 392 | /* Turn a string in input_line_pointer into a floating point constant |
| 393 | of type TYPE, and store the appropriate bytes in *LITP. The number |
| 394 | of LITTLENUMS emitted is stored in *SIZEP. An error message is |
| 395 | returned, or NULL on OK. */ |
| 396 | |
| 397 | const char * |
| 398 | md_atof (int type, char *litP, int *sizeP) |
| 399 | { |
| 400 | return ieee_md_atof (type, litP, sizeP, FALSE); |
| 401 | } |