1 /* tc-bpf.c -- Assembler for the Linux eBPF. 2 Copyright (C) 2019-2022 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 89 90 /* ISA handling. */ 91 static CGEN_BITSET *bpf_isa; 92 93 94 95 /* Command-line options processing. */ 96 97 enum options 98 { 99 OPTION_LITTLE_ENDIAN = OPTION_MD_BASE, 100 OPTION_BIG_ENDIAN, 101 OPTION_XBPF 102 }; 103 104 struct option md_longopts[] = 105 { 106 { "EL", no_argument, NULL, OPTION_LITTLE_ENDIAN }, 107 { "EB", no_argument, NULL, OPTION_BIG_ENDIAN }, 108 { "mxbpf", no_argument, NULL, OPTION_XBPF }, 109 { NULL, no_argument, NULL, 0 }, 110 }; 111 112 size_t md_longopts_size = sizeof (md_longopts); 113 114 const char * md_shortopts = ""; 115 116 extern int target_big_endian; 117 118 /* Whether target_big_endian has been set while parsing command-line 119 arguments. */ 120 static int set_target_endian = 0; 121 122 static int target_xbpf = 0; 123 124 static int set_xbpf = 0; 125 126 int 127 md_parse_option (int c, const char * arg ATTRIBUTE_UNUSED) 128 { 129 switch (c) 130 { 131 case OPTION_BIG_ENDIAN: 132 set_target_endian = 1; 133 target_big_endian = 1; 134 break; 135 case OPTION_LITTLE_ENDIAN: 136 set_target_endian = 1; 137 target_big_endian = 0; 138 break; 139 case OPTION_XBPF: 140 set_xbpf = 1; 141 target_xbpf = 1; 142 break; 143 default: 144 return 0; 145 } 146 147 return 1; 148 } 149 150 void 151 md_show_usage (FILE * stream) 152 { 153 fprintf (stream, _("\nBPF options:\n")); 154 fprintf (stream, _("\ 155 --EL generate code for a little endian machine\n\ 156 --EB generate code for a big endian machine\n\ 157 -mxbpf generate xBPF instructions\n")); 158 } 159 160 161 void 162 md_begin (void) 163 { 164 /* Initialize the `cgen' interface. */ 165 166 /* If not specified in the command line, use the host 167 endianness. */ 168 if (!set_target_endian) 169 { 170 #ifdef WORDS_BIGENDIAN 171 target_big_endian = 1; 172 #else 173 target_big_endian = 0; 174 #endif 175 } 176 177 /* If not specified in the command line, use eBPF rather 178 than xBPF. */ 179 if (!set_xbpf) 180 target_xbpf = 0; 181 182 /* Set the ISA, which depends on the target endianness. */ 183 bpf_isa = cgen_bitset_create (ISA_MAX); 184 if (target_big_endian) 185 { 186 if (target_xbpf) 187 cgen_bitset_set (bpf_isa, ISA_XBPFBE); 188 else 189 cgen_bitset_set (bpf_isa, ISA_EBPFBE); 190 } 191 else 192 { 193 if (target_xbpf) 194 cgen_bitset_set (bpf_isa, ISA_XBPFLE); 195 else 196 cgen_bitset_set (bpf_isa, ISA_EBPFLE); 197 } 198 199 /* Set the machine number and endian. */ 200 gas_cgen_cpu_desc = bpf_cgen_cpu_open (CGEN_CPU_OPEN_ENDIAN, 201 target_big_endian ? 202 CGEN_ENDIAN_BIG : CGEN_ENDIAN_LITTLE, 203 CGEN_CPU_OPEN_INSN_ENDIAN, 204 CGEN_ENDIAN_LITTLE, 205 CGEN_CPU_OPEN_ISAS, 206 bpf_isa, 207 CGEN_CPU_OPEN_END); 208 bpf_cgen_init_asm (gas_cgen_cpu_desc); 209 210 /* This is a callback from cgen to gas to parse operands. */ 211 cgen_set_parse_operand_fn (gas_cgen_cpu_desc, gas_cgen_parse_operand); 212 213 /* Set the machine type. */ 214 bfd_default_set_arch_mach (stdoutput, bfd_arch_bpf, bfd_mach_bpf); 215 } 216 217 valueT 218 md_section_align (segT segment, valueT size) 219 { 220 int align = bfd_section_alignment (segment); 221 222 return ((size + (1 << align) - 1) & -(1 << align)); 223 } 224 225 226 /* Functions concerning relocs. */ 227 228 /* The location from which a PC relative jump should be calculated, 229 given a PC relative reloc. */ 230 231 long 232 md_pcrel_from_section (fixS *fixP, segT sec) 233 { 234 if (fixP->fx_addsy != (symbolS *) NULL 235 && (! S_IS_DEFINED (fixP->fx_addsy) 236 || (S_GET_SEGMENT (fixP->fx_addsy) != sec) 237 || S_IS_EXTERNAL (fixP->fx_addsy) 238 || S_IS_WEAK (fixP->fx_addsy))) 239 { 240 /* The symbol is undefined (or is defined but not in this section). 241 Let the linker figure it out. */ 242 return 0; 243 } 244 245 return fixP->fx_where + fixP->fx_frag->fr_address; 246 } 247 248 /* Write a value out to the object file, using the appropriate endianness. */ 249 250 void 251 md_number_to_chars (char * buf, valueT val, int n) 252 { 253 if (target_big_endian) 254 number_to_chars_bigendian (buf, val, n); 255 else 256 number_to_chars_littleendian (buf, val, n); 257 } 258 259 arelent * 260 tc_gen_reloc (asection *sec, fixS *fix) 261 { 262 return gas_cgen_tc_gen_reloc (sec, fix); 263 } 264 265 /* Return the bfd reloc type for OPERAND of INSN at fixup FIXP. This 266 is called when the operand is an expression that couldn't be fully 267 resolved. Returns BFD_RELOC_NONE if no reloc type can be found. 268 *FIXP may be modified if desired. */ 269 270 bfd_reloc_code_real_type 271 md_cgen_lookup_reloc (const CGEN_INSN *insn ATTRIBUTE_UNUSED, 272 const CGEN_OPERAND *operand, 273 fixS *fixP) 274 { 275 switch (operand->type) 276 { 277 case BPF_OPERAND_OFFSET16: 278 return BFD_RELOC_BPF_16; 279 case BPF_OPERAND_IMM32: 280 return BFD_RELOC_BPF_32; 281 case BPF_OPERAND_IMM64: 282 return BFD_RELOC_BPF_64; 283 case BPF_OPERAND_DISP16: 284 fixP->fx_pcrel = 1; 285 return BFD_RELOC_BPF_DISP16; 286 case BPF_OPERAND_DISP32: 287 fixP->fx_pcrel = 1; 288 return BFD_RELOC_BPF_DISP32; 289 default: 290 break; 291 } 292 return BFD_RELOC_NONE; 293 } 294 295 /* *FRAGP has been relaxed to its final size, and now needs to have 296 the bytes inside it modified to conform to the new size. 297 298 Called after relaxation is finished. 299 fragP->fr_type == rs_machine_dependent. 300 fragP->fr_subtype is the subtype of what the address relaxed to. */ 301 302 void 303 md_convert_frag (bfd *abfd ATTRIBUTE_UNUSED, 304 segT sec ATTRIBUTE_UNUSED, 305 fragS *fragP ATTRIBUTE_UNUSED) 306 { 307 as_fatal (_("convert_frag called")); 308 } 309 310 int 311 md_estimate_size_before_relax (fragS *fragP ATTRIBUTE_UNUSED, 312 segT segment ATTRIBUTE_UNUSED) 313 { 314 as_fatal (_("estimate_size_before_relax called")); 315 return 0; 316 } 317 318 319 void 320 md_apply_fix (fixS *fixP, valueT *valP, segT seg) 321 { 322 /* Some fixups for instructions require special attention. This is 323 handled in the code block below. */ 324 if ((int) fixP->fx_r_type >= (int) BFD_RELOC_UNUSED) 325 { 326 int opindex = (int) fixP->fx_r_type - (int) BFD_RELOC_UNUSED; 327 const CGEN_OPERAND *operand = cgen_operand_lookup_by_num (gas_cgen_cpu_desc, 328 opindex); 329 char *where; 330 331 switch (operand->type) 332 { 333 case BPF_OPERAND_DISP32: 334 /* eBPF supports two kind of CALL instructions: the so 335 called pseudo calls ("bpf to bpf") and external calls 336 ("bpf to kernel"). 337 338 Both kind of calls use the same instruction (CALL). 339 However, external calls are constructed by passing a 340 constant argument to the instruction, whereas pseudo 341 calls result from expressions involving symbols. In 342 practice, instructions requiring a fixup are interpreted 343 as pseudo-calls. If we are executing this code, this is 344 a pseudo call. 345 346 The kernel expects for pseudo-calls to be annotated by 347 having BPF_PSEUDO_CALL in the SRC field of the 348 instruction. But beware the infamous nibble-swapping of 349 eBPF and take endianness into account here. 350 351 Note that the CALL instruction has only one operand, so 352 this code is executed only once per instruction. */ 353 where = fixP->fx_frag->fr_literal + fixP->fx_where + 1; 354 where[0] = target_big_endian ? 0x01 : 0x10; 355 /* Fallthrough. */ 356 case BPF_OPERAND_DISP16: 357 /* The PC-relative displacement fields in jump instructions 358 shouldn't be in bytes. Instead, they hold the number of 359 64-bit words to the target, _minus one_. */ 360 *valP = (((long) (*valP)) - 8) / 8; 361 break; 362 default: 363 break; 364 } 365 } 366 367 /* And now invoke CGEN's handler, which will eventually install 368 *valP into the corresponding operand. */ 369 gas_cgen_md_apply_fix (fixP, valP, seg); 370 } 371 372 void 373 md_assemble (char *str) 374 { 375 const CGEN_INSN *insn; 376 char *errmsg; 377 CGEN_FIELDS fields; 378 379 #if CGEN_INT_INSN_P 380 CGEN_INSN_INT buffer[CGEN_MAX_INSN_SIZE / sizeof (CGEN_INT_INSN_P)]; 381 #else 382 unsigned char buffer[CGEN_MAX_INSN_SIZE]; 383 #endif 384 385 gas_cgen_init_parse (); 386 insn = bpf_cgen_assemble_insn (gas_cgen_cpu_desc, str, &fields, 387 buffer, &errmsg); 388 389 if (insn == NULL) 390 { 391 as_bad ("%s", errmsg); 392 return; 393 } 394 395 gas_cgen_finish_insn (insn, buffer, CGEN_FIELDS_BITSIZE (&fields), 396 0, /* zero to ban relaxable insns. */ 397 NULL); /* NULL so results not returned here. */ 398 } 399 400 void 401 md_operand (expressionS *expressionP) 402 { 403 gas_cgen_md_operand (expressionP); 404 } 405 406 407 symbolS * 408 md_undefined_symbol (char *name ATTRIBUTE_UNUSED) 409 { 410 return NULL; 411 } 412 413 414 /* Turn a string in input_line_pointer into a floating point constant 415 of type TYPE, and store the appropriate bytes in *LITP. The number 416 of LITTLENUMS emitted is stored in *SIZEP. An error message is 417 returned, or NULL on OK. */ 418 419 const char * 420 md_atof (int type, char *litP, int *sizeP) 421 { 422 return ieee_md_atof (type, litP, sizeP, false); 423 } 424