| 1 | /* Target-dependent code for BPF. |
| 2 | |
| 3 | Copyright (C) 2020-2021 Free Software Foundation, Inc. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 7 | This program 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 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 19 | |
| 20 | #include "defs.h" |
| 21 | #include "arch-utils.h" |
| 22 | #include "dis-asm.h" |
| 23 | #include "frame.h" |
| 24 | #include "frame-unwind.h" |
| 25 | #include "trad-frame.h" |
| 26 | #include "symtab.h" |
| 27 | #include "value.h" |
| 28 | #include "gdbcmd.h" |
| 29 | #include "breakpoint.h" |
| 30 | #include "inferior.h" |
| 31 | #include "regcache.h" |
| 32 | #include "target.h" |
| 33 | #include "dwarf2/frame.h" |
| 34 | #include "osabi.h" |
| 35 | #include "target-descriptions.h" |
| 36 | #include "remote.h" |
| 37 | |
| 38 | \f |
| 39 | /* eBPF registers. */ |
| 40 | |
| 41 | enum bpf_regnum |
| 42 | { |
| 43 | BPF_R0_REGNUM, /* return value */ |
| 44 | BPF_R1_REGNUM, |
| 45 | BPF_R2_REGNUM, |
| 46 | BPF_R3_REGNUM, |
| 47 | BPF_R4_REGNUM, |
| 48 | BPF_R5_REGNUM, |
| 49 | BPF_R6_REGNUM, |
| 50 | BPF_R7_REGNUM, |
| 51 | BPF_R8_REGNUM, |
| 52 | BPF_R9_REGNUM, |
| 53 | BPF_R10_REGNUM, /* sp */ |
| 54 | BPF_PC_REGNUM, |
| 55 | }; |
| 56 | |
| 57 | #define BPF_NUM_REGS (BPF_PC_REGNUM + 1) |
| 58 | |
| 59 | /* Target-dependent structure in gdbarch. */ |
| 60 | struct gdbarch_tdep |
| 61 | { |
| 62 | }; |
| 63 | |
| 64 | \f |
| 65 | /* Internal debugging facilities. */ |
| 66 | |
| 67 | /* When this is set to non-zero debugging information will be |
| 68 | printed. */ |
| 69 | |
| 70 | static unsigned int bpf_debug_flag = 0; |
| 71 | |
| 72 | /* The show callback for 'show debug bpf'. */ |
| 73 | |
| 74 | static void |
| 75 | show_bpf_debug (struct ui_file *file, int from_tty, |
| 76 | struct cmd_list_element *c, const char *value) |
| 77 | { |
| 78 | fprintf_filtered (file, _("Debugging of BPF is %s.\n"), value); |
| 79 | } |
| 80 | |
| 81 | \f |
| 82 | /* BPF registers. */ |
| 83 | |
| 84 | static const char *bpf_register_names[] = |
| 85 | { |
| 86 | "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", |
| 87 | "r8", "r9", "r10", "pc" |
| 88 | }; |
| 89 | |
| 90 | /* Return the name of register REGNUM. */ |
| 91 | |
| 92 | static const char * |
| 93 | bpf_register_name (struct gdbarch *gdbarch, int reg) |
| 94 | { |
| 95 | if (reg >= 0 && reg < BPF_NUM_REGS) |
| 96 | return bpf_register_names[reg]; |
| 97 | return NULL; |
| 98 | } |
| 99 | |
| 100 | /* Return the GDB type of register REGNUM. */ |
| 101 | |
| 102 | static struct type * |
| 103 | bpf_register_type (struct gdbarch *gdbarch, int reg) |
| 104 | { |
| 105 | if (reg == BPF_R10_REGNUM) |
| 106 | return builtin_type (gdbarch)->builtin_data_ptr; |
| 107 | else if (reg == BPF_PC_REGNUM) |
| 108 | return builtin_type (gdbarch)->builtin_func_ptr; |
| 109 | return builtin_type (gdbarch)->builtin_int64; |
| 110 | } |
| 111 | |
| 112 | /* Return the GDB register number corresponding to DWARF's REG. */ |
| 113 | |
| 114 | static int |
| 115 | bpf_dwarf2_reg_to_regnum (struct gdbarch *gdbarch, int reg) |
| 116 | { |
| 117 | if (reg >= 0 && reg < BPF_NUM_REGS) |
| 118 | return reg; |
| 119 | return -1; |
| 120 | } |
| 121 | |
| 122 | /* Implement the "print_insn" gdbarch method. */ |
| 123 | |
| 124 | static int |
| 125 | bpf_gdb_print_insn (bfd_vma memaddr, disassemble_info *info) |
| 126 | { |
| 127 | info->symbols = NULL; |
| 128 | return default_print_insn (memaddr, info); |
| 129 | } |
| 130 | |
| 131 | \f |
| 132 | /* Return PC of first real instruction of the function starting at |
| 133 | START_PC. */ |
| 134 | |
| 135 | static CORE_ADDR |
| 136 | bpf_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc) |
| 137 | { |
| 138 | fprintf_unfiltered (gdb_stdlog, |
| 139 | "Skipping prologue: start_pc=%s\n", |
| 140 | paddress (gdbarch, start_pc)); |
| 141 | /* XXX: to be completed. */ |
| 142 | return start_pc + 0; |
| 143 | } |
| 144 | |
| 145 | \f |
| 146 | /* Frame unwinder. |
| 147 | |
| 148 | XXX it is not clear how to unwind in eBPF, since the stack is not |
| 149 | guaranteed to be contiguous, and therefore no relative stack |
| 150 | addressing can be done in the callee in order to access the |
| 151 | caller's stack frame. To explore with xBPF, which will relax this |
| 152 | restriction. */ |
| 153 | |
| 154 | /* Given THIS_FRAME, return its ID. */ |
| 155 | |
| 156 | static void |
| 157 | bpf_frame_this_id (struct frame_info *this_frame, |
| 158 | void **this_prologue_cache, |
| 159 | struct frame_id *this_id) |
| 160 | { |
| 161 | /* Note that THIS_ID defaults to the outermost frame if we don't set |
| 162 | anything here. See frame.c:compute_frame_id. */ |
| 163 | } |
| 164 | |
| 165 | /* Return the reason why we can't unwind past THIS_FRAME. */ |
| 166 | |
| 167 | static enum unwind_stop_reason |
| 168 | bpf_frame_unwind_stop_reason (struct frame_info *this_frame, |
| 169 | void **this_cache) |
| 170 | { |
| 171 | return UNWIND_OUTERMOST; |
| 172 | } |
| 173 | |
| 174 | /* Ask THIS_FRAME to unwind its register. */ |
| 175 | |
| 176 | static struct value * |
| 177 | bpf_frame_prev_register (struct frame_info *this_frame, |
| 178 | void **this_prologue_cache, int regnum) |
| 179 | { |
| 180 | return frame_unwind_got_register (this_frame, regnum, regnum); |
| 181 | } |
| 182 | |
| 183 | /* Frame unwinder machinery for BPF. */ |
| 184 | |
| 185 | static const struct frame_unwind bpf_frame_unwind = |
| 186 | { |
| 187 | NORMAL_FRAME, |
| 188 | bpf_frame_unwind_stop_reason, |
| 189 | bpf_frame_this_id, |
| 190 | bpf_frame_prev_register, |
| 191 | NULL, |
| 192 | default_frame_sniffer |
| 193 | }; |
| 194 | |
| 195 | \f |
| 196 | /* Breakpoints. */ |
| 197 | |
| 198 | /* Enum describing the different kinds of breakpoints. We currently |
| 199 | just support one, implemented by the brkpt xbpf instruction. */ |
| 200 | |
| 201 | enum bpf_breakpoint_kinds |
| 202 | { |
| 203 | BPF_BP_KIND_BRKPT = 0, |
| 204 | }; |
| 205 | |
| 206 | /* Implement the breakpoint_kind_from_pc gdbarch method. */ |
| 207 | |
| 208 | static int |
| 209 | bpf_breakpoint_kind_from_pc (struct gdbarch *gdbarch, CORE_ADDR *start_pc) |
| 210 | { |
| 211 | /* We support just one kind of breakpoint. */ |
| 212 | return BPF_BP_KIND_BRKPT; |
| 213 | } |
| 214 | |
| 215 | /* Implement the sw_breakpoint_from_kind gdbarch method. */ |
| 216 | |
| 217 | static const gdb_byte * |
| 218 | bpf_sw_breakpoint_from_kind (struct gdbarch *gdbarch, int kind, int *size) |
| 219 | { |
| 220 | static unsigned char brkpt_insn[] |
| 221 | = {0x8c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}; |
| 222 | |
| 223 | switch (kind) |
| 224 | { |
| 225 | case BPF_BP_KIND_BRKPT: |
| 226 | *size = 8; |
| 227 | return brkpt_insn; |
| 228 | default: |
| 229 | gdb_assert_not_reached ("unexpected BPF breakpoint kind"); |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | \f |
| 234 | /* Assuming THIS_FRAME is a dummy frame, return its frame ID. */ |
| 235 | |
| 236 | static struct frame_id |
| 237 | bpf_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame) |
| 238 | { |
| 239 | CORE_ADDR sp = get_frame_register_unsigned (this_frame, |
| 240 | gdbarch_sp_regnum (gdbarch)); |
| 241 | return frame_id_build (sp, get_frame_pc (this_frame)); |
| 242 | } |
| 243 | |
| 244 | /* Implement the push dummy call gdbarch callback. */ |
| 245 | |
| 246 | static CORE_ADDR |
| 247 | bpf_push_dummy_call (struct gdbarch *gdbarch, struct value *function, |
| 248 | struct regcache *regcache, CORE_ADDR bp_addr, |
| 249 | int nargs, struct value **args, CORE_ADDR sp, |
| 250 | function_call_return_method return_method, |
| 251 | CORE_ADDR struct_addr) |
| 252 | { |
| 253 | fprintf_unfiltered (gdb_stdlog, "Pushing dummy call: sp=%s\n", |
| 254 | paddress (gdbarch, sp)); |
| 255 | /* XXX writeme */ |
| 256 | return sp; |
| 257 | } |
| 258 | |
| 259 | /* Extract a function return value of TYPE from REGCACHE, |
| 260 | and copy it into VALBUF. */ |
| 261 | |
| 262 | static void |
| 263 | bpf_extract_return_value (struct type *type, struct regcache *regcache, |
| 264 | gdb_byte *valbuf) |
| 265 | { |
| 266 | int len = TYPE_LENGTH (type); |
| 267 | gdb_byte vbuf[8]; |
| 268 | |
| 269 | gdb_assert (len <= 8); |
| 270 | regcache->cooked_read (BPF_R0_REGNUM, vbuf); |
| 271 | memcpy (valbuf, vbuf + 8 - len, len); |
| 272 | } |
| 273 | |
| 274 | /* Store the function return value of type TYPE from VALBUF into REGNAME. */ |
| 275 | |
| 276 | static void |
| 277 | bpf_store_return_value (struct type *type, struct regcache *regcache, |
| 278 | const gdb_byte *valbuf) |
| 279 | { |
| 280 | int len = TYPE_LENGTH (type); |
| 281 | gdb_byte vbuf[8]; |
| 282 | |
| 283 | gdb_assert (len <= 8); |
| 284 | memset (vbuf, 0, sizeof (vbuf)); |
| 285 | memcpy (vbuf + 8 - len, valbuf, len); |
| 286 | regcache->cooked_write (BPF_R0_REGNUM, vbuf); |
| 287 | } |
| 288 | |
| 289 | /* Handle function's return value. */ |
| 290 | |
| 291 | static enum return_value_convention |
| 292 | bpf_return_value (struct gdbarch *gdbarch, struct value *function, |
| 293 | struct type *type, struct regcache *regcache, |
| 294 | gdb_byte *readbuf, const gdb_byte *writebuf) |
| 295 | { |
| 296 | int len = TYPE_LENGTH (type); |
| 297 | |
| 298 | if (len > 8) |
| 299 | return RETURN_VALUE_STRUCT_CONVENTION; |
| 300 | |
| 301 | if (readbuf != NULL) |
| 302 | bpf_extract_return_value (type, regcache, readbuf); |
| 303 | if (writebuf != NULL) |
| 304 | bpf_store_return_value (type, regcache, writebuf); |
| 305 | |
| 306 | return RETURN_VALUE_REGISTER_CONVENTION; |
| 307 | } |
| 308 | |
| 309 | \f |
| 310 | /* Initialize the current architecture based on INFO. If possible, re-use an |
| 311 | architecture from ARCHES, which is a list of architectures already created |
| 312 | during this debugging session. */ |
| 313 | |
| 314 | static struct gdbarch * |
| 315 | bpf_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches) |
| 316 | { |
| 317 | /* If there is already a candidate, use it. */ |
| 318 | arches = gdbarch_list_lookup_by_info (arches, &info); |
| 319 | if (arches != NULL) |
| 320 | return arches->gdbarch; |
| 321 | |
| 322 | /* Allocate space for the new architecture. */ |
| 323 | struct gdbarch_tdep *tdep = XCNEW (struct gdbarch_tdep); |
| 324 | struct gdbarch *gdbarch = gdbarch_alloc (&info, tdep); |
| 325 | |
| 326 | /* Information about registers, etc. */ |
| 327 | set_gdbarch_num_regs (gdbarch, BPF_NUM_REGS); |
| 328 | set_gdbarch_register_name (gdbarch, bpf_register_name); |
| 329 | set_gdbarch_register_type (gdbarch, bpf_register_type); |
| 330 | |
| 331 | /* Register numbers of various important registers. */ |
| 332 | set_gdbarch_sp_regnum (gdbarch, BPF_R10_REGNUM); |
| 333 | set_gdbarch_pc_regnum (gdbarch, BPF_PC_REGNUM); |
| 334 | |
| 335 | /* Map DWARF2 registers to GDB registers. */ |
| 336 | set_gdbarch_dwarf2_reg_to_regnum (gdbarch, bpf_dwarf2_reg_to_regnum); |
| 337 | |
| 338 | /* Call dummy code. */ |
| 339 | set_gdbarch_call_dummy_location (gdbarch, ON_STACK); |
| 340 | set_gdbarch_dummy_id (gdbarch, bpf_dummy_id); |
| 341 | set_gdbarch_push_dummy_call (gdbarch, bpf_push_dummy_call); |
| 342 | |
| 343 | /* Returning results. */ |
| 344 | set_gdbarch_return_value (gdbarch, bpf_return_value); |
| 345 | |
| 346 | /* Advance PC across function entry code. */ |
| 347 | set_gdbarch_skip_prologue (gdbarch, bpf_skip_prologue); |
| 348 | |
| 349 | /* Stack grows downward. */ |
| 350 | set_gdbarch_inner_than (gdbarch, core_addr_lessthan); |
| 351 | |
| 352 | /* Breakpoint manipulation. */ |
| 353 | set_gdbarch_breakpoint_kind_from_pc (gdbarch, bpf_breakpoint_kind_from_pc); |
| 354 | set_gdbarch_sw_breakpoint_from_kind (gdbarch, bpf_sw_breakpoint_from_kind); |
| 355 | |
| 356 | /* Frame handling. */ |
| 357 | set_gdbarch_frame_args_skip (gdbarch, 8); |
| 358 | |
| 359 | /* Disassembly. */ |
| 360 | set_gdbarch_print_insn (gdbarch, bpf_gdb_print_insn); |
| 361 | |
| 362 | /* Hook in ABI-specific overrides, if they have been registered. */ |
| 363 | gdbarch_init_osabi (info, gdbarch); |
| 364 | |
| 365 | /* Install unwinders. */ |
| 366 | frame_unwind_append_unwinder (gdbarch, &bpf_frame_unwind); |
| 367 | |
| 368 | return gdbarch; |
| 369 | } |
| 370 | |
| 371 | void _initialize_bpf_tdep (); |
| 372 | void |
| 373 | _initialize_bpf_tdep (void) |
| 374 | { |
| 375 | register_gdbarch_init (bfd_arch_bpf, bpf_gdbarch_init); |
| 376 | |
| 377 | /* Add commands 'set/show debug bpf'. */ |
| 378 | add_setshow_zuinteger_cmd ("bpf", class_maintenance, |
| 379 | &bpf_debug_flag, |
| 380 | _("Set BPF debugging."), |
| 381 | _("Show BPF debugging."), |
| 382 | _("Enables BPF specific debugging output."), |
| 383 | NULL, |
| 384 | &show_bpf_debug, |
| 385 | &setdebuglist, &showdebuglist); |
| 386 | } |