1 /* Target-dependent code for GNU/Linux m32r. 2 3 Copyright (C) 2004-2014 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 "gdbcore.h" 22 #include "frame.h" 23 #include "value.h" 24 #include "regcache.h" 25 #include "inferior.h" 26 #include "osabi.h" 27 #include "reggroups.h" 28 #include "regset.h" 29 30 #include <string.h> 31 32 #include "glibc-tdep.h" 33 #include "solib-svr4.h" 34 #include "symtab.h" 35 36 #include "trad-frame.h" 37 #include "frame-unwind.h" 38 39 #include "m32r-tdep.h" 40 #include "linux-tdep.h" 41 42 43 44 /* Recognizing signal handler frames. */ 45 46 /* GNU/Linux has two flavors of signals. Normal signal handlers, and 47 "realtime" (RT) signals. The RT signals can provide additional 48 information to the signal handler if the SA_SIGINFO flag is set 49 when establishing a signal handler using `sigaction'. It is not 50 unlikely that future versions of GNU/Linux will support SA_SIGINFO 51 for normal signals too. */ 52 53 /* When the m32r Linux kernel calls a signal handler and the 54 SA_RESTORER flag isn't set, the return address points to a bit of 55 code on the stack. This function returns whether the PC appears to 56 be within this bit of code. 57 58 The instruction sequence for normal signals is 59 ldi r7, #__NR_sigreturn 60 trap #2 61 or 0x67 0x77 0x10 0xf2. 62 63 Checking for the code sequence should be somewhat reliable, because 64 the effect is to call the system call sigreturn. This is unlikely 65 to occur anywhere other than in a signal trampoline. 66 67 It kind of sucks that we have to read memory from the process in 68 order to identify a signal trampoline, but there doesn't seem to be 69 any other way. Therefore we only do the memory reads if no 70 function name could be identified, which should be the case since 71 the code is on the stack. 72 73 Detection of signal trampolines for handlers that set the 74 SA_RESTORER flag is in general not possible. Unfortunately this is 75 what the GNU C Library has been doing for quite some time now. 76 However, as of version 2.1.2, the GNU C Library uses signal 77 trampolines (named __restore and __restore_rt) that are identical 78 to the ones used by the kernel. Therefore, these trampolines are 79 supported too. */ 80 81 static const gdb_byte linux_sigtramp_code[] = { 82 0x67, 0x77, 0x10, 0xf2, 83 }; 84 85 /* If PC is in a sigtramp routine, return the address of the start of 86 the routine. Otherwise, return 0. */ 87 88 static CORE_ADDR 89 m32r_linux_sigtramp_start (CORE_ADDR pc, struct frame_info *this_frame) 90 { 91 gdb_byte buf[4]; 92 93 /* We only recognize a signal trampoline if PC is at the start of 94 one of the instructions. We optimize for finding the PC at the 95 start of the instruction sequence, as will be the case when the 96 trampoline is not the first frame on the stack. We assume that 97 in the case where the PC is not at the start of the instruction 98 sequence, there will be a few trailing readable bytes on the 99 stack. */ 100 101 if (pc % 2 != 0) 102 { 103 if (!safe_frame_unwind_memory (this_frame, pc, buf, 2)) 104 return 0; 105 106 if (memcmp (buf, linux_sigtramp_code, 2) == 0) 107 pc -= 2; 108 else 109 return 0; 110 } 111 112 if (!safe_frame_unwind_memory (this_frame, pc, buf, 4)) 113 return 0; 114 115 if (memcmp (buf, linux_sigtramp_code, 4) != 0) 116 return 0; 117 118 return pc; 119 } 120 121 /* This function does the same for RT signals. Here the instruction 122 sequence is 123 ldi r7, #__NR_rt_sigreturn 124 trap #2 125 or 0x97 0xf0 0x00 0xad 0x10 0xf2 0xf0 0x00. 126 127 The effect is to call the system call rt_sigreturn. */ 128 129 static const gdb_byte linux_rt_sigtramp_code[] = { 130 0x97, 0xf0, 0x00, 0xad, 0x10, 0xf2, 0xf0, 0x00, 131 }; 132 133 /* If PC is in a RT sigtramp routine, return the address of the start 134 of the routine. Otherwise, return 0. */ 135 136 static CORE_ADDR 137 m32r_linux_rt_sigtramp_start (CORE_ADDR pc, struct frame_info *this_frame) 138 { 139 gdb_byte buf[4]; 140 141 /* We only recognize a signal trampoline if PC is at the start of 142 one of the instructions. We optimize for finding the PC at the 143 start of the instruction sequence, as will be the case when the 144 trampoline is not the first frame on the stack. We assume that 145 in the case where the PC is not at the start of the instruction 146 sequence, there will be a few trailing readable bytes on the 147 stack. */ 148 149 if (pc % 2 != 0) 150 return 0; 151 152 if (!safe_frame_unwind_memory (this_frame, pc, buf, 4)) 153 return 0; 154 155 if (memcmp (buf, linux_rt_sigtramp_code, 4) == 0) 156 { 157 if (!safe_frame_unwind_memory (this_frame, pc + 4, buf, 4)) 158 return 0; 159 160 if (memcmp (buf, linux_rt_sigtramp_code + 4, 4) == 0) 161 return pc; 162 } 163 else if (memcmp (buf, linux_rt_sigtramp_code + 4, 4) == 0) 164 { 165 if (!safe_frame_unwind_memory (this_frame, pc - 4, buf, 4)) 166 return 0; 167 168 if (memcmp (buf, linux_rt_sigtramp_code, 4) == 0) 169 return pc - 4; 170 } 171 172 return 0; 173 } 174 175 static int 176 m32r_linux_pc_in_sigtramp (CORE_ADDR pc, const char *name, 177 struct frame_info *this_frame) 178 { 179 /* If we have NAME, we can optimize the search. The trampolines are 180 named __restore and __restore_rt. However, they aren't dynamically 181 exported from the shared C library, so the trampoline may appear to 182 be part of the preceding function. This should always be sigaction, 183 __sigaction, or __libc_sigaction (all aliases to the same function). */ 184 if (name == NULL || strstr (name, "sigaction") != NULL) 185 return (m32r_linux_sigtramp_start (pc, this_frame) != 0 186 || m32r_linux_rt_sigtramp_start (pc, this_frame) != 0); 187 188 return (strcmp ("__restore", name) == 0 189 || strcmp ("__restore_rt", name) == 0); 190 } 191 192 /* From <asm/sigcontext.h>. */ 193 static int m32r_linux_sc_reg_offset[] = { 194 4 * 4, /* r0 */ 195 5 * 4, /* r1 */ 196 6 * 4, /* r2 */ 197 7 * 4, /* r3 */ 198 0 * 4, /* r4 */ 199 1 * 4, /* r5 */ 200 2 * 4, /* r6 */ 201 8 * 4, /* r7 */ 202 9 * 4, /* r8 */ 203 10 * 4, /* r9 */ 204 11 * 4, /* r10 */ 205 12 * 4, /* r11 */ 206 13 * 4, /* r12 */ 207 21 * 4, /* fp */ 208 22 * 4, /* lr */ 209 -1 * 4, /* sp */ 210 16 * 4, /* psw */ 211 -1 * 4, /* cbr */ 212 23 * 4, /* spi */ 213 20 * 4, /* spu */ 214 19 * 4, /* bpc */ 215 17 * 4, /* pc */ 216 15 * 4, /* accl */ 217 14 * 4 /* acch */ 218 }; 219 220 struct m32r_frame_cache 221 { 222 CORE_ADDR base, pc; 223 struct trad_frame_saved_reg *saved_regs; 224 }; 225 226 static struct m32r_frame_cache * 227 m32r_linux_sigtramp_frame_cache (struct frame_info *this_frame, 228 void **this_cache) 229 { 230 struct m32r_frame_cache *cache; 231 CORE_ADDR sigcontext_addr, addr; 232 int regnum; 233 234 if ((*this_cache) != NULL) 235 return (*this_cache); 236 cache = FRAME_OBSTACK_ZALLOC (struct m32r_frame_cache); 237 (*this_cache) = cache; 238 cache->saved_regs = trad_frame_alloc_saved_regs (this_frame); 239 240 cache->base = get_frame_register_unsigned (this_frame, M32R_SP_REGNUM); 241 sigcontext_addr = cache->base + 4; 242 243 cache->pc = get_frame_pc (this_frame); 244 addr = m32r_linux_sigtramp_start (cache->pc, this_frame); 245 if (addr == 0) 246 { 247 /* If this is a RT signal trampoline, adjust SIGCONTEXT_ADDR 248 accordingly. */ 249 addr = m32r_linux_rt_sigtramp_start (cache->pc, this_frame); 250 if (addr) 251 sigcontext_addr += 128; 252 else 253 addr = get_frame_func (this_frame); 254 } 255 cache->pc = addr; 256 257 cache->saved_regs = trad_frame_alloc_saved_regs (this_frame); 258 259 for (regnum = 0; regnum < sizeof (m32r_linux_sc_reg_offset) / 4; regnum++) 260 { 261 if (m32r_linux_sc_reg_offset[regnum] >= 0) 262 cache->saved_regs[regnum].addr = 263 sigcontext_addr + m32r_linux_sc_reg_offset[regnum]; 264 } 265 266 return cache; 267 } 268 269 static void 270 m32r_linux_sigtramp_frame_this_id (struct frame_info *this_frame, 271 void **this_cache, 272 struct frame_id *this_id) 273 { 274 struct m32r_frame_cache *cache = 275 m32r_linux_sigtramp_frame_cache (this_frame, this_cache); 276 277 (*this_id) = frame_id_build (cache->base, cache->pc); 278 } 279 280 static struct value * 281 m32r_linux_sigtramp_frame_prev_register (struct frame_info *this_frame, 282 void **this_cache, int regnum) 283 { 284 struct m32r_frame_cache *cache = 285 m32r_linux_sigtramp_frame_cache (this_frame, this_cache); 286 287 return trad_frame_get_prev_register (this_frame, cache->saved_regs, regnum); 288 } 289 290 static int 291 m32r_linux_sigtramp_frame_sniffer (const struct frame_unwind *self, 292 struct frame_info *this_frame, 293 void **this_cache) 294 { 295 CORE_ADDR pc = get_frame_pc (this_frame); 296 const char *name; 297 298 find_pc_partial_function (pc, &name, NULL, NULL); 299 if (m32r_linux_pc_in_sigtramp (pc, name, this_frame)) 300 return 1; 301 302 return 0; 303 } 304 305 static const struct frame_unwind m32r_linux_sigtramp_frame_unwind = { 306 SIGTRAMP_FRAME, 307 default_frame_unwind_stop_reason, 308 m32r_linux_sigtramp_frame_this_id, 309 m32r_linux_sigtramp_frame_prev_register, 310 NULL, 311 m32r_linux_sigtramp_frame_sniffer 312 }; 313 314 /* Mapping between the registers in `struct pt_regs' 315 format and GDB's register array layout. */ 316 317 static int m32r_pt_regs_offset[] = { 318 4 * 4, /* r0 */ 319 4 * 5, /* r1 */ 320 4 * 6, /* r2 */ 321 4 * 7, /* r3 */ 322 4 * 0, /* r4 */ 323 4 * 1, /* r5 */ 324 4 * 2, /* r6 */ 325 4 * 8, /* r7 */ 326 4 * 9, /* r8 */ 327 4 * 10, /* r9 */ 328 4 * 11, /* r10 */ 329 4 * 12, /* r11 */ 330 4 * 13, /* r12 */ 331 4 * 24, /* fp */ 332 4 * 25, /* lr */ 333 4 * 23, /* sp */ 334 4 * 19, /* psw */ 335 4 * 19, /* cbr */ 336 4 * 26, /* spi */ 337 4 * 23, /* spu */ 338 4 * 22, /* bpc */ 339 4 * 20, /* pc */ 340 4 * 16, /* accl */ 341 4 * 15 /* acch */ 342 }; 343 344 #define PSW_OFFSET (4 * 19) 345 #define BBPSW_OFFSET (4 * 21) 346 #define SPU_OFFSET (4 * 23) 347 #define SPI_OFFSET (4 * 26) 348 349 static void 350 m32r_linux_supply_gregset (const struct regset *regset, 351 struct regcache *regcache, int regnum, 352 const void *gregs, size_t size) 353 { 354 const char *regs = gregs; 355 unsigned long psw, bbpsw; 356 int i; 357 358 psw = *((unsigned long *) (regs + PSW_OFFSET)); 359 bbpsw = *((unsigned long *) (regs + BBPSW_OFFSET)); 360 361 for (i = 0; i < sizeof (m32r_pt_regs_offset) / 4; i++) 362 { 363 if (regnum != -1 && regnum != i) 364 continue; 365 366 switch (i) 367 { 368 case PSW_REGNUM: 369 *((unsigned long *) (regs + m32r_pt_regs_offset[i])) = 370 ((0x00c1 & bbpsw) << 8) | ((0xc100 & psw) >> 8); 371 break; 372 case CBR_REGNUM: 373 *((unsigned long *) (regs + m32r_pt_regs_offset[i])) = 374 ((psw >> 8) & 1); 375 break; 376 case M32R_SP_REGNUM: 377 if (psw & 0x8000) 378 *((unsigned long *) (regs + m32r_pt_regs_offset[i])) = 379 *((unsigned long *) (regs + SPU_OFFSET)); 380 else 381 *((unsigned long *) (regs + m32r_pt_regs_offset[i])) = 382 *((unsigned long *) (regs + SPI_OFFSET)); 383 break; 384 } 385 386 regcache_raw_supply (regcache, i, 387 regs + m32r_pt_regs_offset[i]); 388 } 389 } 390 391 static struct regset m32r_linux_gregset = { 392 NULL, m32r_linux_supply_gregset 393 }; 394 395 static const struct regset * 396 m32r_linux_regset_from_core_section (struct gdbarch *core_arch, 397 const char *sect_name, size_t sect_size) 398 { 399 struct gdbarch_tdep *tdep = gdbarch_tdep (core_arch); 400 if (strcmp (sect_name, ".reg") == 0) 401 return &m32r_linux_gregset; 402 return NULL; 403 } 404 405 static void 406 m32r_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) 407 { 408 struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); 409 410 linux_init_abi (info, gdbarch); 411 412 /* Since EVB register is not available for native debug, we reduce 413 the number of registers. */ 414 set_gdbarch_num_regs (gdbarch, M32R_NUM_REGS - 1); 415 416 frame_unwind_append_unwinder (gdbarch, &m32r_linux_sigtramp_frame_unwind); 417 418 /* GNU/Linux uses SVR4-style shared libraries. */ 419 set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target); 420 set_solib_svr4_fetch_link_map_offsets 421 (gdbarch, svr4_ilp32_fetch_link_map_offsets); 422 423 /* Core file support. */ 424 set_gdbarch_regset_from_core_section 425 (gdbarch, m32r_linux_regset_from_core_section); 426 427 /* Enable TLS support. */ 428 set_gdbarch_fetch_tls_load_module_address (gdbarch, 429 svr4_fetch_objfile_link_map); 430 } 431 432 /* Provide a prototype to silence -Wmissing-prototypes. */ 433 extern void _initialize_m32r_linux_tdep (void); 434 435 void 436 _initialize_m32r_linux_tdep (void) 437 { 438 gdbarch_register_osabi (bfd_arch_m32r, 0, GDB_OSABI_LINUX, 439 m32r_linux_init_abi); 440 } 441