1 /* Target-dependent code for GNU/Linux m32r. 2 3 Copyright 2004 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 2 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, write to the Free Software 19 Foundation, Inc., 59 Temple Place - Suite 330, 20 Boston, MA 02111-1307, USA. */ 21 22 #include "defs.h" 23 #include "gdbcore.h" 24 #include "frame.h" 25 #include "value.h" 26 #include "regcache.h" 27 #include "inferior.h" 28 #include "osabi.h" 29 #include "reggroups.h" 30 31 #include "gdb_string.h" 32 33 #include "glibc-tdep.h" 34 #include "solib-svr4.h" 35 36 #include "trad-frame.h" 37 #include "frame-unwind.h" 38 39 #include "m32r-tdep.h" 40 41 42 /* Recognizing signal handler frames. */ 43 44 /* GNU/Linux has two flavors of signals. Normal signal handlers, and 45 "realtime" (RT) signals. The RT signals can provide additional 46 information to the signal handler if the SA_SIGINFO flag is set 47 when establishing a signal handler using `sigaction'. It is not 48 unlikely that future versions of GNU/Linux will support SA_SIGINFO 49 for normal signals too. */ 50 51 /* When the m32r Linux kernel calls a signal handler and the 52 SA_RESTORER flag isn't set, the return address points to a bit of 53 code on the stack. This function returns whether the PC appears to 54 be within this bit of code. 55 56 The instruction sequence for normal signals is 57 ldi r7, #__NR_sigreturn 58 trap #2 59 or 0x67 0x77 0x10 0xf2. 60 61 Checking for the code sequence should be somewhat reliable, because 62 the effect is to call the system call sigreturn. This is unlikely 63 to occur anywhere other than in a signal trampoline. 64 65 It kind of sucks that we have to read memory from the process in 66 order to identify a signal trampoline, but there doesn't seem to be 67 any other way. Therefore we only do the memory reads if no 68 function name could be identified, which should be the case since 69 the code is on the stack. 70 71 Detection of signal trampolines for handlers that set the 72 SA_RESTORER flag is in general not possible. Unfortunately this is 73 what the GNU C Library has been doing for quite some time now. 74 However, as of version 2.1.2, the GNU C Library uses signal 75 trampolines (named __restore and __restore_rt) that are identical 76 to the ones used by the kernel. Therefore, these trampolines are 77 supported too. */ 78 79 static const unsigned char linux_sigtramp_code[] = { 80 0x67, 0x77, 0x10, 0xf2, 81 }; 82 83 /* If PC is in a sigtramp routine, return the address of the start of 84 the routine. Otherwise, return 0. */ 85 86 static CORE_ADDR 87 m32r_linux_sigtramp_start (CORE_ADDR pc, struct frame_info *next_frame) 88 { 89 unsigned char buf[4]; 90 91 /* We only recognize a signal trampoline if PC is at the start of 92 one of the instructions. We optimize for finding the PC at the 93 start of the instruction sequence, as will be the case when the 94 trampoline is not the first frame on the stack. We assume that 95 in the case where the PC is not at the start of the instruction 96 sequence, there will be a few trailing readable bytes on the 97 stack. */ 98 99 if (pc % 2 != 0) 100 { 101 if (!safe_frame_unwind_memory (next_frame, pc, buf, 2)) 102 return 0; 103 104 if (memcmp (buf, linux_sigtramp_code, 2) == 0) 105 pc -= 2; 106 else 107 return 0; 108 } 109 110 if (!safe_frame_unwind_memory (next_frame, pc, buf, 4)) 111 return 0; 112 113 if (memcmp (buf, linux_sigtramp_code, 4) != 0) 114 return 0; 115 116 return pc; 117 } 118 119 /* This function does the same for RT signals. Here the instruction 120 sequence is 121 ldi r7, #__NR_rt_sigreturn 122 trap #2 123 or 0x97 0xf0 0x00 0xad 0x10 0xf2 0xf0 0x00. 124 125 The effect is to call the system call rt_sigreturn. */ 126 127 static const unsigned char linux_rt_sigtramp_code[] = { 128 0x97, 0xf0, 0x00, 0xad, 0x10, 0xf2, 0xf0, 0x00, 129 }; 130 131 /* If PC is in a RT sigtramp routine, return the address of the start 132 of the routine. Otherwise, return 0. */ 133 134 static CORE_ADDR 135 m32r_linux_rt_sigtramp_start (CORE_ADDR pc, struct frame_info *next_frame) 136 { 137 unsigned char buf[4]; 138 139 /* We only recognize a signal trampoline if PC is at the start of 140 one of the instructions. We optimize for finding the PC at the 141 start of the instruction sequence, as will be the case when the 142 trampoline is not the first frame on the stack. We assume that 143 in the case where the PC is not at the start of the instruction 144 sequence, there will be a few trailing readable bytes on the 145 stack. */ 146 147 if (pc % 2 != 0) 148 return 0; 149 150 if (!safe_frame_unwind_memory (next_frame, pc, buf, 4)) 151 return 0; 152 153 if (memcmp (buf, linux_rt_sigtramp_code, 4) == 0) 154 { 155 if (!safe_frame_unwind_memory (next_frame, pc + 4, buf, 4)) 156 return 0; 157 158 if (memcmp (buf, linux_rt_sigtramp_code + 4, 4) == 0) 159 return pc; 160 } 161 else if (memcmp (buf, linux_rt_sigtramp_code + 4, 4) == 0) 162 { 163 if (!safe_frame_unwind_memory (next_frame, pc - 4, buf, 4)) 164 return 0; 165 166 if (memcmp (buf, linux_rt_sigtramp_code, 4) == 0) 167 return pc - 4; 168 } 169 170 return 0; 171 } 172 173 static int 174 m32r_linux_pc_in_sigtramp (CORE_ADDR pc, char *name, 175 struct frame_info *next_frame) 176 { 177 /* If we have NAME, we can optimize the search. The trampolines are 178 named __restore and __restore_rt. However, they aren't dynamically 179 exported from the shared C library, so the trampoline may appear to 180 be part of the preceding function. This should always be sigaction, 181 __sigaction, or __libc_sigaction (all aliases to the same function). */ 182 if (name == NULL || strstr (name, "sigaction") != NULL) 183 return (m32r_linux_sigtramp_start (pc, next_frame) != 0 184 || m32r_linux_rt_sigtramp_start (pc, next_frame) != 0); 185 186 return (strcmp ("__restore", name) == 0 187 || strcmp ("__restore_rt", name) == 0); 188 } 189 190 /* From <asm/sigcontext.h>. */ 191 static int m32r_linux_sc_reg_offset[] = { 192 4 * 4, /* r0 */ 193 5 * 4, /* r1 */ 194 6 * 4, /* r2 */ 195 7 * 4, /* r3 */ 196 0 * 4, /* r4 */ 197 1 * 4, /* r5 */ 198 2 * 4, /* r6 */ 199 8 * 4, /* r7 */ 200 9 * 4, /* r8 */ 201 10 * 4, /* r9 */ 202 11 * 4, /* r10 */ 203 12 * 4, /* r11 */ 204 13 * 4, /* r12 */ 205 21 * 4, /* fp */ 206 22 * 4, /* lr */ 207 -1 * 4, /* sp */ 208 16 * 4, /* psw */ 209 -1 * 4, /* cbr */ 210 23 * 4, /* spi */ 211 20 * 4, /* spu */ 212 19 * 4, /* bpc */ 213 17 * 4, /* pc */ 214 15 * 4, /* accl */ 215 14 * 4 /* acch */ 216 }; 217 218 struct m32r_frame_cache 219 { 220 CORE_ADDR base, pc; 221 struct trad_frame_saved_reg *saved_regs; 222 }; 223 224 static struct m32r_frame_cache * 225 m32r_linux_sigtramp_frame_cache (struct frame_info *next_frame, 226 void **this_cache) 227 { 228 struct m32r_frame_cache *cache; 229 CORE_ADDR sigcontext_addr, addr; 230 int regnum; 231 232 if ((*this_cache) != NULL) 233 return (*this_cache); 234 cache = FRAME_OBSTACK_ZALLOC (struct m32r_frame_cache); 235 (*this_cache) = cache; 236 cache->saved_regs = trad_frame_alloc_saved_regs (next_frame); 237 238 cache->base = frame_unwind_register_unsigned (next_frame, M32R_SP_REGNUM); 239 sigcontext_addr = cache->base + 4; 240 241 cache->pc = frame_pc_unwind (next_frame); 242 addr = m32r_linux_sigtramp_start (cache->pc, next_frame); 243 if (addr == 0) 244 { 245 /* If this is a RT signal trampoline, adjust SIGCONTEXT_ADDR 246 accordingly. */ 247 addr = m32r_linux_rt_sigtramp_start (cache->pc, next_frame); 248 if (addr) 249 sigcontext_addr += 128; 250 else 251 addr = frame_func_unwind (next_frame); 252 } 253 cache->pc = addr; 254 255 cache->saved_regs = trad_frame_alloc_saved_regs (next_frame); 256 257 for (regnum = 0; regnum < sizeof (m32r_linux_sc_reg_offset) / 4; regnum++) 258 { 259 if (m32r_linux_sc_reg_offset[regnum] >= 0) 260 cache->saved_regs[regnum].addr = 261 sigcontext_addr + m32r_linux_sc_reg_offset[regnum]; 262 } 263 264 return cache; 265 } 266 267 static void 268 m32r_linux_sigtramp_frame_this_id (struct frame_info *next_frame, 269 void **this_cache, 270 struct frame_id *this_id) 271 { 272 struct m32r_frame_cache *cache = 273 m32r_linux_sigtramp_frame_cache (next_frame, this_cache); 274 275 (*this_id) = frame_id_build (cache->base, cache->pc); 276 } 277 278 static void 279 m32r_linux_sigtramp_frame_prev_register (struct frame_info *next_frame, 280 void **this_cache, 281 int regnum, int *optimizedp, 282 enum lval_type *lvalp, 283 CORE_ADDR *addrp, 284 int *realnump, void *valuep) 285 { 286 struct m32r_frame_cache *cache = 287 m32r_linux_sigtramp_frame_cache (next_frame, this_cache); 288 289 trad_frame_get_prev_register (next_frame, cache->saved_regs, regnum, 290 optimizedp, lvalp, addrp, realnump, valuep); 291 } 292 293 static const struct frame_unwind m32r_linux_sigtramp_frame_unwind = { 294 SIGTRAMP_FRAME, 295 m32r_linux_sigtramp_frame_this_id, 296 m32r_linux_sigtramp_frame_prev_register 297 }; 298 299 static const struct frame_unwind * 300 m32r_linux_sigtramp_frame_sniffer (struct frame_info *next_frame) 301 { 302 CORE_ADDR pc = frame_pc_unwind (next_frame); 303 char *name; 304 305 find_pc_partial_function (pc, &name, NULL, NULL); 306 if (m32r_linux_pc_in_sigtramp (pc, name, next_frame)) 307 return &m32r_linux_sigtramp_frame_unwind; 308 309 return NULL; 310 } 311 312 static void 313 m32r_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) 314 { 315 struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); 316 317 /* Since EVB register is not available for native debug, we reduce 318 the number of registers. */ 319 set_gdbarch_num_regs (gdbarch, M32R_NUM_REGS - 1); 320 321 frame_unwind_append_sniffer (gdbarch, m32r_linux_sigtramp_frame_sniffer); 322 323 /* GNU/Linux uses SVR4-style shared libraries. */ 324 set_solib_svr4_fetch_link_map_offsets 325 (gdbarch, svr4_ilp32_fetch_link_map_offsets); 326 } 327 328 /* Provide a prototype to silence -Wmissing-prototypes. */ 329 extern void _initialize_m32r_linux_tdep (void); 330 331 void 332 _initialize_m32r_linux_tdep (void) 333 { 334 gdbarch_register_osabi (bfd_arch_m32r, 0, GDB_OSABI_LINUX, 335 m32r_linux_init_abi); 336 } 337