libgo/runtime/go-signal.c

   1 /* go-signal.c -- signal handling for Go.
   2
   3    Copyright 2009 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include <signal.h>
   8 #include <stdlib.h>
   9 #include <unistd.h>
  10 #include <sys/time.h>
  11 #include <ucontext.h>
  12
  13 #include "runtime.h"
  14
  15 #ifndef SA_RESTART
  16   #define SA_RESTART 0
  17 #endif
  18
  19 #ifdef USING_SPLIT_STACK
  20
  21 extern void __splitstack_getcontext(void *context[10]);
  22
  23 extern void __splitstack_setcontext(void *context[10]);
  24
  25 extern void *__splitstack_find_context(void *context[10], size_t *,
  26                                        void **, void **, void **);
  27
  28 #endif
  29
  30 // The rest of the signal handler, written in Go.
  31
  32 extern void sigtrampgo(uint32, siginfo_t *, void *)
  33         __asm__(GOSYM_PREFIX "runtime.sigtrampgo");
  34
  35 // The Go signal handler, written in C.  This should be running on the
  36 // alternate signal stack.  This is responsible for setting up the
  37 // split stack context so that stack guard checks will work as
  38 // expected.
  39
  40 void sigtramp(int, siginfo_t *, void *)
  41         __attribute__ ((no_split_stack));
  42
  43 void sigtramp(int, siginfo_t *, void *)
  44         __asm__ (GOSYM_PREFIX "runtime.sigtramp");
  45
  46 #ifndef USING_SPLIT_STACK
  47
  48 // When not using split stacks, there are no stack checks, and there
  49 // is nothing special for this function to do.
  50
  51 void
  52 sigtramp(int sig, siginfo_t *info, void *context)
  53 {
  54         sigtrampgo(sig, info, context);
  55 }
  56
  57 #else // USING_SPLIT_STACK
  58
  59 void
  60 sigtramp(int sig, siginfo_t *info, void *context)
  61 {
  62         G *gp;
  63         void *stack_context[10];
  64         void *stack;
  65         size_t stack_size;
  66         void *next_segment;
  67         void *next_sp;
  68         void *initial_sp;
  69         uintptr sp;
  70         stack_t st;
  71         uintptr stsp;
  72
  73         gp = runtime_g();
  74
  75         if (gp == nil) {
  76                 // Let the Go code handle this case.
  77                 // It should only call nosplit functions in this case.
  78                 sigtrampgo(sig, info, context);
  79                 return;
  80         }
  81
  82         // If this signal is one for which we will panic, we are not
  83         // on the alternate signal stack.  It's OK to call split-stack
  84         // functions here.
  85         if (sig == SIGBUS || sig == SIGFPE || sig == SIGSEGV) {
  86                 sigtrampgo(sig, info, context);
  87                 return;
  88         }
  89
  90         // We are running on the alternate signal stack.
  91
  92         __splitstack_getcontext(&stack_context[0]);
  93
  94         stack = __splitstack_find_context((void*)(&gp->m->gsignal->stackcontext[0]),
  95                                           &stack_size, &next_segment,
  96                                           &next_sp, &initial_sp);
  97
  98         // If some non-Go code called sigaltstack, adjust.
  99         sp = (uintptr)(&stack_size);
 100         if (sp < (uintptr)(stack) || sp >= (uintptr)(stack) + stack_size) {
 101                 sigaltstack(nil, &st);
 102                 if ((st.ss_flags & SS_DISABLE) != 0) {
 103                         runtime_printf("signal %d received on thread with no signal stack\n", (int32)(sig));
 104                         runtime_throw("non-Go code disabled sigaltstack");
 105                 }
 106
 107                 stsp = (uintptr)(st.ss_sp);
 108                 if (sp < stsp || sp >= stsp + st.ss_size) {
 109                         runtime_printf("signal %d received but handler not on signal stack\n", (int32)(sig));
 110                         runtime_throw("non-Go code set up signal handler without SA_ONSTACK flag");
 111                 }
 112
 113                 // Unfortunately __splitstack_find_context will return NULL
 114                 // when it is called on a context that has never been used.
 115                 // There isn't much we can do but assume all is well.
 116                 if (stack != NULL) {
 117                         // Here the gc runtime adjusts the gsignal
 118                         // stack guard to match the values returned by
 119                         // sigaltstack.  Unfortunately we have no way
 120                         // to do that.
 121                         runtime_printf("signal %d received on unknown signal stack\n", (int32)(sig));
 122                         runtime_throw("non-Go code changed signal stack");
 123                 }
 124         }
 125
 126         // Set the split stack context so that the stack guards are
 127         // checked correctly.
 128
 129         __splitstack_setcontext((void*)(&gp->m->gsignal->stackcontext[0]));
 130
 131         sigtrampgo(sig, info, context);
 132
 133         // We are going to return back to the signal trampoline and
 134         // then to whatever we were doing before we got the signal.
 135         // Restore the split stack context so that stack guards are
 136         // checked correctly.
 137
 138         __splitstack_setcontext(&stack_context[0]);
 139 }
 140
 141 #endif // USING_SPLIT_STACK
 142
 143 // C function to return the address of the sigtramp function.
 144 uintptr getSigtramp(void) __asm__ (GOSYM_PREFIX "runtime.getSigtramp");
 145
 146 uintptr
 147 getSigtramp()
 148 {
 149   return (uintptr)(void*)sigtramp;
 150 }
 151
 152 // C code to manage the sigaction sa_sigaction field, which is
 153 // typically a union and so hard for mksysinfo.sh to handle.
 154
 155 uintptr getSigactionHandler(struct sigaction*)
 156         __attribute__ ((no_split_stack));
 157
 158 uintptr getSigactionHandler(struct sigaction*)
 159         __asm__ (GOSYM_PREFIX "runtime.getSigactionHandler");
 160
 161 uintptr
 162 getSigactionHandler(struct sigaction* sa)
 163 {
 164         return (uintptr)(sa->sa_sigaction);
 165 }
 166
 167 void setSigactionHandler(struct sigaction*, uintptr)
 168         __attribute__ ((no_split_stack));
 169
 170 void setSigactionHandler(struct sigaction*, uintptr)
 171         __asm__ (GOSYM_PREFIX "runtime.setSigactionHandler");
 172
 173 void
 174 setSigactionHandler(struct sigaction* sa, uintptr handler)
 175 {
 176         sa->sa_sigaction = (void*)(handler);
 177 }
 178
 179 // C code to fetch values from the siginfo_t and ucontext_t pointers
 180 // passed to a signal handler.
 181
 182 struct getSiginfoRet {
 183         uintptr sigaddr;
 184         uintptr sigpc;
 185 };
 186
 187 struct getSiginfoRet getSiginfo(siginfo_t *, void *)
 188         __asm__(GOSYM_PREFIX "runtime.getSiginfo");
 189
 190 struct getSiginfoRet
 191 getSiginfo(siginfo_t *info, void *context __attribute__((unused)))
 192 {
 193         struct getSiginfoRet ret;
 194         Location loc[1];
 195         int32 n;
 196
 197         if (info == nil) {
 198                 ret.sigaddr = 0;
 199         } else {
 200                 ret.sigaddr = (uintptr)(info->si_addr);
 201         }
 202         ret.sigpc = 0;
 203
 204         // There doesn't seem to be a portable way to get the PC.
 205         // Use unportable code to pull it from context, and if that fails
 206         // try a stack backtrace across the signal handler.
 207
 208 #ifdef __x86_64__
 209  #ifdef __linux__
 210         ret.sigpc = ((ucontext_t*)(context))->uc_mcontext.gregs[REG_RIP];
 211  #endif
 212 #endif
 213 #ifdef __i386__
 214   #ifdef __linux__
 215         ret.sigpc = ((ucontext_t*)(context))->uc_mcontext.gregs[REG_EIP];
 216   #endif
 217 #endif
 218
 219         if (ret.sigpc == 0) {
 220                 // Skip getSiginfo/sighandler/sigtrampgo/sigtramp/handler.
 221                 n = runtime_callers(5, &loc[0], 1, false);
 222                 if (n > 0) {
 223                         ret.sigpc = loc[0].pc;
 224                 }
 225         }
 226
 227         return ret;
 228 }
 229
 230 // Dump registers when crashing in a signal.
 231 // There is no portable way to write this,
 232 // so we just have some CPU/OS specific implementations.
 233
 234 void dumpregs(siginfo_t *, void *)
 235         __asm__(GOSYM_PREFIX "runtime.dumpregs");
 236
 237 void
 238 dumpregs(siginfo_t *info __attribute__((unused)), void *context __attribute__((unused)))
 239 {
 240 #ifdef __x86_64__
 241  #ifdef __linux__
 242         {
 243                 mcontext_t *m = &((ucontext_t*)(context))->uc_mcontext;
 244
 245                 runtime_printf("rax    %X\n", m->gregs[REG_RAX]);
 246                 runtime_printf("rbx    %X\n", m->gregs[REG_RBX]);
 247                 runtime_printf("rcx    %X\n", m->gregs[REG_RCX]);
 248                 runtime_printf("rdx    %X\n", m->gregs[REG_RDX]);
 249                 runtime_printf("rdi    %X\n", m->gregs[REG_RDI]);
 250                 runtime_printf("rsi    %X\n", m->gregs[REG_RSI]);
 251                 runtime_printf("rbp    %X\n", m->gregs[REG_RBP]);
 252                 runtime_printf("rsp    %X\n", m->gregs[REG_RSP]);
 253                 runtime_printf("r8     %X\n", m->gregs[REG_R8]);
 254                 runtime_printf("r9     %X\n", m->gregs[REG_R9]);
 255                 runtime_printf("r10    %X\n", m->gregs[REG_R10]);
 256                 runtime_printf("r11    %X\n", m->gregs[REG_R11]);
 257                 runtime_printf("r12    %X\n", m->gregs[REG_R12]);
 258                 runtime_printf("r13    %X\n", m->gregs[REG_R13]);
 259                 runtime_printf("r14    %X\n", m->gregs[REG_R14]);
 260                 runtime_printf("r15    %X\n", m->gregs[REG_R15]);
 261                 runtime_printf("rip    %X\n", m->gregs[REG_RIP]);
 262                 runtime_printf("rflags %X\n", m->gregs[REG_EFL]);
 263                 runtime_printf("cs     %X\n", m->gregs[REG_CSGSFS] & 0xffff);
 264                 runtime_printf("fs     %X\n", (m->gregs[REG_CSGSFS] >> 16) & 0xffff);
 265                 runtime_printf("gs     %X\n", (m->gregs[REG_CSGSFS] >> 32) & 0xffff);
 266           }
 267  #endif
 268 #endif
 269
 270 #ifdef __i386__
 271  #ifdef __linux__
 272         {
 273                 mcontext_t *m = &((ucontext_t*)(context))->uc_mcontext;
 274
 275                 runtime_printf("eax    %X\n", m->gregs[REG_EAX]);
 276                 runtime_printf("ebx    %X\n", m->gregs[REG_EBX]);
 277                 runtime_printf("ecx    %X\n", m->gregs[REG_ECX]);
 278                 runtime_printf("edx    %X\n", m->gregs[REG_EDX]);
 279                 runtime_printf("edi    %X\n", m->gregs[REG_EDI]);
 280                 runtime_printf("esi    %X\n", m->gregs[REG_ESI]);
 281                 runtime_printf("ebp    %X\n", m->gregs[REG_EBP]);
 282                 runtime_printf("esp    %X\n", m->gregs[REG_ESP]);
 283                 runtime_printf("eip    %X\n", m->gregs[REG_EIP]);
 284                 runtime_printf("eflags %X\n", m->gregs[REG_EFL]);
 285                 runtime_printf("cs     %X\n", m->gregs[REG_CS]);
 286                 runtime_printf("fs     %X\n", m->gregs[REG_FS]);
 287                 runtime_printf("gs     %X\n", m->gregs[REG_GS]);
 288           }
 289  #endif
 290 #endif
 291 }