backtrace.c

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>

#define UNW_LOCAL_ONLY
#include <libunwind.h>

#define MAX_FUNC_NAME 128

static void print_frame(unw_cursor_t *cursor) {
 unw_word_t ip, offset, rdi, rsi, rdx;
 char func_name[MAX_FUNC_NAME];
 int got_func_name = 
     !unw_get_proc_name(cursor, func_name, sizeof (func_name), &offset);

 int got_ip = !unw_get_reg(cursor, UNW_REG_IP, &ip);
 int got_rdi = !unw_get_reg(cursor, UNW_X86_64_RDI, &rdi);
 int got_rsi = !unw_get_reg(cursor, UNW_X86_64_RSI, &rsi);
 int got_rdx = !unw_get_reg(cursor, UNW_X86_64_RDX, &rdx);


 if (got_func_name) {
  fprintf(stderr, "%s+%#llx", func_name, offset);
 } else if (got_ip) {
  fprintf(stderr, "%#llx", ip);
 } else {
  fprintf(stderr, "???");
 }

 if (got_rdi) fprintf(stderr, " rdi=%#llx", rdi); 
 if (got_rsi) fprintf(stderr, " rsi=%#llx", rsi);
 if (got_rdx) fprintf(stderr, " rdx=%#llx", rdx);

 fprintf(stderr, "\n");
}

void print_backtrace(size_t skip) {
 unw_context_t uc;
 unw_cursor_t cursor;

 unw_getcontext(&uc);
 unw_init_local(&cursor, &uc);
 size_t i = 0;
 fprintf(stderr, "\n");
 while (unw_step(&cursor) > 0) {
  if (i < skip) {
   i++;
  } else {
   print_frame(&cursor);
  }
 }
}

void exit_backtrace() {
 print_backtrace(1);
 exit(1);
}

void signal_backtrace(int signum) {
 fprintf(stderr, "%s\n", strsignal(signum));
 print_backtrace(2);
 signal(signum, SIG_DFL);
 kill(getpid(), signum);
}

void bar(int y) {
  print_backtrace(0);
}

void foo(int x) {
  bar(2);
}
int main() {
  foo(1);
}