ksym.c

linux下获取一些环境信息的代码

    }
  }

  if(0){
bad_alloc:
    fprintf(stderr, "Warning: not enough memory available\n");
  }
  if(0){
bad_parse:
    fprintf(stderr, "Warning: "KSYMS_FILENAME" not normal\n");
  }
quiet_goodbye:
  idx_room = 0;
  if(ksyms_data) free(ksyms_data) , ksyms_data = NULL;
  ksyms_room = 0;
  if(ksyms_index) free(ksyms_index) , ksyms_index = NULL;
  ksyms_count = 0;
  return 0;
}

/*********************************/

#define VCNT 16

static int sysmap_mmap(const char *restrict const filename, message_fn message) {
  struct stat sbuf;
  char *endp;
  int fd;
  char Version[32];
  fd = open(filename, O_RDONLY|O_NOCTTY|O_NONBLOCK);
  if(fd<0) return 0;
  if(fstat(fd, &sbuf) < 0) goto bad_open;
  if(!S_ISREG(sbuf.st_mode)) goto bad_open;
  if(sbuf.st_size < 5000) goto bad_open;  /* if way too small */
  /* Would be shared read-only, but we want '\0' after each name. */
  endp = mmap(0, sbuf.st_size + 1, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
  sysmap_data = endp;
  while(*endp==' '){  /* damn Alpha machine types */
    if(strncmp(endp,"                 w ", 19)) goto bad_parse;
    endp += 19;
    endp = strchr(endp,'\n');
    if(!endp) goto bad_parse;   /* no newline */
    if(strncmp(endp-3, "_mv\n", 4)) goto bad_parse;
    endp++;
  }
  if(sysmap_data == (caddr_t) -1) goto bad_open;
  close(fd);
  fd = -1;
  sprintf(Version, "Version_%d", linux_version_code);
  sysmap_room = 512;
  for(;;){
    void *vp;
    sysmap_room *= 2;
    vp = realloc(sysmap_index, sizeof(symb)*sysmap_room);
    if(!vp) goto bad_alloc;
    sysmap_index = vp;
    for(;;){
      char *vstart;
      if(endp - sysmap_data >= sbuf.st_size){   /* if we reached the end */
        int i = VCNT;            /* check VCNT times to verify this file */
        if(*Version) goto bad_version;
        if(!ksyms_index) return 1; /* if can not verify, assume success */
        while(i--){
#if 1
          const symb *findme;
          const symb *map_symb;
          /* Choose VCNT entries from /proc/ksyms to test */
          findme = ksyms_index + (ksyms_count*i/VCNT);
          /* Search for them in the System.map */
          map_symb = search(findme->addr, sysmap_index, sysmap_count);
          if(map_symb){
            if(map_symb->addr != findme->addr) continue;
            /* backup to first matching address */
            while (map_symb != sysmap_index){
              if (map_symb->addr != (map_symb-1)->addr) break;
              map_symb--;
            }
            /* search for name in symbols with same address */
            while (map_symb != (sysmap_index+sysmap_count)){
              if (map_symb->addr != findme->addr) break;
              if (!strcmp(map_symb->name,findme->name)) goto good_match;
              map_symb++;
            }
            map_symb--; /* backup to last symbol with matching address */
            message("{%s} {%s}\n",map_symb->name,findme->name);
            goto bad_match;
          }
good_match:;
#endif
        }
        return 1; /* success */
      }
      sysmap_index[sysmap_count].addr = STRTOUKL(endp, &endp, 16);
      if(*endp != ' ') goto bad_parse;
      endp++;
      if(!strchr(SYMBOL_TYPE_CHARS, *endp)) goto bad_parse;
      endp++;
      if(*endp != ' ') goto bad_parse;
      endp++;
      vstart = endp;
      endp = strchr(endp,'\n');
      if(!endp) goto bad_parse;   /* no newline */
      *endp = '\0';
      ++endp;
      vstart = chop_version(vstart);
      sysmap_index[sysmap_count].name = vstart;
      if(*vstart=='V' && *Version && !strcmp(Version,vstart)) *Version='\0';
      if(++sysmap_count >= sysmap_room) break;  /* need more space */
    }
  }

  if(0){
bad_match:
    message("Warning: %s does not match kernel data.\n", filename);
  }
  if(0){
bad_version:
    message("Warning: %s has an incorrect kernel version.\n", filename);
  }
  if(0){
bad_alloc:
    message("Warning: not enough memory available\n");
  }
  if(0){
bad_parse:
    message("Warning: %s not parseable as a System.map\n", filename);
  }
  if(0){
bad_open:
    message("Warning: %s could not be opened as a System.map\n", filename);
  }

  sysmap_room=0;
  sysmap_count=0;
  if(sysmap_index) free(sysmap_index);
  sysmap_index = NULL;
  if(fd>=0) close(fd);
  if(sysmap_data) munmap(sysmap_data, sbuf.st_size + 1);
  sysmap_data = NULL;
  return 0;
}

/*********************************/

static void read_and_parse(void){
  static time_t stamp;    /* after data gets old, load /proc/ksyms again */
  if(time(NULL) != stamp){
    read_file(KSYMS_FILENAME, &ksyms_data, &ksyms_room);
    parse_ksyms();
    memset((void*)hashtable,0,sizeof(hashtable)); /* invalidate cache */
    stamp = time(NULL);
  }
}

/*********************************/

static void default_message(const char *restrict format, ...) __attribute__((format(printf,1,2)));
static void default_message(const char *restrict format, ...) {
    va_list arg;

    va_start (arg, format);
    vfprintf (stderr, format, arg);
    va_end (arg);
}

/*********************************/

static int use_wchan_file;

int open_psdb_message(const char *restrict override, message_fn message) {
  static const char *sysmap_paths[] = {
    "/boot/System.map-%s",
    "/boot/System.map",
    "/lib/modules/%s/System.map",
    "/usr/src/linux/System.map",
    "/System.map",
    NULL
  };
  struct stat sbuf;
  struct utsname uts;
  char path[128];
  const char **fmt = sysmap_paths;
  const char *sm;

#ifdef SYSMAP_FILENAME    /* debug feature */
  override = SYSMAP_FILENAME;
#endif

  // first allow for a user-selected System.map file
  if(
    (sm=override)
    ||
    (sm=getenv("PS_SYSMAP"))
    ||
    (sm=getenv("PS_SYSTEM_MAP"))
  ){
    if(!have_privs){
      read_and_parse();
      if(sysmap_mmap(sm, message)) return 0;
    }
    /* failure is better than ignoring the user & using bad data */
    return -1;           /* ought to return "Namelist not found." */
  }

  // next try the Linux 2.5.xx method
  if(!stat("/proc/self/wchan", &sbuf)){
    use_wchan_file = 1; // hack
    return 0;
  }

  // finally, search for the System.map file
  uname(&uts);
  path[sizeof path - 1] = '\0';
  do{
    int did_ksyms = 0;
    snprintf(path, sizeof path - 1, *fmt, uts.release);
    if(!stat(path, &sbuf)){
      if (did_ksyms++) read_and_parse();
      if (sysmap_mmap(path, message)) return 0;
    }
  }while(*++fmt);
  /* TODO: Without System.map, no need to keep ksyms loaded. */
  return -1;
}

/***************************************/

int open_psdb(const char *restrict override) {
    return open_psdb_message(override, default_message);
}

/***************************************/

static const char * read_wchan_file(unsigned pid){
  static char buf[64];
  const char *ret = buf;
  ssize_t num;
  int fd;

  snprintf(buf, sizeof buf, "/proc/%d/wchan", pid);
  fd = open(buf, O_RDONLY);
  if(fd==-1) return "?";
  num = read(fd, buf, sizeof buf - 1);
  close(fd);
  if(num<1) return "?"; // allow for "0"
  buf[num] = '\0';

  if(buf[0]=='0' && buf[1]=='\0') return "-";

  // would skip over numbers if they existed -- but no

  // lame ppc64 has a '.' in front of every name
  if(*ret=='.') ret++;
  switch(*ret){
    case 's': if(!strncmp(ret, "sys_", 4)) ret += 4;   break;
    case 'd': if(!strncmp(ret, "do_",  3)) ret += 3;   break;
    case '_': while(*ret=='_') ret++;                  break;
  }
  return ret;
}

/***************************************/

static const symb fail = { .name = "?" };
static const char dash[] = "-";
static const char star[] = "*";

#define MAX_OFFSET (0x1000*sizeof(long))  /* past this is generally junk */

/* return pointer to temporary static buffer with function name */
const char * lookup_wchan(unsigned KLONG address, unsigned pid) {
  const symb *mod_symb;
  const symb *map_symb;
  const symb *good_symb;
  const char *ret;
  unsigned hash;

  // can't cache it due to a race condition :-(
  if(use_wchan_file) return read_wchan_file(pid);

  if(!address)  return dash;
  if(!~address) return star;

  read_and_parse();
  hash = (address >> 4) & 0xff;  /* got 56/63 hits & 7/63 misses */
  if(hashtable[hash].addr == address) return hashtable[hash].name;
  mod_symb = search(address, ksyms_index,  ksyms_count);
  if(!mod_symb) mod_symb = &fail;
  map_symb = search(address, sysmap_index, sysmap_count);
  if(!map_symb) map_symb = &fail;

  /* which result is closest? */
  good_symb = (mod_symb->addr > map_symb->addr)
            ? mod_symb
            : map_symb
  ;
  if(address > good_symb->addr + MAX_OFFSET) good_symb = &fail;

  /* good_symb->name has the data, but needs to be trimmed */
  ret = good_symb->name;
  // lame ppc64 has a '.' in front of every name
  if(*ret=='.') ret++;
  switch(*ret){
    case 's': if(!strncmp(ret, "sys_", 4)) ret += 4;   break;
    case 'd': if(!strncmp(ret, "do_",  3)) ret += 3;   break;
    case '_': while(*ret=='_') ret++;                  break;
  }
  /* if(!*ret) ret = fail.name; */  /* not likely (name was "sys_", etc.) */

  /* cache name after abbreviation */
  hashtable[hash].addr = address;
  hashtable[hash].name = ret;

  return ret;
}