mdw@git.distorted.org.uk Git - preload-hacks/blob - uopen.c

   1 #define _GNU_SOURCE
   2 #undef sun
   3
   4 #include <errno.h>
   5 #include <stdarg.h>
   6 #include <stdio.h>
   7 #include <string.h>
   8
   9 #include <unistd.h>
  10 #include <dlfcn.h>
  11 #include <fcntl.h>
  12
  13 #include <sys/socket.h>
  14 #include <sys/stat.h>
  15 #include <sys/un.h>
  16
  17 #define IMPORTS(_)                                                      \
  18   _(open, int, (const char *, int, ...))                                \
  19   _(open64, int, (const char *, int, ...))                              \
  20   _(fopen, FILE *, (const char *, const char *))                        \
  21   _(freopen, FILE *, (const char *, const char *, FILE *))
  22
  23 #define DECL(imp, ret, args) static ret (*real_##imp) args;
  24 IMPORTS(DECL)
  25 #undef DECL
  26
  27 static void setup(void) __attribute__((constructor));
  28 static void import(void)
  29 {
  30 #define IMPORT(imp, ret, args)                                          \
  31     real_##imp = (ret (*)args)dlsym(RTLD_NEXT, #imp);
  32   IMPORTS(IMPORT)
  33 #undef IMPORT
  34 }
  35
  36 #define SA(sa) ((struct sockaddr *)(sa))
  37
  38 #define PRESERVING_ERRNO(body) do {                                     \
  39   int _err = errno; { body } errno = _err;                              \
  40 } while (0)
  41
  42 static int maybe_connect(const char *fn, int *fdp)
  43 {
  44   int fd;
  45   struct sockaddr_un sun;
  46   struct stat st;
  47
  48   if (stat(fn, &st) || !S_ISSOCK(st.st_mode))
  49     return (0);
  50   *fdp = -1;
  51   if (strlen(fn) >= sizeof(sun.sun_path)) {
  52     errno = EINVAL;
  53     return (1);
  54   }
  55   strncpy(sun.sun_path, fn, sizeof(sun.sun_path));
  56   sun.sun_family = AF_UNIX;
  57   if ((fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0 ||
  58       connect(fd, SA(&sun), SUN_LEN(&sun))) {
  59     PRESERVING_ERRNO( if (fd >= 0) close(fd); );
  60     return (1);
  61   }
  62   *fdp = fd;
  63   return (1);
  64 }
  65
  66 #define OPEN_VENEER(open)                                               \
  67   int open(const char *fn, int how, ...)                                \
  68   {                                                                     \
  69     int mode = 0;                                                       \
  70     int fd;                                                             \
  71     va_list ap;                                                         \
  72                                                                         \
  73     PRESERVING_ERRNO({                                                  \
  74       if (how & O_CREAT)                                                \
  75         { va_start(ap, how); mode = va_arg(ap, int); va_end(ap); }      \
  76       if (!maybe_connect(fn, &fd)) fd = real_##open(fn, how, mode);     \
  77       if (fd < 0) return (-1);                                          \
  78     });                                                                 \
  79     return (fd);                                                        \
  80   }
  81 OPEN_VENEER(open)
  82 OPEN_VENEER(open64)
  83
  84 FILE *fopen(const char *fn, const char *how)
  85 {
  86   int fd;
  87   FILE *fp = 0;
  88
  89   PRESERVING_ERRNO({
  90     if (!maybe_connect(fn, &fd))
  91       fp = real_fopen(fn, how);
  92     else if (fd >= 0 && (fp = fdopen(fd, how)) == 0)
  93       PRESERVING_ERRNO( close(fd); );
  94   });
  95   return (fp);
  96 }
  97
  98 FILE *freopen(const char *fn, const char *how, FILE *fp)
  99 {
 100   int fd;
 101
 102   PRESERVING_ERRNO({
 103     if (!maybe_connect(fn, &fd))
 104       fp = real_freopen(fn, how, fp);
 105     else if (fd >= 0) {
 106       if (fflush(fp) || dup2(fd, fileno(fp))) fp = 0;
 107       PRESERVING_ERRNO( close(fd); );
 108     }
 109   });
 110   return (fp);
 111 }
 112
 113 static void setup(void)
 114 {
 115   PRESERVING_ERRNO({
 116     import();
 117   });
 118 }