path: root/src/libc.c

#include <unistd.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <limits.h>
#include <math.h>
#include <dirent.h>
#include <assert.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/syscall.h>
#include <sys/user.h> // PAGE_SIZE, PAGE_SHIFT
#include <netdb.h> // h_errno
#include  "wrapper/verbose.h"

struct bionic_dirent {
   uint64_t d_ino;
   int64_t d_off;
   unsigned short d_reclen;
   unsigned char d_type;
   char d_name[256];
};

#ifdef ANDROID_X86_LINKER
typedef unsigned long bionic_sigset_t;
struct bionic_sigaction {
   union {
      void (*bsa_handler)(int);
      void (*bsa_sigaction)(int, void*, void*);
   };
   bionic_sigset_t sa_mask;
   int sa_flags;
   void (*sa_restorer)(void);
};
#else
#  error "not implemented for this platform"
#endif

// Stuff that doesn't exist in glibc

#define PROP_NAME_MAX   32
#define PROP_VALUE_MAX  92

int
__system_property_get(const char *name, char *value)
{
   verbose("%s", name);

   if (!strcmp(name, "ro.build.version.sdk"))
      return snprintf(value, PROP_VALUE_MAX, "%d", 15);

   *value = 0;
   return 0;
}

pid_t
gettid(void)
{
   return syscall(SYS_gettid);
}

int
tgkill(int tgid, int tid, int sig)
{
   verbose("%d, %d, %d", tgid, tid, sig);
   return syscall(SYS_tgkill, tgid, tid, sig);
}

int
tkill(int tid, int sig)
{
   verbose("%d, %d", tid, sig);
   return syscall(SYS_tkill, tid, sig);
}

// Stuff needed for runtime compatibility, but not neccessary for linking
// Also stuff that exists in glibc, but needs to be wrapped for runtime compatibility

// Some defines from app-stdio.c as per GNU linker's manual for --wrap:
//    You may wish to provide a __real_malloc function as well, so that links without the
//    --wrap option will succeed. If you do this, you should not put the definition of
//    __real_malloc in the same file as __wrap_malloc; if you do, the assembler may resolve
//    the call before the linker has a chance to wrap it to malloc.

size_t __real_IO_file_xsputn(FILE *f, const void *buf, size_t n) { return 0; }

#include "libc-ctype.h"

const unsigned int bionic___page_size = PAGE_SIZE;

__attribute_const__ int*
bionic___errno(void)
{
   return __errno_location();
}

__attribute_const__ int*
bionic___get_h_errno(void)
{
   return &h_errno;
}

int
bionic_stat(const char *restrict path, struct stat *restrict buf)
{
   verbose("%s", path);
   return stat(path, buf);
}

int
bionic_lstat(const char *restrict path, struct stat *restrict buf)
{
   verbose("%s", path);
   return lstat(path, buf);
}

int
bionic_fstat(int fd, struct stat *buf)
{
   verbose("%d", fd);
   return fstat(fd, buf);
}

int
bionic_fstatat(int dirfd, const char *pathname, void *buf, int flags)
{
   verbose("%d, %s", dirfd, pathname);
   return fstatat(dirfd, pathname, buf, flags);
}

static void
glibc_dirent_to_bionic_dirent(const struct dirent *de, struct bionic_dirent *bde)
{
   assert(bde && de);
   *bde = (struct bionic_dirent){
      .d_ino = de->d_ino,
      .d_off = de->d_off,
      .d_reclen = de->d_reclen,
      .d_type = de->d_type,
   };
   _Static_assert(sizeof(bde->d_name) >= sizeof(de->d_name), "bionic_dirent can't hold dirent's d_name");
   memcpy(bde->d_name, de->d_name, sizeof(bde->d_name));
}

struct bionic_dirent*
bionic_readdir(DIR *dirp)
{
   assert(dirp);
   static struct bionic_dirent bde;
   struct dirent *de;
   if (!(de = readdir(dirp)))
      return NULL;
   glibc_dirent_to_bionic_dirent(de, &bde);
   return &bde;
}

int
bionic_readdir_r(DIR *dirp, struct bionic_dirent *entry, struct bionic_dirent **result)
{
   assert(dirp && entry && result);
   struct dirent de, *der = NULL;

   int ret;
   if ((ret = readdir_r(dirp, &de, &der)) != 0 || !der) {
      *result = NULL;
      return ret;
   }

   glibc_dirent_to_bionic_dirent(der, entry);
   *result = entry;
   return 0;
}

// Need to wrap bunch of signal crap
// https://android.googlesource.com/platform/bionic/+/master/docs/32-bit-abi.md

int
bionic_sigaddset(const bionic_sigset_t *set, int sig)
{
   int bit = sig - 1; // Signal numbers start at 1, but bit positions start at 0.
   unsigned long *local_set = (unsigned long*)set;
   if (!set || bit < 0 || bit >= (int)(8 * sizeof(*set))) {
      errno = EINVAL;
      return -1;
   }
   local_set[bit / LONG_BIT] |= 1UL << (bit % LONG_BIT);
   return 0;
}

int
bionic_sigismember(const bionic_sigset_t *set, int sig)
{
   int bit = sig - 1; // Signal numbers start at 1, but bit positions start at 0.
   const unsigned long *local_set = (const unsigned long*)set;
   if (!set || bit < 0 || bit >= (int)(8 * sizeof(*set))) {
      errno = EINVAL;
      return -1;
   }
   return (int)((local_set[bit / LONG_BIT] >> (bit % LONG_BIT)) & 1);
}

int
bionic_sigaction(int sig, const struct bionic_sigaction *restrict act, struct bionic_sigaction *restrict oact)
{
   verbose("%d, %p, %p", sig, (void*)act, (void*)oact);

   // THREAD_SIGNAL on android used by libbacktrace
   if (sig == 33)
      sig = SIGRTMIN;

   struct sigaction goact = {0}, gact = {0};
   if (act) {
      gact.sa_handler = act->bsa_handler;
      gact.sa_flags = act->sa_flags;
      gact.sa_restorer = act->sa_restorer;

      // delete reserved signals
      // 32 (__SIGRTMIN + 0)        POSIX timers
      // 33 (__SIGRTMIN + 1)        libbacktrace
      // 34 (__SIGRTMIN + 2)        libcore
      // 35 (__SIGRTMIN + 3)        debuggerd -b
      assert(35 < SIGRTMAX);
      for (int signo = 35; signo < SIGRTMAX; ++signo) {
         if (bionic_sigismember(&act->sa_mask, signo))
            sigaddset(&gact.sa_mask, signo);
      }
   }

   const int ret = sigaction(sig, (act ? &gact : NULL), (oact ? &goact : NULL));

   if (oact) {
      *oact = (struct bionic_sigaction){0};
      oact->bsa_handler = goact.sa_handler;
      oact->sa_flags = goact.sa_flags;
      oact->sa_restorer = goact.sa_restorer;

      for (int signo = SIGRTMIN + 3; signo < SIGRTMAX; ++signo) {
         if (sigismember(&goact.sa_mask, signo))
            bionic_sigaddset(&oact->sa_mask, signo);
      }
   }

   return ret;
}

int
bionic___isfinitef(float f)
{
   return isfinite(f);
}

int
bionic___isfinite(float f)
{
   return isfinite(f);
}

void
bionic___assert2(const char* file, int line, const char* function, const char* failed_expression)
{
   fprintf(stderr, "%s:%d: %s: assertion \"%s\" failed\n", file, line, function, failed_expression);
   abort();
}

uintptr_t bionic___stack_chk_guard = 4;

__attribute__((noreturn)) void
bionic___stack_chk_fail(void)
{
   abort();
}

size_t
bionic___strlen_chk(const char *s, size_t s_len)
{
   const size_t ret = strlen(s);
   if (__builtin_expect(ret >= s_len, 0)) {
      fprintf(stderr, "*** strlen read overflow detected ***\n");
      abort();
   }
   return ret;
}

size_t
bionic___fwrite_chk(const void * __restrict buf, size_t size, size_t count, FILE * __restrict stream, size_t buf_size)
{
   size_t total;
   if (__builtin_expect(__builtin_mul_overflow(size, count, &total), 0)) {
      // overflow: trigger the error path in fwrite
      return fwrite(buf, size, count, stream);
   }

   if (__builtin_expect(total > buf_size, 0)) {
      fprintf(stderr, "*** fwrite read overflow detected ***\n");
      abort();
   }

   return fwrite(buf, size, count, stream);
}

char*
bionic___strchr_chk(const char* p, int ch, size_t s_len)
{
   for (;; ++p, s_len--) {
      if (__builtin_expect(s_len == 0, 0)) {
         fprintf(stderr, "*** strchr buffer overrun detected ***\n");
         abort();
      }

      if (*p == ch)
         return (char*)p;
      else if (!*p)
         return NULL;
   }
   assert(0 && "should not happen");
}

char*
bionic___strrchr_chk(const char* p, int ch, size_t s_len)
{
   const char *save;
   for (save = NULL;; ++p, s_len--) {
      if (__builtin_expect(s_len == 0, 0)) {
         fprintf(stderr, "*** strchr buffer overrun detected ***\n");
         abort();
      }

      if (*p == ch)
         save = p;
      else if (!*p)
         return (char*)save;
   }
   assert(0 && "should not happen");
}

#include "libc-sysconf.h"

long
bionic_sysconf(int name)
{
   verbose("0x%x", name);
   return sysconf(bionic_sysconf_to_glibc_sysconf(name));
}

static void
__libc_fini(int signal, void *array)
{
   void** fini_array = (void**)array;

   if (!array || (size_t)fini_array[0] != (size_t)~0)
      return;

   fini_array += 1;

   int count;
   for (count = 0; fini_array[count]; ++count);

   for (; count > 0; --count) {
      const union {
         void *ptr;
         void (*fun)(void);
      } fini = { .ptr = fini_array[count] };

      if ((size_t)fini.ptr != (size_t)~0)
         fini.fun();
   }
}

struct bionic_structors {
   void (**preinit_array)(void);
   void (**init_array)(void);
   void (**fini_array)(void);
};

__attribute__((noreturn)) void
bionic___libc_init(void *raw_args, void (*onexit)(void), int (*slingshot)(int, char**, char**), struct bionic_structors const *const structors)
{
   // linker has already called the constructors

   union {
      struct s {
         uintptr_t argc;
         char **argv;
      } s;
      char bytes[sizeof(struct s)];
   } arg;

   memcpy(arg.bytes, raw_args, sizeof(arg.bytes));

   if (structors->fini_array && on_exit(__libc_fini, structors->fini_array)) {
      fprintf(stderr, "__cxa_atexit failed\n");
      abort();
   }

   exit(slingshot(arg.s.argc, arg.s.argv, arg.s.argv + arg.s.argc + 1));
}

#ifdef VERBOSE_FUNCTIONS
#  include "libc-verbose.h"
#endif