OK, buck2obj looks nice now, so let us add it

[libucw.git] / lib / lizard-safe.c

diff --git a/lib/lizard-safe.c b/lib/lizard-safe.c
index fc4b228f22951f6bdf04d9517b09d31643c4ef15..1c46cbdcbb58d211cd27cfb5a316a8917f1d64ae 100644 (file)
--- a/lib/lizard-safe.c
+++ b/lib/lizard-safe.c
@@ -21,31 +21,34 @@
 struct lizard_buffer *
 lizard_alloc(uns max_len)
 {
-  static byte *zero = "/dev/zero";
-  int fd = open(zero, O_RDWR);
-  if (fd < 0)
-    die("open(%s): %m", zero);
   struct lizard_buffer *buf = xmalloc(sizeof(struct lizard_buffer));
-  buf->len = ALIGN(max_len + PAGE_SIZE, PAGE_SIZE);
-  buf->ptr = mmap(NULL, buf->len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-  if (buf->ptr == MAP_FAILED)
-    die("mmap(%s): %m", zero);
+  buf->len = ALIGN(max_len + 3, PAGE_SIZE);            // +3 due to the unaligned access
+  buf->start = mmap(NULL, buf->len + PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  if (buf->start == MAP_FAILED)
+    die("mmap(anonymous): %m");
+  if (mprotect(buf->start + buf->len, PAGE_SIZE, PROT_NONE) < 0)
+    die("mprotect: %m");
+  buf->old_sigsegv_handler = xmalloc(sizeof(struct sigaction));
+  handle_signal(SIGSEGV, buf->old_sigsegv_handler);
   return buf;
 }
 
 void
 lizard_free(struct lizard_buffer *buf)
 {
-  munmap(buf->ptr, buf->len);
+  munmap(buf->start, buf->len + PAGE_SIZE);
+  unhandle_signal(SIGSEGV, buf->old_sigsegv_handler);
+  xfree(buf->old_sigsegv_handler);
   xfree(buf);
 }
 
 static jmp_buf safe_decompress_jump;
-static void
-sigsegv_handler(int UNUSED whatsit)
+static int
+sigsegv_handler(int signal UNUSED)
 {
   log(L_ERROR, "SIGSEGV caught in lizard_decompress()");
   longjmp(safe_decompress_jump, 1);
+  return 1;
 }
 
 int
@@ -55,27 +58,26 @@ lizard_decompress_safe(byte *in, struct lizard_buffer *buf, uns expected_length)
    * is caught in the case of buffer-overflow.  The function is not re-entrant
    * because of a static longjmp handler.  */
 {
-  volatile uns lock_offset = ALIGN(expected_length, PAGE_SIZE);
-  if (lock_offset + PAGE_SIZE > buf->len)
+  uns lock_offset = ALIGN(expected_length + 3, PAGE_SIZE);     // +3 due to the unaligned access
+  if (lock_offset > buf->len)
   {
     errno = EFBIG;
     return -1;
   }
-  mprotect(buf->ptr + lock_offset, PAGE_SIZE, PROT_NONE);
-  volatile sighandler_t old_handler = signal(SIGSEGV, sigsegv_handler);
-  int len, err;
+  volatile sh_sighandler_t old_handler = signal_handler[SIGSEGV];
+  signal_handler[SIGSEGV] = sigsegv_handler;
+  int len;
   if (!setjmp(safe_decompress_jump))
   {
+    buf->ptr = buf->start + buf->len - lock_offset;
     len = lizard_decompress(in, buf->ptr);
-    err = errno;
   }
   else
   {
+    buf->ptr = NULL;
     len = -1;
-    err = EFAULT;
+    errno = EFAULT;
   }
-  signal(SIGSEGV, old_handler);
-  mprotect(buf->ptr + lock_offset, PAGE_SIZE, PROT_READ | PROT_WRITE);
-  errno = err;
+  signal_handler[SIGSEGV] = old_handler;
   return len;
 }