fdcheck: update fdcheck impl

1 store fd in the high position
2 removing the pid information , as the tag information is sufficient.

Signed-off-by: hujun5 <hujun5@xiaomi.com>

include/nuttx/fdcheck.h

@@ -46,49 +46,47 @@ extern "C"
  *
  * Description: Obtain original fd information
  *
- * Val carries the pid, tag and fd information.
+ * Val carries the tag and fd information.
- * The original fd information is stored in low bit of val.
+ * The original fd information is stored in high bit of val.
- * The pid and tag information is stored in the high bit of val.
+ * The tag information is stored in the low bit of val.
  * For ease of understanding, let's give an example where
  * the following information is represented in 32-bit binary format
  *
- *  val       00000000 01010101 00000001 10001010
+ *  val       00000000 00000000 10001010 00000001
  *  fd        00000000 00000000 00000000 10001010
- *  pid       00000000 00000000 00000000 01010101
  *  tag       00000000 00000000 00000000 00000001
  *
- * In this function, we also check if the pid and tag information is correct.
+ * In this function, we also check tag information is correct.
  * If there is an error, it will panic.
  *
  * Input Parameters:
- *   val - this val carrying pid, tag and original fd information
+ *   val - this val carrying tag and original fd information
  *
- * Returned Value: none
+ * Returned Value: The original fd is returned.
  *
  ****************************************************************************/
 
-int fdcheck_restore(int fd);
+int fdcheck_restore(int val);
 
 /****************************************************************************
  * Name: fdcheck_protect
  *
- * Description: Obtain the combined value of fd, pid and tag
+ * Description: Obtain the combined value of fd and tag
  *
- * the return value carries the pid, tag and fd information.
+ * the return value carries the tag and fd information.
  * The original fd information is stored in low bit of val.
- * The pid and tag information is stored in high bit of val.
+ * The tag information is stored in high bit of val.
  * For ease of understanding, let's give an example where
  * the following information is represented in 32-bit binary format
  *
  *  fd        00000000 00000000 00000000 10001010
- *  pid       00000000 00000000 00000000 01010101
  *  tag       00000000 00000000 00000000 00000001
- *  val       00000000 01010101 00000001 10001010
+ *  val       00000000 00000000 10001010 00000001
  *
  * Input Parameters:
  *   fd - original fd
  *
- * Returned Value: the combined value of fd and pid
+ * Returned Value: the combined value of fd and tag
  *
  ****************************************************************************/
 

libs/libc/misc/lib_fdcheck.c

@@ -37,17 +37,15 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define FD_SHIFT  0
+#define TAG_SHIFT 0
-#define FD_BITS   LOG2_CEIL(OPEN_MAX)
-#define FD_MASK   ((1 << FD_BITS) - 1)
-
-#define TAG_SHIFT (FD_BITS + FD_SHIFT)
 #define TAG_BITS  8
 #define TAG_MASK  ((1 << TAG_BITS) - 1)
 
-#define PID_SHIFT (TAG_BITS + TAG_SHIFT)
+#define FD_SHIFT  (TAG_SHIFT + TAG_BITS)
-#define PID_BITS  (8 * sizeof(int) - 1 - PID_SHIFT)
+#define FD_BITS   LOG2_CEIL(OPEN_MAX)
-#define PID_MASK  ((1 << PID_BITS) - 1)
+#define FD_MASK   ((1 << FD_BITS) - 1)
+
+static_assert(FD_BITS <= TAG_BITS, "FD_BITS is too long");
 
 /****************************************************************************
  * Private Data
@@ -60,57 +58,20 @@ static uint8_t    g_fdcheck_tag = 0;
  * Public Functions
  ****************************************************************************/
 
-/****************************************************************************
- * Name: fdcheck_restore
- *
- * Description: Obtain original fd information
- *
- * Val carries the pid, tag and fd information.
- * The original fd information is stored in low bit of val.
- * The pid and tag information is stored in the high bit of val.
- * For ease of understanding, let's give an example where
- * the following information is represented in 32-bit binary format
- *
- *  val       00000000 01010101 00000001 10001010
- *  fd        00000000 00000000 00000000 10001010
- *  pid       00000000 00000000 00000000 01010101
- *  tag       00000000 00000000 00000000 00000001
- *
- * In this function, we also check if the pid and tag information is correct.
- * If there is an error, it will panic.
- *
- * Input Parameters:
- *   val - this val carrying pid, tag and original fd information
- *
- * Returned Value: none
- *
- ****************************************************************************/
-
 int fdcheck_restore(int val)
 {
-  int pid_expect;
+  uint8_t tag_store;
-  int ppid_now;
+  int fd;
-  int pid_now;
 
-  if (val <= 2)
+  /* If val is a bare fd（0~255）, we should return it directly  */
+
+  fd = (val >> FD_SHIFT) & FD_MASK;
+  if (fd == 0 || val < 0)
     {
       return val;
     }
 
-  pid_expect = (val >> PID_SHIFT) & PID_MASK;
+  int ret = ioctl(fd, FIOC_GETTAG_FDCHECK, &tag_store);
-  pid_now = _SCHED_GETPID() & PID_MASK;
-  ppid_now = _SCHED_GETPPID() & PID_MASK;
-  if (pid_expect != pid_now && pid_expect != ppid_now && pid_expect != 0)
-    {
-      ferr("pid_expect %d pid_now %d ppid_now %d\n",
-           pid_expect, pid_now, ppid_now);
-      PANIC();
-    }
-
-  if (pid_expect != 0)
-    {
-      uint8_t tag_store;
-      int ret = ioctl(val & FD_MASK, FIOC_GETTAG_FDCHECK, &tag_store);
   if (ret >= 0)
     {
       uint8_t tag_expect = (val >> TAG_SHIFT) & TAG_MASK;
@@ -121,34 +82,10 @@ int fdcheck_restore(int val)
           PANIC();
         }
     }
-    }
 
-  return val & FD_MASK;
+  return fd;
 }
 
-/****************************************************************************
- * Name: fdcheck_protect
- *
- * Description: Obtain the combined value of fd, pid and tag
- *
- * the return value carries the pid, tag and fd information.
- * The original fd information is stored in low bit of val.
- * The pid and tag information is stored in high bit of val.
- * For ease of understanding, let's give an example where
- * the following information is represented in 32-bit binary format
- *
- *  fd        00000000 00000000 00000000 10001010
- *  pid       00000000 00000000 00000000 01010101
- *  tag       00000000 00000000 00000000 00000001
- *  val       00000000 01010101 00000001 10001010
- *
- * Input Parameters:
- *   fd - original fd
- *
- * Returned Value: the combined value of fd and pid
- *
- ****************************************************************************/
-
 int fdcheck_protect(int fd)
 {
   int protect_fd;
@@ -160,9 +97,7 @@ int fdcheck_protect(int fd)
       return fd;
     }
 
-  protect_fd = fd & FD_MASK;
+  protect_fd = (fd & FD_MASK) << FD_SHIFT;
-  protect_fd |= (_SCHED_GETPID() & PID_MASK) << PID_SHIFT;
-
   ret = ioctl(fd, FIOC_GETTAG_FDCHECK, &tag);
   DEBUGASSERT(ret >= 0);
   if (tag == 0)

libs/libc/stdio/lib_fopen.c

@@ -105,6 +105,12 @@ FAR FILE *fdopen(int fd, FAR const char *mode)
       /* Initialize the mutex the manages access to the buffer */
 
       nxrmutex_init(&filep->fs_lock);
+
+#ifdef CONFIG_FDSAN
+      android_fdsan_exchange_owner_tag(fd, 0,
+          android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_FILE,
+                                        (uintptr_t)filep));
+#endif
     }
   else
     {
@@ -135,12 +141,6 @@ FAR FILE *fdopen(int fd, FAR const char *mode)
   filep->fs_cookie   = (FAR void *)(intptr_t)fd;
   filep->fs_oflags   = oflags;
 
-#ifdef CONFIG_FDSAN
-  android_fdsan_exchange_owner_tag(fd, 0,
-      android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_FILE,
-                                     (uintptr_t)filep));
-#endif
-
   /* Assign custom callbacks to NULL. */
 
   filep->fs_iofunc.read  = NULL;