From f4794f0b484ea7f0f680fafa2cdb649e11065a43 Mon Sep 17 00:00:00 2001
From: Xiang Xiao <xiaoxiang@xiaomi.com>
Date: Thu, 10 Sep 2020 12:10:52 +0800
Subject: [PATCH] libc: Implement access function correctly

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
Change-Id: I6ae3abf79bd9aa8cfb54b8bbe302d69c4d9cb8ff
---
 libs/libc/unistd/lib_access.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/libs/libc/unistd/lib_access.c b/libs/libc/unistd/lib_access.c
index e06f29befd8..42b6bd27cd1 100644
--- a/libs/libc/unistd/lib_access.c
+++ b/libs/libc/unistd/lib_access.c
@@ -39,6 +39,7 @@
 
 #include <nuttx/config.h>
 
+#include <sys/stat.h>
 #include <unistd.h>
 
 /****************************************************************************
@@ -71,8 +72,8 @@
  * Description:
  *   The access() function shall check the file named by the pathname pointed
  *   to by the path argument for accessibility according to the bit pattern
- *   contained in amode, using the real user ID in place of the effective user
- *   ID and the real group ID in place of the effective group ID.
+ *   contained in amode, using the real user ID in place of the effective
+ *   user ID and the real group ID in place of the effective group ID.
  *   As there are no users in NuttX, the function always succeeds.
  *
  * Input Parameters:
@@ -80,7 +81,8 @@
  *   amode - the access mode
  *
  * Returned Value:
- *   Always OK (zero)
+ *   Return OK (zero) if the caller can access the file with the required
+ *   permission, otherwise return -1.
  *
  * Assumptions:
  *
@@ -88,5 +90,27 @@
 
 int access(FAR const char *path, int amode)
 {
+  struct stat s;
+
+  if (stat(path, &s))
+    {
+      return -1;
+    }
+
+  if (s.st_mode & S_IFDIR)
+    {
+      return 0;
+    }
+
+  if (amode & W_OK)
+    {
+      if (s.st_mode & S_IWUSR)
+        {
+          return 0;
+        }
+
+      return -1;
+    }
+
   return 0;
 }