Add basic symlink support.

- sys$readlink + readlink()
- Add a /proc/PID/exe symlink to the process's executable.
- Print symlink contents in ls output.
- Some work on plumbing options into VFS::open().

Userland/cat.cpp

@@ -9,7 +9,7 @@ int main(int argc, char** argv)
         printf("usage: cat <file>\n");
         return 1;
     }
-    int fd = open(argv[1]);
+    int fd = open(argv[1], O_RDONLY);
     if (fd == -1) {
         printf("failed to open %s: %s\n", argv[1], strerror(errno));
         return 1;

Userland/ls.cpp

@@ -65,7 +65,9 @@ int main(int c, char** v)
         const char* endColor = "";
 
         if (colorize) {
-            if (S_ISDIR(st.st_mode))
+            if (S_ISLNK(st.st_mode))
+                beginColor = "\033[36;1m";
+            else if (S_ISDIR(st.st_mode))
                 beginColor = "\033[34;1m";
             else if (st.st_mode & 0111)
                 beginColor = "\033[32;1m";
@@ -76,10 +78,19 @@ int main(int c, char** v)
 
         printf("%s%s%s", beginColor, de->d_name, endColor);
 
-        if (S_ISDIR(st.st_mode))
+        if (S_ISLNK(st.st_mode)) {
+            char linkbuf[256];
+            ssize_t nread = readlink(pathbuf, linkbuf, sizeof(linkbuf));
+            if (nread < 0) {
+                perror("readlink failed");
+            } else {
+                printf(" -> %s", linkbuf);
+            }
+        } else if (S_ISDIR(st.st_mode)) {
             printf("/");
-        else if (st.st_mode & 0111)
+        } else if (st.st_mode & 0111) {
             printf("*");
+        }
         printf("\n");
     }
     return 0;

Userland/mm.cpp

@@ -3,7 +3,7 @@
 
 int main(int c, char** v)
 {
-    int fd = open("/proc/mm");
+    int fd = open("/proc/mm", O_RDONLY);
     if (fd == -1) {
         perror("failed to open /proc/mm");
         return 1;

Userland/ps.cpp

@@ -3,7 +3,7 @@
 
 int main(int c, char** v)
 {
-    int fd = open("/proc/summary");
+    int fd = open("/proc/summary", O_RDONLY);
     if (fd == -1) {
         perror("failed to open /proc/summary");
         return 1;

Userland/sh.cpp

@@ -147,7 +147,7 @@ int main(int, char**)
     int linedx = 0;
     linebuf[0] = '\0';
 
-    int fd = open("/dev/keyboard");
+    int fd = open("/dev/keyboard", O_RDONLY);
     if (fd == -1) {
         printf("failed to open /dev/keyboard :(\n");
         return 1;