libc: Add ctermid

apps/su.cpp

@@ -23,10 +23,13 @@ void signal_handler(int signo)
 
 char* getpass()
 {
-    FILE* f = fopen("/dev/tty", "r");
+    char ctty[L_ctermid];
+    ctermid(ctty);
+
+    FILE* f = fopen(ctty, "r");
     if (!f)
     {
-        perror("Failed to open /dev/tty");
+        perror("Failed to open controlling terminal");
         return nullptr;
     }
 

libc/include/stdio.h

@@ -12,6 +12,8 @@
 
 #define FOPEN_MAX 64 // Make sure this value matches FD_MAX in the kernel source.
 
+#define L_ctermid 9 // /dev/tty + a NULL byte
+
 typedef struct
 {
     int _fd;  // The underlying file descriptor.
@@ -206,6 +208,9 @@ extern "C"
     /* Pipe a stream to or from a process. */
     FILE* popen(const char* command, const char* type);
 
+    /* Return the path of the process's controlling terminal (always /dev/tty on Luna). */
+    char* ctermid(char* s);
+
 #ifdef __cplusplus
 }
 #endif

libc/src/stdio.cpp

@@ -851,4 +851,15 @@ extern "C"
 
         return status;
     }
+
+    char* ctermid(char* s)
+    {
+        static char path[] = "/dev/tty";
+        if (s)
+        {
+            strncpy(s, path, L_ctermid);
+            return s;
+        }
+        return path;
+    }
 }