Kernel, libc: Add access()

kernel/include/sys/Syscall.h

@@ -21,6 +21,7 @@
 #define SYS_mkdir 16
 #define SYS_fork 17
 #define SYS_waitpid 18
+#define SYS_access 19
 
 namespace Syscall
 {
@@ -46,3 +47,4 @@ void sys_clock(Context* context);
 void sys_mkdir(Context* context, const char* filename);
 void sys_fork(Context* context);
 void sys_waitpid(Context* context, long pid, int* wstatus, int options);
+void sys_access(Context* context, const char* path, int amode);

kernel/src/sys/Syscall.cpp

@@ -30,6 +30,7 @@ void Syscall::entry(Context* context)
     case SYS_mkdir: sys_mkdir(context, (const char*)context->rdi); break;
     case SYS_fork: sys_fork(context); break;
     case SYS_waitpid: sys_waitpid(context, (long)context->rdi, (int*)context->rsi, (int)context->rdx); break;
+    case SYS_access: sys_access(context, (const char*)context->rdi, (int)context->rsi); break;
     default: context->rax = -ENOSYS; break;
     }
     VMM::exit_syscall_context();

kernel/src/sys/stdio.cpp

@@ -239,3 +239,12 @@ void sys_mkdir(Context* context, const char* filename)
 
     context->rax = rc;
 }
+
+void sys_access(Context* context, const char* path, int) // FIXME: Use the amode argument.
+{
+    char* kpath = strdup_from_user(path);
+    if (!VFS::exists(kpath)) { context->rax = -ENOENT; }
+    else
+        context->rax = 0;
+    kfree(kpath);
+}

libs/libc/include/sys/syscall.h

@@ -20,5 +20,6 @@
 #define SYS_mkdir 16
 #define SYS_fork 17
 #define SYS_waitpid 18
+#define SYS_access 19
 
 #endif

libs/libc/include/unistd.h

@@ -6,9 +6,14 @@
 #include <luna/os-limits.h>
 #include <sys/types.h>
 
-#define STDIN_FILENO 0
+#define STDIN_FILENO 0  // The standard input stream.
-#define STDOUT_FILENO 1
+#define STDOUT_FILENO 1 // The standard output stream.
-#define STDERR_FILENO 2
+#define STDERR_FILENO 2 // The standard error stream.
+
+#define F_OK 0 // Check for a file's existence.
+#define R_OK 1 // Check whether a file is readable.
+#define W_OK 2 // Check whether a file is writable.
+#define X_OK 4 // Check whether a file is executable.
 
 #ifdef __cplusplus
 extern "C"
@@ -58,6 +63,9 @@ extern "C"
     /* Returns a copy of the file descriptor fd. */
     int dup(int fd);
 
+    /* Checks if the current program can access the file or directory at path. */
+    int access(const char* path, int amode);
+
 #ifdef __cplusplus
 }
 #endif

libs/libc/src/syscall.cpp

@@ -0,0 +1,59 @@
+#include <bits/error.h>
+#include <errno.h>
+#include <luna/syscall.h>
+#include <stdarg.h>
+#include <sys/syscall.h>
+
+extern "C" long syscall(long number, ...)
+{
+    typedef unsigned long arg;
+    long result;
+    va_list ap;
+    va_start(ap, number);
+    switch (number)
+    {
+    case SYS_clock:
+    case SYS_yield:
+    case SYS_fork: result = __luna_syscall0(number); break;
+    case SYS_exit:
+    case SYS_getprocid:
+    case SYS_close:
+    case SYS_exec:
+    case SYS_mkdir:
+    case SYS_sleep: result = __luna_syscall1(number, va_arg(ap, arg)); break;
+    case SYS_munmap:
+    case SYS_access:
+    case SYS_open: {
+        arg arg0 = va_arg(ap, arg);
+        arg arg1 = va_arg(ap, arg);
+        result = __luna_syscall2(number, arg0, arg1);
+        break;
+    }
+    case SYS_fcntl:
+    case SYS_seek:
+    case SYS_write:
+    case SYS_read:
+    case SYS_mprotect:
+    case SYS_waitpid:
+    case SYS_mmap: {
+        arg arg0 = va_arg(ap, arg);
+        arg arg1 = va_arg(ap, arg);
+        arg arg2 = va_arg(ap, arg);
+        result = __luna_syscall3(number, arg0, arg1, arg2);
+        break;
+    }
+    case SYS_paint: {
+        arg arg0 = va_arg(ap, arg);
+        arg arg1 = va_arg(ap, arg);
+        arg arg2 = va_arg(ap, arg);
+        arg arg3 = va_arg(ap, arg);
+        arg arg4 = va_arg(ap, arg);
+        result = __luna_syscall5(number, arg0, arg1, arg2, arg3, arg4);
+        break;
+    }
+    default: result = -ENOSYS; break;
+    }
+    va_end(ap);
+    if (number == SYS_mmap) { _RETURN_WITH_MEMORY_ERRNO(result, long int); }
+    else { _RETURN_WITH_ERRNO(result, long); }
+}

libs/libc/src/unistd.cpp

@@ -1,8 +1,5 @@
-#include <bits/error.h>
 #include <fcntl.h>
 #include <luna.h>
-#include <luna/syscall.h>
-#include <stdarg.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 
@@ -37,59 +34,6 @@ extern "C"
         return getprocid(ID_PPID);
     }
 
-    long syscall(long number, ...)
-    {
-        typedef unsigned long int arg;
-        long result;
-        va_list ap;
-        va_start(ap, number);
-        switch (number)
-        {
-        case SYS_clock:
-        case SYS_yield:
-        case SYS_fork: result = __luna_syscall0(number); break;
-        case SYS_exit:
-        case SYS_getprocid:
-        case SYS_close:
-        case SYS_exec:
-        case SYS_mkdir:
-        case SYS_sleep: result = __luna_syscall1(number, va_arg(ap, arg)); break;
-        case SYS_munmap:
-        case SYS_open: {
-            arg arg0 = va_arg(ap, arg);
-            arg arg1 = va_arg(ap, arg);
-            result = __luna_syscall2(number, arg0, arg1);
-            break;
-        }
-        case SYS_fcntl:
-        case SYS_seek:
-        case SYS_write:
-        case SYS_read:
-        case SYS_mprotect:
-        case SYS_waitpid:
-        case SYS_mmap: {
-            arg arg0 = va_arg(ap, arg);
-            arg arg1 = va_arg(ap, arg);
-            arg arg2 = va_arg(ap, arg);
-            result = __luna_syscall3(number, arg0, arg1, arg2);
-            break;
-        }
-        case SYS_paint: {
-            arg arg0 = va_arg(ap, arg);
-            arg arg1 = va_arg(ap, arg);
-            arg arg2 = va_arg(ap, arg);
-            arg arg3 = va_arg(ap, arg);
-            arg arg4 = va_arg(ap, arg);
-            result = __luna_syscall5(number, arg0, arg1, arg2, arg3, arg4);
-            break;
-        }
-        default: result = -ENOSYS; break;
-        }
-        va_end(ap);
-        if (number == SYS_mmap) { _RETURN_WITH_MEMORY_ERRNO(result, long int); }
-        else { _RETURN_WITH_ERRNO(result, long); }
-    }
-
     unsigned int sleep(unsigned int seconds)
     {
         return msleep(seconds * 1000);
@@ -125,4 +69,9 @@ extern "C"
     {
         return fcntl(fd, F_DUPFD, 0);
     }
+
+    int access(const char* path, int amode)
+    {
+        return (int)syscall(SYS_access, path, amode);
+    }
 }