Add Linux syscall compatibility shims (fork/clone, wait4, mmap, sockets, futex, process bookkeeping) and docs

source/includes/syscalls.h

@@ -37,6 +37,8 @@
 #define LINUX_SYS_DUP2              33
 #define LINUX_SYS_NANOSLEEP         35
 #define LINUX_SYS_GETPID            39
+#define LINUX_SYS_SOCKET            41
+#define LINUX_SYS_CONNECT           42
 #define LINUX_SYS_CLONE             56
 #define LINUX_SYS_FORK              57
 #define LINUX_SYS_WAIT4             61
@@ -103,6 +105,8 @@
 #define LINUX_EINTR      4
 #define LINUX_ETIMEDOUT  110
 #define LINUX_ECHILD     10
+#define LINUX_ENOTSOCK   88
+#define LINUX_EAFNOSUPPORT 97
 
 #define LINUX_PROT_NONE  0x0
 #define LINUX_PROT_READ  0x1

source/kernel/C/syscalls-doc.dox

@@ -33,6 +33,10 @@
  * - `set_robust_list(2)`   -> `sys_set_robust_list()`   -> ABI validation
  * - `tgkill(2)`            -> `sys_tgkill()`            -> argument validation + stubbed signal path
  *
+ * ## Socket compatibility
+ * - `socket(2)`            -> `sys_socket()`            -> returns `-EAFNOSUPPORT` (not wired yet)
+ * - `connect(2)`           -> `sys_connect()`           -> fd validation + `-ENOTSOCK`
+ *
  * ## Time and randomness
  * - `clock_gettime(2)`     -> `sys_clock_gettime()`     -> RTC-backed time fetch
  * - `nanosleep(2)`         -> `sys_nanosleep()`         -> `sleep()`

source/kernel/C/syscalls.c

@@ -758,6 +758,26 @@ static int64 sys_writev(uint64_t fd, const linux_iovec_t* iov, uint64_t iovcnt)
     return total;
 }
 
+static int64 sys_socket(uint64_t domain, uint64_t type, uint64_t protocol) {
+    (void)type;
+    (void)protocol;
+
+    // Networking stack is not exposed through Linux sockets yet.
+    // Return Linux-like "address family not supported" instead of a fake fd.
+    if (domain == 1 || domain == 2 || domain == 10)
+        return -LINUX_EAFNOSUPPORT;
+    return -LINUX_EAFNOSUPPORT;
+}
+
+static int64 sys_connect(uint64_t fd, const void* addr, uint64_t addrlen) {
+    (void)addr;
+    (void)addrlen;
+
+    if (!fd_valid((int)fd))
+        return -LINUX_EBADF;
+    return -LINUX_ENOTSOCK;
+}
+
 static int64 sys_ioctl(uint64_t fd, uint64_t req, uint64_t arg) {
     if (!fd_valid((int)fd))
         return -LINUX_EBADF;
@@ -1359,6 +1379,12 @@ uint64_t syscall_dispatch (
         case LINUX_SYS_GETPID:
             return multitasking_current_pid() ? multitasking_current_pid() : 1;
 
+        case LINUX_SYS_SOCKET:
+            return sys_socket(arg1, arg2, arg3);
+
+        case LINUX_SYS_CONNECT:
+            return sys_connect(arg1, (const void*)arg2, arg3);
+
         case LINUX_SYS_CLONE:
             return sys_fork();
 
@@ -1449,8 +1475,6 @@ uint64_t syscall_dispatch (
             return sys_futex((uint32_t*)arg1, arg2, arg3,
                             (const linux_timespec_t*)arg4,
                             (uint32_t*)arg5, arg6);
-        case 41: // getuid (32-bit ABI compatibility)
-            return 0;
         case 19:
             {
                 linux_iovec_t* iov = (linux_iovec_t*)arg2;