major restructuring, prepare for smp

code/user/personalities/posix/posix_fd.h

@@ -0,0 +1,37 @@
+#pragma once
+// posix_fd.h - file descriptor table (internal to posix.dll)
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef enum {
+    FD_FREE,
+    FD_FILE,
+    FD_CONSOLE_R,   // fd 0 - reads from keyboard via SysKbReadChar
+    FD_CONSOLE_W,   // fd 1, 2 - writes via SysWriteConsole
+    FD_DEVNULL,     // /dev/null
+    FD_DEVZERO,     // /dev/zero
+    FD_SOCKET,      // kernel socket handle
+} FD_TYPE;
+
+typedef struct {
+    FD_TYPE  Type;
+    uint32_t KHandle;   // kernel handle; 0 for console/devnull/devzero
+    bool     Used;
+} FD_ENTRY;
+
+#define FD_MAX        64
+#define FD_TABLE_PIDS 32   // circular, indexed by pid % FD_TABLE_PIDS
+
+// Called from _start before main(); sets up fds 0/1/2 for this process.
+__declspec(dllexport) void PosixFdInit(void);
+
+// Allocate the lowest free fd >= 3. Returns -1 and sets errno=EMFILE on failure.
+__declspec(dllexport) int FdAlloc(uint32_t pid, FD_TYPE type, uint32_t khandle);
+
+// Look up an fd. Returns NULL and sets errno=EBADF if invalid.
+__declspec(dllexport) FD_ENTRY* FdGet(uint32_t pid, int fd);
+
+// Release an fd slot (does NOT close the kernel handle).
+__declspec(dllexport) void FdFree(uint32_t pid, int fd);
+
+int PosixStatusToErrno(uint32_t s);