feat: implement FDT-based memory discovery and add comprehensive debug logging to exec syscalls

1 files changed, 153 insertions, 0 deletions

diff --git a/src/ulib/syscalls.c b/src/ulib/syscalls.c
new file mode 100644
index 0000000..676bf18
--- /dev/null
+++ b/src/ulib/syscalls.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2026 Richard Qin
+ * Libc Syscall Shims
+ */
+
+#include "common/types.h"
+#include "user/user.h"
+
+// Define external raw syscalls from usys.S
+extern int sys_openat(int dfd, const char *filename, int flags, int mode);
+extern int sys_mknodat(int dfd, const char *filename, int mode, int dev);
+extern int sys_mkdirat(int dfd, const char *path, int mode);
+extern int sys_unlinkat(int dfd, const char *path, int flags);
+extern int sys_linkat(int olddfd, const char *oldpath, int newdfd, const char *newpath, int flags);
+extern int sys_chdir(const char *path);
+extern int sys_dup(int oldfd);
+extern int sys_fstat(int fd, void *statbuf);
+extern int sys_read(int fd, void *buf, int count);
+extern int sys_write(int fd, const void *buf, int count);
+extern int sys_close(int fd);
+extern int sys_pipe2(int pipefd[2], int flags);
+extern int sys_clone(unsigned long flags, void *stack, int *ptid, void *tls, int *ctid);
+extern int sys_execve(const char *path, char *const argv[], char *const envp[]);
+extern int sys_wait4(int pid, int *status, int options, void *rusage);
+extern int sys_exit(int status);
+extern int sys_getpid();
+extern int sys_brk(int n);
+extern int sys_kill(int pid, int sig);
+extern int sys_nanosleep(void *req, void *rem);
+extern int sys_reboot(int magic1, int magic2, int cmd, void *arg);
+extern int sys_lseek(int fd, int offset, int whence);
+extern void sys_putc(char c);
+extern int sys_disk_test();
+
+// --- POSIX Implementation ---
+
+int open(const char *path, int flags)
+{
+    return sys_openat(AT_FDCWD, path, flags, 0);
+}
+
+int mknod(const char *path, short major, short minor)
+{
+    // Pack major/minor into simplified dev_t (major << 20 | minor)
+    int dev = (major << 20) | (minor & 0xFFFFF);
+    return sys_mknodat(AT_FDCWD, path, 0, dev);
+}
+
+int mkdir(const char *path)
+{
+    return sys_mkdirat(AT_FDCWD, path, 0);
+}
+
+int unlink(const char *path)
+{
+    return sys_unlinkat(AT_FDCWD, path, 0);
+}
+
+int link(const char *oldpath, const char *newpath)
+{
+    return sys_linkat(AT_FDCWD, oldpath, AT_FDCWD, newpath, 0);
+}
+
+int chdir(const char *path)
+{
+    return sys_chdir(path);
+}
+
+int fork()
+{
+    return sys_clone(0, 0, 0, 0, 0);
+}
+
+int exec(char *path, char **argv)
+{
+    return sys_execve(path, argv, 0);
+}
+
+int wait(uint64 status_addr)
+{
+    return sys_wait4(-1, (int *)status_addr, 0, 0);
+}
+
+int pipe(int p[])
+{
+    return sys_pipe2(p, 0);
+}
+
+int read(int fd, void *buf, int n)
+{
+    return sys_read(fd, buf, n);
+}
+
+int write(int fd, const void *buf, int n)
+{
+    return sys_write(fd, buf, n);
+}
+
+int close(int fd)
+{
+    return sys_close(fd);
+}
+
+int fstat(int fd, void *st)
+{
+    return sys_fstat(fd, st);
+}
+
+int dup(int fd)
+{
+    return sys_dup(fd);
+}
+
+int getpid()
+{
+    return sys_getpid();
+}
+
+char *sbrk(int n)
+{
+    return (char *)(long)sys_brk(n);
+}
+
+int kill(int pid)
+{
+    return sys_kill(pid, 0);
+}
+
+int sleep(int ticks)
+{
+    return sys_nanosleep((void *)(long)ticks, 0);
+}
+
+int shutdown()
+{
+    return sys_reboot(0, 0, 0, 0);
+}
+
+void putc(char c)
+{
+    sys_putc(c);
+}
+
+int disk_test()
+{
+    return sys_disk_test();
+}
+
+int lseek(int fd, int offset, int whence)
+{
+    return sys_lseek(fd, offset, whence);
+}
\ No newline at end of file