mount syscall and simple mount program

kernel-src/arch/x86-64/syscall.asm

@@ -36,6 +36,7 @@ extern syscall_umask
 extern syscall_poll
 extern syscall_nanosleep
 extern syscall_ftruncate
+extern syscall_mount
 syscalltab:
 dq syscall_print
 dq syscall_mmap
@@ -74,7 +75,8 @@ dq syscall_umask
 dq syscall_poll
 dq syscall_nanosleep
 dq syscall_ftruncate
-syscallcount equ 37
+dq syscall_mount
+syscallcount equ 38
 section .text
 global arch_syscall_entry
 ; on entry:

kernel-src/arch/x86-64/syscalllog.c

@@ -4,7 +4,7 @@
 
 #ifdef SYSCALL_LOGGING
 
-#define SYSCALL_COUNT 35
+#define SYSCALL_COUNT 38
 #define LOGSTR(x) arch_e9_puts(x)
 
 static char *name[] = {
@@ -44,7 +44,8 @@ static char *name[] = {
 	"umask",
 	"poll",
 	"nanosleep",
-	"ftruncate"
+	"ftruncate",
+	"mount"
 };
 
 static char *args[] = {
@@ -84,7 +85,8 @@ static char *args[] = {
 	"mode %o", // umask
 	"fds %p nfds %d timeout %d", // poll
 	"time %p remaining %p", // nanosleep
-	"fd %d size %lu" // ftruncate
+	"fd %d size %lu", // ftruncate
+	"backing %s mountpoint %s fs %s flags %d data %p" // mount
 };
 
 #endif

kernel-src/sys/syscalls/mount.c

@@ -0,0 +1,71 @@
+#include <kernel/syscalls.h>
+#include <kernel/vmm.h>
+#include <kernel/alloc.h>
+#include <kernel/vfs.h>
+#include <logging.h>
+
+syscallret_t syscall_mount(context_t *context, const char *ubacking, const char *umountpoint, const char *ufs, unsigned long flags, void *data) {
+	syscallret_t ret = {
+		.ret = -1
+	};
+	__assert(flags == 0);
+
+	if ((void *)ubacking > USERSPACE_END || (void *)umountpoint > USERSPACE_END || (void *)ufs > USERSPACE_END) {
+		ret.errno = EFAULT;
+		return ret;
+	}
+
+	ret.errno = ENOMEM;
+	char *mountpoint = alloc(strlen(umountpoint) + 1);
+	if (mountpoint == NULL) {
+		return ret;
+	}
+
+	char *fs = alloc(strlen(ufs) + 1);
+	if (fs == NULL) {
+		free(mountpoint);
+		return ret;
+	}
+
+	char *backing = NULL;
+	if (ubacking) {
+		backing = alloc(strlen(ubacking) + 1);
+		if (backing == NULL) {
+			free(mountpoint);
+			free(fs);
+			return ret;
+		}
+		strcpy(backing, ubacking);
+	}
+	strcpy(fs, ufs);
+	strcpy(mountpoint, umountpoint);
+
+	vnode_t *backingrefnode = NULL;
+	if (ubacking)
+		backingrefnode = *backing == '/' ? sched_getroot() : sched_getcwd();
+	vnode_t *mountpointrefnode = *mountpoint == '/' ? sched_getroot() : sched_getcwd();
+	vnode_t *backingnode = NULL;
+
+	if (ubacking) {
+		ret.errno = vfs_lookup(&backingnode, backingrefnode, backing, NULL, 0);
+		if (ret.errno)
+			goto cleanup;
+	}
+
+	ret.errno = vfs_mount(backingnode, mountpointrefnode, mountpoint, fs, data);
+	if (ubacking) {
+		VOP_RELEASE(backingnode);
+	}
+
+	cleanup:
+	if (ubacking) {
+		VOP_RELEASE(backingrefnode);
+		free(backing);
+	}
+
+	VOP_RELEASE(mountpointrefnode);
+
+	free(mountpoint);
+	free(fs);
+	return ret;
+}