syscalls: readlinkat

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

@@ -29,6 +29,7 @@ extern syscall_ioctl
 extern syscall_mkdirat
 extern syscall_clockget
 extern syscall_linkat
+extern syscall_readlinkat
 syscalltab:
 dq syscall_print
 dq syscall_mmap
@@ -60,7 +61,8 @@ dq syscall_ioctl
 dq syscall_mkdirat
 dq syscall_clockget
 dq syscall_linkat
-syscallcount equ 30
+dq syscall_readlinkat
+syscallcount equ 31
 section .text
 global arch_syscall_entry
 ; on entry:

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

@@ -37,7 +37,8 @@ static char *name[] = {
 	"ioctl",
 	"mkdirat",
 	"clockget",
-	"linkat"
+	"linkat",
+	"readlinkat"
 };
 
 static char *args[] = {
@@ -70,7 +71,8 @@ static char *args[] = {
 	"fd %d request %lu argument %d", // ioctl
 	"dirfd %d path %s mode %o", // mkdirat
 	"clockid %d timespec %p", // clockget
-	"olddirfd %d oldpath %s newdirfd %d oldpath %s flags %d type %d" // linkat
+	"olddirfd %d oldpath %s newdirfd %d oldpath %s flags %d type %d", // linkat
+	"dirfd %d path %s buffer %p buffer length %lu" // readlinkat
 };
 
 #endif

kernel-src/sys/syscalls/readlinkat.c

@@ -0,0 +1,57 @@
+#include <kernel/syscalls.h>
+#include <kernel/vfs.h>
+#include <kernel/file.h>
+#include <kernel/alloc.h>
+#include <arch/cpu.h>
+
+syscallret_t syscall_readlinkat(context_t *, int dirfd, const char *upath, char *ubuffer, size_t ubuffersize) {
+	syscallret_t ret = {
+		.ret = -1
+	};
+
+	char *path = alloc(strlen(upath + 1));
+
+	if (path == NULL) {
+		ret.errno = ENOMEM;
+		return ret;
+	}
+
+	strcpy(path, upath);
+
+	file_t *file = NULL;
+	vnode_t *dirnode = NULL;
+	ret.errno = dirfd_enter(path, dirfd, &file, &dirnode);
+	if (ret.errno)
+		goto cleanup;
+
+	vnode_t *node = NULL;
+	ret.errno = vfs_lookup(&node, dirnode, path, NULL, VFS_LOOKUP_NOLINK);
+	if (ret.errno)
+		goto cleanup;
+
+	char *buffer = NULL;
+
+	ret.errno = VOP_READLINK(node, &buffer, &_cpu()->thread->proc->cred);
+	if (ret.errno)
+		goto cleanup;
+
+	size_t bufferlen = strlen(buffer);
+	size_t copylen = bufferlen > ubuffersize ? ubuffersize : bufferlen;
+
+	memcpy(ubuffer, buffer, copylen);
+
+	ret.ret = copylen;
+
+	cleanup:
+
+	if (buffer)
+		free(buffer);
+
+	if (node)
+		VOP_RELEASE(node);
+
+	if (dirnode)
+		dirfd_leave(dirnode, file);
+
+	return ret;
+}