kernel: ksud: add commonized execve/compat_execve hooks for ksud

This commit squashes the following:
- kernel: ksud: commonize execve_ksud handlers
- kernel: ksud: provide ksu_handle_compat_execve_ksud v2
- kernel: ksud: add ksu_handle_execve_ksud v2

This finalizes syscall-only hooking for KernelSU as we provide
both native and compat.

- sys_execve - ksu_handle_execve_ksud
- compat_sys_execve - ksu_handle_compat_execve_ksud

since these two share common logic, we commonize them to
ksu_common_execve_ksud sinc only the argv field is different.
(.native vs .compat)

usage:
	ksu_handle_execve_ksud(filename, argv);  // for sys_execve
	ksu_handle_compat_execve_ksud(filename, argv);  // for compat_sys_execve

This implementations avoids any dependency on struct filename
making it also usable on Ultra-Legacy.

Requires:
- kernel: ksud: dont create structs just to deconstruct them for a string (tiann#2595)

original logic was taken from sys_execve_handler_pre
upstream: tiann@2027ac3

Tested-by: selfmusing <[email protected]>
Tested-by: Adam W. Willis <[email protected]>
Tested-by: alternoegraha <[email protected]>
Tested-by: iDead XD <[email protected]>
Tested-by: rsuntk <[email protected]>
Signed-off-by: backslashxx <[email protected]>
Co-Authored-By: Another Guy <[email protected]>

Author: 2 people

kernel/ksud.c

@@ -484,6 +484,41 @@ bool ksu_is_safe_mode()
 	return false;
 }
 
+// execve_ksud handlers for non kprobe
+static int ksu_common_execve_ksud(const char __user *filename_user,
+			struct user_arg_ptr *argv)
+{
+	char path[32];
+
+	// return early if disabled.
+	if (!ksu_execveat_hook)
+		return 0;
+
+	if (!filename_user)
+		return 0;
+
+	memset(path, 0, sizeof(path));
+	ksu_strncpy_from_user_nofault(path, filename_user, 32);
+
+	return __ksu_handle_execveat_ksud(AT_FDCWD, path, argv, NULL, NULL);
+}
+
+int ksu_handle_execve_ksud(const char __user *filename_user,
+			const char __user *const __user *__argv)
+{
+	struct user_arg_ptr argv = { .ptr.native = __argv };
+	return ksu_common_execve_ksud(filename_user, &argv);
+}
+
+#if defined(CONFIG_COMPAT)
+int ksu_handle_compat_execve_ksud(const char __user *filename_user,
+			const compat_uptr_t __user *__argv)
+{
+	struct user_arg_ptr argv = { .ptr.compat = __argv };
+	return ksu_common_execve_ksud(filename_user, &argv);
+}
+#endif
+
 static void stop_vfs_read_hook()
 {
 	ksu_vfs_read_hook = false;