fix(native): scripts on session mounts outside the rootfs run with the rootfs shell

tools/nativeguest/hook/exec.c

@@ -245,7 +245,7 @@ static int ddnatv_execve(const char *filename, char *const argv[], char *const e
     char resolved_target[PATH_MAX];
 
     // Only intercept binaries/scripts within DDNATV_ROOT
-    if (g_ddnatv_root[0] != '\0' && strncmp(target, g_ddnatv_root, g_ddnatv_root_len) == 0) {
+    if ((g_ddnatv_root[0] != '\0' && strncmp(target, g_ddnatv_root, g_ddnatv_root_len) == 0) || is_mapped_guest_path(filename)) {
         struct exec_probe probe;
         const char *elf_target = select_exec_target(target, resolved_target, sizeof(resolved_target), &probe);
         if (probe.is_elf && !probe.is_dynamic) static_elf = elf_target;
@@ -798,7 +798,7 @@ static int ddnatv_posix_spawn(pid_t *pid, const char *path,
     }
 
     char *const *orig_ep = envp ? envp : environ;
-    int in_root = g_ddnatv_root[0] != '\0' && strncmp(target, g_ddnatv_root, g_ddnatv_root_len) == 0;
+    int in_root = (g_ddnatv_root[0] != '\0' && strncmp(target, g_ddnatv_root, g_ddnatv_root_len) == 0) || is_mapped_guest_path(path);
 
     struct exec_probe probe;
     char resolved_target[PATH_MAX];

tools/nativeguest/hook/paths.c

@@ -100,6 +100,18 @@ static inline const char *get_rootfs_subpath(const char *target) {
     return NULL;
 }
 
+// A guest path that a session mount puts outside the rootfs (/run/droiddeck, a game library): a
+// program or script there is the guest's, and a script's "#!/bin/sh" is the rootfs shell. The
+// kernel ran them with Android's /system/bin/sh, which found no /usr/bin/kwin_wayland.
+static int is_mapped_guest_path(const char *path) {
+    if (!path || path[0] != '/') return 0;
+    for (int i = 0; i < g_nbinds; i++) {
+        const struct ddnatv_bind *b = &g_binds[i];
+        if (!b->identity && is_path_prefix(path, b->dst, b->dst_len)) return 1;
+    }
+    return 0;
+}
+
 // Android's own mounts and files, which must never be redirected into the rootfs.
 // `path` starts with '/'; a prefix can only match when its second character does.
 static int is_android_host_path(const char *path) {