feat(apps): permission manager equips apps (manifest+consent+decisions in /system), launches via init w/ file grant; shell unprivileged (/home); install/apps/allow/revoke; revoke stops running app; app-image tool; counter app

crates/apps/counter/src/main.rs

@@ -0,0 +1,59 @@
+//! Counts its runs in its own data folder: the `storage` capability, which
+//! it can do without (then it remembers nothing).
+
+#![no_std]
+#![forbid(unsafe_code)]
+#![no_main]
+
+extern crate libkos;
+
+use libkos::fs::Storage;
+use libkos::println;
+use types::address::VirtualAddress;
+
+const DATA_BUF_VA: VirtualAddress = VirtualAddress::from_raw(0x0180_0000);
+const COUNT: &[u8] = b"count";
+
+/// The number in the file, 0 if there is none yet.
+fn read_count(fs: &mut Storage) -> u64 {
+    let Ok(h) = fs.open(COUNT) else { return 0 };
+    let mut buf = [0u8; 20];
+    let n = fs.read(h, &mut buf).unwrap_or(0);
+    let _ = fs.close(h);
+    core::str::from_utf8(&buf[..n]).ok().and_then(|s| s.trim().parse().ok()).unwrap_or(0)
+}
+
+fn write_count(fs: &mut Storage, count: u64) -> bool {
+    let mut digits = [0u8; 20];
+    let mut n = 0;
+    let mut v = count;
+    loop {
+        digits[n] = b'0' + (v % 10) as u8;
+        n += 1;
+        v /= 10;
+        if v == 0 {
+            break;
+        }
+    }
+    digits[..n].reverse();
+    let _ = fs.delete(COUNT);
+    let Ok(h) = fs.create(COUNT) else { return false };
+    let ok = fs.write(h, &digits[..n]) == Ok(n);
+    let _ = fs.close(h);
+    ok
+}
+
+fn main() {
+    let Some(mut fs) = libkos::start::data().and_then(|d| Storage::attach(d, DATA_BUF_VA).ok()) else {
+        println!("counter: not allowed to keep anything, so this is run 1 as far as it knows");
+        return;
+    };
+    let count = read_count(&mut fs) + 1;
+    if write_count(&mut fs, count) {
+        println!("counter: run {} (kept in its own data folder)", count);
+    } else {
+        println!("counter: run {}, but it could not save that", count);
+    }
+}
+
+libkos::entry!(main);