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tundra/boot/init.c

@@ -0,0 +1,108 @@
+/* SPDX-License-Identifier: MPL-2.0
+ * Stage-zero diagnostic init. No disks, network or Android framework.
+ * Keep this executable independent of libc to use it on both test targets.
+ */
+#if defined(__x86_64__)
+#define NR_write 1
+#define NR_read 0
+#define NR_close 3
+#define NR_openat 257
+#define NR_mount 165
+#define NR_getpid 39
+#define NR_exit 60
+#define NR_reboot 169
+#define NR_nanosleep 35
+static long call(long n, long a, long b, long c, long d, long e) {
+  register long r10 __asm__("r10") = d;
+  register long r8 __asm__("r8") = e;
+  long result;
+  __asm__ volatile("syscall" : "=a"(result)
+                   : "a"(n), "D"(a), "S"(b), "d"(c), "r"(r10), "r"(r8)
+                   : "rcx", "r11", "memory");
+  return result;
+}
+#elif defined(__aarch64__)
+#define NR_write 64
+#define NR_read 63
+#define NR_close 57
+#define NR_openat 56
+#define NR_mount 40
+#define NR_getpid 172
+#define NR_exit 93
+#define NR_reboot 142
+#define NR_nanosleep 101
+static long call(long n, long a, long b, long c, long d, long e) {
+  register long x8 __asm__("x8") = n;
+  register long x0 __asm__("x0") = a;
+  register long x1 __asm__("x1") = b;
+  register long x2 __asm__("x2") = c;
+  register long x3 __asm__("x3") = d;
+  register long x4 __asm__("x4") = e;
+  __asm__ volatile("svc 0" : "+r"(x0)
+                   : "r"(x8), "r"(x1), "r"(x2), "r"(x3), "r"(x4)
+                   : "memory");
+  return x0;
+}
+#else
+#error Unsupported architecture
+#endif
+
+static void say(const char *s) {
+  long n = 0;
+  while (s[n]) ++n;
+  while (n > 0) {
+    long written = call(NR_write, 1, (long)s, n, 0, 0);
+    if (written <= 0) break;
+    s += written;
+    n -= written;
+  }
+}
+
+static int contains(const char *s, const char *needle) {
+  for (; *s; ++s) {
+    long i = 0;
+    while (needle[i] && s[i] == needle[i]) ++i;
+    if (!needle[i]) return 1;
+  }
+  return 0;
+}
+
+static void file(const char *path, char *buffer, long capacity) {
+  long fd = call(NR_openat, -100, (long)path, 0, 0, 0);
+  buffer[0] = 0;
+  if (fd < 0) return;
+  long n = call(NR_read, fd, (long)buffer, capacity - 1, 0, 0);
+  if (n > 0) buffer[n] = 0;
+  call(NR_close, fd, 0, 0, 0, 0);
+}
+
+__attribute__((noreturn)) void _start(void) {
+  if (call(NR_getpid, 0, 0, 0, 0, 0) != 1) {
+    say("Tundra init must only run as PID 1 in the diagnostic ramdisk.\n");
+    call(NR_exit, 2, 0, 0, 0, 0);
+    for (;;) {}
+  }
+  say("TUNDRA_STAGE0_START\n");
+  long proc = call(NR_mount, (long)"proc", (long)"/proc", (long)"proc", 14, 0);
+  long sys = call(NR_mount, (long)"sysfs", (long)"/sys", (long)"sysfs", 14, 0);
+  char buffer[4096];
+  file("/proc/version", buffer, sizeof(buffer));
+  say(buffer);
+  file("/proc/cmdline", buffer, sizeof(buffer));
+  int selftest = contains(buffer, "tundra.selftest=1");
+  if (proc == 0 && sys == 0 && buffer[0]) {
+    say("TUNDRA_STAGE0_OK pid1 proc sysfs cmdline\n");
+  } else {
+    say("TUNDRA_STAGE0_FAILED pseudo-filesystems\n");
+  }
+  say("Diagnostic only: no Gecko, Gaia, HAL, USB service or persistent mounts.\n");
+  if (selftest) {
+    say("TUNDRA_STAGE0_POWEROFF\n");
+    call(NR_reboot, 0xfee1dead, 672274793, 0x4321fedc, 0, 0);
+  }
+  for (;;) {
+    long delay[2] = {15, 0};
+    call(NR_nanosleep, (long)delay, 0, 0, 0, 0);
+    say("TUNDRA_STAGE0_ALIVE\n");
+  }
+}