internal/outcome: rename from app

This is less ambiguous, and more accurately describes the purpose of the package.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/outcome/shim-signal.c

@@ -0,0 +1,65 @@
+#include "shim-signal.h"
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static pid_t hakurei_shim_param_ppid = -1;
+static int hakurei_shim_fd = -1;
+
+static ssize_t hakurei_shim_write(const void *buf, size_t count) {
+  int savedErrno = errno;
+  ssize_t ret = write(hakurei_shim_fd, buf, count);
+  if (ret == -1 && errno != EAGAIN)
+    exit(EXIT_FAILURE);
+  errno = savedErrno;
+  return ret;
+}
+
+/* see shim_linux.go for handling of the value */
+static void hakurei_shim_sigaction(int sig, siginfo_t *si, void *ucontext) {
+  if (sig != SIGCONT || si == NULL) {
+    /* unreachable */
+    hakurei_shim_write("\2", 1);
+    return;
+  }
+
+  if (si->si_pid == hakurei_shim_param_ppid) {
+    /* monitor requests shim exit */
+    hakurei_shim_write("\0", 1);
+    return;
+  }
+
+  /* unexpected si_pid */
+  hakurei_shim_write("\3", 1);
+
+  if (getppid() != hakurei_shim_param_ppid)
+    /* shim orphaned before monitor delivers a signal */
+    hakurei_shim_write("\1", 1);
+}
+
+void hakurei_shim_setup_cont_signal(pid_t ppid, int fd) {
+  if (hakurei_shim_param_ppid != -1 || hakurei_shim_fd != -1)
+    *(int *)NULL = 0; /* unreachable */
+
+  struct sigaction new_action = {0}, old_action = {0};
+  if (sigaction(SIGCONT, NULL, &old_action) != 0)
+    return;
+  if (old_action.sa_handler != SIG_DFL) {
+    errno = ENOTRECOVERABLE;
+    return;
+  }
+
+  new_action.sa_sigaction = hakurei_shim_sigaction;
+  if (sigemptyset(&new_action.sa_mask) != 0)
+    return;
+  new_action.sa_flags = SA_ONSTACK | SA_SIGINFO;
+
+  if (sigaction(SIGCONT, &new_action, NULL) != 0)
+    return;
+
+  errno = 0;
+  hakurei_shim_param_ppid = ppid;
+  hakurei_shim_fd = fd;
+}