--- /dev/null
+/* -*- mode: C; c-basic-offset: 3; -*- */
+
+#include <assert.h>
+#include <elf.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <sys/user.h>
+#include <sys/wait.h>
+
+static int
+err_out(const char *msg)
+{
+ perror(msg);
+ return 1;
+}
+
+static int
+non_empty(const char *buf, size_t len)
+{
+ size_t i;
+ int c;
+ volatile const char *p = buf;
+
+ for (i = 0; i != len; i++)
+ c |= p[i];
+ return c;
+}
+
+static int
+do_child(void)
+{
+ if (ptrace(PTRACE_TRACEME, 0, NULL, NULL) == -1)
+ return err_out("ptrace traceme");
+ raise(SIGUSR1);
+ return 0;
+}
+
+int
+main(void)
+{
+ char buf[1024];
+ struct iovec iov;
+ pid_t cpid, pid;
+ int status;
+
+ cpid = fork();
+ if (cpid == -1)
+ return err_out("fork");
+ if (cpid == 0)
+ return do_child();
+
+ pid = wait(&status);
+ if (pid == -1)
+ return err_out("wait");
+
+ /* Intentionally provide an uninitialized buffer to ptrace. */
+ iov.iov_len = sizeof(buf);
+ iov.iov_base = buf;
+ if (ptrace(0x4204, cpid, NT_PRSTATUS, &iov) == -1)
+ return err_out("ptrace getregset");
+
+ assert(iov.iov_base == buf);
+ assert(iov.iov_len > 0 && iov.iov_len < sizeof(buf));
+
+ /* We're assuming here that NT_PRSTATUS never contains
+ all-zeros. */
+ assert(non_empty(buf, iov.iov_len));
+ puts("OK");
+ return 0;
+}