tools/nolibc: add support for prctl()

It will be used to disable core dumps from the child spawned to validate
the stack protector functionality.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/sys.h

@@ -22,6 +22,7 @@
 #include <linux/fcntl.h> /* for O_* and AT_* */
 #include <linux/stat.h>  /* for statx() */
 #include <linux/reboot.h> /* for LINUX_REBOOT_* */
+#include <linux/prctl.h>
 
 #include "arch.h"
 #include "errno.h"
@@ -875,6 +876,32 @@ int open(const char *path, int flags, ...)
 }
 
 
+/*
+ * int prctl(int option, unsigned long arg2, unsigned long arg3,
+ *                       unsigned long arg4, unsigned long arg5);
+ */
+
+static __attribute__((unused))
+int sys_prctl(int option, unsigned long arg2, unsigned long arg3,
+		          unsigned long arg4, unsigned long arg5)
+{
+	return my_syscall5(__NR_prctl, option, arg2, arg3, arg4, arg5);
+}
+
+static __attribute__((unused))
+int prctl(int option, unsigned long arg2, unsigned long arg3,
+		      unsigned long arg4, unsigned long arg5)
+{
+	int ret = sys_prctl(option, arg2, arg3, arg4, arg5);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+
 /*
  * int pivot_root(const char *new, const char *old);
  */

tools/testing/selftests/nolibc/nolibc-test.c

@@ -22,6 +22,7 @@
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <sys/mount.h>
+#include <sys/prctl.h>
 #include <sys/reboot.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
@@ -580,6 +581,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(poll_null);         EXPECT_SYSZR(1, poll(NULL, 0, 0)); break;
 		CASE_TEST(poll_stdout);       EXPECT_SYSNE(1, ({ struct pollfd fds = { 1, POLLOUT, 0}; poll(&fds, 1, 0); }), -1); break;
 		CASE_TEST(poll_fault);        EXPECT_SYSER(1, poll((void *)1, 1, 0), -1, EFAULT); break;
+		CASE_TEST(prctl);             EXPECT_SYSER(1, prctl(PR_SET_NAME, (unsigned long)NULL, 0, 0, 0), -1, EFAULT); break;
 		CASE_TEST(read_badf);         EXPECT_SYSER(1, read(-1, &tmp, 1), -1, EBADF); break;
 		CASE_TEST(sched_yield);       EXPECT_SYSZR(1, sched_yield()); break;
 		CASE_TEST(select_null);       EXPECT_SYSZR(1, ({ struct timeval tv = { 0 }; select(0, NULL, NULL, NULL, &tv); })); break;