libc: Implement _exit(), which is needed by libc

_exit() is called by libc functions such as abort() or exit(). This
implementation replaces the one from newlib's libnosys.

BRANCH=none
BUG=b:234181908
TEST=make buildall

Signed-off-by: Tom Hughes <tomhughes@chromium.org>
Change-Id: I1d8f65fa206b3544a2772f38be854ee905532ad3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3933256
Reviewed-by: Andrea Grandi <agrandi@google.com>

2 files changed, 34 insertions, 0 deletions

diff --git a/libc/build.mk b/libc/build.mk
new file mode 100644
index 0000000000..594f3061d6
--- /dev/null
+++ b/libc/build.mk
@@ -0,0 +1,5 @@
+# Copyright 2022 The ChromiumOS Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+libc-y=syscalls.o
diff --git a/libc/syscalls.c b/libc/syscalls.c
new file mode 100644
index 0000000000..9c683a2732
--- /dev/null
+++ b/libc/syscalls.c
@@ -0,0 +1,29 @@
+/* Copyright 2022 The ChromiumOS Authors
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/**
+ *@brief Provides implementations of syscalls needed by libc. The newlib
+ * documentation provides a list of the required syscalls:
+ * https://sourceware.org/newlib/libc.html#Syscalls and minimal implementations
+ * can be found in newlib's "nosys" library:
+ * https://sourceware.org/git/?p=newlib-cygwin.git;a=tree;f=libgloss/libnosys.
+ */
+
+#include "panic.h"
+#include "software_panic.h"
+#include "task.h"
+
+/**
+ * Reboot the system.
+ *
+ * This function is called from libc functions such as abort() or exit().
+ *
+ * @param rc exit code
+ */
+void _exit(int rc)
+{
+	panic_printf("%s called with rc: %d\n", __func__, rc);
+	software_panic(PANIC_SW_EXIT, task_get_current());
+}