Add needstack, get_stack_direction, get_stack_limit, and get_stack_space

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 53 insertions, 0 deletions

diff --git a/needstack.c b/needstack.c
new file mode 100644
index 0000000..11d8ed4
--- /dev/null
+++ b/needstack.c
@@ -0,0 +1,53 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+
+int
+libsimple_needstack(size_t n)
+{
+	size_t limit1, limit2, limit, used;
+	uintptr_t low, high, current;
+	void *currentptr;
+
+	currentptr = __builtin_frame_address(0);
+	current = (uintptr_t)currentptr;
+	if (libsimple_get_stack_space(&low, &high))
+		return -1;
+	if (libsimple_get_stack_limit(&limit1, NULL))
+		return -1;
+	limit2 = (size_t)(high - low);
+	limit = limit1 < limit2 ? limit1 : limit2;
+
+	switch (libsimple_get_stack_direction()) {
+	case +1:
+		if (current < low)
+			goto enotsup;
+		used = (size_t)(current - low);
+		break;
+	case -1:
+		if (current > high)
+			goto enotsup;
+		used = (size_t)(high - current);
+		break;
+	default:
+	enotsup:
+		errno = ENOTSUP;
+		return -1;
+	}
+
+	/* TODO it would be nice to be able to grow the stack */
+	return used <= limit && n <= limit - used;
+}
+
+
+#else
+#include "test.h"
+
+int
+main(void)
+{
+	return 0;
+}
+
+#endif