/*
   +----------------------------------------------------------------------+
   | Zend Engine                                                          |
   +----------------------------------------------------------------------+
   | Copyright © Zend Technologies Ltd., a subsidiary company of          |
   |     Perforce Software, Inc., and Contributors.                       |
   +----------------------------------------------------------------------+
   | This source file is subject to the Modified BSD License that is      |
   | bundled with this package in the file LICENSE, and is available      |
   | through the World Wide Web at <https://www.php.net/license/>.        |
   |                                                                      |
   | SPDX-License-Identifier: BSD-3-Clause                                |
   +----------------------------------------------------------------------+
   | Authors: Arnaud Le Blanc <arnaud.lb@gmail.com>                       |
   +----------------------------------------------------------------------+
*/

#ifndef ZEND_CALL_STACK_H
#define ZEND_CALL_STACK_H

#include "zend.h"
#include "zend_portability.h"
#ifdef _MSC_VER
# include <intrin.h>
#endif
#ifdef __APPLE__
# include <pthread.h>
#endif

#ifdef _MSC_VER
#include <intrin.h>
#endif

#ifdef ZEND_CHECK_STACK_LIMIT

typedef struct _zend_call_stack {
	void *base; /* high address of the stack */
	size_t max_size;
} zend_call_stack;

ZEND_API void zend_call_stack_init(void);

ZEND_API bool zend_call_stack_get(zend_call_stack *stack);

/** Returns an approximation of the current stack position */
static zend_always_inline void *zend_call_stack_position(void) {
#ifdef _MSC_VER
	return _AddressOfReturnAddress();
#elif defined(PHP_HAVE_BUILTIN_FRAME_ADDRESS)
	return __builtin_frame_address(0);
#else
	void *a;
	void *pos = (void*)&a;
	return pos;
#endif
}

static zend_always_inline bool zend_call_stack_overflowed(void *stack_limit) {
	return (uintptr_t) zend_call_stack_position() <= (uintptr_t) stack_limit;
}

static inline void* zend_call_stack_limit(void *base, size_t size, size_t reserved_size)
{
	if (UNEXPECTED(size > (uintptr_t)base)) {
		return (void*)0;
	}

	base = (int8_t*)base - size;

	if (UNEXPECTED(UINTPTR_MAX - (uintptr_t)base < reserved_size)) {
		return (void*)UINTPTR_MAX;
	}

	return (int8_t*)base + reserved_size;
}

static inline size_t zend_call_stack_default_size(void)
{
#ifdef __linux__
	return 8 * 1024 * 1024;
#endif
#if defined(__FreeBSD__) || defined(__NetBSD__)
	return 4 * 1024 * 1024;
#endif
#if defined(__DragonFly__)
	return 2 * 1024 * 1024;
#endif
#ifdef __OpenBSD__
	return 512 * 1024;
#endif
#ifdef __APPLE__
	// https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Multithreading/CreatingThreads/CreatingThreads.html
	if (pthread_main_np()) {
		return 8 * 1024 * 1024;
	}
	return 512 * 1024;
#endif
#ifdef __HAIKU__
	return 64 * 4096;
#endif
#ifdef __sun
	return 8 * 4096;
#endif
#ifdef _AIX
	/*
	 * default pthread stack limit is 96 KB on 32-bit, 192 KB on 64-bit
	 * https://www.ibm.com/docs/en/aix/7.1.0?topic=programming-threads-library-options
	 */
#ifdef HAVE_PTHREAD_GETTHRDS_NP /* if we have pthread linked (not in libc) */
	if (pthread_self() != 1) {
#ifdef __64BIT__
		return 192 * 1024;
#else
		return 96 * 1024;
#endif
	}
#endif
	/*
	 * default AIX ulimit -s value is allegedly 32 MB, default values per:
	 * https://www.ibm.com/docs/en/aix/7.1.0?topic=u-ulimit-command
	 * N.B.: the the file uses 512b blocks, but the command uses kilobytes
	 * https://www.ibm.com/support/pages/ibm-aix-security-ulimit-and-ulimit-d-output-differs-value-etcsecuritylimits
	 *
	 * note PASE uses an unlimited stack size by default, which is capped
	 * at the PowerPC segment size (256 MB)
	 */
	return 32 * 1024 * 1024;
#endif


	return 2 * 1024 * 1024;
}

#endif /* ZEND_CHECK_STACK_LIMIT */
#endif /* ZEND_CALL_STACK_H */
