From: David Carlier <devnexen@gmail.com>
Date: Wed, 29 Aug 2018 20:04:32 +0000 (+0100)
Subject: Support fixed address mmap without replacement
X-Git-Tag: php-7.3.0RC1~16
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f7b573b4e96f3cf421dc92063b11121da2370e46;p=php

Support fixed address mmap without replacement

Reapply changes for Zend fixed mapping but only for FreeBSD.
Other BSD might expose some day a similar flag (private
for OpenBSD for the moment for example).
The Linux's part could be brought back but not before 7.4,
at this time, distributions with kernel > 4.17 will be
more widely available.
---

diff --git a/Zend/zend_alloc.c b/Zend/zend_alloc.c
index 11691d8377..302f9e7281 100644
--- a/Zend/zend_alloc.c
+++ b/Zend/zend_alloc.c
@@ -423,11 +423,15 @@ static void *zend_mm_mmap_fixed(void *addr, size_t size)
 #ifdef _WIN32
 	return VirtualAlloc(addr, size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
 #else
+	int flags = MAP_PRIVATE | MAP_ANON;
+#if defined(MAP_EXCL)
+	flags |= MAP_FIXED | MAP_EXCL;
+#endif
 	/* MAP_FIXED leads to discarding of the old mapping, so it can't be used. */
-	void *ptr = mmap(addr, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON /*| MAP_POPULATE | MAP_HUGETLB*/, -1, 0);
+	void *ptr = mmap(addr, size, PROT_READ | PROT_WRITE, flags /*| MAP_POPULATE | MAP_HUGETLB*/, -1, 0);
 
 	if (ptr == MAP_FAILED) {
-#if ZEND_MM_ERROR
+#if ZEND_MM_ERROR && !defined(MAP_EXCL)
 		fprintf(stderr, "\nmmap() failed: [%d] %s\n", errno, strerror(errno));
 #endif
 		return NULL;