Try memory leak workaround with zeroed mem (#1229)

This PR attempts to fix the memory leak reported in #1128 and is an
iteration on PR #1189 which had problems with "memory out of bounds"
errors.

## What problem is it solving?

It stops PHP from leaking memory throughout the runtime of a script and
hopefully stops memory out of bounds errors by zeroing all memory given
to PHP.

## How is the problem addressed?

- By avoiding mmap()/munmap() which have incomplete implementations in
Emscripten
- By using posix_memalign() to allocate memory instead and manually
zeroing the memory before handing it to PHP

## Testing Instructions

- Observe CI test results
- Use `npm run dev` and exercise Playground locally in the browser

packages/php-wasm/compile/php-wasm-memory-storage/.gitignore

@@ -0,0 +1,41 @@
+*.lo
+*.la
+.libs
+acinclude.m4
+aclocal.m4
+autom4te.cache
+build
+config.guess
+config.h
+config.h.in
+config.log
+config.nice
+config.status
+config.sub
+configure
+configure.ac
+configure.in
+include
+install-sh
+libtool
+ltmain.sh
+Makefile
+Makefile.fragments
+Makefile.global
+Makefile.objects
+missing
+mkinstalldirs
+modules
+php_test_results_*.txt
+phpt.*
+run-test-info.php
+run-tests.php
+tests/**/*.diff
+tests/**/*.out
+tests/**/*.php
+tests/**/*.exp
+tests/**/*.log
+tests/**/*.sh
+tests/**/*.db
+tests/**/*.mem
+tmp-php.ini

packages/php-wasm/compile/php-wasm-memory-storage/config.m4

@@ -0,0 +1,94 @@
+dnl config.m4 for extension wasm_memory_storage
+
+dnl Comments in this file start with the string 'dnl'.
+dnl Remove where necessary.
+
+dnl If your extension references something external, use 'with':
+
+dnl PHP_ARG_WITH([wasm_memory_storage],
+dnl   [for wasm_memory_storage support],
+dnl   [AS_HELP_STRING([--with-wasm_memory_storage],
+dnl     [Include wasm_memory_storage support])])
+
+dnl Otherwise use 'enable':
+
+PHP_ARG_ENABLE([wasm_memory_storage],
+  [whether to enable wasm_memory_storage support],
+  [AS_HELP_STRING([--enable-wasm_memory_storage],
+    [Enable wasm_memory_storage support])],
+  [no])
+
+if test "$PHP_WASM_MEMORY_STORAGE" != "no"; then
+  dnl Write more examples of tests here...
+
+  dnl Remove this code block if the library does not support pkg-config.
+  dnl PKG_CHECK_MODULES([LIBFOO], [foo])
+  dnl PHP_EVAL_INCLINE($LIBFOO_CFLAGS)
+  dnl PHP_EVAL_LIBLINE($LIBFOO_LIBS, WASM_MEMORY_STORAGE_SHARED_LIBADD)
+
+  dnl If you need to check for a particular library version using PKG_CHECK_MODULES,
+  dnl you can use comparison operators. For example:
+  dnl PKG_CHECK_MODULES([LIBFOO], [foo >= 1.2.3])
+  dnl PKG_CHECK_MODULES([LIBFOO], [foo < 3.4])
+  dnl PKG_CHECK_MODULES([LIBFOO], [foo = 1.2.3])
+
+  dnl Remove this code block if the library supports pkg-config.
+  dnl --with-wasm_memory_storage -> check with-path
+  dnl SEARCH_PATH="/usr/local /usr"     # you might want to change this
+  dnl SEARCH_FOR="/include/wasm_memory_storage.h"  # you most likely want to change this
+  dnl if test -r $PHP_WASM_MEMORY_STORAGE/$SEARCH_FOR; then # path given as parameter
+  dnl   WASM_MEMORY_STORAGE_DIR=$PHP_WASM_MEMORY_STORAGE
+  dnl else # search default path list
+  dnl   AC_MSG_CHECKING([for wasm_memory_storage files in default path])
+  dnl   for i in $SEARCH_PATH ; do
+  dnl     if test -r $i/$SEARCH_FOR; then
+  dnl       WASM_MEMORY_STORAGE_DIR=$i
+  dnl       AC_MSG_RESULT(found in $i)
+  dnl     fi
+  dnl   done
+  dnl fi
+  dnl
+  dnl if test -z "$WASM_MEMORY_STORAGE_DIR"; then
+  dnl   AC_MSG_RESULT([not found])
+  dnl   AC_MSG_ERROR([Please reinstall the wasm_memory_storage distribution])
+  dnl fi
+
+  dnl Remove this code block if the library supports pkg-config.
+  dnl --with-wasm_memory_storage -> add include path
+  dnl PHP_ADD_INCLUDE($WASM_MEMORY_STORAGE_DIR/include)
+
+  dnl Remove this code block if the library supports pkg-config.
+  dnl --with-wasm_memory_storage -> check for lib and symbol presence
+  dnl LIBNAME=WASM_MEMORY_STORAGE # you may want to change this
+  dnl LIBSYMBOL=WASM_MEMORY_STORAGE # you most likely want to change this
+
+  dnl If you need to check for a particular library function (e.g. a conditional
+  dnl or version-dependent feature) and you are using pkg-config:
+  dnl PHP_CHECK_LIBRARY($LIBNAME, $LIBSYMBOL,
+  dnl [
+  dnl   AC_DEFINE(HAVE_WASM_MEMORY_STORAGE_FEATURE, 1, [ ])
+  dnl ],[
+  dnl   AC_MSG_ERROR([FEATURE not supported by your wasm_memory_storage library.])
+  dnl ], [
+  dnl   $LIBFOO_LIBS
+  dnl ])
+
+  dnl If you need to check for a particular library function (e.g. a conditional
+  dnl or version-dependent feature) and you are not using pkg-config:
+  dnl PHP_CHECK_LIBRARY($LIBNAME, $LIBSYMBOL,
+  dnl [
+  dnl   PHP_ADD_LIBRARY_WITH_PATH($LIBNAME, $WASM_MEMORY_STORAGE_DIR/$PHP_LIBDIR, WASM_MEMORY_STORAGE_SHARED_LIBADD)
+  dnl   AC_DEFINE(HAVE_WASM_MEMORY_STORAGE_FEATURE, 1, [ ])
+  dnl ],[
+  dnl   AC_MSG_ERROR([FEATURE not supported by your wasm_memory_storage library.])
+  dnl ],[
+  dnl   -L$WASM_MEMORY_STORAGE_DIR/$PHP_LIBDIR -lm
+  dnl ])
+  dnl
+  dnl PHP_SUBST(WASM_MEMORY_STORAGE_SHARED_LIBADD)
+
+  dnl In case of no dependencies
+  AC_DEFINE(HAVE_WASM_MEMORY_STORAGE, 1, [ Have wasm_memory_storage support ])
+
+  PHP_NEW_EXTENSION(wasm_memory_storage, wasm_memory_storage.c, $ext_shared)
+fi

packages/php-wasm/compile/php-wasm-memory-storage/config.w32

@@ -0,0 +1,7 @@
+ARG_ENABLE('wasm_memory_storage', 'wasm_memory_storage support', 'no');
+
+if (PHP_WASM_MEMORY_STORAGE != 'no') {
+	AC_DEFINE('HAVE_WASM_MEMORY_STORAGE', 1, 'wasm_memory_storage support enabled');
+
+	EXTENSION('wasm_memory_storage', 'wasm_memory_storage.c', null, '/DZEND_ENABLE_STATIC_TSRMLS_CACHE=1');
+}

packages/php-wasm/compile/php-wasm-memory-storage/php_wasm_memory_storage.h

@@ -0,0 +1,11 @@
+/* wasm_memory_storage extension for PHP */
+
+#ifndef PHP_WASM_MEMORY_STORAGE_H
+# define PHP_WASM_MEMORY_STORAGE_H
+
+extern zend_module_entry wasm_memory_storage_module_entry;
+# define phpext_wasm_memory_storage_ptr &wasm_memory_storage_module_entry
+
+# define PHP_WASM_MEMORY_STORAGE_VERSION "0.0.1"
+
+#endif	/* PHP_WASM_MEMORY_STORAGE_H */

packages/php-wasm/compile/php-wasm-memory-storage/wasm_memory_storage.c

@@ -0,0 +1,137 @@
+/**
+ * wasm_memory_storage extension for PHP.
+ *
+ * The purpose of this extension is to work around a memory leak caused by
+ * failing attempts to partially unmap memory allocated with mmap().
+ * By providing custom memory storage, we can avoid mmap()/munmap() calls and
+ * use posix_memalign()/free() instead.
+ *
+ * Background:
+ * Issue: https://github.com/WordPress/wordpress-playground/issues/1128
+ * PR: https://github.com/WordPress/wordpress-playground/pull/1189
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include "php.h"
+#include "ext/standard/info.h"
+#include "Zend/zend_alloc.h"
+#include "php_wasm_memory_storage.h"
+
+/**
+ * Allocate a chunk of memory.
+ *
+ * This function implements the PHP Zend custom memory storage operation "chunk_free()".
+ *
+ * Here is an example offered in the PHP source code:
+ * https://github.com/php/php-src/blob/dbaeb62ab1e34067057170ab50cf39d1bde584d8/Zend/zend_alloc.h#L325
+ *
+ * @param storage   The zend_mm_storage struct for this allocation.
+ * @param size      The number of bytes to allocate.
+ * @param alignment The byte alignment of the memory allocation.
+ * @returns A pointer to allocated memory or NULL on failure.
+ */
+void* wasm_memory_storage_chunk_alloc(zend_mm_storage* storage, size_t size, size_t alignment)
+{
+	void* ptr = NULL;
+	if (posix_memalign(&ptr, alignment, size) == 0)
+	{
+		memset(ptr, 0, size);
+		return ptr;
+	} else {
+		return NULL;
+	}
+}
+
+/**
+ * Free a chunk of memory.
+ *
+ * This function implements the PHP Zend custom memory storage operation "chunk_free()".
+ *
+ * Here is an example offered in the PHP source code:
+ * https://github.com/php/php-src/blob/dbaeb62ab1e34067057170ab50cf39d1bde584d8/Zend/zend_alloc.h#L352
+ *
+ * @param storage The zend_mm_storage struct for this memory.
+ * @param ptr	  The pointer to the memory to free.
+ * @param size    The size of the memory to free. Ignored.
+ * @returns void
+ */
+void wasm_memory_storage_chunk_free(zend_mm_storage* storage, void* ptr, size_t size)
+{
+	free(ptr);
+}
+
+zend_mm_storage wasm_memory_storage_struct = {
+	.handlers = {
+		.chunk_alloc = &wasm_memory_storage_chunk_alloc,
+		.chunk_free = &wasm_memory_storage_chunk_free,
+		.chunk_truncate = NULL,
+		.chunk_extend = NULL,
+	},
+	.data = NULL,
+};
+
+// These definitions are mirrored from zend_alloc.c:
+// https://github.com/php/php-src/blob/dbaeb62ab1e34067057170ab50cf39d1bde584d8/Zend/zend_alloc.c#L131-L137
+#ifndef ZEND_MM_CUSTOM
+# define ZEND_MM_CUSTOM 1  /* support for custom memory allocator            */
+#endif
+#ifndef ZEND_MM_STORAGE
+# define ZEND_MM_STORAGE 1 /* support for custom memory storage              */
+#endif
+
+// This struct mirrors the heap structure, which is declared privately
+// in zend_alloc.c. We use this to more easily and clearly assign our custom memory storage handler.
+// https://github.com/php/php-src/blob/dbaeb62ab1e34067057170ab50cf39d1bde584d8/Zend/zend_alloc.c#L234-L240
+typedef struct _wasm_memory_storage_heap {
+#if ZEND_MM_CUSTOM
+	int custom;
+#endif
+#if ZEND_MM_STORAGE
+	zend_mm_storage   *storage;
+#endif
+} wasm_memory_storage_heap;
+
+PHP_MINIT_FUNCTION(wasm_memory_storage)
+{
+	wasm_memory_storage_heap* heap = (wasm_memory_storage_heap*) zend_mm_get_heap();
+	heap->storage = &wasm_memory_storage_struct;
+
+	return SUCCESS;
+}
+
+PHP_MSHUTDOWN_FUNCTION(wasm_memory_storage)
+{
+	wasm_memory_storage_heap* heap = (wasm_memory_storage_heap*) zend_mm_get_heap();
+	heap->storage = NULL;
+
+	return SUCCESS;
+}
+
+/* {{{ PHP_MINFO_FUNCTION */
+PHP_MINFO_FUNCTION(wasm_memory_storage)
+{
+	php_info_print_table_start();
+	php_info_print_table_row(2, "wasm_memory_storage support", "enabled");
+	php_info_print_table_end();
+}
+/* }}} */
+
+/* {{{ wasm_memory_storage_module_entry */
+zend_module_entry wasm_memory_storage_module_entry = {
+	STANDARD_MODULE_HEADER,
+	"wasm_memory_storage",              /* Extension name */
+	NULL,                               /* zend_function_entry */
+	PHP_MINIT(wasm_memory_storage),     /* PHP_MINIT - Module initialization */
+	PHP_MSHUTDOWN(wasm_memory_storage), /* PHP_MSHUTDOWN - Module shutdown */
+	NULL,                               /* PHP_RINIT - Request initialization */
+	NULL,                               /* PHP_RSHUTDOWN - Request shutdown */
+	PHP_MINFO(wasm_memory_storage),     /* PHP_MINFO - Module info */
+	PHP_WASM_MEMORY_STORAGE_VERSION,    /* Version */
+	STANDARD_MODULE_PROPERTIES
+};
+/* }}} */

packages/php-wasm/compile/php/Dockerfile

@@ -14,6 +14,9 @@ RUN git clone https://github.com/php/php-src.git php-src \
 	--single-branch          \
 	--depth 1;
 
+# Work around memory leak due to PHP using Emscripten's incomplete mmap/munmap support
+COPY ./php-wasm-memory-storage /root/php-src/ext/wasm_memory_storage
+
 RUN cd php-src && ./buildconf --force
 
 # Bring in the libraries
@@ -214,6 +217,10 @@ RUN if [ "$WITH_MBREGEX" = "yes" ] && [ "${PHP_VERSION:0:3}" != "7.0" ]; \
 COPY ./php/php*.patch /root/
 RUN cd /root && \
 	git apply --no-index /root/php${PHP_VERSION:0:3}*.patch -v && \
+	( [[ "${PHP_VERSION:0:3}" == '8.3' ]] && \
+		git apply --no-index /root/php-chunk-alloc-zend-assert-8.3.patch -v || \
+		git apply --no-index /root/php-chunk-alloc-zend-assert.patch -v \
+	) && \
 	touch php-src/patched
 
 # Add VRZNO if needed
@@ -270,6 +277,7 @@ RUN source /root/emsdk/emsdk_env.sh && \
 	--enable-bcmath    \
 	--enable-ctype     \
 	--enable-tokenizer \
+	--enable-wasm_memory_storage \
 	$(cat /root/.php-configure-flags)
 
 # Silence the errors "munmap() failed: [28] Invalid argument"

packages/php-wasm/compile/php/php-chunk-alloc-zend-assert-8.3.patch

@@ -0,0 +1,13 @@
+diff --git a/php-src/Zend/zend_alloc.c b/php-src/Zend/zend_alloc.c
+index bf2116fc91..bec65453d8 100644
+--- a/php-src/Zend/zend_alloc.c
++++ b/php-src/Zend/zend_alloc.c
+@@ -773,7 +773,7 @@ static void *zend_mm_chunk_alloc(zend_mm_heap *heap, size_t size, size_t alignme
+ #if ZEND_MM_STORAGE
+ 	if (UNEXPECTED(heap->storage)) {
+ 		void *ptr = heap->storage->handlers.chunk_alloc(heap->storage, size, alignment);
+-		ZEND_ASSERT(((uintptr_t)((char*)ptr + (alignment-1)) & (alignment-1)) == (uintptr_t)ptr);
++		ZEND_ASSERT(((uintptr_t)((char*)ptr + (alignment-1)) & ~(alignment-1)) == (uintptr_t)ptr);
+ 		return ptr;
+ 	}
+ #endif

packages/php-wasm/compile/php/php-chunk-alloc-zend-assert.patch

@@ -0,0 +1,13 @@
+diff --git a/php-src/Zend/zend_alloc.c b/php-src/Zend/zend_alloc.c
+index bf2116fc91..bec65453d8 100644
+--- a/php-src/Zend/zend_alloc.c
++++ b/php-src/Zend/zend_alloc.c
+@@ -773,7 +773,7 @@ static void *zend_mm_chunk_alloc(zend_mm_heap *heap, size_t size, size_t alignme
+ #if ZEND_MM_STORAGE
+ 	if (UNEXPECTED(heap->storage)) {
+ 		void *ptr = heap->storage->handlers.chunk_alloc(heap->storage, size, alignment);
+-		ZEND_ASSERT(((zend_uintptr_t)((char*)ptr + (alignment-1)) & (alignment-1)) == (zend_uintptr_t)ptr);
++		ZEND_ASSERT(((zend_uintptr_t)((char*)ptr + (alignment-1)) & ~(alignment-1)) == (zend_uintptr_t)ptr);
+ 		return ptr;
+ 	}
+ #endif

packages/php-wasm/node/public/php_7_0.js

@@ -1,6 +1,6 @@
 const dependencyFilename = __dirname + '/7_0_33/php_7_0.wasm'; 
 export { dependencyFilename }; 
-export const dependenciesTotalSize = 12778149; 
+export const dependenciesTotalSize = 12778840; 
 export function init(RuntimeName, PHPLoader) {
     /**
      * Overrides Emscripten's default ExitStatus object which gets

packages/php-wasm/node/public/php_7_1.js

@@ -1,6 +1,6 @@
 const dependencyFilename = __dirname + '/7_1_30/php_7_1.wasm'; 
 export { dependencyFilename }; 
-export const dependenciesTotalSize = 13300133; 
+export const dependenciesTotalSize = 13301175; 
 export function init(RuntimeName, PHPLoader) {
     /**
      * Overrides Emscripten's default ExitStatus object which gets

packages/php-wasm/node/public/php_7_2.js

@@ -1,6 +1,6 @@
 const dependencyFilename = __dirname + '/7_2_34/php_7_2.wasm'; 
 export { dependencyFilename }; 
-export const dependenciesTotalSize = 13991154; 
+export const dependenciesTotalSize = 13992133; 
 export function init(RuntimeName, PHPLoader) {
     /**
      * Overrides Emscripten's default ExitStatus object which gets

packages/php-wasm/node/public/php_7_3.js

@@ -1,6 +1,6 @@
 const dependencyFilename = __dirname + '/7_3_33/php_7_3.wasm'; 
 export { dependencyFilename }; 
-export const dependenciesTotalSize = 14097593; 
+export const dependenciesTotalSize = 14098611; 
 export function init(RuntimeName, PHPLoader) {
     /**
      * Overrides Emscripten's default ExitStatus object which gets

packages/php-wasm/node/public/php_7_4.js

@@ -1,6 +1,6 @@
 const dependencyFilename = __dirname + '/7_4_33/php_7_4.wasm'; 
 export { dependencyFilename }; 
-export const dependenciesTotalSize = 14330034; 
+export const dependenciesTotalSize = 14331012; 
 export function init(RuntimeName, PHPLoader) {
     /**
      * Overrides Emscripten's default ExitStatus object which gets

packages/php-wasm/node/public/php_8_0.js

@@ -1,6 +1,6 @@
 const dependencyFilename = __dirname + '/8_0_30/php_8_0.wasm'; 
 export { dependencyFilename }; 
-export const dependenciesTotalSize = 13597144; 
+export const dependenciesTotalSize = 13597816; 
 export function init(RuntimeName, PHPLoader) {
     /**
      * Overrides Emscripten's default ExitStatus object which gets