Protect memory layout (#113)

* libfaasm: add dummy function to preserve memory layout

* gh: bump code version to have a new libfaasm installed in the sysroot

* libfaasm: make include more reliable by being included in core.h

* mpi: debug funcs

* faasmtools: remove unnecessary initial memory, wasm-ld should pick up the optimal value

* mpi: revert debugging changes in mpi functions

* faasmtools: export malloc and free symbols for wamr's memory management

* nit: remove unnecessary whitespace

* libfaasm: remove __wasm__ conditional inclusion

* libfaasm: reintroduce __wasm__

* wasi-libc: disable memory growth using mmap

Author: csegarragonz

.env

@@ -1,3 +1,3 @@
-SYSROOT_VERSION=0.2.4
-SYSROOT_CLI_IMAGE=faasm.azurecr.io/cpp-sysroot:0.2.4
+SYSROOT_VERSION=0.2.5
+SYSROOT_CLI_IMAGE=faasm.azurecr.io/cpp-sysroot:0.2.5
 COMPOSE_PROJECT_NAME=cpp-dev

.github/workflows/tests.yml

@@ -19,7 +19,7 @@ jobs:
     if: github.event.pull_request.draft == false
     runs-on: ubuntu-latest
     container:
-      image: faasm.azurecr.io/cpp-sysroot:0.2.4
+      image: faasm.azurecr.io/cpp-sysroot:0.2.5
       credentials:
         username: ${{ secrets.ACR_SERVICE_PRINCIPAL_ID }}
         password: ${{ secrets.ACR_SERVICE_PRINCIPAL_PASSWORD }}

VERSION

@@ -1 +1 @@
-0.2.4
+0.2.5

faasmtools/build.py

@@ -137,12 +137,13 @@
     "-Xlinker --stack-first",
     "-Xlinker --export=__heap_base",
     "-Xlinker --export=__data_end",
+    "-Xlinker --export=free",
+    "-Xlinker --export=malloc",
     "-Xlinker --export={}".format(FAASM_WASM_CTORS_FUNC_NAME),
     "-Xlinker --export=__stack_pointer",
     "-Xlinker --max-memory={}".format(FAASM_WASM_MAX_MEMORY),
     "-Xlinker --features=mutable-globals,simd128",
     "-Wl,-z,stack-size={} -Wl".format(FAASM_WASM_STACK_SIZE),
-    "-Wl,--initial-memory={}".format(FAASM_WASM_INITIAL_MEMORY_SIZE),
 ]
 
 WASM_EXE_LDFLAGS += WASM_WASI_LIBC_LDFLAGS

libfaasm/CMakeLists.txt

@@ -13,6 +13,7 @@ set(PUBLIC_HEADERS
         faasm/faasm.h
         faasm/files.h
         faasm/input.h
+        faasm/memory.h
         faasm/migrate.h
         faasm/print.h
         faasm/random.h

libfaasm/faasm/core.h

@@ -5,6 +5,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include "faasm/memory.h"
+
 #ifdef __cplusplus
 extern "C"
 {

libfaasm/faasm/memory.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#ifdef __wasm__
+// WAMR performs some optimisations on the WASM modules at load time, whereby
+// if no memory.grow op-code is found, memory is shrunk to the minimum
+// (as specified by the default heap and stack size). This optimisation breaks
+// Faasm's memory management, as we may sometimes want to enlarge the WASM's
+// memory from outside WASM code. To prevent this optimisation, every time we
+// build a WASM function for its usage in faasm (and include the faasm/faasm.h
+// header) we link with this dummy function that uses the memory.grow op-code.
+// Note that this function is actually not called. See:
+// https://github.com/bytecodealliance/wasm-micro-runtime/issues/1706
+inline void __attribute__((used)) __faasm_memory_layout_protection()
+{
+    __builtin_wasm_memory_grow(0, 0);
+}
+#endif