Don't use WASI emulated mmap

It does not return aligned memory (WebAssembly/wasi-libc#207) and we don't need it for anything fancy. Instead, just use posix_memalign() and free() for the GC functions.
MLton · Feb 25, 2024 · 9eb4b36 · 9eb4b36
1 parent 62c1ffb
commit 9eb4b36
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Showing 4 changed files with 17 additions and 22 deletions.
diff --git a/bin/mlton-script b/bin/mlton-script
@@ -131,7 +131,6 @@ for arg in "$@"; do
                -target-cc-opt wasi '-D_WASI_EMULATED_SIGNAL'            \
                -target-cc-opt wasi '-D_WASI_EMULATED_PROCESS_CLOCKS'    \
                -target-cc-opt wasi '-D_WASI_EMULATED_GETPID'            \
-               -target-cc-opt wasi '-D_WASI_EMULATED_MMAN'              \
                -target-cc-opt x86 '-m32'                                \
                -target-link-opt aix '-maix64'                           \
                -target-link-opt alpha                                   \
@@ -150,7 +149,6 @@ for arg in "$@"; do
                -target-link-opt wasi '-lwasi-emulated-signal'           \
                -target-link-opt wasi '-lwasi-emulated-process-clocks'   \
                -target-link-opt wasi '-lwasi-emulated-getpid'           \
-               -target-link-opt wasi '-lwasi-emulated-mman'             \
                -target-link-opt x86 '-m32'                              \
                -profile-exclude '\$\(SML_LIB\)'
     fi

diff --git a/runtime/Makefile b/runtime/Makefile
@@ -121,12 +121,10 @@ ifeq ($(TARGET_OS), wasi)
 WASMTIME := wasmtime
 XCPPFLAGS += -D_WASI_EMULATED_SIGNAL \
              -D_WASI_EMULATED_PROCESS_CLOCKS \
-             -D_WASI_EMULATED_GETPID \
-             -D_WASI_EMULATED_MMAN
+             -D_WASI_EMULATED_GETPID
 XLDFLAGS += -lwasi-emulated-signal \
             -lwasi-emulated-process-clocks \
-            -lwasi-emulated-getpid \
-            -lwasi-emulated-mman
+            -lwasi-emulated-getpid
 endif
 
 ifeq ($(TARGET_OS), mingw)

diff --git a/runtime/platform/wasi.c b/runtime/platform/wasi.c
@@ -1,8 +1,5 @@
 #include "platform.h"
 
-#include "platform/mremap.c"
-#include "platform/use-mmap.c"
-
 /* WASI only implements a subset of POSIX, and given how it works it doesn't
  * make too much sense to try too hard to emulate missing functionality.
  *
@@ -18,13 +15,7 @@
  */
 
 size_t GC_pageSize (void) {
-        long int pageSize;
-
-        pageSize = sysconf (_SC_PAGESIZE);
-        if (pageSize < 0)
-                diee ("GC_pageSize error: sysconf (_SC_PAGESIZE) failed");
-
-        return (size_t)pageSize;
+        return PAGESIZE;
 }
 
 uintmax_t GC_physMem (void) {
@@ -34,12 +25,21 @@ uintmax_t GC_physMem (void) {
         return 1 << 30;  /* 1 GiB */
 }
 
-void* GC_extendHead (void *base, size_t length) {
-        return mmapAnon (base, length);
+void *GC_mmapAnon (__attribute__ ((unused)) void *start, size_t length) {
+        void *mem;
+        int err = posix_memalign (&mem, PAGESIZE, length);
+        if (err) {
+                return (void *) -1;
+        }
+        return memset(mem, 0, length);
+}
+
+void *GC_mmapAnonFlags (void *start, size_t length, __attribute__ ((unused)) int flags) {
+        return GC_mmapAnon(start, length);
 }
 
-void* GC_extendTail (void *base, size_t length) {
-        return mmapAnon (base, length);
+void GC_release (void *base, __attribute__ ((unused)) size_t length) {
+        free (base);
 }
 
 void GC_displayMem (void) {

diff --git a/runtime/platform/wasi.h b/runtime/platform/wasi.h
@@ -8,7 +8,6 @@
 #include <netinet/tcp.h>
 #include <poll.h>
 #include <sys/ioctl.h>
-#include <sys/mman.h>
 #include <sys/resource.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ -20,7 +19,7 @@
 
 #define HAS_FEROUND TRUE
 #define HAS_MSG_DONTWAIT TRUE
-#define HAS_REMAP TRUE
+#define HAS_REMAP FALSE
 #define HAS_SIGALTSTACK FALSE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE