Make halfword emulator with valgrind target allocate low memory

Limit ERTS_MSEG_FAKE_SEGMENTS (that is otherwise set for valgrind
target) to not apply to low memory needed by halfword emulator. This
will reduce the fault detection capability of valgrind for low memory.

Also correct a bug in the initial mmap and make sure the returned
memory region does not reach into high memory.

1 files changed, 43 insertions, 23 deletions

diff --git a/erts/emulator/sys/common/erl_mseg.c b/erts/emulator/sys/common/erl_mseg.c
index 8421eb415c..ceb290b644 100644
--- a/erts/emulator/sys/common/erl_mseg.c
+++ b/erts/emulator/sys/common/erl_mseg.c
@@ -125,6 +125,9 @@ static int mmap_fd;
 #error "Not supported"
 #endif /* #if HAVE_MMAP */
 
+#if defined(ERTS_MSEG_FAKE_SEGMENTS) && HALFWORD_HEAP
+#  warning "ERTS_MSEG_FAKE_SEGMENTS will only be used for high memory segments" 
+#endif 
 
 #if defined(ERTS_MSEG_FAKE_SEGMENTS)
 #undef CAN_PARTLY_DESTROY
@@ -334,9 +337,6 @@ mseg_create(MemKind* mk, Uint size)
 
     ASSERT(size % page_size == 0);
 
-#if defined(ERTS_MSEG_FAKE_SEGMENTS)
-    seg = erts_sys_alloc(ERTS_ALC_N_INVALID, NULL, size);
-#elif HAVE_MMAP
 #if HALFWORD_HEAP
     if (mk == &low_mem) {
 	seg = pmmap(size);
@@ -348,14 +348,19 @@ mseg_create(MemKind* mk, Uint size)
     else
 #endif
     {
-	seg = (void *) mmap((void *) 0, (size_t) size,
-			    MMAP_PROT, MMAP_FLAGS, MMAP_FD, 0);
-	if (seg == (void *) MAP_FAILED)
-	    seg = NULL;
-    }
+#if defined(ERTS_MSEG_FAKE_SEGMENTS)
+	seg = erts_sys_alloc(ERTS_ALC_N_INVALID, NULL, size);
+#elif HAVE_MMAP
+	{
+	    seg = (void *) mmap((void *) 0, (size_t) size,
+				MMAP_PROT, MMAP_FLAGS, MMAP_FD, 0);
+	    if (seg == (void *) MAP_FAILED)
+		seg = NULL;
+	}
 #else
-#error "Missing mseg_create() implementation"
+# error "Missing mseg_create() implementation"
 #endif
+    }
 
     INC_CC(create);
 
@@ -365,9 +370,6 @@ mseg_create(MemKind* mk, Uint size)
 static ERTS_INLINE void
 mseg_destroy(MemKind* mk, void *seg, Uint size)
 {
-#if defined(ERTS_MSEG_FAKE_SEGMENTS)
-    erts_sys_free(ERTS_ALC_N_INVALID, NULL, seg);
-#elif HAVE_MMAP
     int res;
 
 #if HALFWORD_HEAP
@@ -377,14 +379,18 @@ mseg_destroy(MemKind* mk, void *seg, Uint size)
     else
 #endif
     {
+#ifdef ERTS_MSEG_FAKE_SEGMENTS
+	erts_sys_free(ERTS_ALC_N_INVALID, NULL, seg);
+	res = 0;
+#elif HAVE_MMAP
 	res = munmap((void *) seg, size);
+#else
+# error "Missing mseg_destroy() implementation"
+#endif
     }
 
     ASSERT(size % page_size == 0);
     ASSERT(res == 0);
-#else
-#error "Missing mseg_destroy() implementation"
-#endif
 
     INC_CC(destroy);
 
@@ -400,9 +406,6 @@ mseg_recreate(MemKind* mk, void *old_seg, Uint old_size, Uint new_size)
     ASSERT(old_size % page_size == 0);
     ASSERT(new_size % page_size == 0);
 
-#if defined(ERTS_MSEG_FAKE_SEGMENTS)
-    new_seg = erts_sys_realloc(ERTS_ALC_N_INVALID, NULL, old_seg, new_size);
-#elif HAVE_MREMAP
 #if HALFWORD_HEAP
     if (mk == &low_mem) {
 	new_seg = (void *) pmremap((void *) old_seg,
@@ -412,6 +415,10 @@ mseg_recreate(MemKind* mk, void *old_seg, Uint old_size, Uint new_size)
     else
 #endif
     {
+#if defined(ERTS_MSEG_FAKE_SEGMENTS)
+	new_seg = erts_sys_realloc(ERTS_ALC_N_INVALID, NULL, old_seg, new_size);
+#elif HAVE_MREMAP
+
     #if defined(__NetBSD__)
 	new_seg = (void *) mremap((void *) old_seg,
 				  (size_t) old_size,
@@ -426,10 +433,10 @@ mseg_recreate(MemKind* mk, void *old_seg, Uint old_size, Uint new_size)
     #endif
 	if (new_seg == (void *) MAP_FAILED)
 	    new_seg = NULL;
-    }
 #else
 #error "Missing mseg_recreate() implementation"
 #endif
+    }
 
     INC_CC(recreate);
 
@@ -726,6 +733,7 @@ mseg_alloc(ErtsAlcType_t atype, Uint *size_p, const ErtsMsegOpt_t *opt)
 
     if (seg)
 	ERTS_MSEG_ALLOC_STAT(mk,size);
+
     return seg;
 }
 
@@ -1685,11 +1693,14 @@ static void *do_map(void *ptr, size_t sz)
 	return NULL;
     }
 
-
+#if HAVE_MMAP
     res = mmap(ptr, sz,
 	       PROT_READ | PROT_WRITE, MAP_PRIVATE |
 	       MAP_ANONYMOUS | MAP_FIXED,
 	       -1 , 0);
+#else
+#  error "Missing mmap support"
+#endif
 
     if (res == MAP_FAILED) {
 #ifdef HARDDEBUG
@@ -1789,10 +1800,19 @@ static int initialize_pmmap(void)
 		MAP_NORESERVE | EXTRA_MAP_FLAGS,
 		-1 , 0);
 #ifdef HARDDEBUG
-    printf("rsz = %ld, pages = %ld, rptr = %p\r\n",
-	   (unsigned long) rsz, (unsigned long) (rsz / pagsz),
-	   (void *) rptr);
+    printf("p=%p, rsz = %ld, pages = %ld, got range = %p -> %p\r\n",
+	   p, (unsigned long) rsz, (unsigned long) (rsz / pagsz),
+	   (void *) rptr, (void*)(rptr + rsz));
 #endif
+    if ((UWord)(rptr + rsz) > RANGE_MAX) {
+	size_t rsz_trunc = RANGE_MAX - (UWord)rptr;
+#ifdef HARDDEBUG
+	printf("Reducing mmap'ed memory from %lu to %lu Mb, reduced range = %p -> %p\r\n",
+		rsz/(1024*1024), rsz_trunc/(1024*1024), rptr, rptr+rsz_trunc);
+#endif
+	munmap((void*)RANGE_MAX, rsz - rsz_trunc);
+	rsz = rsz_trunc;
+    }
     if (!do_map(rptr,pagsz)) {
 	erl_exit(1,"Could not actually mmap first page for halfword emulator...\n");
     }