From c185c751bdfe6ac315be834b810336f7a5bed756 Mon Sep 17 00:00:00 2001
From: Sean McBride <spmcbride1201@gmail.com>
Date: Thu, 23 Sep 2021 16:26:12 -0400
Subject: [PATCH] feat: -1 on wasm memory.grow instruction failure

---
 runtime/include/runtime.h      |  2 +-
 runtime/src/memory/64bit_nix.c | 73 +++++++++++++++++++++++++++++++---
 2 files changed, 68 insertions(+), 7 deletions(-)

diff --git a/runtime/include/runtime.h b/runtime/include/runtime.h
index 0a07045..bbb8a0d 100644
--- a/runtime/include/runtime.h
+++ b/runtime/include/runtime.h
@@ -40,7 +40,7 @@ extern void runtime_set_resource_limits_to_max(void);
 
 /* External Symbols */
 extern void  alloc_linear_memory(void);
-extern void  expand_memory(void);
+extern int   expand_memory(void);
 INLINE char *get_function_from_table(uint32_t idx, uint32_t type_id);
 INLINE char *get_memory_ptr_for_runtime(uint32_t offset, uint32_t bounds_check);
 extern void  stub_init(int32_t offset);
diff --git a/runtime/src/memory/64bit_nix.c b/runtime/src/memory/64bit_nix.c
index ef1e5ef..b98ffdc 100644
--- a/runtime/src/memory/64bit_nix.c
+++ b/runtime/src/memory/64bit_nix.c
@@ -6,24 +6,36 @@
 
 #include <sys/mman.h>
 
-void
+/**
+ * @brief Expand the linear memory of the active WebAssembly sandbox by a single page
+ *
+ * @return int
+ */
+int
 expand_memory(void)
 {
 	struct sandbox *sandbox = current_sandbox_get();
 
 	assert(sandbox->state == SANDBOX_RUNNING);
+	assert(local_sandbox_context_cache.memory.size % WASM_PAGE_SIZE == 0);
 
-	// TODO: Refactor to return RC signifying out-of-mem to caller. Issue #96.
-	if (local_sandbox_context_cache.memory.size + WASM_PAGE_SIZE >= local_sandbox_context_cache.memory.max)
-		panic("expand_memory - Out of Memory!. %u out of %lu\n", local_sandbox_context_cache.memory.size,
-		      local_sandbox_context_cache.memory.max);
+	/* Return -1 if we've hit the linear memory max */
+	if (unlikely(local_sandbox_context_cache.memory.size + WASM_PAGE_SIZE
+	             >= local_sandbox_context_cache.memory.max)) {
+		debuglog("expand_memory - Out of Memory!. %u out of %lu\n", local_sandbox_context_cache.memory.size,
+		         local_sandbox_context_cache.memory.max);
+		return -1;
+	}
 
 	// Remap the relevant wasm page to readable
 	char *mem_as_chars = local_sandbox_context_cache.memory.start;
 	char *page_address = &mem_as_chars[local_sandbox_context_cache.memory.size];
 	void *map_result   = mmap(page_address, WASM_PAGE_SIZE, PROT_READ | PROT_WRITE,
                                 MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
-	if (map_result == MAP_FAILED) panic("Mapping of new memory failed");
+	if (map_result == MAP_FAILED) {
+		debuglog("Mapping of new memory failed");
+		return -1;
+	}
 
 	local_sandbox_context_cache.memory.size += WASM_PAGE_SIZE;
 
@@ -38,6 +50,7 @@ expand_memory(void)
 
 	// local_sandbox_context_cache is "forked state", so update authoritative member
 	sandbox->memory.size = local_sandbox_context_cache.memory.size;
+	return 0;
 }
 
 INLINE char *
@@ -54,3 +67,51 @@ get_memory_ptr_for_runtime(uint32_t offset, uint32_t bounds_check)
 
 	return address;
 }
+
+/**
+ * @brief Stub that implements the WebAssembly memory.grow instruction
+ *
+ * @param count number of pages to grow the WebAssembly linear memory by
+ * @return The previous size of the linear memory in pages or -1 if enough memory cannot be allocated
+ */
+int32_t
+instruction_memory_grow(uint32_t count)
+{
+	int rc = local_sandbox_context_cache.memory.size / WASM_PAGE_SIZE;
+
+	for (int i = 0; i < count; i++) {
+		if (unlikely(expand_memory() != 0)) {
+			rc = -1;
+			break;
+		}
+	}
+
+	return rc;
+}
+
+/*
+ * Table handling functionality
+ * This was moved from compiletime in order to place the
+ * function in the callstack in GDB. It can be moved back
+ * to runtime/compiletime/memory/64bit_nix.c to remove the
+ * additional function call
+ */
+char *
+get_function_from_table(uint32_t idx, uint32_t type_id)
+{
+#ifdef LOG_FUNCTION_TABLE
+	fprintf(stderr, "get_function_from_table(idx: %u, type_id: %u)\n", idx, type_id);
+	fprintf(stderr, "indirect_table_size: %u\n", INDIRECT_TABLE_SIZE);
+#endif
+	assert(idx < INDIRECT_TABLE_SIZE);
+
+	struct indirect_table_entry f = local_sandbox_context_cache.module_indirect_table[idx];
+#ifdef LOG_FUNCTION_TABLE
+	fprintf(stderr, "assumed type: %u, type in table: %u\n", type_id, f.type_id);
+#endif
+	assert(f.type_id == type_id);
+
+	assert(f.func_pointer != NULL);
+
+	return f.func_pointer;
+}