From d16756bc64f70dae2ca12654b66e8557c828f6b7 Mon Sep 17 00:00:00 2001
From: shravanrn <shravanrn@gmail.com>
Date: Mon, 2 Nov 2026 14:29:02 -0600
Subject: [PATCH] wasm2c: cache os page size queries

---
 wasm2c/wasm-rt-impl.c     | 19 ++++++++++++++++++-
 wasm2c/wasm-rt-impl.h     |  2 ++
 wasm2c/wasm-rt-mem-impl.c | 26 ++++++++------------------
 3 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/wasm2c/wasm-rt-impl.c b/wasm2c/wasm-rt-impl.c
index 0cf0723a95..039bf5daa8 100644
--- a/wasm2c/wasm-rt-impl.c
+++ b/wasm2c/wasm-rt-impl.c
@@ -27,13 +27,13 @@
 
 #if WASM_RT_INSTALL_SIGNAL_HANDLER && !defined(_WIN32)
 #include <signal.h>
-#include <unistd.h>
 #endif
 
 #ifdef _WIN32
 #include <windows.h>
 #else
 #include <sys/mman.h>
+#include <unistd.h>
 #endif
 
 #ifndef NDEBUG
@@ -78,6 +78,8 @@ WASM_RT_THREAD_LOCAL uint32_t wasm_rt_saved_call_stack_depth;
 static WASM_RT_THREAD_LOCAL void* g_alt_stack = NULL;
 #endif
 
+size_t g_native_page_size = 0;
+
 #ifndef WASM_RT_TRAP_HANDLER
 WASM_RT_THREAD_LOCAL wasm_rt_jmp_buf g_wasm_rt_jmp_buf;
 #endif
@@ -102,6 +104,12 @@ void wasm_rt_trap(wasm_rt_trap_t code) {
 
 #ifdef _WIN32
 
+static size_t os_page_size(void) {
+  SYSTEM_INFO info;
+  GetSystemInfo(&info);
+  return info.dwPageSize;
+}
+
 #if WASM_RT_INSTALL_SIGNAL_HANDLER
 
 static LONG os_signal_handler(PEXCEPTION_POINTERS info) {
@@ -126,6 +134,14 @@ static void os_cleanup_signal_handler(void) {
 
 #else
 
+#define DEFAULT_OS_PAGE_SIZE 4096
+
+static size_t os_page_size(void) {
+  long size = sysconf(_SC_PAGESIZE);
+  // Fall back to a default size if sysconf returns bad data for any reason
+  return size > 0 ? (size_t)size : DEFAULT_OS_PAGE_SIZE;
+}
+
 #if WASM_RT_INSTALL_SIGNAL_HANDLER
 static void os_signal_handler(int sig, siginfo_t* si, void* unused) {
   if (si->si_code == SEGV_ACCERR) {
@@ -254,6 +270,7 @@ static void call_cpuid(uint64_t* rax,
 #endif
 
 void wasm_rt_init(void) {
+  g_native_page_size = os_page_size();
   wasm_rt_init_thread();
 #if WASM_RT_INSTALL_SIGNAL_HANDLER
   if (!g_signal_handler_installed) {
diff --git a/wasm2c/wasm-rt-impl.h b/wasm2c/wasm-rt-impl.h
index ed46b09721..50acdba07f 100644
--- a/wasm2c/wasm-rt-impl.h
+++ b/wasm2c/wasm-rt-impl.h
@@ -27,6 +27,8 @@
 extern "C" {
 #endif
 
+extern size_t g_native_page_size;
+
 #ifndef WASM_RT_TRAP_HANDLER
 /** A setjmp buffer used for handling traps. */
 extern WASM_RT_THREAD_LOCAL wasm_rt_jmp_buf g_wasm_rt_jmp_buf;
diff --git a/wasm2c/wasm-rt-mem-impl.c b/wasm2c/wasm-rt-mem-impl.c
index e27f79934c..c993bc1011 100644
--- a/wasm2c/wasm-rt-mem-impl.c
+++ b/wasm2c/wasm-rt-mem-impl.c
@@ -23,7 +23,6 @@
 #include <windows.h>
 #else
 #include <sys/mman.h>
-#include <unistd.h>
 #endif
 
 #ifdef WASM_RT_GROW_FAILED_HANDLER
@@ -63,12 +62,6 @@ static bool u64_mult_overflow(uint64_t a, uint64_t b, uint64_t* result) {
 #if WASM_RT_USE_MMAP
 
 #ifdef _WIN32
-static size_t os_page_size(void) {
-  SYSTEM_INFO info;
-  GetSystemInfo(&info);
-  return info.dwPageSize;
-}
-
 static void* os_mmap(size_t size) {
   void* ret = VirtualAlloc(NULL, size, MEM_RESERVE, PAGE_NOACCESS);
   return ret;
@@ -113,14 +106,6 @@ static void os_print_last_error(const char* msg) {
 
 #else /* !_WIN32 */
 
-#define DEFAULT_OS_PAGE_SIZE 4096
-
-static size_t os_page_size(void) {
-  long size = sysconf(_SC_PAGESIZE);
-  // Fall back to a default size if sysconf returns bad data for any reason
-  return size > 0 ? (size_t)size : DEFAULT_OS_PAGE_SIZE;
-}
-
 static void* os_mmap(size_t size) {
   int map_prot = PROT_NONE;
   int map_flags = MAP_ANONYMOUS | MAP_PRIVATE;
@@ -148,10 +133,15 @@ static void os_print_last_error(const char* msg) {
 #endif /* _WIN32 */
 
 static uint64_t round_up_to_os_page_size(uint64_t size) {
-  uint64_t page_size = os_page_size();
-  uint64_t remainder = size % page_size;
+  // page size should be initialized
+  assert(g_native_page_size);
+  // Keep an explicit check that isn't removed from the release builds
+  if (!g_native_page_size) {
+    return 0;
+  }
+  uint64_t remainder = size % g_native_page_size;
   if (remainder != 0) {
-    uint64_t increment = page_size - remainder;
+    uint64_t increment = g_native_page_size - remainder;
     uint64_t new_size = size + increment;
     if (new_size < size) {
       // overflow. Return 0 on error