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wasm2c: cache os page size queries #2912

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Merged
shravanrn merged 1 commit into from
Nov 2, 2026
Merged

wasm2c: cache os page size queries #2912

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19 changes: 18 additions & 1 deletion wasm2c/wasm-rt-impl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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;
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#ifndef WASM_RT_TRAP_HANDLER
WASM_RT_THREAD_LOCAL wasm_rt_jmp_buf g_wasm_rt_jmp_buf;
#endif
Expand All @@ -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) {
Expand All @@ -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) {
Expand Down Expand Up @@ -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) {
Expand Down
2 changes: 2 additions & 0 deletions wasm2c/wasm-rt-impl.h
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Expand Up @@ -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;
Expand Down
26 changes: 8 additions & 18 deletions wasm2c/wasm-rt-mem-impl.c
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Expand Up @@ -23,7 +23,6 @@
#include <windows.h>
#else
#include <sys/mman.h>
#include <unistd.h>
#endif

#ifdef WASM_RT_GROW_FAILED_HANDLER
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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) {
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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
Expand Down
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