ensure accessible memory around mmapped files

This commit is contained in:
dzaima 2025-06-15 03:41:58 +03:00
parent 200d4f6900
commit 307be40ac7
4 changed files with 30 additions and 14 deletions

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@ -1,9 +1,7 @@
#define MM_C 1
#define ALLOC_PADDING 1024 // number of accessible padding bytes always required around an object
#include "../core.h"
#include "../utils/mem.h"
ux getPageSize(void);
static u64 prepAllocSize(u64 sz) {
u64 psz = getPageSize();
u64 minTotPad = ALLOC_PADDING*2 + 128;

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@ -1,5 +1,6 @@
#include "../core.h"
#include "file.h"
#include "mem.h"
#include "talloc.h"
#include "cstr.h"
#include <dirent.h>
@ -44,7 +45,7 @@ void fileRef_freeO(Value* v) {
fclose(((FileRef*)v)->file);
}
NOINLINE FILE* fileRef_open(FILE* f) {
FileRef* fr = m_customObj(sizeof(FileRef), noop_visit, fileRef_freeO);
FileRef* fr = m_customObj(sizeof(FileRef), noop_visit, fileRef_freeO); // TODO uhh this could OOM
fr->file = f;
gsAdd(tag(fr, OBJ_TAG));
return f;
@ -315,7 +316,8 @@ typedef struct MmapHolder {
struct Arr;
#if !defined(_WIN32)
int fd;
u64 size;
void* mmap_start;
u64 mmap_size;
#else
HANDLE hFile;
HANDLE hMapFile;
@ -327,7 +329,7 @@ void mmapH_visit(Value* v) { }
DEF_FREE(mmapH) {
MmapHolder* p = (MmapHolder*)x;
#if !defined(_WIN32)
if (munmap(p->a, p->size)) thrF("Failed to unmap: %S", strerror(errno));
if (munmap(p->mmap_start, p->mmap_size)) thrF("Failed to unmap: %S", strerror(errno));
if (close(p->fd)) thrF("Failed to close file: %S", strerror(errno));
#else
if (!UnmapViewOfFile(p->a)) thrF("Failed to unmap: %S", winError());
@ -342,6 +344,7 @@ static NOINLINE Arr* mmapH_slice(B x, usz s, usz ia) {
}
B mmap_file(B path) {
// TODO count mapped memory in some memory usage counter
#if !defined(_WIN32)
char* p = toCStr(path);
dec(path);
@ -350,8 +353,18 @@ B mmap_file(B path) {
if (fd==-1) thrF("Failed to open file: %S", strerror(errno));
u64 len = lseek(fd, 0, SEEK_END);
u8* data = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0); // TODO count in some memory usage counter
if (data==MAP_FAILED) {
u64 pgsz = getPageSize();
u64 head = pgsz;
PLAINLOOP while (head < ALLOC_PADDING) head+= pgsz;
u64 mmap_size = len+head*2;
u8* mmap_start = mmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (mmap_start==MAP_FAILED) {
close(fd);
thrM("failed to pre-allocate mmap region");
}
u8* arr_data = mmap(mmap_start+head, len, PROT_READ, MAP_PRIVATE|MAP_FIXED, fd, 0);
if (arr_data==MAP_FAILED) {
munmap(mmap_start, mmap_size);
close(fd);
thrM("failed to mmap file");
}
@ -376,19 +389,21 @@ B mmap_file(B path) {
CloseHandle(hFile);
thrF("Failed to create file mapping: %S", winError());
}
u8* data = MapViewOfFile(hMapFile, FILE_MAP_READ, 0, 0, 0);
if (data==NULL) {
u8* arr_data = MapViewOfFile(hMapFile, FILE_MAP_READ, 0, 0, 0);
// TODO should ensure ALLOC_PADDING padding around allocated memory
if (arr_data==NULL) {
CloseHandle(hFile);
CloseHandle(hMapFile);
thrF("Failed to map view of file: %S", winError());
}
#endif
MmapHolder* holder = m_arrUnchecked(sizeof(MmapHolder), t_mmapH, len);
holder->a = data;
MmapHolder* holder = m_arrUnchecked(sizeof(MmapHolder), t_mmapH, len); // TODO this can OOM
holder->a = arr_data;
#if !defined(_WIN32)
holder->fd = fd;
holder->size = len;
holder->mmap_start = mmap_start;
holder->mmap_size = mmap_size;
#else
holder->hFile = hFile;
holder->hMapFile = hMapFile;

3
src/utils/mem.h Normal file
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@ -0,0 +1,3 @@
#pragma once
ux getPageSize(void);
#define ALLOC_PADDING 1024 // number of accessible padding bytes always required around an object

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@ -1,4 +1,5 @@
#pragma once
#include "utils/mem.h"
#if !NO_MMAP
#include <sys/mman.h>
#endif
@ -248,7 +249,6 @@ NOINLINE B vm_fmtPoint(B src, B prepend, B path, usz cs, usz ce); // consumes pr
NOINLINE void printErrMsg(B msg);
NOINLINE void unwindEnv(Env* envNew); // envNew==envStart-1 for emptying the env stack
NOINLINE void unwindCompiler(void); // unwind to the env of the invocation of the compiler; UB when not in compiler!
ux getPageSize(void);