Open fastfading opened 4 months ago
memfd_create
is a Linux-specific system call used to create an anonymous file that resides in memory. Since it is specific to Linux, there is no direct equivalent in macOS. However, similar functionality can be achieved using other methods, such as mmap
or shm_open
. Here are some alternatives on macOS:
mmap
mmap
can create an anonymous mapping in memory, which can be used to create a temporary in-memory file.
package main
import (
"fmt"
"os"
"syscall"
)
func createMemfd(size int) ([]byte, error) {
// Create an anonymous memory mapping
data, err := syscall.Mmap(-1, 0, size, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANON|syscall.MAP_PRIVATE)
if err != nil {
return nil, err
}
return data, nil
}
func main() {
size := 4096 // 4KB
data, err := createMemfd(size)
if err != nil {
fmt.Println("Error:", err)
os.Exit(1)
}
defer syscall.Munmap(data)
// Use the memory
copy(data, "Hello, mmap!")
fmt.Println("Memory content:", string(data[:11]))
}
shm_open
shm_open
and shm_unlink
can be used to create and delete file descriptors on shared memory objects.
package main
import (
"fmt"
"os"
"syscall"
"unsafe"
)
func createShm(size int) ([]byte, error) {
shmName := "/myshm"
// Create shared memory object
fd, err := syscall.ShmOpen(shmName, syscall.O_CREAT|syscall.O_RDWR, 0600)
if err != nil {
return nil, err
}
// Resize the memory object
if err := syscall.Ftruncate(fd, int64(size)); err != nil {
syscall.Close(fd)
syscall.ShmUnlink(shmName)
return nil, err
}
// Create a memory mapping
data, err := syscall.Mmap(fd, 0, size, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
if err != nil {
syscall.Close(fd)
syscall.ShmUnlink(shmName)
return nil, err
}
return data, nil
}
func main() {
size := 4096 // 4KB
data, err := createShm(size)
if err != nil {
fmt.Println("Error:", err)
os.Exit(1)
}
defer syscall.Munmap(data)
// Use the memory
copy(data, "Hello, shm_open!")
fmt.Println("Memory content:", string(data[:15]))
}
Although macOS does not support memfd_create
, you can use mmap
or shm_open
to create anonymous memory files or shared memory objects to achieve similar functionality. The example code above demonstrates how to use these two methods on macOS.
@fastfading thank you for the proposal and for the detailed code examples!
For example, if the caller embedded /bin/cat
in the binary, cat
could not be executed directly from the mmap'ed memory. To exec cat
, would involve reimplementing the linker and exec() for each supported platform.
A fallback option for platforms without memfd support might be:
memfd_create
是 Linux 特有的系统调用,用于创建一个匿名文件,该文件驻留在内存中。由于它是 Linux 特有的,在 macOS 上没有直接等效的功能。不过,可以使用其他方法来实现类似的功能,例如使用mmap
或shm_open
。以下是一些在 macOS 上的替代方案:使用
mmap
mmap
可以在内存中创建一个匿名映射,可以用于创建临时的内存文件。使用
shm_open
shm_open
和shm_unlink
可以用于在共享内存对象上创建和删除文件描述符。总结
虽然 macOS 不支持
memfd_create
,但可以使用mmap
或shm_open
来创建匿名内存文件或共享内存对象,以实现类似的功能。上述示例代码展示了如何在 macOS 上使用这两种方法。