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//go:build (darwin || linux || freebsd) && !tinygo
package platform
import (
"syscall"
"unsafe"
)
const (
mmapProtAMD64 = syscall.PROT_READ | syscall.PROT_WRITE | syscall.PROT_EXEC
mmapProtARM64 = syscall.PROT_READ | syscall.PROT_WRITE
)
func munmapCodeSegment(code []byte) error {
return syscall.Munmap(code)
}
// mmapCodeSegmentAMD64 gives all read-write-exec permission to the mmap region
// to enter the function. Otherwise, segmentation fault exception is raised.
func mmapCodeSegmentAMD64(size int) ([]byte, error) {
// The region must be RWX: RW for writing native codes, X for executing the region.
return mmapCodeSegment(size, mmapProtAMD64)
}
// mmapCodeSegmentARM64 cannot give all read-write-exec permission to the mmap region.
// Otherwise, the mmap systemcall would raise an error. Here we give read-write
// to the region so that we can write contents at call-sites. Callers are responsible to
// execute MprotectRX on the returned buffer.
func mmapCodeSegmentARM64(size int) ([]byte, error) {
// The region must be RW: RW for writing native codes.
return mmapCodeSegment(size, mmapProtARM64)
}
// MprotectRX is like syscall.Mprotect with RX permission, defined locally so that freebsd compiles.
func MprotectRX(b []byte) (err error) {
var _p0 unsafe.Pointer
if len(b) > 0 {
_p0 = unsafe.Pointer(&b[0])
}
const prot = syscall.PROT_READ | syscall.PROT_EXEC
_, _, e1 := syscall.Syscall(syscall.SYS_MPROTECT, uintptr(_p0), uintptr(len(b)), uintptr(prot))
if e1 != 0 {
err = syscall.Errno(e1)
}
return
}
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