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//go:build unix
package util
import (
"context"
"os"
"unsafe"
"github.com/tetratelabs/wazero/api"
"golang.org/x/sys/unix"
)
type mmapState struct {
regions []*MappedRegion
}
func (s *mmapState) new(ctx context.Context, mod api.Module, size int32) *MappedRegion {
// Find unused region.
for _, r := range s.regions {
if !r.used && r.size == size {
return r
}
}
// Allocate page aligned memmory.
alloc := mod.ExportedFunction("aligned_alloc")
stack := [...]uint64{
uint64(unix.Getpagesize()),
uint64(size),
}
if err := alloc.CallWithStack(ctx, stack[:]); err != nil {
panic(err)
}
if stack[0] == 0 {
panic(OOMErr)
}
// Save the newly allocated region.
ptr := uint32(stack[0])
buf := View(mod, ptr, uint64(size))
res := &MappedRegion{
Ptr: ptr,
size: size,
addr: unsafe.Pointer(&buf[0]),
}
s.regions = append(s.regions, res)
return res
}
type MappedRegion struct {
addr unsafe.Pointer
Ptr uint32
size int32
used bool
}
func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, size int32, readOnly bool) (*MappedRegion, error) {
s := ctx.Value(moduleKey{}).(*moduleState)
r := s.new(ctx, mod, size)
err := r.mmap(f, offset, readOnly)
if err != nil {
return nil, err
}
return r, nil
}
func (r *MappedRegion) Unmap() error {
// We can't munmap the region, otherwise it could be remaped.
// Instead, convert it to a protected, private, anonymous mapping.
// If successful, it can be reused for a subsequent mmap.
_, err := unix.MmapPtr(-1, 0, r.addr, uintptr(r.size),
unix.PROT_NONE, unix.MAP_PRIVATE|unix.MAP_FIXED|unix.MAP_ANON)
r.used = err != nil
return err
}
func (r *MappedRegion) mmap(f *os.File, offset int64, readOnly bool) error {
prot := unix.PROT_READ
if !readOnly {
prot |= unix.PROT_WRITE
}
_, err := unix.MmapPtr(int(f.Fd()), offset, r.addr, uintptr(r.size),
prot, unix.MAP_SHARED|unix.MAP_FIXED)
r.used = err == nil
return err
}
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