88 lines
1.9 KiB
Go
88 lines
1.9 KiB
Go
//go:build unix && !sqlite3_nosys
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package util
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import (
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"context"
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"os"
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"unsafe"
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"github.com/tetratelabs/wazero/api"
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"golang.org/x/sys/unix"
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)
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type mmapState struct {
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regions []*MappedRegion
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}
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func (s *mmapState) new(ctx context.Context, mod api.Module, size int32) *MappedRegion {
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// Find unused region.
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for _, r := range s.regions {
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if !r.used && r.size == size {
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return r
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}
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}
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// Allocate page aligned memmory.
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alloc := mod.ExportedFunction("aligned_alloc")
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stack := [...]uint64{
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uint64(unix.Getpagesize()),
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uint64(size),
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}
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if err := alloc.CallWithStack(ctx, stack[:]); err != nil {
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panic(err)
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}
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if stack[0] == 0 {
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panic(OOMErr)
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}
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// Save the newly allocated region.
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ptr := uint32(stack[0])
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buf := View(mod, ptr, uint64(size))
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addr := unsafe.Pointer(&buf[0])
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s.regions = append(s.regions, &MappedRegion{
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Ptr: ptr,
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addr: addr,
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size: size,
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})
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return s.regions[len(s.regions)-1]
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}
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type MappedRegion struct {
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addr unsafe.Pointer
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Ptr uint32
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size int32
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used bool
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}
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func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, size int32, readOnly bool) (*MappedRegion, error) {
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s := ctx.Value(moduleKey{}).(*moduleState)
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r := s.new(ctx, mod, size)
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err := r.mmap(f, offset, readOnly)
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if err != nil {
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return nil, err
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}
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return r, nil
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}
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func (r *MappedRegion) Unmap() error {
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// We can't munmap the region, otherwise it could be remaped.
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// Instead, convert it to a protected, private, anonymous mapping.
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// If successful, it can be reused for a subsequent mmap.
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_, err := unix.MmapPtr(-1, 0, r.addr, uintptr(r.size),
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unix.PROT_NONE, unix.MAP_PRIVATE|unix.MAP_FIXED|unix.MAP_ANON)
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r.used = err != nil
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return err
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}
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func (r *MappedRegion) mmap(f *os.File, offset int64, readOnly bool) error {
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prot := unix.PROT_READ
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if !readOnly {
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prot |= unix.PROT_WRITE
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}
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_, err := unix.MmapPtr(int(f.Fd()), offset, r.addr, uintptr(r.size),
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prot, unix.MAP_SHARED|unix.MAP_FIXED)
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r.used = err == nil
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return err
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}
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