260 lines
6.6 KiB
Go
260 lines
6.6 KiB
Go
// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build ignore
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// Code to check that pointer writes follow the cgo rules.
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// These functions are invoked via the write barrier when debug.cgocheck > 1.
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package runtime
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import (
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"runtime/internal/sys"
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"unsafe"
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)
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const cgoWriteBarrierFail = "Go pointer stored into non-Go memory"
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// cgoCheckWriteBarrier is called whenever a pointer is stored into memory.
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// It throws if the program is storing a Go pointer into non-Go memory.
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//go:nosplit
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//go:nowritebarrier
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func cgoCheckWriteBarrier(dst *uintptr, src uintptr) {
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if !cgoIsGoPointer(unsafe.Pointer(src)) {
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return
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}
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if cgoIsGoPointer(unsafe.Pointer(dst)) {
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return
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}
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// If we are running on the system stack then dst might be an
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// address on the stack, which is OK.
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g := getg()
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if g == g.m.g0 || g == g.m.gsignal {
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return
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}
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// Allocating memory can write to various mfixalloc structs
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// that look like they are non-Go memory.
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if g.m.mallocing != 0 {
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return
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}
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systemstack(func() {
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println("write of Go pointer", hex(src), "to non-Go memory", hex(uintptr(unsafe.Pointer(dst))))
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throw(cgoWriteBarrierFail)
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})
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}
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// cgoCheckMemmove is called when moving a block of memory.
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// dst and src point off bytes into the value to copy.
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// size is the number of bytes to copy.
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// It throws if the program is copying a block that contains a Go pointer
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// into non-Go memory.
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//go:nosplit
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//go:nowritebarrier
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func cgoCheckMemmove(typ *_type, dst, src unsafe.Pointer, off, size uintptr) {
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if typ.kind&kindNoPointers != 0 {
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return
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}
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if !cgoIsGoPointer(src) {
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return
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}
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if cgoIsGoPointer(dst) {
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return
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}
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cgoCheckTypedBlock(typ, src, off, size)
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}
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// cgoCheckSliceCopy is called when copying n elements of a slice from
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// src to dst. typ is the element type of the slice.
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// It throws if the program is copying slice elements that contain Go pointers
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// into non-Go memory.
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//go:nosplit
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//go:nowritebarrier
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func cgoCheckSliceCopy(typ *_type, dst, src slice, n int) {
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if typ.kind&kindNoPointers != 0 {
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return
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}
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if !cgoIsGoPointer(src.array) {
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return
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}
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if cgoIsGoPointer(dst.array) {
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return
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}
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p := src.array
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for i := 0; i < n; i++ {
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cgoCheckTypedBlock(typ, p, 0, typ.size)
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p = add(p, typ.size)
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}
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}
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// cgoCheckTypedBlock checks the block of memory at src, for up to size bytes,
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// and throws if it finds a Go pointer. The type of the memory is typ,
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// and src is off bytes into that type.
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//go:nosplit
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//go:nowritebarrier
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func cgoCheckTypedBlock(typ *_type, src unsafe.Pointer, off, size uintptr) {
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// Anything past typ.ptrdata is not a pointer.
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if typ.ptrdata <= off {
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return
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}
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if ptrdataSize := typ.ptrdata - off; size > ptrdataSize {
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size = ptrdataSize
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}
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if typ.kind&kindGCProg == 0 {
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cgoCheckBits(src, typ.gcdata, off, size)
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return
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}
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// The type has a GC program. Try to find GC bits somewhere else.
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for datap := &firstmoduledata; datap != nil; datap = datap.next {
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if cgoInRange(src, datap.data, datap.edata) {
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doff := uintptr(src) - datap.data
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cgoCheckBits(add(src, -doff), datap.gcdatamask.bytedata, off+doff, size)
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return
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}
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if cgoInRange(src, datap.bss, datap.ebss) {
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boff := uintptr(src) - datap.bss
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cgoCheckBits(add(src, -boff), datap.gcbssmask.bytedata, off+boff, size)
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return
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}
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}
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aoff := uintptr(src) - mheap_.arena_start
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idx := aoff >> _PageShift
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s := h_spans[idx]
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if s.state == _MSpanStack {
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// There are no heap bits for value stored on the stack.
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// For a channel receive src might be on the stack of some
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// other goroutine, so we can't unwind the stack even if
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// we wanted to.
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// We can't expand the GC program without extra storage
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// space we can't easily get.
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// Fortunately we have the type information.
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systemstack(func() {
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cgoCheckUsingType(typ, src, off, size)
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})
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return
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}
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// src must be in the regular heap.
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hbits := heapBitsForAddr(uintptr(src))
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for i := uintptr(0); i < off+size; i += sys.PtrSize {
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bits := hbits.bits()
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if i >= off && bits&bitPointer != 0 {
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v := *(*unsafe.Pointer)(add(src, i))
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if cgoIsGoPointer(v) {
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systemstack(func() {
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throw(cgoWriteBarrierFail)
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})
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}
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}
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hbits = hbits.next()
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}
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}
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// cgoCheckBits checks the block of memory at src, for up to size
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// bytes, and throws if it finds a Go pointer. The gcbits mark each
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// pointer value. The src pointer is off bytes into the gcbits.
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//go:nosplit
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//go:nowritebarrier
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func cgoCheckBits(src unsafe.Pointer, gcbits *byte, off, size uintptr) {
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skipMask := off / sys.PtrSize / 8
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skipBytes := skipMask * sys.PtrSize * 8
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ptrmask := addb(gcbits, skipMask)
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src = add(src, skipBytes)
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off -= skipBytes
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size += off
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var bits uint32
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for i := uintptr(0); i < size; i += sys.PtrSize {
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if i&(sys.PtrSize*8-1) == 0 {
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bits = uint32(*ptrmask)
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ptrmask = addb(ptrmask, 1)
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} else {
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bits >>= 1
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}
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if off > 0 {
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off -= sys.PtrSize
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} else {
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if bits&1 != 0 {
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v := *(*unsafe.Pointer)(add(src, i))
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if cgoIsGoPointer(v) {
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systemstack(func() {
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throw(cgoWriteBarrierFail)
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})
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}
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}
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}
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}
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}
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// cgoCheckUsingType is like cgoCheckTypedBlock, but is a last ditch
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// fall back to look for pointers in src using the type information.
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// We only use this when looking at a value on the stack when the type
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// uses a GC program, because otherwise it's more efficient to use the
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// GC bits. This is called on the system stack.
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//go:nowritebarrier
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//go:systemstack
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func cgoCheckUsingType(typ *_type, src unsafe.Pointer, off, size uintptr) {
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if typ.kind&kindNoPointers != 0 {
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return
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}
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// Anything past typ.ptrdata is not a pointer.
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if typ.ptrdata <= off {
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return
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}
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if ptrdataSize := typ.ptrdata - off; size > ptrdataSize {
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size = ptrdataSize
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}
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if typ.kind&kindGCProg == 0 {
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cgoCheckBits(src, typ.gcdata, off, size)
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return
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}
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switch typ.kind & kindMask {
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default:
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throw("can't happen")
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case kindArray:
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at := (*arraytype)(unsafe.Pointer(typ))
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for i := uintptr(0); i < at.len; i++ {
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if off < at.elem.size {
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cgoCheckUsingType(at.elem, src, off, size)
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}
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src = add(src, at.elem.size)
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skipped := off
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if skipped > at.elem.size {
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skipped = at.elem.size
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}
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checked := at.elem.size - skipped
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off -= skipped
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if size <= checked {
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return
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}
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size -= checked
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}
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case kindStruct:
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st := (*structtype)(unsafe.Pointer(typ))
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for _, f := range st.fields {
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if off < f.typ.size {
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cgoCheckUsingType(f.typ, src, off, size)
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}
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src = add(src, f.typ.size)
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skipped := off
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if skipped > f.typ.size {
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skipped = f.typ.size
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}
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checked := f.typ.size - skipped
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off -= skipped
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if size <= checked {
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return
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}
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size -= checked
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}
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}
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}
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