113 lines
3.3 KiB
Go
113 lines
3.3 KiB
Go
// Copyright 2019 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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//go:build ignore
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// +build ignore
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package runtime
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import "unsafe"
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func checkptrAlignment(p unsafe.Pointer, elem *_type, n uintptr) {
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// nil pointer is always suitably aligned (#47430).
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if p == nil {
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return
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}
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// Check that (*[n]elem)(p) is appropriately aligned.
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// Note that we allow unaligned pointers if the types they point to contain
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// no pointers themselves. See issue 37298.
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// TODO(mdempsky): What about fieldAlign?
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if elem.ptrdata != 0 && uintptr(p)&(uintptr(elem.align)-1) != 0 {
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throw("checkptr: misaligned pointer conversion")
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}
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// Check that (*[n]elem)(p) doesn't straddle multiple heap objects.
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// TODO(mdempsky): Fix #46938 so we don't need to worry about overflow here.
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if checkptrStraddles(p, n*elem.size) {
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throw("checkptr: converted pointer straddles multiple allocations")
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}
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}
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// checkptrStraddles reports whether the first size-bytes of memory
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// addressed by ptr is known to straddle more than one Go allocation.
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func checkptrStraddles(ptr unsafe.Pointer, size uintptr) bool {
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if size <= 1 {
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return false
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}
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// Check that add(ptr, size-1) won't overflow. This avoids the risk
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// of producing an illegal pointer value (assuming ptr is legal).
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if uintptr(ptr) >= -(size - 1) {
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return true
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}
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end := add(ptr, size-1)
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// TODO(mdempsky): Detect when [ptr, end] contains Go allocations,
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// but neither ptr nor end point into one themselves.
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return checkptrBase(ptr) != checkptrBase(end)
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}
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func checkptrArithmetic(p unsafe.Pointer, originals []unsafe.Pointer) {
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if 0 < uintptr(p) && uintptr(p) < minLegalPointer {
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throw("checkptr: pointer arithmetic computed bad pointer value")
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}
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// Check that if the computed pointer p points into a heap
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// object, then one of the original pointers must have pointed
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// into the same object.
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base := checkptrBase(p)
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if base == 0 {
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return
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}
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for _, original := range originals {
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if base == checkptrBase(original) {
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return
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}
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}
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throw("checkptr: pointer arithmetic result points to invalid allocation")
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}
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// checkptrBase returns the base address for the allocation containing
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// the address p.
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//
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// Importantly, if p1 and p2 point into the same variable, then
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// checkptrBase(p1) == checkptrBase(p2). However, the converse/inverse
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// is not necessarily true as allocations can have trailing padding,
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// and multiple variables may be packed into a single allocation.
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func checkptrBase(p unsafe.Pointer) uintptr {
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// stack
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if gp := getg(); gp.stack.lo <= uintptr(p) && uintptr(p) < gp.stack.hi {
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// TODO(mdempsky): Walk the stack to identify the
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// specific stack frame or even stack object that p
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// points into.
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//
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// In the mean time, use "1" as a pseudo-address to
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// represent the stack. This is an invalid address on
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// all platforms, so it's guaranteed to be distinct
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// from any of the addresses we might return below.
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return 1
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}
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// heap (must check after stack because of #35068)
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if base, _, _ := findObject(uintptr(p), 0, 0); base != 0 {
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return base
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}
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// data or bss
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for _, datap := range activeModules() {
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if datap.data <= uintptr(p) && uintptr(p) < datap.edata {
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return datap.data
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}
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if datap.bss <= uintptr(p) && uintptr(p) < datap.ebss {
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return datap.bss
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}
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}
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return 0
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}
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