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