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// Copyright 2014 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.
// +build amd64 arm64 mips64 mips64le ppc64 ppc64le s390x arm64be alpha mipsn64 sparc64
package runtime
import "unsafe"
const (
// addrBits is the number of bits needed to represent a virtual address.
//
// In Linux the user address space for each architecture is limited as
// follows (taken from the processor.h file for the architecture):
//
// Architecture Name Maximum Value (exclusive)
// ---------------------------------------------------------------------
// arm64 TASK_SIZE_64 Depends on configuration.
// ppc64{,le} TASK_SIZE_USER64 0x400000000000UL (46 bit addresses)
// mips64{,le} TASK_SIZE64 0x010000000000UL (40 bit addresses)
// s390x TASK_SIZE 0x020000000000UL (41 bit addresses)
//
// These values may increase over time.
//
// On AMD64, virtual addresses are 48-bit numbers sign extended to 64.
// We shift the address left 16 to eliminate the sign extended part and make
// room in the bottom for the count.
addrBits = 48
// In addition to the 16 bits taken from the top, we can take 3 from the
// bottom, because node must be pointer-aligned, giving a total of 19 bits
// of count.
cntBits = 64 - addrBits + 3
)
func lfstackPack(node *lfnode, cnt uintptr) uint64 {
return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | uint64(cnt&(1<<cntBits-1))
}
func lfstackUnpack(val uint64) *lfnode {
if GOARCH == "amd64" || GOOS == "solaris" {
// amd64 or Solaris systems can place the stack above the VA hole, so we need to sign extend
// val before unpacking.
return (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> cntBits << 3)))
}
return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3)))
}
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