1 // Copyright 2014 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // +build amd64 arm64 mips64 mips64le ppc64 ppc64le s390x wasm 6 7 package runtime 8 9 import "unsafe" 10 11 const ( 12 // addrBits is the number of bits needed to represent a virtual address. 13 // 14 // See heapAddrBits for a table of address space sizes on 15 // various architectures. 48 bits is enough for all 16 // architectures except s390x. 17 // 18 // On AMD64, virtual addresses are 48-bit (or 57-bit) numbers sign extended to 64. 19 // We shift the address left 16 to eliminate the sign extended part and make 20 // room in the bottom for the count. 21 // 22 // On s390x, virtual addresses are 64-bit. There's not much we 23 // can do about this, so we just hope that the kernel doesn't 24 // get to really high addresses and panic if it does. 25 addrBits = 48 26 27 // In addition to the 16 bits taken from the top, we can take 3 from the 28 // bottom, because node must be pointer-aligned, giving a total of 19 bits 29 // of count. 30 cntBits = 64 - addrBits + 3 31 32 // On AIX, 64-bit addresses are split into 36-bit segment number and 28-bit 33 // offset in segment. Segment numbers in the range 0x0A0000000-0x0AFFFFFFF(LSA) 34 // are available for mmap. 35 // We assume all lfnode addresses are from memory allocated with mmap. 36 // We use one bit to distinguish between the two ranges. 37 aixAddrBits = 57 38 aixCntBits = 64 - aixAddrBits + 3 39 ) 40 41 func lfstackPack(node *lfnode, cnt uintptr) uint64 { 42 if GOARCH == "ppc64" && GOOS == "aix" { 43 return uint64(uintptr(unsafe.Pointer(node)))<<(64-aixAddrBits) | uint64(cnt&(1<<aixCntBits-1)) 44 } 45 return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | uint64(cnt&(1<<cntBits-1)) 46 } 47 48 func lfstackUnpack(val uint64) *lfnode { 49 if GOARCH == "amd64" { 50 // amd64 systems can place the stack above the VA hole, so we need to sign extend 51 // val before unpacking. 52 return (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> cntBits << 3))) 53 } 54 if GOARCH == "ppc64" && GOOS == "aix" { 55 return (*lfnode)(unsafe.Pointer(uintptr((val >> aixCntBits << 3) | 0xa<<56))) 56 } 57 return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3))) 58 } 59