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 //go:build amd64 || arm64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x || wasm 6 // +build amd64 arm64 mips64 mips64le ppc64 ppc64le riscv64 s390x wasm 7 8 package runtime 9 10 import "unsafe" 11 12 const ( 13 // addrBits is the number of bits needed to represent a virtual address. 14 // 15 // See heapAddrBits for a table of address space sizes on 16 // various architectures. 48 bits is enough for all 17 // architectures except s390x. 18 // 19 // On AMD64, virtual addresses are 48-bit (or 57-bit) numbers sign extended to 64. 20 // We shift the address left 16 to eliminate the sign extended part and make 21 // room in the bottom for the count. 22 // 23 // On s390x, virtual addresses are 64-bit. There's not much we 24 // can do about this, so we just hope that the kernel doesn't 25 // get to really high addresses and panic if it does. 26 addrBits = 48 27 28 // In addition to the 16 bits taken from the top, we can take 3 from the 29 // bottom, because node must be pointer-aligned, giving a total of 19 bits 30 // of count. 31 cntBits = 64 - addrBits + 3 32 33 // On AIX, 64-bit addresses are split into 36-bit segment number and 28-bit 34 // offset in segment. Segment numbers in the range 0x0A0000000-0x0AFFFFFFF(LSA) 35 // are available for mmap. 36 // We assume all lfnode addresses are from memory allocated with mmap. 37 // We use one bit to distinguish between the two ranges. 38 aixAddrBits = 57 39 aixCntBits = 64 - aixAddrBits + 3 40 ) 41 42 func lfstackPack(node *lfnode, cnt uintptr) uint64 { 43 if GOARCH == "ppc64" && GOOS == "aix" { 44 return uint64(uintptr(unsafe.Pointer(node)))<<(64-aixAddrBits) | uint64(cnt&(1<<aixCntBits-1)) 45 } 46 return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | uint64(cnt&(1<<cntBits-1)) 47 } 48 49 func lfstackUnpack(val uint64) *lfnode { 50 if GOARCH == "amd64" { 51 // amd64 systems can place the stack above the VA hole, so we need to sign extend 52 // val before unpacking. 53 return (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> cntBits << 3))) 54 } 55 if GOARCH == "ppc64" && GOOS == "aix" { 56 return (*lfnode)(unsafe.Pointer(uintptr((val >> aixCntBits << 3) | 0xa<<56))) 57 } 58 return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3))) 59 } 60