mirror of https://go.googlesource.com/go
90 lines
3.2 KiB
Go
90 lines
3.2 KiB
Go
// 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.
|
|
|
|
//go:build amd64 || arm64 || loong64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x || wasm
|
|
|
|
package runtime
|
|
|
|
import (
|
|
"internal/goarch"
|
|
"internal/goos"
|
|
"unsafe"
|
|
)
|
|
|
|
const (
|
|
// addrBits is the number of bits needed to represent a virtual address.
|
|
//
|
|
// See heapAddrBits for a table of address space sizes on
|
|
// various architectures. 48 bits is enough for all
|
|
// architectures except s390x.
|
|
//
|
|
// On AMD64, virtual addresses are 48-bit (or 57-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.
|
|
//
|
|
// On s390x, virtual addresses are 64-bit. There's not much we
|
|
// can do about this, so we just hope that the kernel doesn't
|
|
// get to really high addresses and panic if it does.
|
|
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.
|
|
tagBits = 64 - addrBits + 3
|
|
|
|
// On AIX, 64-bit addresses are split into 36-bit segment number and 28-bit
|
|
// offset in segment. Segment numbers in the range 0x0A0000000-0x0AFFFFFFF(LSA)
|
|
// are available for mmap.
|
|
// We assume all tagged addresses are from memory allocated with mmap.
|
|
// We use one bit to distinguish between the two ranges.
|
|
aixAddrBits = 57
|
|
aixTagBits = 64 - aixAddrBits + 3
|
|
|
|
// riscv64 SV57 mode gives 56 bits of userspace VA.
|
|
// tagged pointer code supports it,
|
|
// but broader support for SV57 mode is incomplete,
|
|
// and there may be other issues (see #54104).
|
|
riscv64AddrBits = 56
|
|
riscv64TagBits = 64 - riscv64AddrBits + 3
|
|
)
|
|
|
|
// The number of bits stored in the numeric tag of a taggedPointer
|
|
const taggedPointerBits = (goos.IsAix * aixTagBits) + (goarch.IsRiscv64 * riscv64TagBits) + ((1 - goos.IsAix) * (1 - goarch.IsRiscv64) * tagBits)
|
|
|
|
// taggedPointerPack created a taggedPointer from a pointer and a tag.
|
|
// Tag bits that don't fit in the result are discarded.
|
|
func taggedPointerPack(ptr unsafe.Pointer, tag uintptr) taggedPointer {
|
|
if GOOS == "aix" {
|
|
if GOARCH != "ppc64" {
|
|
throw("check this code for aix on non-ppc64")
|
|
}
|
|
return taggedPointer(uint64(uintptr(ptr))<<(64-aixAddrBits) | uint64(tag&(1<<aixTagBits-1)))
|
|
}
|
|
if GOARCH == "riscv64" {
|
|
return taggedPointer(uint64(uintptr(ptr))<<(64-riscv64AddrBits) | uint64(tag&(1<<riscv64TagBits-1)))
|
|
}
|
|
return taggedPointer(uint64(uintptr(ptr))<<(64-addrBits) | uint64(tag&(1<<tagBits-1)))
|
|
}
|
|
|
|
// Pointer returns the pointer from a taggedPointer.
|
|
func (tp taggedPointer) pointer() unsafe.Pointer {
|
|
if GOARCH == "amd64" {
|
|
// amd64 systems can place the stack above the VA hole, so we need to sign extend
|
|
// val before unpacking.
|
|
return unsafe.Pointer(uintptr(int64(tp) >> tagBits << 3))
|
|
}
|
|
if GOOS == "aix" {
|
|
return unsafe.Pointer(uintptr((tp >> aixTagBits << 3) | 0xa<<56))
|
|
}
|
|
if GOARCH == "riscv64" {
|
|
return unsafe.Pointer(uintptr(tp >> riscv64TagBits << 3))
|
|
}
|
|
return unsafe.Pointer(uintptr(tp >> tagBits << 3))
|
|
}
|
|
|
|
// Tag returns the tag from a taggedPointer.
|
|
func (tp taggedPointer) tag() uintptr {
|
|
return uintptr(tp & (1<<taggedPointerBits - 1))
|
|
}
|