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https://github.com/golang/go
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e6f36f0cd5
Change-Id: I51c0a332e3cbdab348564e5dcd27583e75e4b881 Reviewed-on: https://go-review.googlesource.com/20946 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
46 lines
1.3 KiB
Go
46 lines
1.3 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import "unsafe"
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// adjust Gobuf as if it executed a call to fn with context ctxt
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// and then did an immediate Gosave.
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func gostartcall(buf *gobuf, fn, ctxt unsafe.Pointer) {
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if buf.lr != 0 {
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throw("invalid use of gostartcall")
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}
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buf.lr = buf.pc
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buf.pc = uintptr(fn)
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buf.ctxt = ctxt
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}
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// Called to rewind context saved during morestack back to beginning of function.
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// To help us, the linker emits a jmp back to the beginning right after the
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// call to morestack. We just have to decode and apply that jump.
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func rewindmorestack(buf *gobuf) {
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var inst uint64
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if buf.pc&1 == 0 && buf.pc != 0 {
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inst = *(*uint64)(unsafe.Pointer(buf.pc))
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switch inst >> 48 {
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case 0xa7f4: // BRC (branch relative on condition) instruction.
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inst >>= 32
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inst &= 0xFFFF
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offset := int64(int16(inst))
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offset <<= 1
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buf.pc += uintptr(offset)
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return
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case 0xc0f4: // BRCL (branch relative on condition long) instruction.
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inst >>= 16
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inst = inst & 0xFFFFFFFF
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inst = (inst << 1) & 0xFFFFFFFF
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buf.pc += uintptr(int32(inst))
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return
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}
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}
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print("runtime: pc=", hex(buf.pc), " ", hex(inst), "\n")
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throw("runtime: misuse of rewindmorestack")
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}
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