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// Copyright 2013 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 amd64p32 386
package runtime
import "unsafe"
// adjust Gobuf as it if executed a call to fn with context ctxt
// and then did an immediate gosave.
func gostartcall(buf *gobuf, fn, ctxt unsafe.Pointer) {
sp := buf.sp
if regSize > ptrSize {
sp -= ptrSize
*(*uintptr)(unsafe.Pointer(sp)) = 0
}
sp -= ptrSize
*(*uintptr)(unsafe.Pointer(sp)) = buf.pc
buf.sp = sp
buf.pc = uintptr(fn)
buf.ctxt = ctxt
}
// Called to rewind context saved during morestack back to beginning of function.
// To help us, the linker emits a jmp back to the beginning right after the
// call to morestack. We just have to decode and apply that jump.
func rewindmorestack(buf *gobuf) {
pc := (*[8]byte)(unsafe.Pointer(buf.pc))
if pc[0] == 0xe9 { // jmp 4-byte offset
buf.pc = buf.pc + 5 + uintptr(int64(*(*int32)(unsafe.Pointer(&pc[1]))))
return
}
if pc[0] == 0xeb { // jmp 1-byte offset
buf.pc = buf.pc + 2 + uintptr(int64(*(*int8)(unsafe.Pointer(&pc[1]))))
return
}
if pc[0] == 0xcc {
// This is a breakpoint inserted by gdb. We could use
// runtime·findfunc to find the function. But if we
// do that, then we will continue execution at the
// function entry point, and we will not hit the gdb
// breakpoint. So for this case we don't change
// buf.pc, so that when we return we will execute
// the jump instruction and carry on. This means that
// stack unwinding may not work entirely correctly
// (http://golang.org/issue/5723) but the user is
// running under gdb anyhow.
return
}
print("runtime: pc=", pc, " ", hex(pc[0]), " ", hex(pc[1]), " ", hex(pc[2]), " ", hex(pc[3]), " ", hex(pc[4]), "\n")
gothrow("runtime: misuse of rewindmorestack")
}
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