| // 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") |
| throw("runtime: misuse of rewindmorestack") |
| } |
