rsc.io/go@v0.0.0-20150416155037-e040fd465409/src/runtime/sys_arm.go (about)

     1  // Copyright 2013 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  package runtime
     6  
     7  import "unsafe"
     8  
     9  // adjust Gobuf as if it executed a call to fn with context ctxt
    10  // and then did an immediate Gosave.
    11  func gostartcall(buf *gobuf, fn, ctxt unsafe.Pointer) {
    12  	if buf.lr != 0 {
    13  		throw("invalid use of gostartcall")
    14  	}
    15  	buf.lr = buf.pc
    16  	buf.pc = uintptr(fn)
    17  	buf.ctxt = ctxt
    18  }
    19  
    20  // Called to rewind context saved during morestack back to beginning of function.
    21  // To help us, the linker emits a jmp back to the beginning right after the
    22  // call to morestack. We just have to decode and apply that jump.
    23  func rewindmorestack(buf *gobuf) {
    24  	var inst uint32
    25  	if buf.pc&3 == 0 && buf.pc != 0 {
    26  		inst = *(*uint32)(unsafe.Pointer(buf.pc))
    27  		if inst>>24 == 0x9a {
    28  			buf.pc += uintptr(int32(inst<<8)>>6) + 8
    29  			return
    30  		}
    31  	}
    32  
    33  	print("runtime: pc=", hex(buf.pc), " ", hex(inst), "\n")
    34  	throw("runtime: misuse of rewindmorestack")
    35  }