1// Copyright 2014 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
5package runtime
6
7import "unsafe"
8
9type sigctxt struct {
10	info *siginfo
11	ctxt unsafe.Pointer
12}
13
14//go:nosplit
15//go:nowritebarrierrec
16func (c *sigctxt) regs() *regs32 { return &(*ucontext)(c.ctxt).uc_mcontext.ss }
17
18func (c *sigctxt) r0() uint32  { return c.regs().r[0] }
19func (c *sigctxt) r1() uint32  { return c.regs().r[1] }
20func (c *sigctxt) r2() uint32  { return c.regs().r[2] }
21func (c *sigctxt) r3() uint32  { return c.regs().r[3] }
22func (c *sigctxt) r4() uint32  { return c.regs().r[4] }
23func (c *sigctxt) r5() uint32  { return c.regs().r[5] }
24func (c *sigctxt) r6() uint32  { return c.regs().r[6] }
25func (c *sigctxt) r7() uint32  { return c.regs().r[7] }
26func (c *sigctxt) r8() uint32  { return c.regs().r[8] }
27func (c *sigctxt) r9() uint32  { return c.regs().r[9] }
28func (c *sigctxt) r10() uint32 { return c.regs().r[10] }
29func (c *sigctxt) fp() uint32  { return c.regs().r[11] }
30func (c *sigctxt) ip() uint32  { return c.regs().r[12] }
31func (c *sigctxt) sp() uint32  { return c.regs().sp }
32func (c *sigctxt) lr() uint32  { return c.regs().lr }
33
34//go:nosplit
35//go:nowritebarrierrec
36func (c *sigctxt) pc() uint32 { return c.regs().pc }
37
38func (c *sigctxt) cpsr() uint32    { return c.regs().cpsr }
39func (c *sigctxt) fault() uintptr  { return uintptr(c.info.si_addr) }
40func (c *sigctxt) sigcode() uint32 { return uint32(c.info.si_code) }
41func (c *sigctxt) trap() uint32    { return 0 }
42func (c *sigctxt) error() uint32   { return 0 }
43func (c *sigctxt) oldmask() uint32 { return 0 }
44
45func (c *sigctxt) set_pc(x uint32)  { c.regs().pc = x }
46func (c *sigctxt) set_sp(x uint32)  { c.regs().sp = x }
47func (c *sigctxt) set_lr(x uint32)  { c.regs().lr = x }
48func (c *sigctxt) set_r10(x uint32) { c.regs().r[10] = x }
49
50func (c *sigctxt) set_sigcode(x uint32) { c.info.si_code = int32(x) }
51func (c *sigctxt) set_sigaddr(x uint32) { c.info.si_addr = x }
52
53//go:nosplit
54func (c *sigctxt) fixsigcode(sig uint32) {
55	switch sig {
56	case _SIGTRAP:
57		// OS X sets c.sigcode() == TRAP_BRKPT unconditionally for all SIGTRAPs,
58		// leaving no way to distinguish a breakpoint-induced SIGTRAP
59		// from an asynchronous signal SIGTRAP.
60		// They all look breakpoint-induced by default.
61		// Try looking at the code to see if it's a breakpoint.
62		// The assumption is that we're very unlikely to get an
63		// asynchronous SIGTRAP at just the moment that the
64		// PC started to point at unmapped memory.
65		pc := uintptr(c.pc())
66		// OS X will leave the pc just after the instruction.
67		code := (*uint32)(unsafe.Pointer(pc - 4))
68		if *code != 0xe7f001f0 {
69			// SIGTRAP on something other than breakpoint.
70			c.set_sigcode(_SI_USER)
71		}
72	}
73}
74