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      1 // Copyright 2015 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 type sigctxt struct {
     10 	info *siginfo
     11 	ctxt unsafe.Pointer
     12 }
     13 
     14 //go:nosplit
     15 //go:nowritebarrierrec
     16 func (c *sigctxt) regs() *regs64 { return &(*ucontext)(c.ctxt).uc_mcontext.ss }
     17 
     18 func (c *sigctxt) r0() uint64  { return c.regs().x[0] }
     19 func (c *sigctxt) r1() uint64  { return c.regs().x[1] }
     20 func (c *sigctxt) r2() uint64  { return c.regs().x[2] }
     21 func (c *sigctxt) r3() uint64  { return c.regs().x[3] }
     22 func (c *sigctxt) r4() uint64  { return c.regs().x[4] }
     23 func (c *sigctxt) r5() uint64  { return c.regs().x[5] }
     24 func (c *sigctxt) r6() uint64  { return c.regs().x[6] }
     25 func (c *sigctxt) r7() uint64  { return c.regs().x[7] }
     26 func (c *sigctxt) r8() uint64  { return c.regs().x[8] }
     27 func (c *sigctxt) r9() uint64  { return c.regs().x[9] }
     28 func (c *sigctxt) r10() uint64 { return c.regs().x[10] }
     29 func (c *sigctxt) r11() uint64 { return c.regs().x[11] }
     30 func (c *sigctxt) r12() uint64 { return c.regs().x[12] }
     31 func (c *sigctxt) r13() uint64 { return c.regs().x[13] }
     32 func (c *sigctxt) r14() uint64 { return c.regs().x[14] }
     33 func (c *sigctxt) r15() uint64 { return c.regs().x[15] }
     34 func (c *sigctxt) r16() uint64 { return c.regs().x[16] }
     35 func (c *sigctxt) r17() uint64 { return c.regs().x[17] }
     36 func (c *sigctxt) r18() uint64 { return c.regs().x[18] }
     37 func (c *sigctxt) r19() uint64 { return c.regs().x[19] }
     38 func (c *sigctxt) r20() uint64 { return c.regs().x[20] }
     39 func (c *sigctxt) r21() uint64 { return c.regs().x[21] }
     40 func (c *sigctxt) r22() uint64 { return c.regs().x[22] }
     41 func (c *sigctxt) r23() uint64 { return c.regs().x[23] }
     42 func (c *sigctxt) r24() uint64 { return c.regs().x[24] }
     43 func (c *sigctxt) r25() uint64 { return c.regs().x[25] }
     44 func (c *sigctxt) r26() uint64 { return c.regs().x[26] }
     45 func (c *sigctxt) r27() uint64 { return c.regs().x[27] }
     46 func (c *sigctxt) r28() uint64 { return c.regs().x[28] }
     47 func (c *sigctxt) r29() uint64 { return c.regs().fp }
     48 func (c *sigctxt) lr() uint64  { return c.regs().lr }
     49 func (c *sigctxt) sp() uint64  { return c.regs().sp }
     50 
     51 //go:nosplit
     52 //go:nowritebarrierrec
     53 func (c *sigctxt) pc() uint64 { return c.regs().pc }
     54 
     55 func (c *sigctxt) fault() uint64 { return uint64(uintptr(unsafe.Pointer(c.info.si_addr))) }
     56 
     57 func (c *sigctxt) sigcode() uint64 { return uint64(c.info.si_code) }
     58 func (c *sigctxt) sigaddr() uint64 { return uint64(uintptr(unsafe.Pointer(c.info.si_addr))) }
     59 
     60 func (c *sigctxt) set_pc(x uint64)  { c.regs().pc = x }
     61 func (c *sigctxt) set_sp(x uint64)  { c.regs().sp = x }
     62 func (c *sigctxt) set_lr(x uint64)  { c.regs().lr = x }
     63 func (c *sigctxt) set_r28(x uint64) { c.regs().x[28] = x }
     64 
     65 func (c *sigctxt) set_sigcode(x uint64) { c.info.si_code = int32(x) }
     66 func (c *sigctxt) set_sigaddr(x uint64) {
     67 	c.info.si_addr = (*byte)(unsafe.Pointer(uintptr(x)))
     68 }
     69 
     70 func (c *sigctxt) fixsigcode(sig uint32) {
     71 	switch sig {
     72 	case _SIGTRAP:
     73 		// OS X sets c.sigcode() == TRAP_BRKPT unconditionally for all SIGTRAPs,
     74 		// leaving no way to distinguish a breakpoint-induced SIGTRAP
     75 		// from an asynchronous signal SIGTRAP.
     76 		// They all look breakpoint-induced by default.
     77 		// Try looking at the code to see if it's a breakpoint.
     78 		// The assumption is that we're very unlikely to get an
     79 		// asynchronous SIGTRAP at just the moment that the
     80 		// PC started to point at unmapped memory.
     81 		pc := uintptr(c.pc())
     82 		// OS X will leave the pc just after the instruction.
     83 		code := (*uint32)(unsafe.Pointer(pc - 4))
     84 		if *code != 0xd4200000 {
     85 			// SIGTRAP on something other than breakpoint.
     86 			c.set_sigcode(_SI_USER)
     87 		}
     88 	}
     89 }
     90