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Source file src/runtime/signal_darwin_amd64.go

Documentation: runtime

  // 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.
  
  package runtime
  
  import "unsafe"
  
  type sigctxt struct {
  	info *siginfo
  	ctxt unsafe.Pointer
  }
  
  //go:nosplit
  //go:nowritebarrierrec
  func (c *sigctxt) regs() *regs64 { return &(*ucontext)(c.ctxt).uc_mcontext.ss }
  
  func (c *sigctxt) rax() uint64 { return c.regs().rax }
  func (c *sigctxt) rbx() uint64 { return c.regs().rbx }
  func (c *sigctxt) rcx() uint64 { return c.regs().rcx }
  func (c *sigctxt) rdx() uint64 { return c.regs().rdx }
  func (c *sigctxt) rdi() uint64 { return c.regs().rdi }
  func (c *sigctxt) rsi() uint64 { return c.regs().rsi }
  func (c *sigctxt) rbp() uint64 { return c.regs().rbp }
  func (c *sigctxt) rsp() uint64 { return c.regs().rsp }
  func (c *sigctxt) r8() uint64  { return c.regs().r8 }
  func (c *sigctxt) r9() uint64  { return c.regs().r9 }
  func (c *sigctxt) r10() uint64 { return c.regs().r10 }
  func (c *sigctxt) r11() uint64 { return c.regs().r11 }
  func (c *sigctxt) r12() uint64 { return c.regs().r12 }
  func (c *sigctxt) r13() uint64 { return c.regs().r13 }
  func (c *sigctxt) r14() uint64 { return c.regs().r14 }
  func (c *sigctxt) r15() uint64 { return c.regs().r15 }
  
  //go:nosplit
  //go:nowritebarrierrec
  func (c *sigctxt) rip() uint64 { return c.regs().rip }
  
  func (c *sigctxt) rflags() uint64  { return c.regs().rflags }
  func (c *sigctxt) cs() uint64      { return c.regs().cs }
  func (c *sigctxt) fs() uint64      { return c.regs().fs }
  func (c *sigctxt) gs() uint64      { return c.regs().gs }
  func (c *sigctxt) sigcode() uint64 { return uint64(c.info.si_code) }
  func (c *sigctxt) sigaddr() uint64 { return c.info.si_addr }
  
  func (c *sigctxt) set_rip(x uint64)     { c.regs().rip = x }
  func (c *sigctxt) set_rsp(x uint64)     { c.regs().rsp = x }
  func (c *sigctxt) set_sigcode(x uint64) { c.info.si_code = int32(x) }
  func (c *sigctxt) set_sigaddr(x uint64) { c.info.si_addr = x }
  
  func (c *sigctxt) fixsigcode(sig uint32) {
  	switch sig {
  	case _SIGTRAP:
  		// OS X sets c.sigcode() == TRAP_BRKPT unconditionally for all SIGTRAPs,
  		// leaving no way to distinguish a breakpoint-induced SIGTRAP
  		// from an asynchronous signal SIGTRAP.
  		// They all look breakpoint-induced by default.
  		// Try looking at the code to see if it's a breakpoint.
  		// The assumption is that we're very unlikely to get an
  		// asynchronous SIGTRAP at just the moment that the
  		// PC started to point at unmapped memory.
  		pc := uintptr(c.rip())
  		// OS X will leave the pc just after the INT 3 instruction.
  		// INT 3 is usually 1 byte, but there is a 2-byte form.
  		code := (*[2]byte)(unsafe.Pointer(pc - 2))
  		if code[1] != 0xCC && (code[0] != 0xCD || code[1] != 3) {
  			// SIGTRAP on something other than INT 3.
  			c.set_sigcode(_SI_USER)
  		}
  
  	case _SIGSEGV:
  		// x86-64 has 48-bit virtual addresses. The top 16 bits must echo bit 47.
  		// The hardware delivers a different kind of fault for a malformed address
  		// than it does for an attempt to access a valid but unmapped address.
  		// OS X 10.9.2 mishandles the malformed address case, making it look like
  		// a user-generated signal (like someone ran kill -SEGV ourpid).
  		// We pass user-generated signals to os/signal, or else ignore them.
  		// Doing that here - and returning to the faulting code - results in an
  		// infinite loop. It appears the best we can do is rewrite what the kernel
  		// delivers into something more like the truth. The address used below
  		// has very little chance of being the one that caused the fault, but it is
  		// malformed, it is clearly not a real pointer, and if it does get printed
  		// in real life, people will probably search for it and find this code.
  		// There are no Google hits for b01dfacedebac1e or 0xb01dfacedebac1e
  		// as I type this comment.
  		if c.sigcode() == _SI_USER {
  			c.set_sigcode(_SI_USER + 1)
  			c.set_sigaddr(0xb01dfacedebac1e)
  		}
  	}
  }
  

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