Source file src/runtime/signal_darwin_amd64.go

     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	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) rax() uint64 { return c.regs().rax }
    19	func (c *sigctxt) rbx() uint64 { return c.regs().rbx }
    20	func (c *sigctxt) rcx() uint64 { return c.regs().rcx }
    21	func (c *sigctxt) rdx() uint64 { return c.regs().rdx }
    22	func (c *sigctxt) rdi() uint64 { return c.regs().rdi }
    23	func (c *sigctxt) rsi() uint64 { return c.regs().rsi }
    24	func (c *sigctxt) rbp() uint64 { return c.regs().rbp }
    25	func (c *sigctxt) rsp() uint64 { return c.regs().rsp }
    26	func (c *sigctxt) r8() uint64  { return c.regs().r8 }
    27	func (c *sigctxt) r9() uint64  { return c.regs().r9 }
    28	func (c *sigctxt) r10() uint64 { return c.regs().r10 }
    29	func (c *sigctxt) r11() uint64 { return c.regs().r11 }
    30	func (c *sigctxt) r12() uint64 { return c.regs().r12 }
    31	func (c *sigctxt) r13() uint64 { return c.regs().r13 }
    32	func (c *sigctxt) r14() uint64 { return c.regs().r14 }
    33	func (c *sigctxt) r15() uint64 { return c.regs().r15 }
    34	
    35	//go:nosplit
    36	//go:nowritebarrierrec
    37	func (c *sigctxt) rip() uint64 { return c.regs().rip }
    38	
    39	func (c *sigctxt) rflags() uint64  { return c.regs().rflags }
    40	func (c *sigctxt) cs() uint64      { return c.regs().cs }
    41	func (c *sigctxt) fs() uint64      { return c.regs().fs }
    42	func (c *sigctxt) gs() uint64      { return c.regs().gs }
    43	func (c *sigctxt) sigcode() uint64 { return uint64(c.info.si_code) }
    44	func (c *sigctxt) sigaddr() uint64 { return c.info.si_addr }
    45	
    46	func (c *sigctxt) set_rip(x uint64)     { c.regs().rip = x }
    47	func (c *sigctxt) set_rsp(x uint64)     { c.regs().rsp = x }
    48	func (c *sigctxt) set_sigcode(x uint64) { c.info.si_code = int32(x) }
    49	func (c *sigctxt) set_sigaddr(x uint64) { c.info.si_addr = x }
    50	
    51	//go:nosplit
    52	func (c *sigctxt) fixsigcode(sig uint32) {
    53		switch sig {
    54		case _SIGTRAP:
    55			// OS X sets c.sigcode() == TRAP_BRKPT unconditionally for all SIGTRAPs,
    56			// leaving no way to distinguish a breakpoint-induced SIGTRAP
    57			// from an asynchronous signal SIGTRAP.
    58			// They all look breakpoint-induced by default.
    59			// Try looking at the code to see if it's a breakpoint.
    60			// The assumption is that we're very unlikely to get an
    61			// asynchronous SIGTRAP at just the moment that the
    62			// PC started to point at unmapped memory.
    63			pc := uintptr(c.rip())
    64			// OS X will leave the pc just after the INT 3 instruction.
    65			// INT 3 is usually 1 byte, but there is a 2-byte form.
    66			code := (*[2]byte)(unsafe.Pointer(pc - 2))
    67			if code[1] != 0xCC && (code[0] != 0xCD || code[1] != 3) {
    68				// SIGTRAP on something other than INT 3.
    69				c.set_sigcode(_SI_USER)
    70			}
    71	
    72		case _SIGSEGV:
    73			// x86-64 has 48-bit virtual addresses. The top 16 bits must echo bit 47.
    74			// The hardware delivers a different kind of fault for a malformed address
    75			// than it does for an attempt to access a valid but unmapped address.
    76			// OS X 10.9.2 mishandles the malformed address case, making it look like
    77			// a user-generated signal (like someone ran kill -SEGV ourpid).
    78			// We pass user-generated signals to os/signal, or else ignore them.
    79			// Doing that here - and returning to the faulting code - results in an
    80			// infinite loop. It appears the best we can do is rewrite what the kernel
    81			// delivers into something more like the truth. The address used below
    82			// has very little chance of being the one that caused the fault, but it is
    83			// malformed, it is clearly not a real pointer, and if it does get printed
    84			// in real life, people will probably search for it and find this code.
    85			// There are no Google hits for b01dfacedebac1e or 0xb01dfacedebac1e
    86			// as I type this comment.
    87			if c.sigcode() == _SI_USER {
    88				c.set_sigcode(_SI_USER + 1)
    89				c.set_sigaddr(0xb01dfacedebac1e)
    90			}
    91		}
    92	}
    93	

View as plain text