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 func (c *sigctxt) fixsigcode(sig uint32) { 52 switch sig { 53 case _SIGTRAP: 54 // OS X sets c.sigcode() == TRAP_BRKPT unconditionally for all SIGTRAPs, 55 // leaving no way to distinguish a breakpoint-induced SIGTRAP 56 // from an asynchronous signal SIGTRAP. 57 // They all look breakpoint-induced by default. 58 // Try looking at the code to see if it's a breakpoint. 59 // The assumption is that we're very unlikely to get an 60 // asynchronous SIGTRAP at just the moment that the 61 // PC started to point at unmapped memory. 62 pc := uintptr(c.rip()) 63 // OS X will leave the pc just after the INT 3 instruction. 64 // INT 3 is usually 1 byte, but there is a 2-byte form. 65 code := (*[2]byte)(unsafe.Pointer(pc - 2)) 66 if code[1] != 0xCC && (code[0] != 0xCD || code[1] != 3) { 67 // SIGTRAP on something other than INT 3. 68 c.set_sigcode(_SI_USER) 69 } 70 71 case _SIGSEGV: 72 // x86-64 has 48-bit virtual addresses. The top 16 bits must echo bit 47. 73 // The hardware delivers a different kind of fault for a malformed address 74 // than it does for an attempt to access a valid but unmapped address. 75 // OS X 10.9.2 mishandles the malformed address case, making it look like 76 // a user-generated signal (like someone ran kill -SEGV ourpid). 77 // We pass user-generated signals to os/signal, or else ignore them. 78 // Doing that here - and returning to the faulting code - results in an 79 // infinite loop. It appears the best we can do is rewrite what the kernel 80 // delivers into something more like the truth. The address used below 81 // has very little chance of being the one that caused the fault, but it is 82 // malformed, it is clearly not a real pointer, and if it does get printed 83 // in real life, people will probably search for it and find this code. 84 // There are no Google hits for b01dfacedebac1e or 0xb01dfacedebac1e 85 // as I type this comment. 86 if c.sigcode() == _SI_USER { 87 c.set_sigcode(_SI_USER + 1) 88 c.set_sigaddr(0xb01dfacedebac1e) 89 } 90 } 91 } 92
