// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import "unsafe"
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type sigctxt struct {
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info *siginfo
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ctxt unsafe.Pointer
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}
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//go:nosplit
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//go:nowritebarrierrec
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func (c *sigctxt) regs() *regs64 { return &(*ucontext)(c.ctxt).uc_mcontext.ss }
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func (c *sigctxt) rax() uint64 { return c.regs().rax }
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func (c *sigctxt) rbx() uint64 { return c.regs().rbx }
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func (c *sigctxt) rcx() uint64 { return c.regs().rcx }
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func (c *sigctxt) rdx() uint64 { return c.regs().rdx }
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func (c *sigctxt) rdi() uint64 { return c.regs().rdi }
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func (c *sigctxt) rsi() uint64 { return c.regs().rsi }
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func (c *sigctxt) rbp() uint64 { return c.regs().rbp }
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func (c *sigctxt) rsp() uint64 { return c.regs().rsp }
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func (c *sigctxt) r8() uint64 { return c.regs().r8 }
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func (c *sigctxt) r9() uint64 { return c.regs().r9 }
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func (c *sigctxt) r10() uint64 { return c.regs().r10 }
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func (c *sigctxt) r11() uint64 { return c.regs().r11 }
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func (c *sigctxt) r12() uint64 { return c.regs().r12 }
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func (c *sigctxt) r13() uint64 { return c.regs().r13 }
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func (c *sigctxt) r14() uint64 { return c.regs().r14 }
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func (c *sigctxt) r15() uint64 { return c.regs().r15 }
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//go:nosplit
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//go:nowritebarrierrec
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func (c *sigctxt) rip() uint64 { return c.regs().rip }
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func (c *sigctxt) rflags() uint64 { return c.regs().rflags }
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func (c *sigctxt) cs() uint64 { return c.regs().cs }
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func (c *sigctxt) fs() uint64 { return c.regs().fs }
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func (c *sigctxt) gs() uint64 { return c.regs().gs }
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func (c *sigctxt) sigcode() uint64 { return uint64(c.info.si_code) }
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func (c *sigctxt) sigaddr() uint64 { return c.info.si_addr }
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func (c *sigctxt) set_rip(x uint64) { c.regs().rip = x }
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func (c *sigctxt) set_rsp(x uint64) { c.regs().rsp = x }
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func (c *sigctxt) set_sigcode(x uint64) { c.info.si_code = int32(x) }
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func (c *sigctxt) set_sigaddr(x uint64) { c.info.si_addr = x }
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func (c *sigctxt) fixsigcode(sig uint32) {
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switch sig {
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case _SIGTRAP:
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// OS X sets c.sigcode() == TRAP_BRKPT unconditionally for all SIGTRAPs,
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// leaving no way to distinguish a breakpoint-induced SIGTRAP
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// from an asynchronous signal SIGTRAP.
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// They all look breakpoint-induced by default.
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// Try looking at the code to see if it's a breakpoint.
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// The assumption is that we're very unlikely to get an
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// asynchronous SIGTRAP at just the moment that the
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// PC started to point at unmapped memory.
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pc := uintptr(c.rip())
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// OS X will leave the pc just after the INT 3 instruction.
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// INT 3 is usually 1 byte, but there is a 2-byte form.
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code := (*[2]byte)(unsafe.Pointer(pc - 2))
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if code[1] != 0xCC && (code[0] != 0xCD || code[1] != 3) {
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// SIGTRAP on something other than INT 3.
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c.set_sigcode(_SI_USER)
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}
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case _SIGSEGV:
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// x86-64 has 48-bit virtual addresses. The top 16 bits must echo bit 47.
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// The hardware delivers a different kind of fault for a malformed address
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// than it does for an attempt to access a valid but unmapped address.
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// OS X 10.9.2 mishandles the malformed address case, making it look like
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// a user-generated signal (like someone ran kill -SEGV ourpid).
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// We pass user-generated signals to os/signal, or else ignore them.
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// Doing that here - and returning to the faulting code - results in an
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// infinite loop. It appears the best we can do is rewrite what the kernel
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// delivers into something more like the truth. The address used below
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// has very little chance of being the one that caused the fault, but it is
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// malformed, it is clearly not a real pointer, and if it does get printed
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// in real life, people will probably search for it and find this code.
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// There are no Google hits for b01dfacedebac1e or 0xb01dfacedebac1e
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// as I type this comment.
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if c.sigcode() == _SI_USER {
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c.set_sigcode(_SI_USER + 1)
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c.set_sigaddr(0xb01dfacedebac1e)
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}
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}
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}
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