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https://github.com/golang/go
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d03e8b226c
If we get a SIGPROF on a non-Go thread, and the program has not called runtime.SetCgoTraceback so we have no way to collect a stack trace, then record a profile that is just the PC where the signal occurred. That will at least point the user to the right area. Retrieving the PC from the sigctxt in a signal handler on a non-G thread required marking a number of trivial sigctxt methods as nosplit, and, for extra safety, nowritebarrierrec. The test shows that the existing test CgoPprofThread test does not test the stack trace, just the profile signal. Leaving that for later. Change-Id: I8f8f3ff09ac099fc9d9df94b5a9d210ffc20c4ab Reviewed-on: https://go-review.googlesource.com/30252 Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
92 lines
3.8 KiB
Go
92 lines
3.8 KiB
Go
// 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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