| Date | Fri, 25 Aug 2017 11:10:57 -0400 | From | Steven Rostedt <> | Subject | Re: [patch 06/41] x86/traps: Simplify pagefault tracing logic |
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On Fri, 25 Aug 2017 12:31:09 +0200 Thomas Gleixner <tglx@linutronix.de> wrote:
> dotraplinkage void notrace > -trace_do_page_fault(struct pt_regs *regs, unsigned long error_code) > +do_page_fault(struct pt_regs *regs, unsigned long error_code) > { > + unsigned long address = read_cr2(); /* Get the faulting address */ > + enum ctx_state prev_state; > + > /* > - * The exception_enter and tracepoint processing could > - * trigger another page faults (user space callchain > - * reading) and destroy the original cr2 value, so read > - * the faulting address now. > + * We must have this function tagged with __kprobes, notrace and call > + * read_cr2() before calling anything else. To avoid calling any kind > + * of tracing machinery before we've observed the CR2 value. > + * > + * exception_{enter,exit}() contain all sorts of tracepoints. > */ > - unsigned long address = read_cr2(); > - enum ctx_state prev_state; > + if (trace_irqvectors_enabled()) > + trace_page_fault_entries(address, regs, error_code); > > prev_state = exception_enter(); > - trace_page_fault_entries(address, regs, error_code);
I believe you need to keep the tracing after the "exception_enter()", as for NO_HZ_FULL, that enables RCU again, and the tracepoint needs RCU enabled.
-- Steve
> __do_page_fault(regs, error_code, address); > exception_exit(prev_state); > } > -NOKPROBE_SYMBOL(trace_do_page_fault); > -#endif /* CONFIG_TRACING */ > +NOKPROBE_SYMBOL(do_page_fault); >
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