65a7f03f6b
I noticed on some of my systems that page fault tracing doesn't
work:
cd /sys/kernel/debug/tracing
echo 1 > events/exceptions/enable
cat trace;
# nothing shows up
I eventually traced it down to CONFIG_KVM_GUEST. At least in a
KVM VM, enabling that option breaks page fault tracing, and
disabling fixes it. I tried on some old kernels and this does
not appear to be a regression: it never worked.
There are two page-fault entry functions today. One when tracing
is on and another when it is off. The KVM code calls do_page_fault()
directly instead of calling the traced version:
> dotraplinkage void __kprobes
> do_async_page_fault(struct pt_regs *regs, unsigned long
> error_code)
> {
> enum ctx_state prev_state;
>
> switch (kvm_read_and_reset_pf_reason()) {
> default:
> do_page_fault(regs, error_code);
> break;
> case KVM_PV_REASON_PAGE_NOT_PRESENT:
I'm also having problems with the page fault tracing on bare
metal (same symptom of no trace output). I'm unsure if it's
related.
Steven had an alternative to this which has zero overhead when
tracing is off where this includes the standard noops even when
tracing is disabled. I'm unconvinced that the extra complexity
of his apporach:
http://lkml.kernel.org/r/20140508194508.561ed220@gandalf.local.home
is worth it, expecially considering that the KVM code is already
making page fault entry slower here. This solution is
dirt-simple.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
139 lines
4.9 KiB
C
139 lines
4.9 KiB
C
#ifndef _ASM_X86_TRAPS_H
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#define _ASM_X86_TRAPS_H
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#include <linux/kprobes.h>
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#include <asm/debugreg.h>
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#include <asm/siginfo.h> /* TRAP_TRACE, ... */
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#define dotraplinkage __visible
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asmlinkage void divide_error(void);
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asmlinkage void debug(void);
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asmlinkage void nmi(void);
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asmlinkage void int3(void);
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asmlinkage void xen_debug(void);
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asmlinkage void xen_int3(void);
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asmlinkage void xen_stack_segment(void);
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asmlinkage void overflow(void);
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asmlinkage void bounds(void);
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asmlinkage void invalid_op(void);
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asmlinkage void device_not_available(void);
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#ifdef CONFIG_X86_64
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asmlinkage void double_fault(void);
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#endif
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asmlinkage void coprocessor_segment_overrun(void);
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asmlinkage void invalid_TSS(void);
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asmlinkage void segment_not_present(void);
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asmlinkage void stack_segment(void);
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asmlinkage void general_protection(void);
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asmlinkage void page_fault(void);
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asmlinkage void async_page_fault(void);
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asmlinkage void spurious_interrupt_bug(void);
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asmlinkage void coprocessor_error(void);
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asmlinkage void alignment_check(void);
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#ifdef CONFIG_X86_MCE
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asmlinkage void machine_check(void);
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#endif /* CONFIG_X86_MCE */
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asmlinkage void simd_coprocessor_error(void);
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#ifdef CONFIG_TRACING
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asmlinkage void trace_page_fault(void);
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#define trace_divide_error divide_error
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#define trace_bounds bounds
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#define trace_invalid_op invalid_op
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#define trace_device_not_available device_not_available
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#define trace_coprocessor_segment_overrun coprocessor_segment_overrun
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#define trace_invalid_TSS invalid_TSS
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#define trace_segment_not_present segment_not_present
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#define trace_general_protection general_protection
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#define trace_spurious_interrupt_bug spurious_interrupt_bug
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#define trace_coprocessor_error coprocessor_error
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#define trace_alignment_check alignment_check
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#define trace_simd_coprocessor_error simd_coprocessor_error
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#define trace_async_page_fault async_page_fault
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#endif
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dotraplinkage void do_divide_error(struct pt_regs *, long);
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dotraplinkage void do_debug(struct pt_regs *, long);
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dotraplinkage void do_nmi(struct pt_regs *, long);
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dotraplinkage void do_int3(struct pt_regs *, long);
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dotraplinkage void do_overflow(struct pt_regs *, long);
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dotraplinkage void do_bounds(struct pt_regs *, long);
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dotraplinkage void do_invalid_op(struct pt_regs *, long);
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dotraplinkage void do_device_not_available(struct pt_regs *, long);
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dotraplinkage void do_coprocessor_segment_overrun(struct pt_regs *, long);
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dotraplinkage void do_invalid_TSS(struct pt_regs *, long);
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dotraplinkage void do_segment_not_present(struct pt_regs *, long);
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dotraplinkage void do_stack_segment(struct pt_regs *, long);
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#ifdef CONFIG_X86_64
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dotraplinkage void do_double_fault(struct pt_regs *, long);
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asmlinkage __kprobes struct pt_regs *sync_regs(struct pt_regs *);
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#endif
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dotraplinkage void do_general_protection(struct pt_regs *, long);
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dotraplinkage void do_page_fault(struct pt_regs *, unsigned long);
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#ifdef CONFIG_TRACING
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dotraplinkage void trace_do_page_fault(struct pt_regs *, unsigned long);
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#else
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static inline void trace_do_page_fault(struct pt_regs *regs, unsigned long error)
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{
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do_page_fault(regs, error);
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}
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#endif
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dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *, long);
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dotraplinkage void do_coprocessor_error(struct pt_regs *, long);
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dotraplinkage void do_alignment_check(struct pt_regs *, long);
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#ifdef CONFIG_X86_MCE
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dotraplinkage void do_machine_check(struct pt_regs *, long);
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#endif
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dotraplinkage void do_simd_coprocessor_error(struct pt_regs *, long);
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#ifdef CONFIG_X86_32
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dotraplinkage void do_iret_error(struct pt_regs *, long);
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#endif
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static inline int get_si_code(unsigned long condition)
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{
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if (condition & DR_STEP)
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return TRAP_TRACE;
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else if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))
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return TRAP_HWBKPT;
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else
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return TRAP_BRKPT;
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}
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extern int panic_on_unrecovered_nmi;
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void math_error(struct pt_regs *, int, int);
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void math_emulate(struct math_emu_info *);
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#ifndef CONFIG_X86_32
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asmlinkage void smp_thermal_interrupt(void);
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asmlinkage void mce_threshold_interrupt(void);
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#endif
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/* Interrupts/Exceptions */
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enum {
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X86_TRAP_DE = 0, /* 0, Divide-by-zero */
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X86_TRAP_DB, /* 1, Debug */
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X86_TRAP_NMI, /* 2, Non-maskable Interrupt */
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X86_TRAP_BP, /* 3, Breakpoint */
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X86_TRAP_OF, /* 4, Overflow */
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X86_TRAP_BR, /* 5, Bound Range Exceeded */
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X86_TRAP_UD, /* 6, Invalid Opcode */
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X86_TRAP_NM, /* 7, Device Not Available */
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X86_TRAP_DF, /* 8, Double Fault */
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X86_TRAP_OLD_MF, /* 9, Coprocessor Segment Overrun */
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X86_TRAP_TS, /* 10, Invalid TSS */
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X86_TRAP_NP, /* 11, Segment Not Present */
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X86_TRAP_SS, /* 12, Stack Segment Fault */
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X86_TRAP_GP, /* 13, General Protection Fault */
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X86_TRAP_PF, /* 14, Page Fault */
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X86_TRAP_SPURIOUS, /* 15, Spurious Interrupt */
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X86_TRAP_MF, /* 16, x87 Floating-Point Exception */
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X86_TRAP_AC, /* 17, Alignment Check */
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X86_TRAP_MC, /* 18, Machine Check */
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X86_TRAP_XF, /* 19, SIMD Floating-Point Exception */
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X86_TRAP_IRET = 32, /* 32, IRET Exception */
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};
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#endif /* _ASM_X86_TRAPS_H */
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