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    Subject[tip:x86/apic] x86/traps: Simplify pagefault tracing logic
    Commit-ID:  11a7ffb01703c3bbb1e9b968893f4487a1b0b5a8
    Gitweb: http://git.kernel.org/tip/11a7ffb01703c3bbb1e9b968893f4487a1b0b5a8
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Mon, 28 Aug 2017 08:47:22 +0200
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Tue, 29 Aug 2017 11:42:23 +0200

    x86/traps: Simplify pagefault tracing logic

    Make use of the new irqvector tracing static key and remove the duplicated
    trace_do_pagefault() implementation.

    If irq vector tracing is disabled, then the overhead of this is a single
    NOP5, which is a reasonable tradeoff to avoid duplicated code and the
    unholy macro mess.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Link: http://lkml.kernel.org/r/20170828064956.672965407@linutronix.de
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/entry/entry_32.S | 8 --------
    arch/x86/entry/entry_64.S | 13 +-----------
    arch/x86/include/asm/traps.h | 10 +--------
    arch/x86/kernel/kvm.c | 2 +-
    arch/x86/mm/fault.c | 49 ++++++++++++--------------------------------
    5 files changed, 16 insertions(+), 66 deletions(-)

    diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
    index 48ef7bb..0092da1 100644
    --- a/arch/x86/entry/entry_32.S
    +++ b/arch/x86/entry/entry_32.S
    @@ -891,14 +891,6 @@ BUILD_INTERRUPT3(hyperv_callback_vector, HYPERVISOR_CALLBACK_VECTOR,

    #endif /* CONFIG_HYPERV */

    -#ifdef CONFIG_TRACING
    -ENTRY(trace_page_fault)
    - ASM_CLAC
    - pushl $trace_do_page_fault
    - jmp common_exception
    -END(trace_page_fault)
    -#endif
    -
    ENTRY(page_fault)
    ASM_CLAC
    pushl $do_page_fault
    diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
    index 4dbb336..2731b94 100644
    --- a/arch/x86/entry/entry_64.S
    +++ b/arch/x86/entry/entry_64.S
    @@ -918,17 +918,6 @@ ENTRY(\sym)
    END(\sym)
    .endm

    -#ifdef CONFIG_TRACING
    -.macro trace_idtentry sym do_sym has_error_code:req
    -idtentry trace(\sym) trace(\do_sym) has_error_code=\has_error_code
    -idtentry \sym \do_sym has_error_code=\has_error_code
    -.endm
    -#else
    -.macro trace_idtentry sym do_sym has_error_code:req
    -idtentry \sym \do_sym has_error_code=\has_error_code
    -.endm
    -#endif
    -
    idtentry divide_error do_divide_error has_error_code=0
    idtentry overflow do_overflow has_error_code=0
    idtentry bounds do_bounds has_error_code=0
    @@ -1096,7 +1085,7 @@ idtentry xen_stack_segment do_stack_segment has_error_code=1
    #endif

    idtentry general_protection do_general_protection has_error_code=1
    -trace_idtentry page_fault do_page_fault has_error_code=1
    +idtentry page_fault do_page_fault has_error_code=1

    #ifdef CONFIG_KVM_GUEST
    idtentry async_page_fault do_async_page_fault has_error_code=1
    diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
    index 01fd0a7..b4f322d 100644
    --- a/arch/x86/include/asm/traps.h
    +++ b/arch/x86/include/asm/traps.h
    @@ -39,7 +39,6 @@ asmlinkage void machine_check(void);
    asmlinkage void simd_coprocessor_error(void);

    #ifdef CONFIG_TRACING
    -asmlinkage void trace_page_fault(void);
    #define trace_stack_segment stack_segment
    #define trace_divide_error divide_error
    #define trace_bounds bounds
    @@ -54,6 +53,7 @@ asmlinkage void trace_page_fault(void);
    #define trace_alignment_check alignment_check
    #define trace_simd_coprocessor_error simd_coprocessor_error
    #define trace_async_page_fault async_page_fault
    +#define trace_page_fault page_fault
    #endif

    dotraplinkage void do_divide_error(struct pt_regs *, long);
    @@ -74,14 +74,6 @@ asmlinkage struct pt_regs *sync_regs(struct pt_regs *);
    #endif
    dotraplinkage void do_general_protection(struct pt_regs *, long);
    dotraplinkage void do_page_fault(struct pt_regs *, unsigned long);
    -#ifdef CONFIG_TRACING
    -dotraplinkage void trace_do_page_fault(struct pt_regs *, unsigned long);
    -#else
    -static inline void trace_do_page_fault(struct pt_regs *regs, unsigned long error)
    -{
    - do_page_fault(regs, error);
    -}
    -#endif
    dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *, long);
    dotraplinkage void do_coprocessor_error(struct pt_regs *, long);
    dotraplinkage void do_alignment_check(struct pt_regs *, long);
    diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
    index d04e30e..6ed9242 100644
    --- a/arch/x86/kernel/kvm.c
    +++ b/arch/x86/kernel/kvm.c
    @@ -263,7 +263,7 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code)

    switch (kvm_read_and_reset_pf_reason()) {
    default:
    - trace_do_page_fault(regs, error_code);
    + do_page_fault(regs, error_code);
    break;
    case KVM_PV_REASON_PAGE_NOT_PRESENT:
    /* page is swapped out by the host. */
    diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
    index 2a1fa10c..58d7b3a 100644
    --- a/arch/x86/mm/fault.c
    +++ b/arch/x86/mm/fault.c
    @@ -1254,10 +1254,6 @@ static inline bool smap_violation(int error_code, struct pt_regs *regs)
    * This routine handles page faults. It determines the address,
    * and the problem, and then passes it off to one of the appropriate
    * routines.
    - *
    - * This function must have noinline because both callers
    - * {,trace_}do_page_fault() have notrace on. Having this an actual function
    - * guarantees there's a function trace entry.
    */
    static noinline void
    __do_page_fault(struct pt_regs *regs, unsigned long error_code,
    @@ -1490,27 +1486,6 @@ good_area:
    }
    NOKPROBE_SYMBOL(__do_page_fault);

    -dotraplinkage void notrace
    -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;
    -
    - /*
    - * 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.
    - */
    -
    - prev_state = exception_enter();
    - __do_page_fault(regs, error_code, address);
    - exception_exit(prev_state);
    -}
    -NOKPROBE_SYMBOL(do_page_fault);
    -
    -#ifdef CONFIG_TRACING
    static nokprobe_inline void
    trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
    unsigned long error_code)
    @@ -1521,22 +1496,24 @@ trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
    trace_page_fault_kernel(address, regs, error_code);
    }

    +/*
    + * We must have this function blacklisted from kprobes, tagged with 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}() contains all sorts of tracepoints.
    + */
    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)
    {
    - /*
    - * 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.
    - */
    - unsigned long address = read_cr2();
    + unsigned long address = read_cr2(); /* Get the faulting address */
    enum ctx_state prev_state;

    prev_state = exception_enter();
    - trace_page_fault_entries(address, regs, error_code);
    + if (trace_irqvectors_enabled())
    + trace_page_fault_entries(address, regs, error_code);
    +
    __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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