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Commit 11a7ffb0 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

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: default avatarThomas 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: default avatarIngo Molnar <mingo@kernel.org>
parent 2feb1b31

arch/x86/entry/entry_32.S

+0 −8
Original line number Diff line number Diff line
@@ -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

arch/x86/entry/entry_64.S

+1 −12
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/traps.h

+1 −9
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/kvm.c

+1 −1
Original line number Diff line number Diff line
@@ -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. */

arch/x86/mm/fault.c

+13 −36
Original line number Diff line number Diff line
@@ -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 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, 
}

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);

}



dotraplinkage void notrace

trace_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.

 * 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.

 */

	unsigned long address = read_cr2();

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;



	prev_state = exception_enter();

	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);