[patch V3 07/44] x86/traps: Simplify pagefault tracing logic

Thomas Gleixner
2017-08-28T07:03:31Z

[-- Attachment #1: x86-traps--Simplyfy-pagefault-tracing-logic.patch --]
[-- Type: text/plain, Size: 6319 bytes --]

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>
---
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(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -891,14 +891,6 @@ BUILD_INTERRUPT3(hyperv_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
--- 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_segm
#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
--- 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(str
#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);
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -263,7 +263,7 @@ do_async_page_fault(struct pt_regs *regs

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. */
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1254,10 +1254,6 @@ static inline bool smap_violation(int er
* 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 @@ static noinline void
}
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 a
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);