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Subject[RFC][PATCH] Introduce page fault tracepoint
This patch introduces page fault tracepoints to x86 architecture
by switching IDT.

[Use case of page fault events]

Two events, for user and kernel spaces, are introduced at the beginning of
page fault handler.

- User space event
There is a request of page fault event for user space as below.

http://marc.info/?l=linux-mm&m=136807959830182&w=2
http://marc.info/?l=linux-mm&m=136807959130175&w=2

- Kernel space event:
Overhead in kernel space is measurable by enabling it.

[Creating IDT]

A way to create IDT is as below.

- Introduce set_intr_gate_raw() to register just non-trace handler to IDT.
This is used at boot time which tracing is disabled.
- Make set_intr_gate() macro so that it can register trace handler to
trace IDT and non-trace handler to normal IDT.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
---
arch/x86/include/asm/desc.h | 33 +++++++++++++++++---
arch/x86/include/asm/hw_irq.h | 14 ++++++++-
arch/x86/include/asm/trace/exceptions.h | 51 +++++++++++++++++++++++++++++++
arch/x86/include/asm/traps.h | 22 +++++++++++++
arch/x86/kernel/entry_32.S | 10 ++++++
arch/x86/kernel/entry_64.S | 13 +++++++-
arch/x86/kernel/head64.c | 2 +-
arch/x86/kernel/irqinit.c | 2 +-
arch/x86/kernel/kvm.c | 2 +-
arch/x86/kernel/traps.c | 28 ++++++++--------
arch/x86/mm/Makefile | 2 +
arch/x86/mm/fault.c | 22 +++++++++++++
12 files changed, 177 insertions(+), 24 deletions(-)
create mode 100644 arch/x86/include/asm/trace/exceptions.h

diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index b90e5df..c04302b 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -327,10 +327,28 @@ static inline void write_trace_idt_entry(int entry, const gate_desc *gate)
{
write_idt_entry(trace_idt_table, entry, gate);
}
+
+static inline void _trace_set_gate(int gate, unsigned type, void *addr,
+ unsigned dpl, unsigned ist, unsigned seg)
+{
+ gate_desc s;
+
+ pack_gate(&s, type, (unsigned long)addr, dpl, ist, seg);
+ /*
+ * does not need to be atomic because it is only done once at
+ * setup time
+ */
+ write_trace_idt_entry(gate, &s);
+}
#else
static inline void write_trace_idt_entry(int entry, const gate_desc *gate)
{
}
+
+static inline void _trace_set_gate(int gate, unsigned type, void *addr,
+ unsigned dpl, unsigned ist, unsigned seg)
+{
+}
#endif

static inline void _set_gate(int gate, unsigned type, void *addr,
@@ -353,12 +371,20 @@ static inline void _set_gate(int gate, unsigned type, void *addr,
* Pentium F0 0F bugfix can have resulted in the mapped
* IDT being write-protected.
*/
-static inline void set_intr_gate(unsigned int n, void *addr)
+static inline void set_intr_gate_raw(unsigned int n, void *addr)
{
BUG_ON((unsigned)n > 0xFF);
_set_gate(n, GATE_INTERRUPT, addr, 0, 0, __KERNEL_CS);
}

+#define set_intr_gate(n, addr) \
+ do { \
+ BUG_ON((unsigned)n > 0xFF); \
+ _set_gate(n, GATE_INTERRUPT, addr, 0, 0, __KERNEL_CS); \
+ _trace_set_gate(n, GATE_INTERRUPT, trace_##addr, 0, 0, \
+ __KERNEL_CS); \
+ } while (0)
+
extern int first_system_vector;
/* used_vectors is BITMAP for irq is not managed by percpu vector_irq */
extern unsigned long used_vectors[];
@@ -395,10 +421,7 @@ static inline void trace_set_intr_gate(unsigned int gate, void *addr)
#define __trace_alloc_intr_gate(n, addr)
#endif

-static inline void __alloc_intr_gate(unsigned int n, void *addr)
-{
- set_intr_gate(n, addr);
-}
+#define __alloc_intr_gate(n, addr) set_intr_gate(n, addr)

#define alloc_intr_gate(n, addr) \
do { \
diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index e4ac559..fbd73b7 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -89,10 +89,22 @@ extern void trace_reschedule_interrupt(void);
extern void trace_threshold_interrupt(void);
extern void trace_call_function_interrupt(void);
extern void trace_call_function_single_interrupt(void);
+#else /* CONFIG_TRACING */
+#define trace_apic_timer_interrupt apic_timer_interrupt
+#define trace_x86_platform_ipi x86_platform_ipi
+#define trace_error_interrupt error_interrupt
+#define trace_irq_work_interrupt irq_work_interrupt
+#define trace_spurious_interrupt spurious_interrupt
+#define trace_thermal_interrupt thermal_interrupt
+#define trace_reschedule_interrupt reschedule_interrupt
+#define trace_threshold_interrupt threshold_interrupt
+#define trace_call_function_interrupt call_function_interrupt
+#define trace_call_function_single_interrupt call_function_single_interrupt
+#endif
+
#define trace_irq_move_cleanup_interrupt irq_move_cleanup_interrupt
#define trace_reboot_interrupt reboot_interrupt
#define trace_kvm_posted_intr_ipi kvm_posted_intr_ipi
-#endif /* CONFIG_TRACING */

/* IOAPIC */
#define IO_APIC_IRQ(x) (((x) >= NR_IRQS_LEGACY) || ((1<<(x)) & io_apic_irqs))
diff --git a/arch/x86/include/asm/trace/exceptions.h b/arch/x86/include/asm/trace/exceptions.h
new file mode 100644
index 0000000..660fcf1
--- /dev/null
+++ b/arch/x86/include/asm/trace/exceptions.h
@@ -0,0 +1,51 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM exceptions
+
+#if !defined(_TRACE_PAGE_FAULT_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_PAGE_FAULT_H
+
+#include <linux/tracepoint.h>
+
+extern void trace_irq_vector_regfunc(void);
+extern void trace_irq_vector_unregfunc(void);
+
+DECLARE_EVENT_CLASS(x86_exceptions,
+
+ TP_PROTO(unsigned long address, struct pt_regs *regs,
+ unsigned long error_code),
+
+ TP_ARGS(address, regs, error_code),
+
+ TP_STRUCT__entry(
+ __field( unsigned long, address )
+ __field( struct pt_regs *, regs )
+ __field( unsigned long, error_code )
+ ),
+
+ TP_fast_assign(
+ __entry->address = address;
+ __entry->regs = regs;
+ __entry->error_code = error_code;
+ ),
+
+ TP_printk("address=0x%lx regs=0x%p error_code=0x%lx",
+ __entry->address, __entry->regs, __entry->error_code) );
+
+#define DEFINE_PAGE_FAULT_EVENT(name) \
+DEFINE_EVENT_FN(x86_exceptions, name, \
+ TP_PROTO(unsigned long address, struct pt_regs *regs, \
+ unsigned long error_code), \
+ TP_ARGS(address, regs, error_code), \
+ trace_irq_vector_regfunc, \
+ trace_irq_vector_unregfunc);
+
+DEFINE_PAGE_FAULT_EVENT(user_page_fault);
+DEFINE_PAGE_FAULT_EVENT(kernel_page_fault);
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#define TRACE_INCLUDE_FILE exceptions
+#endif /* _TRACE_PAGE_FAULT_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 88eae2a..adf9258 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -41,6 +41,25 @@ asmlinkage void machine_check(void);
#endif /* CONFIG_X86_MCE */
asmlinkage void simd_coprocessor_error(void);

+#ifdef CONFIG_TRACING
+asmlinkage void trace_page_fault(void);
+#else
+#define trace_page_fault page_fault
+#endif
+#define trace_divide_error divide_error
+#define trace_bounds bounds
+#define trace_invalid_op invalid_op
+#define trace_device_not_available device_not_available
+#define trace_coprocessor_segment_overrun coprocessor_segment_overrun
+#define trace_invalid_TSS invalid_TSS
+#define trace_segment_not_present segment_not_present
+#define trace_general_protection general_protection
+#define trace_spurious_interrupt_bug spurious_interrupt_bug
+#define trace_coprocessor_error coprocessor_error
+#define trace_alignment_check alignment_check
+#define trace_simd_coprocessor_error simd_coprocessor_error
+#define trace_async_page_fault async_page_fault
+
dotraplinkage void do_divide_error(struct pt_regs *, long);
dotraplinkage void do_debug(struct pt_regs *, long);
dotraplinkage void do_nmi(struct pt_regs *, long);
@@ -59,6 +78,9 @@ asmlinkage __kprobes 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);
+#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/entry_32.S b/arch/x86/kernel/entry_32.S
index 2cfbc3a..c9eb4e2 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1244,6 +1244,16 @@ return_to_handler:
*/
.pushsection .kprobes.text, "ax"

+#ifdef CONFIG_TRACING
+ENTRY(trace_page_fault)
+ RING0_EC_FRAME
+ ASM_CLAC
+ pushl_cfi $trace_do_page_fault
+ jmp error_code
+ CFI_ENDPROC
+END(trace_page_fault)
+#endif
+
ENTRY(page_fault)
RING0_EC_FRAME
ASM_CLAC
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 1b69951..5136404 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1295,6 +1295,17 @@ ENTRY(\sym)
END(\sym)
.endm

+#ifdef CONFIG_TRACING
+.macro trace_errorentry sym do_sym
+errorentry trace(\sym) trace(\do_sym)
+errorentry \sym \do_sym
+.endm
+#else
+.macro trace_errorentry sym do_sym
+errorentry \sym \do_sym
+.endm
+#endif
+
/* error code is on the stack already */
.macro paranoiderrorentry sym do_sym
ENTRY(\sym)
@@ -1497,7 +1508,7 @@ zeroentry xen_int3 do_int3
errorentry xen_stack_segment do_stack_segment
#endif
errorentry general_protection do_general_protection
-errorentry page_fault do_page_fault
+trace_errorentry page_fault do_page_fault
#ifdef CONFIG_KVM_GUEST
errorentry async_page_fault do_async_page_fault
#endif
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 55b6761..67a0649 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -162,7 +162,7 @@ void __init x86_64_start_kernel(char * real_mode_data)
clear_bss();

for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
- set_intr_gate(i, &early_idt_handlers[i]);
+ set_intr_gate_raw(i, &early_idt_handlers[i]);
load_idt((const struct desc_ptr *)&idt_descr);

copy_bootdata(__va(real_mode_data));
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index a2a1fbc..2ca2354 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -206,7 +206,7 @@ void __init native_init_IRQ(void)
i = FIRST_EXTERNAL_VECTOR;
for_each_clear_bit_from(i, used_vectors, NR_VECTORS) {
/* IA32_SYSCALL_VECTOR could be used in trap_init already. */
- set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
+ set_intr_gate_raw(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
}

if (!acpi_ioapic && !of_ioapic)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index a96d32c..12b384e 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -462,7 +462,7 @@ static struct notifier_block kvm_cpu_notifier = {

static void __init kvm_apf_trap_init(void)
{
- set_intr_gate(14, &async_page_fault);
+ set_intr_gate(14, async_page_fault);
}

void __init kvm_guest_init(void)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 1b23a1c..eadd251 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -709,7 +709,7 @@ void __init early_trap_init(void)
/* int3 can be called from all */
set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK);
#ifdef CONFIG_X86_32
- set_intr_gate(X86_TRAP_PF, &page_fault);
+ set_intr_gate(X86_TRAP_PF, page_fault);
#endif
load_idt(&idt_descr);
}
@@ -717,7 +717,7 @@ void __init early_trap_init(void)
void __init early_trap_pf_init(void)
{
#ifdef CONFIG_X86_64
- set_intr_gate(X86_TRAP_PF, &page_fault);
+ set_intr_gate(X86_TRAP_PF, page_fault);
#endif
}

@@ -733,30 +733,30 @@ void __init trap_init(void)
early_iounmap(p, 4);
#endif

- set_intr_gate(X86_TRAP_DE, &divide_error);
+ set_intr_gate(X86_TRAP_DE, divide_error);
set_intr_gate_ist(X86_TRAP_NMI, &nmi, NMI_STACK);
/* int4 can be called from all */
set_system_intr_gate(X86_TRAP_OF, &overflow);
- set_intr_gate(X86_TRAP_BR, &bounds);
- set_intr_gate(X86_TRAP_UD, &invalid_op);
- set_intr_gate(X86_TRAP_NM, &device_not_available);
+ set_intr_gate(X86_TRAP_BR, bounds);
+ set_intr_gate(X86_TRAP_UD, invalid_op);
+ set_intr_gate(X86_TRAP_NM, device_not_available);
#ifdef CONFIG_X86_32
set_task_gate(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS);
#else
set_intr_gate_ist(X86_TRAP_DF, &double_fault, DOUBLEFAULT_STACK);
#endif
- set_intr_gate(X86_TRAP_OLD_MF, &coprocessor_segment_overrun);
- set_intr_gate(X86_TRAP_TS, &invalid_TSS);
- set_intr_gate(X86_TRAP_NP, &segment_not_present);
+ set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun);
+ set_intr_gate(X86_TRAP_TS, invalid_TSS);
+ set_intr_gate(X86_TRAP_NP, segment_not_present);
set_intr_gate_ist(X86_TRAP_SS, &stack_segment, STACKFAULT_STACK);
- set_intr_gate(X86_TRAP_GP, &general_protection);
- set_intr_gate(X86_TRAP_SPURIOUS, &spurious_interrupt_bug);
- set_intr_gate(X86_TRAP_MF, &coprocessor_error);
- set_intr_gate(X86_TRAP_AC, &alignment_check);
+ set_intr_gate(X86_TRAP_GP, general_protection);
+ set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug);
+ set_intr_gate(X86_TRAP_MF, coprocessor_error);
+ set_intr_gate(X86_TRAP_AC, alignment_check);
#ifdef CONFIG_X86_MCE
set_intr_gate_ist(X86_TRAP_MC, &machine_check, MCE_STACK);
#endif
- set_intr_gate(X86_TRAP_XF, &simd_coprocessor_error);
+ set_intr_gate(X86_TRAP_XF, simd_coprocessor_error);

/* Reserve all the builtin and the syscall vector: */
for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++)
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 23d8e5f..6a19ad9 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -6,6 +6,8 @@ nostackp := $(call cc-option, -fno-stack-protector)
CFLAGS_physaddr.o := $(nostackp)
CFLAGS_setup_nx.o := $(nostackp)

+CFLAGS_fault.o := -I$(src)/../include/asm/trace
+
obj-$(CONFIG_X86_PAT) += pat_rbtree.o
obj-$(CONFIG_SMP) += tlb.o

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 654be4a..f515154 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -20,6 +20,9 @@
#include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
#include <asm/fixmap.h> /* VSYSCALL_START */

+#define CREATE_TRACE_POINTS
+#include <asm/trace/exceptions.h>
+
/*
* Page fault error code bits:
*
@@ -1230,3 +1233,22 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
__do_page_fault(regs, error_code);
exception_exit(prev_state);
}
+
+static void trace_page_fault_entries(struct pt_regs *regs,
+ unsigned long error_code)
+{
+ if (user_mode(regs))
+ trace_user_page_fault(read_cr2(), regs, error_code);
+ else
+ trace_kernel_page_fault(read_cr2(), regs, error_code);
+}
+
+dotraplinkage void __kprobes
+trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
+{
+ enum ctx_state prev_state;
+ prev_state = exception_enter();
+ trace_page_fault_entries(regs, error_code);
+ __do_page_fault(regs, error_code);
+ exception_exit(prev_state);
+}
--
1.7.1


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