[page fault tracepoint 2/2] x86:Instruments page fault trace event

[Francis Deslauriers <fdeslaur@xxxxxxxxx>]

Signed-off-by: Francis Deslauriers <fdeslaur@xxxxxxxxx>
Reviewed-by: Raphaël Beamonte <raphael.beamonte@xxxxxxxxx>
---
 arch/x86/mm/fault.c |   11 +++++++++++
 mm/memory.c         |    5 +++++
 2 files changed, 16 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 654be4a..e227828 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 <trace/events/fault.h>		/* trace_page_fault_*(), ...	*/
+
 /*
  * Page fault error code bits:
  *
@@ -756,12 +759,18 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 		if (likely(show_unhandled_signals))
 			show_signal_msg(regs, error_code, address, tsk);
+		trace_page_fault_entry(regs, address, error_code & PF_WRITE);
 
 		tsk->thread.cr2		= address;
 		tsk->thread.error_code	= error_code;
 		tsk->thread.trap_nr	= X86_TRAP_PF;
 
 		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
+		/*
+		 * Using -1 here, since there is no VM_FAULT flag to identify
+		 * user accesses triggering SIGSEGV.
+		 */
+		trace_page_fault_exit(-1);
 
 		return;
 	}
@@ -1185,7 +1194,9 @@ good_area:
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault:
 	 */
+	trace_page_fault_entry(regs, address, write);
 	fault = handle_mm_fault(mm, vma, address, flags);
+	trace_page_fault_exit(fault);
 
 	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
 		if (mm_fault_error(regs, error_code, address, fault))
diff --git a/mm/memory.c b/mm/memory.c
index 6dc1882..0bd86f8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -67,6 +67,8 @@
 #include <asm/tlbflush.h>
 #include <asm/pgtable.h>
 
+#include <trace/events/fault.h>
+
 #include "internal.h"
 
 #ifdef LAST_NID_NOT_IN_PAGE_FLAGS
@@ -1829,8 +1831,11 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 				if (foll_flags & FOLL_NOWAIT)
 					fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
 
+				trace_page_fault_entry(0, start,
+						foll_flags & FOLL_WRITE);
 				ret = handle_mm_fault(mm, vma, start,
 							fault_flags);
+				trace_page_fault_exit(ret);
 
 				if (ret & VM_FAULT_ERROR) {
 					if (ret & VM_FAULT_OOM)
-- 
1.7.10.4

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