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Date: Wed, 5 Mar 2014 13:36:35 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: mingo@...nel.org, hpa@...or.com, paulus@...ba.org,
linux-kernel@...r.kernel.org, acme@...stprotocols.net,
seiji.aguchi@....com, jolsa@...hat.com, vincent.weaver@...ne.edu,
tglx@...utronix.de, hpa@...ux.intel.com,
linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86, trace: Fix CR2 corruption when tracing
page faults
On Wed, Mar 05, 2014 at 01:25:35PM +0100, Peter Zijlstra wrote:
> On Wed, Mar 05, 2014 at 07:20:22AM -0500, Steven Rostedt wrote:
> > On Wed, 5 Mar 2014 12:14:15 +0100
> > Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > Please no! I used tracing of the do_page_fault function all the time.
> > It is very useful.
>
> Why do you trace do_page_fault and not the __do_page_fault() function?
> do_page_fault() is a minimal wrapper which doesn't actually do all that
> much?
Here, something like so; then you can still trace your do_page_fault().
It also fixes up trace_page_fault_entries() to not re-read the cr2.
---
arch/x86/include/asm/traps.h | 2 +-
arch/x86/kernel/entry_32.S | 2 +-
arch/x86/kernel/entry_64.S | 2 +-
arch/x86/kernel/kvm.c | 2 +-
arch/x86/mm/fault.c | 21 ++++++++++-----------
5 files changed, 14 insertions(+), 15 deletions(-)
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 58d66fe06b61..1280f72deea8 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -71,7 +71,7 @@ dotraplinkage void do_double_fault(struct pt_regs *, long);
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);
+dotraplinkage void normal_do_page_fault(struct pt_regs *, unsigned long);
#ifdef CONFIG_TRACING
dotraplinkage void trace_do_page_fault(struct pt_regs *, unsigned long);
#endif
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index a2a4f4697889..9a9f64755da8 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1257,7 +1257,7 @@ END(trace_page_fault)
ENTRY(page_fault)
RING0_EC_FRAME
ASM_CLAC
- pushl_cfi $do_page_fault
+ pushl_cfi $normal_do_page_fault
ALIGN
error_code:
/* the function address is in %gs's slot on the stack */
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 1e96c3628bf2..7d49812741ac 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1491,7 +1491,7 @@ zeroentry xen_int3 do_int3
errorentry xen_stack_segment do_stack_segment
#endif
errorentry general_protection do_general_protection
-trace_errorentry page_fault do_page_fault
+trace_errorentry page_fault normal_do_page_fault
#ifdef CONFIG_KVM_GUEST
errorentry async_page_fault do_async_page_fault
#endif
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 713f1b3bad52..9e7db22ec437 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -259,7 +259,7 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
switch (kvm_read_and_reset_pf_reason()) {
default:
- do_page_fault(regs, error_code);
+ normal_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 e7fa28bf3262..576cfc3d0086 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1022,8 +1022,7 @@ static inline bool smap_violation(int error_code, struct pt_regs *regs)
* routines.
*/
static void __kprobes
-__do_page_fault(struct pt_regs *regs, unsigned long error_code,
- unsigned long address)
+do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
struct vm_area_struct *vma;
struct task_struct *tsk;
@@ -1245,28 +1244,28 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
up_read(&mm->mmap_sem);
}
-dotraplinkage void __kprobes
-do_page_fault(struct pt_regs *regs, unsigned long error_code)
+dotraplinkage void __kprobes notrace
+normal_do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
enum ctx_state prev_state;
/* Get the faulting address: */
unsigned long address = read_cr2();
prev_state = exception_enter();
- __do_page_fault(regs, error_code, address);
+ do_page_fault(regs, error_code, address);
exception_exit(prev_state);
}
-static void trace_page_fault_entries(struct pt_regs *regs,
+static void trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
unsigned long error_code)
{
if (user_mode(regs))
- trace_page_fault_user(read_cr2(), regs, error_code);
+ trace_page_fault_user(address, regs, error_code);
else
- trace_page_fault_kernel(read_cr2(), regs, error_code);
+ trace_page_fault_kernel(address, regs, error_code);
}
-dotraplinkage void __kprobes
+dotraplinkage void __kprobes notrace
trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
enum ctx_state prev_state;
@@ -1279,7 +1278,7 @@ trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
unsigned long address = read_cr2();
prev_state = exception_enter();
- trace_page_fault_entries(regs, error_code);
- __do_page_fault(regs, error_code, address);
+ trace_page_fault_entries(address, regs, error_code);
+ do_page_fault(regs, error_code, address);
exception_exit(prev_state);
}
--
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