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Date: Wed, 02 Jan 2008 17:05:23 -0800
From: Harvey Harrison <harvey.harrison@...il.com>
To: Ingo Molnar <mingo@...e.hu>, qbarnes <qbarnes@...il.com>
Cc: "H. Peter Anvin" <hpa@...or.com>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] x86: Use is_kprobe_fault to better match usage
Currently the notify_page_fault helper is used to test it the page
fault was caused by a kprobe causing an early return from do_page_fault.
Change the name of the helper to is_kprobe_fault to match the usage and
remove the preempt_disable/enable pair around kprobe_running() with an
explicit test for preemption. The idea for this comes from a patch
by Quentin Barnes to kprobes.c
Signed-off-by: Harvey Harrison <harvey.harrison@...il.com>
---
Ingo, this may not be functionally equivalent, feel free to yank it out
if there is any trouble, but from what I've seen it should be OK.
Did you ever find a good kprobes test?
arch/x86/mm/fault_32.c | 30 ++++++++++++++----------------
arch/x86/mm/fault_64.c | 30 ++++++++++++++----------------
2 files changed, 28 insertions(+), 32 deletions(-)
diff --git a/arch/x86/mm/fault_32.c b/arch/x86/mm/fault_32.c
index 051a4ec..5c48cc2 100644
--- a/arch/x86/mm/fault_32.c
+++ b/arch/x86/mm/fault_32.c
@@ -12,6 +12,7 @@
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/smp.h>
+#include <linux/hardirq.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/tty.h>
@@ -42,23 +43,20 @@
#define PF_RSVD (1<<3)
#define PF_INSTR (1<<4)
-static inline int notify_page_fault(struct pt_regs *regs)
+static inline int is_kprobe_fault(struct pt_regs *regs)
{
-#ifdef CONFIG_KPROBES
int ret = 0;
-
- /* kprobe_running() needs smp_processor_id() */
- if (!user_mode_vm(regs)) {
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, 14))
- ret = 1;
- preempt_enable();
- }
-
- return ret;
-#else
- return 0;
+#ifdef CONFIG_KPROBES
+ /*
+ * If it is a kprobe fault we can not be premptible so return before
+ * calling kprobe_running() as it will assert on smp_processor_id if
+ * preemption is enabled.
+ */
+ if (!user_mode_vm(regs) && !preemptible() && kprobe_running() &&
+ kprobe_fault_handler(regs, 14))
+ ret = 1;
#endif
+ return ret;
}
#ifdef CONFIG_X86_32
@@ -428,7 +426,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
return;
}
#endif
- if (notify_page_fault(regs))
+ if (is_kprobe_fault(regs))
return;
/*
* Don't take the mm semaphore here. If we fixup a prefetch
@@ -437,7 +435,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
goto bad_area_nosemaphore;
}
- if (notify_page_fault(regs))
+ if (is_kprobe_fault(regs))
return;
/* It's safe to allow irq's after cr2 has been saved and the vmalloc
diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c
index 97b92b6..09008e5 100644
--- a/arch/x86/mm/fault_64.c
+++ b/arch/x86/mm/fault_64.c
@@ -13,6 +13,7 @@
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/smp.h>
+#include <linux/hardirq.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/tty.h>
@@ -45,23 +46,20 @@
#define PF_RSVD (1<<3)
#define PF_INSTR (1<<4)
-static inline int notify_page_fault(struct pt_regs *regs)
+static inline int is_kprobe_fault(struct pt_regs *regs)
{
-#ifdef CONFIG_KPROBES
int ret = 0;
-
- /* kprobe_running() needs smp_processor_id() */
- if (!user_mode(regs)) {
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, 14))
- ret = 1;
- preempt_enable();
- }
-
- return ret;
-#else
- return 0;
+#ifdef CONFIG_KPROBES
+ /*
+ * If it is a kprobe fault we can not be premptible so return before
+ * calling kprobe_running() as it will assert on smp_processor_id if
+ * preemption is enabled.
+ */
+ if (!user_mode_vm(regs) && !preemptible() && kprobe_running() &&
+ kprobe_fault_handler(regs, 14))
+ ret = 1;
#endif
+ return ret;
}
#ifdef CONFIG_X86_32
@@ -478,7 +476,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
return;
}
#endif
- if (notify_page_fault(regs))
+ if (is_kprobe_fault(regs))
return;
/*
* Don't take the mm semaphore here. If we fixup a prefetch
@@ -487,7 +485,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
goto bad_area_nosemaphore;
}
- if (notify_page_fault(regs))
+ if (is_kprobe_fault(regs))
return;
if (likely(regs->flags & X86_EFLAGS_IF))
--
1.5.4.rc2.1097.gb6e0d
--
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