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 <[email protected]>
---
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
Hi Harvey,
Harvey Harrison wrote:
> 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
Sure, that's right.
However, since other architectures also have notify_page_fault(),
I think all of those code might better be changed same time for
maintainability.
Thanks,
> Signed-off-by: Harvey Harrison <[email protected]>
> ---
> 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))
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: [email protected], [email protected]
On Wed, 2008-01-02 at 21:36 -0500, Masami Hiramatsu wrote:
> Hi Harvey,
>
> Harvey Harrison wrote:
> > 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
>
> Sure, that's right.
> However, since other architectures also have notify_page_fault(),
> I think all of those code might better be changed same time for
> maintainability.
>
How about a static inline in linux/kprobes.h with a big comment above
about when/why the !preemptible() check is sufficient?
Harvey
Harvey Harrison wrote:
> On Wed, 2008-01-02 at 21:36 -0500, Masami Hiramatsu wrote:
>> Hi Harvey,
>>
>> Harvey Harrison wrote:
>>> 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
>> Sure, that's right.
>> However, since other architectures also have notify_page_fault(),
>> I think all of those code might better be changed same time for
>> maintainability.
>>
>
> How about a static inline in linux/kprobes.h with a big comment above
> about when/why the !preemptible() check is sufficient?
Hmm, fault handling depends on the architecture. But current
notify_page_fault()s are very similar. I think unifying it is good idea.
We will be happy to review that if you send it.
Many thanks!
>
> Harvey
>
>
>
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: [email protected], [email protected]
* Harvey Harrison <[email protected]> wrote:
> 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 <[email protected]>
hm, this doesnt apply:
Hunk #3 FAILED at 426.
Hunk #4 succeeded at 413 (offset -22 lines).
1 out of 4 hunks FAILED -- rejects in file arch/x86/mm/fault_32.c
patching file arch/x86/mm/fault_64.c
Hunk #3 FAILED at 476.
Hunk #4 succeeded at 475 (offset -10 lines).
1 out of 4 hunks FAILED -- rejects in file arch/x86/mm/fault_64.c
could you double-check x86.git#mm, perhaps we are out of sync with a
patch somewhere?
Ingo