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Message-ID: <477C4A42.1010701@redhat.com>
Date: Wed, 02 Jan 2008 21:36:50 -0500
From: Masami Hiramatsu <mhiramat@...hat.com>
To: Harvey Harrison <harvey.harrison@...il.com>
CC: Ingo Molnar <mingo@...e.hu>, qbarnes <qbarnes@...il.com>,
"H. Peter Anvin" <hpa@...or.com>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Jim Keniston <jkenisto@...ibm.com>, davem@...emloft.net,
Keshavamurthy Anil S <anil.s.keshavamurthy@...el.com>
Subject: Re: [PATCH] x86: Use is_kprobe_fault to better match usage
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 <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))
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@...hat.com, masami.hiramatsu.pt@...achi.com
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