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    Subject[PATCHv2] kprobes: Introduce is_kprobe_fault()
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    Date
    Use a central is_kprobe_fault() inline in kprobes.h to remove all
    of the arch-dependant, practically identical implementations in
    avr32, ia64, powerpc, s390, sparc64, and x86.

    avr32 was the only arch without the preempt_disable/enable pair
    in its notify_page_fault implementation.

    This uncovered a possible bug in the s390 version as that purely
    copied the x86 version unconditionally passing 14 as the trapnr
    rather than the error_code parameter.

    Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
    ---
    Andrew, update to my previous patch, with relevant (I hope)
    maintainers CC'd. Patch against v2.6.24-rc7

    X86_32 is ignored for now as it truly needs user_mode_vm
    in the implementation.

    arch/avr32/mm/fault.c | 21 +--------------------
    arch/ia64/mm/fault.c | 24 +-----------------------
    arch/powerpc/mm/fault.c | 25 +------------------------
    arch/s390/mm/fault.c | 25 +------------------------
    arch/sparc64/mm/fault.c | 23 +----------------------
    arch/x86/mm/fault_64.c | 26 ++------------------------
    include/linux/kprobes.h | 19 +++++++++++++++++++
    7 files changed, 26 insertions(+), 137 deletions(-)

    diff --git a/arch/avr32/mm/fault.c b/arch/avr32/mm/fault.c
    index 6560cb1..a95cce2 100644
    --- a/arch/avr32/mm/fault.c
    +++ b/arch/avr32/mm/fault.c
    @@ -20,25 +20,6 @@
    #include <asm/tlb.h>
    #include <asm/uaccess.h>

    -#ifdef CONFIG_KPROBES
    -static inline int notify_page_fault(struct pt_regs *regs, int trap)
    -{
    - int ret = 0;
    -
    - if (!user_mode(regs)) {
    - if (kprobe_running() && kprobe_fault_handler(regs, trap))
    - ret = 1;
    - }
    -
    - return ret;
    -}
    -#else
    -static inline int notify_page_fault(struct pt_regs *regs, int trap)
    -{
    - return 0;
    -}
    -#endif
    -
    int exception_trace = 1;

    /*
    @@ -66,7 +47,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
    int code;
    int fault;

    - if (notify_page_fault(regs, ecr))
    + if (is_kprobe_fault(regs, ecr))
    return;

    address = sysreg_read(TLBEAR);
    diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
    index 7571076..1696805 100644
    --- a/arch/ia64/mm/fault.c
    +++ b/arch/ia64/mm/fault.c
    @@ -18,28 +18,6 @@

    extern void die (char *, struct pt_regs *, long);

    -#ifdef CONFIG_KPROBES
    -static inline int notify_page_fault(struct pt_regs *regs, int trap)
    -{
    - int ret = 0;
    -
    - if (!user_mode(regs)) {
    - /* kprobe_running() needs smp_processor_id() */
    - preempt_disable();
    - if (kprobe_running() && kprobes_fault_handler(regs, trap))
    - ret = 1;
    - preempt_enable();
    - }
    -
    - return ret;
    -}
    -#else
    -static inline int notify_page_fault(struct pt_regs *regs, int trap)
    -{
    - return 0;
    -}
    -#endif
    -
    /*
    * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
    * (inside region 5, on ia64) and that page is present.
    @@ -106,7 +84,7 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
    /*
    * This is to handle the kprobes on user space access instructions
    */
    - if (notify_page_fault(regs, TRAP_BRKPT))
    + if (is_kprobe_fault(regs, TRAP_BRKPT))
    return;

    down_read(&mm->mmap_sem);
    diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
    index 8135da0..00df6f9 100644
    --- a/arch/powerpc/mm/fault.c
    +++ b/arch/powerpc/mm/fault.c
    @@ -39,29 +39,6 @@
    #include <asm/tlbflush.h>
    #include <asm/siginfo.h>

    -
    -#ifdef CONFIG_KPROBES
    -static inline int notify_page_fault(struct pt_regs *regs)
    -{
    - int ret = 0;
    -
    - /* kprobe_running() needs smp_processor_id() */
    - if (!user_mode(regs)) {
    - preempt_disable();
    - if (kprobe_running() && kprobe_fault_handler(regs, 11))
    - ret = 1;
    - preempt_enable();
    - }
    -
    - return ret;
    -}
    -#else
    -static inline int notify_page_fault(struct pt_regs *regs)
    -{
    - return 0;
    -}
    -#endif
    -
    /*
    * Check whether the instruction at regs->nip is a store using
    * an update addressing form which will update r1.
    @@ -164,7 +141,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
    is_write = error_code & ESR_DST;
    #endif /* CONFIG_4xx || CONFIG_BOOKE */

    - if (notify_page_fault(regs))
    + if (is_kprobe_fault(regs, 11))
    return 0;

    if (trap == 0x300) {
    diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
    index 2456b52..59d3f0e 100644
    --- a/arch/s390/mm/fault.c
    +++ b/arch/s390/mm/fault.c
    @@ -51,29 +51,6 @@ extern int sysctl_userprocess_debug;

    extern void die(const char *,struct pt_regs *,long);

    -#ifdef CONFIG_KPROBES
    -static inline int notify_page_fault(struct pt_regs *regs, long err)
    -{
    - 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
    -static inline int notify_page_fault(struct pt_regs *regs, long err)
    -{
    - return 0;
    -}
    -#endif
    -
    -
    /*
    * Unlock any spinlocks which will prevent us from getting the
    * message out.
    @@ -309,7 +286,7 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int write)
    int si_code;
    int fault;

    - if (notify_page_fault(regs, error_code))
    + if (is_kprobe_fault(regs, 14))
    return;

    tsk = current;
    diff --git a/arch/sparc64/mm/fault.c b/arch/sparc64/mm/fault.c
    index e2027f2..bb5c36a 100644
    --- a/arch/sparc64/mm/fault.c
    +++ b/arch/sparc64/mm/fault.c
    @@ -31,27 +31,6 @@
    #include <asm/sections.h>
    #include <asm/mmu_context.h>

    -#ifdef CONFIG_KPROBES
    -static inline int notify_page_fault(struct pt_regs *regs)
    -{
    - int ret = 0;
    -
    - /* kprobe_running() needs smp_processor_id() */
    - if (!user_mode(regs)) {
    - preempt_disable();
    - if (kprobe_running() && kprobe_fault_handler(regs, 0))
    - ret = 1;
    - preempt_enable();
    - }
    - return ret;
    -}
    -#else
    -static inline int notify_page_fault(struct pt_regs *regs)
    -{
    - return 0;
    -}
    -#endif
    -
    /*
    * To debug kernel to catch accesses to certain virtual/physical addresses.
    * Mode = 0 selects physical watchpoints, mode = 1 selects virtual watchpoints.
    @@ -280,7 +259,7 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)

    fault_code = get_thread_fault_code();

    - if (notify_page_fault(regs))
    + if (is_kprobe_fault(regs, 0))
    return;

    si_code = SEGV_MAPERR;
    diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c
    index 0e26230..376e218 100644
    --- a/arch/x86/mm/fault_64.c
    +++ b/arch/x86/mm/fault_64.c
    @@ -41,28 +41,6 @@
    #define PF_RSVD (1<<3)
    #define PF_INSTR (1<<4)

    -#ifdef CONFIG_KPROBES
    -static inline int notify_page_fault(struct pt_regs *regs)
    -{
    - 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
    -static inline int notify_page_fault(struct pt_regs *regs)
    -{
    - return 0;
    -}
    -#endif
    -
    /* Sometimes the CPU reports invalid exceptions on prefetch.
    Check that here and ignore.
    Opcode checker based on code by Richard Brunner */
    @@ -343,7 +321,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
    if (vmalloc_fault(address) >= 0)
    return;
    }
    - if (notify_page_fault(regs))
    + if (is_kprobe_fault(regs, 14))
    return;
    /*
    * Don't take the mm semaphore here. If we fixup a prefetch
    @@ -352,7 +330,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
    goto bad_area_nosemaphore;
    }

    - if (notify_page_fault(regs))
    + if (is_kprobe_fault(regs, 14))
    return;

    if (likely(regs->eflags & X86_EFLAGS_IF))
    diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
    index 8189158..65c1ffb 100644
    --- a/include/linux/kprobes.h
    +++ b/include/linux/kprobes.h
    @@ -36,6 +36,7 @@
    #include <linux/spinlock.h>
    #include <linux/rcupdate.h>
    #include <linux/mutex.h>
    +#include <linux/hardirq.h>

    #ifdef CONFIG_KPROBES
    #include <asm/kprobes.h>
    @@ -203,6 +204,20 @@ static inline struct kprobe *kprobe_running(void)
    return (__get_cpu_var(current_kprobe));
    }

    +/*
    + * If it is a kprobe pagefault we can not be premptible so return before
    + * calling kprobe_running() as it will assert on smp_processor_id if
    + * preemption is enabled.
    + */
    +static inline int is_kprobe_fault(struct pt_regs *regs, int trapnr)
    +{
    + if (!user_mode(regs) && !preemptible() && kprobe_running() &&
    + kprobe_fault_handler(regs, trapnr))
    + return 1;
    + else
    + return 0;
    +}
    +
    static inline void reset_current_kprobe(void)
    {
    __get_cpu_var(current_kprobe) = NULL;
    @@ -237,6 +252,10 @@ static inline struct kprobe *kprobe_running(void)
    {
    return NULL;
    }
    +static inline int is_kprobe_fault(struct pt_regs *regs, int trapnr)
    +{
    + return 0;
    +}
    static inline int register_kprobe(struct kprobe *p)
    {
    return -ENOSYS;
    --
    1.5.4.rc2.1117.ge5809


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