Ping?
I guess this should go to 3.16 branch, shouldn't it?
(2014/05/30 12:18), Masami Hiramatsu wrote:
> On ia64 and ppc64, the function pointer does not point the
> entry address of the function, but the address of function
> discriptor (which contains the entry address and misc
> data.) Since the kprobes passes the function pointer stored
> by NOKPROBE_SYMBOL() to kallsyms_lookup_size_offset() for
> initalizing its blacklist, it fails and reports many errors
> as below.
>
> Failed to find blacklist 0001013168300000
> Failed to find blacklist 0001013000f0a000
> Failed to find blacklist 000101315f70a000
> Failed to find blacklist 000101324c80a000
> Failed to find blacklist 0001013063f0a000
> Failed to find blacklist 000101327800a000
> Failed to find blacklist 0001013277f0a000
> Failed to find blacklist 000101315a70a000
> Failed to find blacklist 0001013277e0a000
> Failed to find blacklist 000101305a20a000
> Failed to find blacklist 0001013277d0a000
> Failed to find blacklist 00010130bdc0a000
> Failed to find blacklist 00010130dc20a000
> Failed to find blacklist 000101309a00a000
> Failed to find blacklist 0001013277c0a000
> Failed to find blacklist 0001013277b0a000
> Failed to find blacklist 0001013277a0a000
> Failed to find blacklist 000101327790a000
> Failed to find blacklist 000101303140a000
> Failed to find blacklist 0001013a3280a000
>
> To fix this bug, this introduces function_entry() macro to
> retrieve the entry address from the given function pointer,
> and uses for kallsyms_lookup_size_offset() while initializing
> blacklist.
>
> Changes in v3:
> - Fix a bug to get blacklist address based on function entry
> instead of function descriptor. (Suzuki's work, Thanks!)
>
> Changes in V2:
> - Use function_entry() macro when lookin up symbols instead
> of storing it.
> - Update for the latest -next.
>
> Signed-off-by: Masami Hiramatsu <[email protected]>
> Signed-off-by: Suzuki K. Poulose <[email protected]>
> Reported-by: Tony Luck <[email protected]>
> Cc: Suzuki K. Poulose <[email protected]>
> Cc: Tony Luck <[email protected]>
> Cc: Fenghua Yu <[email protected]>
> Cc: Benjamin Herrenschmidt <[email protected]>
> Cc: Paul Mackerras <[email protected]>
> Cc: Ananth N Mavinakayanahalli <[email protected]>
> Cc: Kevin Hao <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> ---
> arch/ia64/include/asm/types.h | 2 ++
> arch/powerpc/include/asm/types.h | 11 +++++++++++
> include/linux/types.h | 4 ++++
> kernel/kprobes.c | 11 +++++++----
> 4 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/arch/ia64/include/asm/types.h b/arch/ia64/include/asm/types.h
> index 4c351b1..95279dd 100644
> --- a/arch/ia64/include/asm/types.h
> +++ b/arch/ia64/include/asm/types.h
> @@ -27,5 +27,7 @@ struct fnptr {
> unsigned long gp;
> };
>
> +#define function_entry(fn) (((struct fnptr *)(fn))->ip)
> +
> #endif /* !__ASSEMBLY__ */
> #endif /* _ASM_IA64_TYPES_H */
> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
> index bfb6ded..8b89d65 100644
> --- a/arch/powerpc/include/asm/types.h
> +++ b/arch/powerpc/include/asm/types.h
> @@ -25,6 +25,17 @@ typedef struct {
> unsigned long env;
> } func_descr_t;
>
> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
> +/*
> + * On PPC64 ABIv1 the function pointer actually points to the
> + * function's descriptor. The first entry in the descriptor is the
> + * address of the function text.
> + */
> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
> +#else
> +#define function_entry(fn) ((unsigned long)(fn))
> +#endif
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_POWERPC_TYPES_H */
> diff --git a/include/linux/types.h b/include/linux/types.h
> index a0bb704..3b95369 100644
> --- a/include/linux/types.h
> +++ b/include/linux/types.h
> @@ -213,5 +213,9 @@ struct callback_head {
> };
> #define rcu_head callback_head
>
> +#ifndef function_entry
> +#define function_entry(fn) ((unsigned long)(fn))
> +#endif
> +
> #endif /* __ASSEMBLY__ */
> #endif /* _LINUX_TYPES_H */
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 2ac9f13..3f2d6d4 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -32,6 +32,7 @@
> * <[email protected]> added function-return probes.
> */
> #include <linux/kprobes.h>
> +#include <linux/types.h>
> #include <linux/hash.h>
> #include <linux/init.h>
> #include <linux/slab.h>
> @@ -2042,16 +2043,18 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
> unsigned long offset = 0, size = 0;
>
> for (iter = start; iter < end; iter++) {
> - if (!kallsyms_lookup_size_offset(*iter, &size, &offset)) {
> - pr_err("Failed to find blacklist %p\n", (void *)*iter);
> + unsigned long entry = function_entry(*iter);
> + if (!kallsyms_lookup_size_offset(entry, &size, &offset)) {
> + pr_err("Failed to find blacklist at %p\n",
> + (void *)entry);
> continue;
> }
>
> ent = kmalloc(sizeof(*ent), GFP_KERNEL);
> if (!ent)
> return -ENOMEM;
> - ent->start_addr = *iter;
> - ent->end_addr = *iter + size;
> + ent->start_addr = entry;
> + ent->end_addr = entry + size;
> INIT_LIST_HEAD(&ent->list);
> list_add_tail(&ent->list, &kprobe_blacklist);
> }
>
>
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
On Thu, Jun 5, 2014 at 11:38 PM, Masami Hiramatsu
<[email protected]> wrote:
> Ping?
>
> I guess this should go to 3.16 branch, shouldn't it?
>
> (2014/05/30 12:18), Masami Hiramatsu wrote:
>> On ia64 and ppc64, the function pointer does not point the
>> entry address of the function, but the address of function
>> discriptor (which contains the entry address and misc
>> data.) Since the kprobes passes the function pointer stored
>> by NOKPROBE_SYMBOL() to kallsyms_lookup_size_offset() for
>> initalizing its blacklist, it fails and reports many errors
>> as below.
>>
>> Failed to find blacklist 0001013168300000
Yes please ... just found this problem on ia64 in mainline
and was happy to see this fix for it.
Tested-by: Tony Luck <[email protected]>
-Tony
On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
> Ping?
>
> I guess this should go to 3.16 branch, shouldn't it?
> > diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
> > index bfb6ded..8b89d65 100644
> > --- a/arch/powerpc/include/asm/types.h
> > +++ b/arch/powerpc/include/asm/types.h
> > @@ -25,6 +25,17 @@ typedef struct {
> > unsigned long env;
> > } func_descr_t;
> >
> > +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
> > +/*
> > + * On PPC64 ABIv1 the function pointer actually points to the
> > + * function's descriptor. The first entry in the descriptor is the
> > + * address of the function text.
> > + */
> > +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
> > +#else
> > +#define function_entry(fn) ((unsigned long)(fn))
> > +#endif
We already have ppc_function_entry(), can't you use that?
cheers
(2014/06/18 16:56), Michael Ellerman wrote:
> On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
>> Ping?
>>
>> I guess this should go to 3.16 branch, shouldn't it?
>
>>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>>> index bfb6ded..8b89d65 100644
>>> --- a/arch/powerpc/include/asm/types.h
>>> +++ b/arch/powerpc/include/asm/types.h
>>> @@ -25,6 +25,17 @@ typedef struct {
>>> unsigned long env;
>>> } func_descr_t;
>>>
>>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
>>> +/*
>>> + * On PPC64 ABIv1 the function pointer actually points to the
>>> + * function's descriptor. The first entry in the descriptor is the
>>> + * address of the function text.
>>> + */
>>> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
>>> +#else
>>> +#define function_entry(fn) ((unsigned long)(fn))
>>> +#endif
>
> We already have ppc_function_entry(), can't you use that?
I'd like to ask you whether the address which ppc_function_entry() returns on
PPC ABIv2 is really same address in kallsyms or not.
As you can see, kprobes uses function_entry() to get the actual entry address
where kallsyms knows. I have not much information about that, but it seems that
the "global entry point" is the address which kallsyms knows, isn't it?
Thank you,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
On Wed, 2014-06-18 at 17:46 +0900, Masami Hiramatsu wrote:
> (2014/06/18 16:56), Michael Ellerman wrote:
> > On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
> >> Ping?
> >>
> >> I guess this should go to 3.16 branch, shouldn't it?
> >
> >>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
> >>> index bfb6ded..8b89d65 100644
> >>> --- a/arch/powerpc/include/asm/types.h
> >>> +++ b/arch/powerpc/include/asm/types.h
> >>> @@ -25,6 +25,17 @@ typedef struct {
> >>> unsigned long env;
> >>> } func_descr_t;
> >>>
> >>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
> >>> +/*
> >>> + * On PPC64 ABIv1 the function pointer actually points to the
> >>> + * function's descriptor. The first entry in the descriptor is the
> >>> + * address of the function text.
> >>> + */
> >>> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
> >>> +#else
> >>> +#define function_entry(fn) ((unsigned long)(fn))
> >>> +#endif
> >
> > We already have ppc_function_entry(), can't you use that?
>
> I'd like to ask you whether the address which ppc_function_entry() returns on
> PPC ABIv2 is really same address in kallsyms or not.
> As you can see, kprobes uses function_entry() to get the actual entry address
> where kallsyms knows. I have not much information about that, but it seems that
> the "global entry point" is the address which kallsyms knows, isn't it?
OK. I'm not sure off the top of my head which address kallsyms knows about, but
yes it's likely that it is the global entry point.
I recently sent a patch to add ppc_global_function_entry(), because we need it
in the ftrace code. Once that is merged you could use that.
How do you hit the original problem, you don't actually specify in your commit
message? Something with kprobes obviously, but what exactly? I'll try and
reproduce it here.
cheers
(2014/06/19 10:30), Michael Ellerman wrote:
> On Wed, 2014-06-18 at 17:46 +0900, Masami Hiramatsu wrote:
>> (2014/06/18 16:56), Michael Ellerman wrote:
>>> On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
>>>> Ping?
>>>>
>>>> I guess this should go to 3.16 branch, shouldn't it?
>>>
>>>>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>>>>> index bfb6ded..8b89d65 100644
>>>>> --- a/arch/powerpc/include/asm/types.h
>>>>> +++ b/arch/powerpc/include/asm/types.h
>>>>> @@ -25,6 +25,17 @@ typedef struct {
>>>>> unsigned long env;
>>>>> } func_descr_t;
>>>>>
>>>>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
>>>>> +/*
>>>>> + * On PPC64 ABIv1 the function pointer actually points to the
>>>>> + * function's descriptor. The first entry in the descriptor is the
>>>>> + * address of the function text.
>>>>> + */
>>>>> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
>>>>> +#else
>>>>> +#define function_entry(fn) ((unsigned long)(fn))
>>>>> +#endif
>>>
>>> We already have ppc_function_entry(), can't you use that?
>>
>> I'd like to ask you whether the address which ppc_function_entry() returns on
>> PPC ABIv2 is really same address in kallsyms or not.
>> As you can see, kprobes uses function_entry() to get the actual entry address
>> where kallsyms knows. I have not much information about that, but it seems that
>> the "global entry point" is the address which kallsyms knows, isn't it?
>
> OK. I'm not sure off the top of my head which address kallsyms knows about, but
> yes it's likely that it is the global entry point.
>
> I recently sent a patch to add ppc_global_function_entry(), because we need it
> in the ftrace code. Once that is merged you could use that.
Yeah, I could use that. But since this is used in arch-independent code (e.g. IA64
needs similar macro), I think we'd better define function_entry() in asm/types.h for
general use (for kallsyms), and rename ppc_function_entry to local_function_entry()
in asm/code-patching.h.
> How do you hit the original problem, you don't actually specify in your commit
> message? Something with kprobes obviously, but what exactly? I'll try and
> reproduce it here.
Ah, those messages should be shown in dmesg when booting if it doesn't work,
because the messages are printed by initialization process of kprobe blacklist.
So, reproducing it is just enabling CONFIG_KPROBES and boot it.
Thank you,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
On 06/19/2014 10:22 AM, Masami Hiramatsu wrote:
> (2014/06/19 10:30), Michael Ellerman wrote:
>> On Wed, 2014-06-18 at 17:46 +0900, Masami Hiramatsu wrote:
>>> (2014/06/18 16:56), Michael Ellerman wrote:
>>>> On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
>>>>> Ping?
>>>>>
>>>>> I guess this should go to 3.16 branch, shouldn't it?
>>>>
>>>>>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>>>>>> index bfb6ded..8b89d65 100644
>>>>>> --- a/arch/powerpc/include/asm/types.h
>>>>>> +++ b/arch/powerpc/include/asm/types.h
>>>>>> @@ -25,6 +25,17 @@ typedef struct {
>>>>>> unsigned long env;
>>>>>> } func_descr_t;
>>>>>>
>>>>>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
>>>>>> +/*
>>>>>> + * On PPC64 ABIv1 the function pointer actually points to the
>>>>>> + * function's descriptor. The first entry in the descriptor is the
>>>>>> + * address of the function text.
>>>>>> + */
>>>>>> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
>>>>>> +#else
>>>>>> +#define function_entry(fn) ((unsigned long)(fn))
>>>>>> +#endif
>>>>
>>>> We already have ppc_function_entry(), can't you use that?
>>>
>>> I'd like to ask you whether the address which ppc_function_entry() returns on
>>> PPC ABIv2 is really same address in kallsyms or not.
>>> As you can see, kprobes uses function_entry() to get the actual entry address
>>> where kallsyms knows. I have not much information about that, but it seems that
>>> the "global entry point" is the address which kallsyms knows, isn't it?
>>
>> OK. I'm not sure off the top of my head which address kallsyms knows about, but
>> yes it's likely that it is the global entry point.
>>
>> I recently sent a patch to add ppc_global_function_entry(), because we need it
>> in the ftrace code. Once that is merged you could use that.
>
> Yeah, I could use that. But since this is used in arch-independent code (e.g. IA64
> needs similar macro), I think we'd better define function_entry() in asm/types.h for
> general use (for kallsyms), and rename ppc_function_entry to local_function_entry()
> in asm/code-patching.h.
>
>
>> How do you hit the original problem, you don't actually specify in your commit
>> message? Something with kprobes obviously, but what exactly? I'll try and
>> reproduce it here.
>
> Ah, those messages should be shown in dmesg when booting if it doesn't work,
> because the messages are printed by initialization process of kprobe blacklist.
> So, reproducing it is just enabling CONFIG_KPROBES and boot it.
Well, we don't get those messages on Power, since the kallsyms has the
entries for ".function_name". The correct way to verify is, either :
1) Dump the black_list via xmon ( see :
https://lkml.org/lkml/2014/5/29/893 ) and verify the entries.
or
2) Issue a kprobe on a black listed entry and hit a success,(which we
will, since we don't check the actual function address).
Thanks
Suzuki
>
> Thank you,
>
(2014/06/19 15:40), Suzuki K. Poulose wrote:
> On 06/19/2014 10:22 AM, Masami Hiramatsu wrote:
>> (2014/06/19 10:30), Michael Ellerman wrote:
>>> On Wed, 2014-06-18 at 17:46 +0900, Masami Hiramatsu wrote:
>>>> (2014/06/18 16:56), Michael Ellerman wrote:
>>>>> On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
>>>>>> Ping?
>>>>>>
>>>>>> I guess this should go to 3.16 branch, shouldn't it?
>>>>>
>>>>>>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>>>>>>> index bfb6ded..8b89d65 100644
>>>>>>> --- a/arch/powerpc/include/asm/types.h
>>>>>>> +++ b/arch/powerpc/include/asm/types.h
>>>>>>> @@ -25,6 +25,17 @@ typedef struct {
>>>>>>> unsigned long env;
>>>>>>> } func_descr_t;
>>>>>>>
>>>>>>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
>>>>>>> +/*
>>>>>>> + * On PPC64 ABIv1 the function pointer actually points to the
>>>>>>> + * function's descriptor. The first entry in the descriptor is the
>>>>>>> + * address of the function text.
>>>>>>> + */
>>>>>>> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
>>>>>>> +#else
>>>>>>> +#define function_entry(fn) ((unsigned long)(fn))
>>>>>>> +#endif
>>>>>
>>>>> We already have ppc_function_entry(), can't you use that?
>>>>
>>>> I'd like to ask you whether the address which ppc_function_entry() returns on
>>>> PPC ABIv2 is really same address in kallsyms or not.
>>>> As you can see, kprobes uses function_entry() to get the actual entry address
>>>> where kallsyms knows. I have not much information about that, but it seems that
>>>> the "global entry point" is the address which kallsyms knows, isn't it?
>>>
>>> OK. I'm not sure off the top of my head which address kallsyms knows about, but
>>> yes it's likely that it is the global entry point.
>>>
>>> I recently sent a patch to add ppc_global_function_entry(), because we need it
>>> in the ftrace code. Once that is merged you could use that.
>>
>> Yeah, I could use that. But since this is used in arch-independent code (e.g. IA64
>> needs similar macro), I think we'd better define function_entry() in asm/types.h for
>> general use (for kallsyms), and rename ppc_function_entry to local_function_entry()
>> in asm/code-patching.h.
>>
>>
>>> How do you hit the original problem, you don't actually specify in your commit
>>> message? Something with kprobes obviously, but what exactly? I'll try and
>>> reproduce it here.
>>
>> Ah, those messages should be shown in dmesg when booting if it doesn't work,
>> because the messages are printed by initialization process of kprobe blacklist.
>> So, reproducing it is just enabling CONFIG_KPROBES and boot it.
> Well, we don't get those messages on Power, since the kallsyms has the
> entries for ".function_name". The correct way to verify is, either :
Hmm, that seems another issue on powerpc. Is that expected(and designed)
behavior? And if so, how I can verify when initializing blacklist?
(should I better use kallsyms_lookup() and kallsyms_lookup_name() for
verification?)
Thank you,
>
> 1) Dump the black_list via xmon ( see :
> https://lkml.org/lkml/2014/5/29/893 ) and verify the entries.
>
> or
>
> 2) Issue a kprobe on a black listed entry and hit a success,(which we
> will, since we don't check the actual function address).
>
> Thanks
> Suzuki
>
>
>>
>> Thank you,
>>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
On 06/19/2014 12:56 PM, Masami Hiramatsu wrote:
> (2014/06/19 15:40), Suzuki K. Poulose wrote:
>> On 06/19/2014 10:22 AM, Masami Hiramatsu wrote:
>>> (2014/06/19 10:30), Michael Ellerman wrote:
>>>> On Wed, 2014-06-18 at 17:46 +0900, Masami Hiramatsu wrote:
>>>>> (2014/06/18 16:56), Michael Ellerman wrote:
>>>>>> On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
>>>>>>> Ping?
>>>>>>>
>>>>>>> I guess this should go to 3.16 branch, shouldn't it?
>>>>>>
>>>>>>>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>>>>>>>> index bfb6ded..8b89d65 100644
>>>>>>>> --- a/arch/powerpc/include/asm/types.h
>>>>>>>> +++ b/arch/powerpc/include/asm/types.h
>>>>>>>> @@ -25,6 +25,17 @@ typedef struct {
>>>>>>>> unsigned long env;
>>>>>>>> } func_descr_t;
>>>>>>>>
>>>>>>>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
>>>>>>>> +/*
>>>>>>>> + * On PPC64 ABIv1 the function pointer actually points to the
>>>>>>>> + * function's descriptor. The first entry in the descriptor is the
>>>>>>>> + * address of the function text.
>>>>>>>> + */
>>>>>>>> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
>>>>>>>> +#else
>>>>>>>> +#define function_entry(fn) ((unsigned long)(fn))
>>>>>>>> +#endif
>>>>>>
>>>>>> We already have ppc_function_entry(), can't you use that?
>>>>>
>>>>> I'd like to ask you whether the address which ppc_function_entry() returns on
>>>>> PPC ABIv2 is really same address in kallsyms or not.
>>>>> As you can see, kprobes uses function_entry() to get the actual entry address
>>>>> where kallsyms knows. I have not much information about that, but it seems that
>>>>> the "global entry point" is the address which kallsyms knows, isn't it?
>>>>
>>>> OK. I'm not sure off the top of my head which address kallsyms knows about, but
>>>> yes it's likely that it is the global entry point.
>>>>
>>>> I recently sent a patch to add ppc_global_function_entry(), because we need it
>>>> in the ftrace code. Once that is merged you could use that.
>>>
>>> Yeah, I could use that. But since this is used in arch-independent code (e.g. IA64
>>> needs similar macro), I think we'd better define function_entry() in asm/types.h for
>>> general use (for kallsyms), and rename ppc_function_entry to local_function_entry()
>>> in asm/code-patching.h.
>>>
>>>
>>>> How do you hit the original problem, you don't actually specify in your commit
>>>> message? Something with kprobes obviously, but what exactly? I'll try and
>>>> reproduce it here.
>>>
>>> Ah, those messages should be shown in dmesg when booting if it doesn't work,
>>> because the messages are printed by initialization process of kprobe blacklist.
>>> So, reproducing it is just enabling CONFIG_KPROBES and boot it.
>> Well, we don't get those messages on Power, since the kallsyms has the
>> entries for ".function_name". The correct way to verify is, either :
>
> Hmm, that seems another issue on powerpc. Is that expected(and designed)
> behavior?
AFAIK, yes, it is.
To be more precise :
we have 'foo' and '.foo' for a function foo(), where 'foo' points to the
function_entry and '.foo' points to the actual function.
So, a kallsyms_lookup_size_offset() on both 'foo' and '.foo' will return
a hit. So, if we make sure we use the value of '.foo' (by using the
appropriate macros) we should be fine.
And if so, how I can verify when initializing blacklist?
> (should I better use kallsyms_lookup() and kallsyms_lookup_name() for
> verification?)
One way to verify would be to make sure the symbol starts with '.' from
the result of the current kallsyms_lookup_size_offset() for PPC.
Thanks
Suzuki
>
> Thank you,
>
>>
>> 1) Dump the black_list via xmon ( see :
>> https://lkml.org/lkml/2014/5/29/893 ) and verify the entries.
>>
>> or
>>
>> 2) Issue a kprobe on a black listed entry and hit a success,(which we
>> will, since we don't check the actual function address).
>>
>> Thanks
>> Suzuki
>>
>>
>>>
>>> Thank you,
>>>
(2014/06/19 18:45), Suzuki K. Poulose wrote:
> On 06/19/2014 12:56 PM, Masami Hiramatsu wrote:
>> (2014/06/19 15:40), Suzuki K. Poulose wrote:
>>> On 06/19/2014 10:22 AM, Masami Hiramatsu wrote:
>>>> (2014/06/19 10:30), Michael Ellerman wrote:
>>>>> On Wed, 2014-06-18 at 17:46 +0900, Masami Hiramatsu wrote:
>>>>>> (2014/06/18 16:56), Michael Ellerman wrote:
>>>>>>> On Fri, 2014-06-06 at 15:38 +0900, Masami Hiramatsu wrote:
>>>>>>>> Ping?
>>>>>>>>
>>>>>>>> I guess this should go to 3.16 branch, shouldn't it?
>>>>>>>
>>>>>>>>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>>>>>>>>> index bfb6ded..8b89d65 100644
>>>>>>>>> --- a/arch/powerpc/include/asm/types.h
>>>>>>>>> +++ b/arch/powerpc/include/asm/types.h
>>>>>>>>> @@ -25,6 +25,17 @@ typedef struct {
>>>>>>>>> unsigned long env;
>>>>>>>>> } func_descr_t;
>>>>>>>>>
>>>>>>>>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
>>>>>>>>> +/*
>>>>>>>>> + * On PPC64 ABIv1 the function pointer actually points to the
>>>>>>>>> + * function's descriptor. The first entry in the descriptor is the
>>>>>>>>> + * address of the function text.
>>>>>>>>> + */
>>>>>>>>> +#define function_entry(fn) (((func_descr_t *)(fn))->entry)
>>>>>>>>> +#else
>>>>>>>>> +#define function_entry(fn) ((unsigned long)(fn))
>>>>>>>>> +#endif
>>>>>>>
>>>>>>> We already have ppc_function_entry(), can't you use that?
>>>>>>
>>>>>> I'd like to ask you whether the address which ppc_function_entry() returns on
>>>>>> PPC ABIv2 is really same address in kallsyms or not.
>>>>>> As you can see, kprobes uses function_entry() to get the actual entry address
>>>>>> where kallsyms knows. I have not much information about that, but it seems that
>>>>>> the "global entry point" is the address which kallsyms knows, isn't it?
>>>>>
>>>>> OK. I'm not sure off the top of my head which address kallsyms knows about, but
>>>>> yes it's likely that it is the global entry point.
>>>>>
>>>>> I recently sent a patch to add ppc_global_function_entry(), because we need it
>>>>> in the ftrace code. Once that is merged you could use that.
>>>>
>>>> Yeah, I could use that. But since this is used in arch-independent code (e.g. IA64
>>>> needs similar macro), I think we'd better define function_entry() in asm/types.h for
>>>> general use (for kallsyms), and rename ppc_function_entry to local_function_entry()
>>>> in asm/code-patching.h.
>>>>
>>>>
>>>>> How do you hit the original problem, you don't actually specify in your commit
>>>>> message? Something with kprobes obviously, but what exactly? I'll try and
>>>>> reproduce it here.
>>>>
>>>> Ah, those messages should be shown in dmesg when booting if it doesn't work,
>>>> because the messages are printed by initialization process of kprobe blacklist.
>>>> So, reproducing it is just enabling CONFIG_KPROBES and boot it.
>>> Well, we don't get those messages on Power, since the kallsyms has the
>>> entries for ".function_name". The correct way to verify is, either :
>>
>> Hmm, that seems another issue on powerpc. Is that expected(and designed)
>> behavior?
> AFAIK, yes, it is.
> To be more precise :
>
> we have 'foo' and '.foo' for a function foo(), where 'foo' points to the
> function_entry and '.foo' points to the actual function.
Ah, I see. So if we run
func_ptr p = foo;
return p == kallsyms_lookup_name(".foo");
it returns true.
> So, a kallsyms_lookup_size_offset() on both 'foo' and '.foo' will return
> a hit. So, if we make sure we use the value of '.foo' (by using the
> appropriate macros) we should be fine.
>
> And if so, how I can verify when initializing blacklist?
>> (should I better use kallsyms_lookup() and kallsyms_lookup_name() for
>> verification?)
> One way to verify would be to make sure the symbol starts with '.' from
> the result of the current kallsyms_lookup_size_offset() for PPC.
OK, I'll do that as another enhancement, since the bug reported here
will be fixed with our patch.
Anyway, this patch itself should go into 3.16 tree to fix actual bug.
Thanks,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
(2014/06/19 20:01), Masami Hiramatsu wrote:
>>>>> Ah, those messages should be shown in dmesg when booting if it doesn't work,
>>>>> because the messages are printed by initialization process of kprobe blacklist.
>>>>> So, reproducing it is just enabling CONFIG_KPROBES and boot it.
>>>> Well, we don't get those messages on Power, since the kallsyms has the
>>>> entries for ".function_name". The correct way to verify is, either :
>>>
>>> Hmm, that seems another issue on powerpc. Is that expected(and designed)
>>> behavior?
>> AFAIK, yes, it is.
>> To be more precise :
>>
>> we have 'foo' and '.foo' for a function foo(), where 'foo' points to the
>> function_entry and '.foo' points to the actual function.
>
> Ah, I see. So if we run
>
> func_ptr p = foo;
> return p == kallsyms_lookup_name(".foo");
>
> it returns true.
One more thing I should know, is the address of ".function_name" within the
kernel text? In other words, does kernel_text_address() return true for that
address? If not, it's easy to verify the address.
Thank you,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
On Thu, 2014-06-19 at 20:20 +0900, Masami Hiramatsu wrote:
> (2014/06/19 20:01), Masami Hiramatsu wrote:
>
> >>>>> Ah, those messages should be shown in dmesg when booting if it doesn't work,
> >>>>> because the messages are printed by initialization process of kprobe blacklist.
> >>>>> So, reproducing it is just enabling CONFIG_KPROBES and boot it.
> >>>> Well, we don't get those messages on Power, since the kallsyms has the
> >>>> entries for ".function_name". The correct way to verify is, either :
> >>>
> >>> Hmm, that seems another issue on powerpc. Is that expected(and designed)
> >>> behavior?
> >> AFAIK, yes, it is.
> >> To be more precise :
> >>
> >> we have 'foo' and '.foo' for a function foo(), where 'foo' points to the
> >> function_entry and '.foo' points to the actual function.
> >
> > Ah, I see. So if we run
> >
> > func_ptr p = foo;
> > return p == kallsyms_lookup_name(".foo");
> >
> > it returns true.
>
> One more thing I should know, is the address of ".function_name" within the
> kernel text? In other words, does kernel_text_address() return true for that
> address? If not, it's easy to verify the address.
Yes. That is the text address, kernel_text_address() should definitely return
true.
On 64-bit, ABIv1, "foo" points to the function descriptor, in the ".opd"
section.
".foo" points to the actual text of the function, in ".text".
On 64-bit, ABIv2, "foo" points to the text in ".text". There are no dot
symbols.
cheers
(2014/06/20 9:37), Michael Ellerman wrote:
> On Thu, 2014-06-19 at 20:20 +0900, Masami Hiramatsu wrote:
>> (2014/06/19 20:01), Masami Hiramatsu wrote:
>>
>>>>>>> Ah, those messages should be shown in dmesg when booting if it doesn't work,
>>>>>>> because the messages are printed by initialization process of kprobe blacklist.
>>>>>>> So, reproducing it is just enabling CONFIG_KPROBES and boot it.
>>>>>> Well, we don't get those messages on Power, since the kallsyms has the
>>>>>> entries for ".function_name". The correct way to verify is, either :
>>>>>
>>>>> Hmm, that seems another issue on powerpc. Is that expected(and designed)
>>>>> behavior?
>>>> AFAIK, yes, it is.
>>>> To be more precise :
>>>>
>>>> we have 'foo' and '.foo' for a function foo(), where 'foo' points to the
>>>> function_entry and '.foo' points to the actual function.
>>>
>>> Ah, I see. So if we run
>>>
>>> func_ptr p = foo;
>>> return p == kallsyms_lookup_name(".foo");
>>>
>>> it returns true.
>>
>> One more thing I should know, is the address of ".function_name" within the
>> kernel text? In other words, does kernel_text_address() return true for that
>> address? If not, it's easy to verify the address.
>
> Yes. That is the text address, kernel_text_address() should definitely return
> true.
>
> On 64-bit, ABIv1, "foo" points to the function descriptor, in the ".opd"
> section.
>
> ".foo" points to the actual text of the function, in ".text".
Hmm, I misunderstood that. Anyway, we can verify it by kernel_text_address().
>
> On 64-bit, ABIv2, "foo" points to the text in ".text". There are no dot
> symbols.
OK, in that case, kernel_text_address() check is still available. :)
Thank you,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]