Re: [lldb-dev] add custom vendor commands

[Giusti, Valentina via lldb-dev]

> On Oct 18, 2016, at 6:43 PM, Clayton, Greg  wrote:
>
> > On Oct 18, 2016, at 7:48 AM, Giusti, Valentina 
> wrote:
> >
> > Hi Greg,
> >
> > Thanks a lot for your reply, please find below my answers.
> >
> >> You can install new python commands that can do the job to work out
> >> the details.
> >>
> >> http://lldb.llvm.org/python-reference.html
> >>
> >> See the section named "CREATE A NEW LLDB COMMAND USING A PYTHON
> >> FUNCTION".
> >>
> >> You can basically install a new "intel" command and parse all of the
> >> options "show mpx-bounds ..." or "set mpx-bounds ..." from within this new
> command.
> >> You can use the public LLDB API to look through the process and do
> >> things. Let me know if you need any help with this. There is also a
> >> API to add custom commands from C++ plug-ins. Enrico Granata did this
> >> work and can answer more questions on that. Either way, both commands
> >> (python and C++ plug-ins) have access to the public API for LLDB, so
> >> the code you will write will use the same API. So I would stick with 
> >> python for
> now to get things working.
> >>
> >
> > I think I would rather start right away with the C++ approach. If I 
> > understand
> correctly, it means to create a specific Intel plugin under the directory
> source/Plugins and use the LLDB API to add the custom command.
> 
> That is one way to do this, but any change you make will require a recompile 
> of
> LLDB.
> 
> The only external plug-ins we currently have with LLDB are for adding
> commands. See the following code in our test suite where $(trunk) is the root 
> of
> your LLDB checkout:
> 
> $(trunk)/packages/Python/lldbsuite/test/functionalities/plugins/commands
> 
> This show you how to compile a C++ plug-in that will be loaded by LLDB if it 
> is
> placed in the right plug-in location.  So this would allow you to distribute 
> a plug-
> in that can work with existing released LLDB in case you care to do so.
> 

Thanks for mentioning this, I will keep it in mind. However I think I prefer to 
implement a builtin command.

> >
> >> Some questions for you:
> >> - How do plan on detecting that you have an intel processor?
> >
> > I thought of checking if the target architecture is either 
> > llvm::Triple::x86 or
> llvm::Triple::x86_64. Do you think there is a better approach to this?
> 
> I guess just checking for the "BNDCFGU" register is what you will need to do?
> 

Yeah, I can probably skip the arch checking step.

> >
> >> - Do you need access to any process registers? If so, are these
> >> registers thread specific? Are these registers available currently on 
> >> linux and
> MacOS?
> >
> > I only need to access the MPX configuration register, BNDCFGU. As far as I
> know, MacOS doesn't have MPX support, so I also didn't implement the MPX
> support for MacOS in LLDB, which means it is only available in Linux at the
> moment.
> >
> >> - How do you locate the BT? (or do you even need to?). Is there
> >> symbol? Can you extract all values in the bounds table once you locate it?
> >>
> >
> > The bound tables are allocated contiguously in the process memory, starting
> from the Bound Directory address which is stored in the BNDCFGU register.
> Therefore, in the plugin I only need to access this register, do the 
> appropriate
> calculations and then access the process memory to get the requested bound
> table entry.
> 
> Great. This sounds easy to do. Just decide if you prefer a built in command 
> or to
> create an external command shared library plug-in and you are all set to go!
> 

Seems so, thanks!

- Val

Intel Deutschland GmbH
Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Christian Lamprechter
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928

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Re: [lldb-dev] add custom vendor commands

[Greg Clayton via lldb-dev]

> On Oct 18, 2016, at 7:48 AM, Giusti, Valentina  
> wrote:
> 
> Hi Greg,
> 
> Thanks a lot for your reply, please find below my answers.
> 
>> You can install new python commands that can do the job to work out the
>> details.
>> 
>> http://lldb.llvm.org/python-reference.html
>> 
>> See the section named "CREATE A NEW LLDB COMMAND USING A PYTHON
>> FUNCTION".
>> 
>> You can basically install a new "intel" command and parse all of the options
>> "show mpx-bounds ..." or "set mpx-bounds ..." from within this new command.
>> You can use the public LLDB API to look through the process and do things. 
>> Let
>> me know if you need any help with this. There is also a API to add custom
>> commands from C++ plug-ins. Enrico Granata did this work and can answer
>> more questions on that. Either way, both commands (python and C++ plug-ins)
>> have access to the public API for LLDB, so the code you will write will use 
>> the
>> same API. So I would stick with python for now to get things working.
>> 
> 
> I think I would rather start right away with the C++ approach. If I 
> understand correctly, it means to create a specific Intel plugin under the 
> directory source/Plugins and use the LLDB API to add the custom command. 

That is one way to do this, but any change you make will require a recompile of 
LLDB. 

The only external plug-ins we currently have with LLDB are for adding commands. 
See the following code in our test suite where $(trunk) is the root of your 
LLDB checkout:

$(trunk)/packages/Python/lldbsuite/test/functionalities/plugins/commands

This show you how to compile a C++ plug-in that will be loaded by LLDB if it 
is placed in the right plug-in location.  So this would allow you to distribute 
a plug-in that can work with existing released LLDB in case you care to do so.

> 
>> Some questions for you:
>> - How do plan on detecting that you have an intel processor?
> 
> I thought of checking if the target architecture is either llvm::Triple::x86 
> or llvm::Triple::x86_64. Do you think there is a better approach to this?

I guess just checking for the "BNDCFGU" register is what you will need to do?

> 
>> - Do you need access to any process registers? If so, are these registers 
>> thread
>> specific? Are these registers available currently on linux and MacOS?
> 
> I only need to access the MPX configuration register, BNDCFGU. As far as I 
> know, MacOS doesn't have MPX support, so I also didn't implement the MPX 
> support for MacOS in LLDB, which means it is only available in Linux at the 
> moment.
> 
>> - How do you locate the BT? (or do you even need to?). Is there symbol? Can
>> you extract all values in the bounds table once you locate it?
>> 
> 
> The bound tables are allocated contiguously in the process memory, starting 
> from the Bound Directory address which is stored in the BNDCFGU register. 
> Therefore, in the plugin I only need to access this register, do the 
> appropriate calculations and then access the process memory to get the 
> requested bound table entry.

Great. This sounds easy to do. Just decide if you prefer a built in command or 
to create an external command shared library plug-in and you are all set to go!

Greg

> 
> - Val 
> 
> Intel Deutschland GmbH
> Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
> Tel: +49 89 99 8853-0, www.intel.de
> Managing Directors: Christin Eisenschmid, Christian Lamprechter
> Chairperson of the Supervisory Board: Nicole Lau
> Registered Office: Munich
> Commercial Register: Amtsgericht Muenchen HRB 186928
> 

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Re: [lldb-dev] add custom vendor commands

[Giusti, Valentina via lldb-dev]

Hi Greg,

Thanks a lot for your reply, please find below my answers.

> You can install new python commands that can do the job to work out the
> details.
> 
> http://lldb.llvm.org/python-reference.html
> 
> See the section named "CREATE A NEW LLDB COMMAND USING A PYTHON
> FUNCTION".
> 
> You can basically install a new "intel" command and parse all of the options
> "show mpx-bounds ..." or "set mpx-bounds ..." from within this new command.
> You can use the public LLDB API to look through the process and do things. Let
> me know if you need any help with this. There is also a API to add custom
> commands from C++ plug-ins. Enrico Granata did this work and can answer
> more questions on that. Either way, both commands (python and C++ plug-ins)
> have access to the public API for LLDB, so the code you will write will use 
> the
> same API. So I would stick with python for now to get things working.
> 

I think I would rather start right away with the C++ approach. If I understand 
correctly, it means to create a specific Intel plugin under the directory 
source/Plugins and use the LLDB API to add the custom command. 

> Some questions for you:
> - How do plan on detecting that you have an intel processor?

I thought of checking if the target architecture is either llvm::Triple::x86 or 
llvm::Triple::x86_64. Do you think there is a better approach to this?

> - Do you need access to any process registers? If so, are these registers 
> thread
> specific? Are these registers available currently on linux and MacOS?

I only need to access the MPX configuration register, BNDCFGU. As far as I 
know, MacOS doesn't have MPX support, so I also didn't implement the MPX 
support for MacOS in LLDB, which means it is only available in Linux at the 
moment.

> - How do you locate the BT? (or do you even need to?). Is there symbol? Can
> you extract all values in the bounds table once you locate it?
> 

The bound tables are allocated contiguously in the process memory, starting 
from the Bound Directory address which is stored in the BNDCFGU register. 
Therefore, in the plugin I only need to access this register, do the 
appropriate calculations and then access the process memory to get the 
requested bound table entry.

- Val 

Intel Deutschland GmbH
Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Christian Lamprechter
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928

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Re: [lldb-dev] add custom vendor commands

[Greg Clayton via lldb-dev]

> On Oct 13, 2016, at 2:24 AM, Giusti, Valentina via lldb-dev 
>  wrote:
> 
> Hello all,
> 
> Background: 
> Intel CPUs that support MPX have a limited number of bound registers. For any 
> program that has more objects than fit into these registers, the bounds must 
> be kept elsewhere. For this purpose, Bounds Tables (BT) are stored in 
> application memory: for each pointer there is a bound table entry with lower 
> bound, upper bound, check pointer value.
> 
> It would be convenient for the user to be able to access the BT and possibly 
> also manipulate it, through commands like: 'set/show mpx-bounds 
>   '.
> 
> Is there a way to add customized commands for vendor features, such as this 
> one?
> I have seen that CommandObjectCommands has a class to add commands 
> interpreted by command interpreter scripts and an interface for command 
> aliases, so I wonder if it would make sense to add something else for vendor 
> commands. For example, I could create a new class CommandObjectVendor that 
> allows vendors to create their own specific commands. In my case, for the MPX 
> bound table, the commands could be:
>   
>   intel show mpx-bounds   
> 
>   intel set mpx-bounds
> 
> 
> Thanks in advance for your help,
> 

You can install new python commands that can do the job to work out the 
details. 

http://lldb.llvm.org/python-reference.html

See the section named "CREATE A NEW LLDB COMMAND USING A PYTHON FUNCTION".

You can basically install a new "intel" command and parse all of the options 
"show mpx-bounds ..." or "set mpx-bounds ..." from within this new command. You 
can use the public LLDB API to look through the process and do things. Let me 
know if you need any help with this. There is also a API to add custom commands 
from C++ plug-ins. Enrico Granata did this work and can answer more questions 
on that. Either way, both commands (python and C++ plug-ins) have access to the 
public API for LLDB, so the code you will write will use the same API. So I 
would stick with python for now to get things working.

Some questions for you:
- How do plan on detecting that you have an intel processor? 
- Do you need access to any process registers? If so, are these registers 
thread specific? Are these registers available currently on linux and MacOS?
- How do you locate the BT? (or do you even need to?). Is there symbol? Can you 
extract all values in the bounds table once you locate it?

Let me know if you have any questions,

Greg Clayton

> - V.
> 
> 
> Intel Deutschland GmbH
> Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
> Tel: +49 89 99 8853-0, www.intel.de
> Managing Directors: Christin Eisenschmid, Christian Lamprechter
> Chairperson of the Supervisory Board: Nicole Lau
> Registered Office: Munich
> Commercial Register: Amtsgericht Muenchen HRB 186928
> 
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[lldb-dev] add custom vendor commands

[Giusti, Valentina via lldb-dev]

Hello all,

Background: 
Intel CPUs that support MPX have a limited number of bound registers. For any 
program that has more objects than fit into these registers, the bounds must be 
kept elsewhere. For this purpose, Bounds Tables (BT) are stored in application 
memory: for each pointer there is a bound table entry with lower bound, upper 
bound, check pointer value.

It would be convenient for the user to be able to access the BT and possibly 
also manipulate it, through commands like: 'set/show mpx-bounds  
 '.

Is there a way to add customized commands for vendor features, such as this one?
I have seen that CommandObjectCommands has a class to add commands interpreted 
by command interpreter scripts and an interface for command aliases, so I 
wonder if it would make sense to add something else for vendor commands. For 
example, I could create a new class CommandObjectVendor that allows vendors to 
create their own specific commands. In my case, for the MPX bound table, the 
commands could be:

intel show mpx-bounds   

intel set mpx-bounds


Thanks in advance for your help,

- V.


Intel Deutschland GmbH
Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Christian Lamprechter
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928

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