Before I implement the user land solution recommended by reviewers, I just want
an opinion on where the code should reside.
I am thinking glibc. The other choice would be a separate library, say,
libtramp.
What do you recommend?
Madhavan
On 9/26/20 10:55 AM, Arvind Sankar wrote:
> On Fri, Sep 25, 2020 at 05:44:56PM -0500, Madhavan T. Venkataraman wrote:
>>
>>
>> On 9/24/20 6:43 PM, Arvind Sankar wrote:
>>>
>>> The source PC will generally not be available if the compiler decided to
>>> tail-call optimize the call to the trampoli
On Fri, Sep 25, 2020 at 05:44:56PM -0500, Madhavan T. Venkataraman wrote:
>
>
> On 9/24/20 6:43 PM, Arvind Sankar wrote:
> >
> > The source PC will generally not be available if the compiler decided to
> > tail-call optimize the call to the trampoline into a jump.
> >
>
> This is still work in
On 9/24/20 6:43 PM, Arvind Sankar wrote:
> On Thu, Sep 24, 2020 at 03:23:52PM -0500, Madhavan T. Venkataraman wrote:
>>
>>
>>> Which ISA does not support PIC objects? You mentioned i386 below, but
>>> i386 does support them, it just needs to copy the PC into a GPR first
>>> (see below).
>>
>> Po
On 9/24/20 3:52 PM, Florian Weimer wrote:
> * Madhavan T. Venkataraman:
>
>> Otherwise, using an ABI quirk or a calling convention side effect to
>> load the PC into a GPR is, IMO, non-standard or non-compliant or
>> non-approved or whatever you want to call it. I would be
>> conservative and n
On 25/09/2020 00:05, Pavel Machek wrote:
> Hi!
>
> I believe you should simply delete confusing "introduction" and
> provide details of super-secure system where your patches would be
> useful, instead.
This RFC talks about converting dynamic code (which cannot be
aut
On Thu, Sep 24, 2020 at 03:23:52PM -0500, Madhavan T. Venkataraman wrote:
>
>
> > Which ISA does not support PIC objects? You mentioned i386 below, but
> > i386 does support them, it just needs to copy the PC into a GPR first
> > (see below).
>
> Position Independent Code needs PC-relative branc
Hi!
> PC-relative data referencing
>
>
> I agree that the current PC value can be loaded in a GPR using the trick
> of call, pop on i386.
>
> Perhaps, on other architectures, we can do similar things. For instance,
> in architectures that load the return address in a
Hi!
> >>> I believe you should simply delete confusing "introduction" and
> >>> provide details of super-secure system where your patches would be
> >>> useful, instead.
> >>
> >> This RFC talks about converting dynamic code (which cannot be
> >> authenticated)
> >> to static code that can be aut
* Madhavan T. Venkataraman:
> Otherwise, using an ABI quirk or a calling convention side effect to
> load the PC into a GPR is, IMO, non-standard or non-compliant or
> non-approved or whatever you want to call it. I would be
> conservative and not use it. Who knows what incompatibility there
> wil
On 9/23/20 2:51 PM, Arvind Sankar wrote:
> On Wed, Sep 23, 2020 at 02:17:30PM -0500, Madhavan T. Venkataraman wrote:
>>
>>
>> On 9/23/20 4:11 AM, Arvind Sankar wrote:
>>> For libffi, I think the proposed standard trampoline won't actually
>>> work, because not all ABIs have two scratch registers
On 23/09/2020 22:51, Pavel Machek wrote:
> Hi!
>
Scenario 2
--
We know what code we need in advance. User trampolines are a good example
of
this. It is possible to define such code statically with some help from the
kernel.
This RFC addresses
On 9/23/20 9:39 AM, Florian Weimer wrote:
> * Solar Designer:
>
>> While I share my opinion here, I don't mean that to block Madhavan's
>> work. I'd rather defer to people more knowledgeable in current userland
>> and ABI issues/limitations and plans on dealing with those, especially
>> to Flo
On 9/23/20 2:51 PM, Arvind Sankar wrote:
> On Wed, Sep 23, 2020 at 02:17:30PM -0500, Madhavan T. Venkataraman wrote:
>>
>>
>> On 9/23/20 4:11 AM, Arvind Sankar wrote:
>>> For libffi, I think the proposed standard trampoline won't actually
>>> work, because not all ABIs have two scratch registers
On 9/23/20 3:51 PM, Pavel Machek wrote:
> Hi!
>
Scenario 2
--
We know what code we need in advance. User trampolines are a good example
of
this. It is possible to define such code statically with some help from the
kernel.
This RFC addresses
Hi!
> >> Scenario 2
> >> --
> >>
> >> We know what code we need in advance. User trampolines are a good example
> >> of
> >> this. It is possible to define such code statically with some help from the
> >> kernel.
> >>
> >> This RFC addresses (2). (1) needs a general purpose trusted code
On Wed, Sep 23, 2020 at 02:17:30PM -0500, Madhavan T. Venkataraman wrote:
>
>
> On 9/23/20 4:11 AM, Arvind Sankar wrote:
> > For libffi, I think the proposed standard trampoline won't actually
> > work, because not all ABIs have two scratch registers available to use
> > as code_reg and data_reg.
On 9/23/20 4:14 AM, Solar Designer wrote:
>>> The W^X implementation today is not complete. There exist many user level
>>> tricks that can be used to load and execute dynamic code. E.g.,
>>>
>>> - Load the code into a file and map the file with R-X.
>>>
>>> - Load the code in an RW- page. Chang
On 9/23/20 4:11 AM, Arvind Sankar wrote:
> For libffi, I think the proposed standard trampoline won't actually
> work, because not all ABIs have two scratch registers available to use
> as code_reg and data_reg. Eg i386 fastcall only has one, and register
> has zero scratch registers. I believe
On 9/23/20 3:42 AM, Pavel Machek wrote:
> Hi!
>
>> Solution proposed in this RFC
>> =
>>
>> >From this RFC's perspective, there are two scenarios for dynamic code:
>>
>> Scenario 1
>> --
>>
>> We know what code we need only at runtime. For instance, JIT code
On Wed, Sep 23, 2020 at 08:11:36PM +0200, Solar Designer wrote:
> On Wed, Sep 23, 2020 at 04:39:31PM +0200, Florian Weimer wrote:
> > * Solar Designer:
> >
> > > While I share my opinion here, I don't mean that to block Madhavan's
> > > work. I'd rather defer to people more knowledgeable in curre
On Wed, 23 Sep 2020, Pavel Machek wrote:
> This is not first crazy patch from your company. Perhaps you should
> have a person with strong Unix/Linux experience performing "straight
> face test" on outgoing patches?
Just for the record: the author of the code has 30+ years experience in
SunOS, S
...
>> The W^X implementation today is not complete. There exist many user level
>> tricks that can be used to load and execute dynamic code. E.g.,
>>
>> - Load the code into a file and map the file with R-X.
>>
>> - Load the code in an RW- page. Change the permissions to R--. Then,
>> change the
On Wed, Sep 23, 2020 at 08:00:07PM +0200, Solar Designer wrote:
> A couple of other things Brad kindly pointed out:
>
> SELinux already has similar protections (execmem, execmod):
>
> http://lkml.iu.edu/hypermail/linux/kernel/0508.2/0194.html
> https://danwalsh.livejournal.com/6117.html
Actually
On Wed, Sep 23, 2020 at 04:39:31PM +0200, Florian Weimer wrote:
> * Solar Designer:
>
> > While I share my opinion here, I don't mean that to block Madhavan's
> > work. I'd rather defer to people more knowledgeable in current userland
> > and ABI issues/limitations and plans on dealing with those
On Wed, Sep 23, 2020 at 7:39 AM Florian Weimer wrote:
>
> * Solar Designer:
>
> > While I share my opinion here, I don't mean that to block Madhavan's
> > work. I'd rather defer to people more knowledgeable in current userland
> > and ABI issues/limitations and plans on dealing with those, especi
On Wed, Sep 23, 2020 at 05:18:35PM +0200, Pavel Machek wrote:
> > It sure does make sense to combine ret2libc/ROP to mprotect() with one's
> > own injected shellcode. Compared to doing everything from ROP, this is
> > easier and more reliable across versions/builds if the desired
> > payload
>
>
Hi!
> > > > The W^X implementation today is not complete. There exist many user
> > > > level
> > > > tricks that can be used to load and execute dynamic code. E.g.,
> > > >
> > > > - Load the code into a file and map the file with R-X.
> > > >
> > > > - Load the code in an RW- page. Change the
* Solar Designer:
> While I share my opinion here, I don't mean that to block Madhavan's
> work. I'd rather defer to people more knowledgeable in current userland
> and ABI issues/limitations and plans on dealing with those, especially
> to Florian Weimer. I haven't seen Florian say anything spe
On Wed, Sep 23, 2020 at 11:14:56AM +0200, Solar Designer wrote:
> On Wed, Sep 23, 2020 at 10:14:26AM +0200, Pavel Machek wrote:
> > > Introduction
> > >
> > >
> > > Dynamic code is used in many different user applications. Dynamic code is
> > > often generated at runtime. Dynamic code
On Wed, Sep 23, 2020 at 10:14:26AM +0200, Pavel Machek wrote:
> > Introduction
> >
> >
> > Dynamic code is used in many different user applications. Dynamic code is
> > often generated at runtime. Dynamic code can also just be a pre-defined
> > sequence of machine instructions in a da
On Tue, Sep 22, 2020 at 09:46:16PM -0400, Arvind Sankar wrote:
> On Thu, Sep 17, 2020 at 10:36:02AM -0500, Madhavan T. Venkataraman wrote:
> >
> >
> > On 9/16/20 8:04 PM, Florian Weimer wrote:
> > > * madvenka:
> > >
> > >> Examples of trampolines
> > >> ===
> > >>
> > >> lib
Hi!
> Solution proposed in this RFC
> =
>
> >From this RFC's perspective, there are two scenarios for dynamic code:
>
> Scenario 1
> --
>
> We know what code we need only at runtime. For instance, JIT code generated
> for frequently executed Java methods. Onl
Hi!
> Introduction
>
>
> Dynamic code is used in many different user applications. Dynamic code is
> often generated at runtime. Dynamic code can also just be a pre-defined
> sequence of machine instructions in a data buffer. Examples of dynamic
> code are trampolines, JIT code, DBT
On Thu, Sep 17, 2020 at 10:36:02AM -0500, Madhavan T. Venkataraman wrote:
>
>
> On 9/16/20 8:04 PM, Florian Weimer wrote:
> > * madvenka:
> >
> >> Examples of trampolines
> >> ===
> >>
> >> libffi (A Portable Foreign Function Interface Library):
> >>
> >> libffi allows a user
I just resent the trampfd v2 RFC. I forgot to CC the reviewers who provided
comments before.
So sorry.
Madhavan
On 9/22/20 4:53 PM, madve...@linux.microsoft.com wrote:
> From: "Madhavan T. Venkataraman"
>
> Introduction
>
>
> Dynamic code is used in many different user applicatio
From: "Madhavan T. Venkataraman"
Introduction
Dynamic code is used in many different user applications. Dynamic code is
often generated at runtime. Dynamic code can also just be a pre-defined
sequence of machine instructions in a data buffer. Examples of dynamic
code are trampolines
On 9/17/20 10:36 AM, Madhavan T. Venkataraman wrote:
>>> libffi
>>> ==
>>>
>>> I have implemented my solution for libffi and provided the changes for
>>> X86 and ARM, 32-bit and 64-bit. Here is the reference patch:
>>>
>>> http://linux.microsoft.com/~madvenka/libffi/libffi.v2.txt
>> The URL
* Madhavan T. Venkataraman:
> On 9/17/20 10:36 AM, Madhavan T. Venkataraman wrote:
libffi
==
I have implemented my solution for libffi and provided the changes for
X86 and ARM, 32-bit and 64-bit. Here is the reference patch:
http://linux.microsoft.com/~madven
On 9/16/20 8:04 PM, Florian Weimer wrote:
> * madvenka:
>
>> Examples of trampolines
>> ===
>>
>> libffi (A Portable Foreign Function Interface Library):
>>
>> libffi allows a user to define functions with an arbitrary list of
>> arguments and return value through a feature
* madvenka:
> Examples of trampolines
> ===
>
> libffi (A Portable Foreign Function Interface Library):
>
> libffi allows a user to define functions with an arbitrary list of
> arguments and return value through a feature called "Closures".
> Closures use trampolines to jump to
From: "Madhavan T. Venkataraman"
Introduction
Dynamic code is used in many different user applications. Dynamic code is
often generated at runtime. Dynamic code can also just be a pre-defined
sequence of machine instructions in a data buffer. Examples of dynamic
code are trampolines
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