llvm dev - Oct 2013 - [LLVMdev] [lld] Verifying the Architecture of files read

On 10/4/2013 11:16 PM, Michael Spencer wrote:
> On Fri, Oct 4, 2013 at 8:50 PM, Shankar Easwaran <shankare at
codeaurora.org>wrote:
>
>> Hi,
>>
>> It is needed that lld verifies the input to the linker.
>>
>> For example : a x86 ELF file can be given to lld when the target is
>> x86_64. Similiarly with other flavors.
>>
>> I was thinking to have a varargs function in the LinkingContext that
would
>> be overridden by each of the LinkingContexts to verify files after
being
>> read.
>>
>> The reader would call the varargs function in the LinkingContext and
raise
>> an error if the input is not suitable with the current link mode.
>>
>> Thanks
>>
>> Shankar Easwaran
>>
>> --
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted
>> by the Linux Foundation
>>
>>
> Why would it need to be varargs?
LinkingContext for ELF would require fields from the ELF header to 
verify if the file thats being read belongs to the current target 
architecture.

I am not sure of how many fields would determine the same for Darwin and 
COFF.

This is the reason I thought it should be varargs.
> Also, parse can just return an error that
> specifies the format is wrong.
It would still need to call the LinkingContext to figure out if the 
format is associated with the target.
> Specifically this would be a good place to use the user data part of
> ErrorOr to specify what was expected and what was received.
Couldnt follow this. Can you elaborate ?

Thanks

Shankar Easwaran

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the
Linux Foundation

On Sun, Oct 6, 2013 at 7:38 PM, Shankar Easwaran <shankare at
codeaurora.org>wrote:
> On 10/4/2013 11:16 PM, Michael Spencer wrote:
>
>> On Fri, Oct 4, 2013 at 8:50 PM, Shankar Easwaran <shankare at
codeaurora.org
>> >**wrote:
>>
>>  Hi,
>>>
>>> It is needed that lld verifies the input to the linker.
>>>
>>> For example : a x86 ELF file can be given to lld when the target is
>>> x86_64. Similiarly with other flavors.
>>>
>>> I was thinking to have a varargs function in the LinkingContext
that
>>> would
>>> be overridden by each of the LinkingContexts to verify files after
being
>>> read.
>>>
>>> The reader would call the varargs function in the LinkingContext
and
>>> raise
>>> an error if the input is not suitable with the current link mode.
>>>
>>> Thanks
>>>
>>> Shankar Easwaran
>>>
>>> --
>>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted
>>> by the Linux Foundation
>>>
>>>
>>>  Why would it need to be varargs?
>>
> LinkingContext for ELF would require fields from the ELF header to verify
> if the file thats being read belongs to the current target architecture.
>
> I am not sure of how many fields would determine the same for Darwin and
> COFF.
>
> This is the reason I thought it should be varargs.

The reader has an {ELF,COFF,Darwin}LinkingContext. It can just ask the
context.

>
>  Also, parse can just return an error that
>> specifies the format is wrong.
>>
> It would still need to call the LinkingContext to figure out if the format
> is associated with the target.

Exactly.

>
>  Specifically this would be a good place to use the user data part of
>> ErrorOr to specify what was expected and what was received.
>>
> Couldnt follow this. Can you elaborate ?

ErrorOr supports user data. See unittests/Support/ErrorOrTest.cpp.

It would simply be: return ArchMismatch(expected, actual);

Then an error handler higher up can extract that to form a proper error
message.

- Michael Spencer

>
>
> Thanks
>
> Shankar Easwaran
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
> by the Linux Foundation
>
>
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On 10/7/2013 5:13 PM, Michael Spencer wrote:
> On Sun, Oct 6, 2013 at 7:38 PM, Shankar Easwaran <shankare at
codeaurora.org>wrote:
>
>> On 10/4/2013 11:16 PM, Michael Spencer wrote:
>>
>>> On Fri, Oct 4, 2013 at 8:50 PM, Shankar Easwaran <shankare at
codeaurora.org
>>>> **wrote:
>>>   Hi,
>>>> It is needed that lld verifies the input to the linker.
>>>>
>>>> For example : a x86 ELF file can be given to lld when the
target is
>>>> x86_64. Similiarly with other flavors.
>>>>
>>>> I was thinking to have a varargs function in the LinkingContext
that
>>>> would
>>>> be overridden by each of the LinkingContexts to verify files
after being
>>>> read.
>>>>
>>>> The reader would call the varargs function in the
LinkingContext and
>>>> raise
>>>> an error if the input is not suitable with the current link
mode.
>>>>
>>>> Thanks
>>>>
>>>> Shankar Easwaran
>>>>
>>>> --
>>>> Qualcomm Innovation Center, Inc. is a member of Code Aurora
Forum, hosted
>>>> by the Linux Foundation
>>>>
>>>>
>>>>   Why would it need to be varargs?
>> LinkingContext for ELF would require fields from the ELF header to
verify
>> if the file thats being read belongs to the current target
architecture.
>>
>> I am not sure of how many fields would determine the same for Darwin
and
>> COFF.
>>
>> This is the reason I thought it should be varargs.
>
> The reader has an {ELF,COFF,Darwin}LinkingContext. It can just ask the
> context.
This would make it not part of the LinkingContext interface then. I was 
thinking of a pure virtual function defined in LinkingContext and all
LinkingContexts to implement the function in their code.
> Specifically this would be a good place to use the user data part of
>>> ErrorOr to specify what was expected and what was received.
>>>
>> Couldnt follow this. Can you elaborate ?
>
> ErrorOr supports user data. See unittests/Support/ErrorOrTest.cpp.
>
> It would simply be: return ArchMismatch(expected, actual);
>
> Then an error handler higher up can extract that to form a proper error
> message.
Ok.

Thanks

Shankar Easwaran