Re: Prelinking on ARM with Debug Link

[Torsten Polle <Torsten.Polle@gmx.de>]

> Am 28.02.2016 um 21:51 schrieb Torsten Polle <Torsten.Polle@gmx.de>:
> 
> 
>> Am 23.02.2016 um 23:16 schrieb Torsten Polle <Torsten.Polle@gmx.de>:
>> 
>> 
>>> Am 23.02.2016 um 17:46 schrieb Mark Wielaard <mjw@redhat.com>:
>>> 
>>> On Mon, 2016-02-22 at 22:45 +0100, Torsten Polle wrote:
>>>> the principle idea of your patch works. But I had to rewrite it to
>>>> really work in my environment. Could you please have a look at my
>>>> proposal? Would something like that be acceptable?
>>> 
>>> Could you give an example of what didn't work?
>>> You cast both debug_frame_off and dwbias to uint32_t before
>>> substracting. Is that really necessary/correct? Both are Dwarf_Addrs
>>> which are always uint64_t. And we care about the difference here.
>> 
>> In my case debug_frame_off is larger than dwbias. If for instance debug_frame_off is 0 and dwbias is -1, the result is -1. As the arithmethics on the 64bit host is unsigned, the result is 0xffffffffffffffff in hex notation and 18446744073709551615 in decimal notation. As stap-symbols.h is used for the target, the values are too large for the 32bit wide unsigned int, which is the data type for the field sec_load_offset. Therefore the compiler complains. The type cast to uint32_t forces the host compiler to use only a 32bit value. Therefore the result is 0xffffffff (4294967295). At least that is what happens on my host. I need the „u“ because even 4294967295 is considered to be too large.
>> 
>>>> I would like to double check in my environment if we could fall back to the hex notation again.
>>> 
>>> Isn't it simpler and consistent to just always use decimal in this case?
>>> There should at least be a comment why we use a different notation for
>>> elf32 vs elf64 targets.
>> 
>> I would go for a consistent notation. Personally, I prefer the hex notation for the addresses. I hope to be able to check whether the hex notation with casts works tomorrow and get back to you.
>> 
>> Regards,
>> Torsten
> 
> Mark,
> 
> Please find a new version of the patch attached. I changed the patch to use hexadecimal numbers consistently.
> 
> Kind Regards,
> Torsten
> <0001-PATCH-v2-Fix-Compilation-fails-for-prelinked-librari.patch>

Mark,

any comments or thoughts on my proposal?

Kind Regards,
Torsten