On Wed, Aug 31, 2016 at 5:13 PM, Benoît Canet <[email protected]>
wrote:
> case R_X86_64_TPOFF64:
> // FIXME: assumes TLS segment comes before DYNAMIC segment
>
I'm not sure this code even runs when loading a shared object. I think it
only runs when loading the kernel, and there is another piece of code with
R_X86_64_TPOFF64 which gets used when loading objects.
>
>
> This is not the case:
>
> See in the dump:
>
I don't understand what I see in that dump.
To understand this FIXME, please refer to commit f09e0059:
I think the FIXME refers to that we need t->tls.size() to have been
previously set. You can add a printout to see if hasn't been set.
I'm more worried about the symbol(sym) part of this code... What if there
is no symbol involved? In this case (again see readelf --relocs for your
object), there is no object...
I think the code involved is the one added in commit
b9b73661543e614c7dfb3616bd3a75acfa30911e:
x64: Fix R_X86_64_TPOFF64 relocation without symbol
Maybe this code (the no-symbol case) has a bug?
>
> 00000000000c8d90 <runtime.c128hash>:
> c8d90: 48 8b 0d 29 72 38 00 mov 0x387229(%rip),%rcx #
> 44ffc0 <_DYNAMIC+0x200>
> c8d97: 64 48 8b 09 mov %fs:(%rcx),%rcx
> c8d9b: 48 3b 61 10 cmp 0x10(%rcx),%rsp
> c8d9f: 76 60 jbe c8e01 <runtime.c128hash+0x71>
>
> *static_cast<u64*>(addr) = t->dyn_tabs.lookup(sym)->st_value -
> t->tls.size;
> break;
> case R_X86_64_IRELATIVE:
>
>
> On Wed, Aug 31, 2016 at 4:07 PM, Benoît Canet <[email protected]
> > wrote:
>
>> This is what I saw in the code managing the flags.
>>
>> By anyway I think you are right and shared is an "impasse".
>>
>> On Wed, Aug 31, 2016 at 4:06 PM, Nadav Har'El <[email protected]> wrote:
>>
>>>
>>> On Wed, Aug 31, 2016 at 4:26 PM, Benoît Canet <
>>> [email protected]> wrote:
>>>
>>>>
>>>> Buildmode shared alone crash.
>>>>
>>>>
>>>>
>>> the flags are |= between them.
>>>>
>>>
>>> This is not what I see in https://golang.org/src/cmd/go/build.go
>>>
>>> But it seems these two options indeed have a funny interaction between
>>> them - shared enables "dynlink" which gets remembered even when the build
>>> mode is switched to PIE.
>>>
>>>
>>>
>>
>
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