From: Jacob Kroon <jacob.kroon@gmail.com>
To: Florian Weimer <fweimer@redhat.com>,
cltang@codesourcery.com, adhemerval.zanella@linaro.org
Cc: Jacob Kroon via Gdb <gdb@sourceware.org>
Subject: Re: Debugging ld.so in gdb
Date: Mon, 7 Feb 2022 14:45:30 +0100 [thread overview]
Message-ID: <c9a8a265-e6c7-6bab-5c95-042da808f84f@gmail.com> (raw)
In-Reply-To: <dcd8e268-c80e-1abe-f8d6-c6a462c98438@gmail.com>
On 2/7/22 14:39, Jacob Kroon wrote:
> On 2/7/22 13:32, Jacob Kroon wrote:
>> On 2/7/22 13:27, Florian Weimer wrote:
>>> * Jacob Kroon:
>>>
>>>>> What I find really confusing is that this is not the result of a dlopen
>>>>> call. I definitely would expect that the maps array contains *all*
>>>>> objects that are being loaded. Clearly this is not the case here.
>>>>> Somehow certain objects are missing, and then they get written into the
>>>>> rpo array.
>>>>>
>>>>> Please try to find libjvm.so among the l_initfini arrays of the objects.
>>>>
>>>> I do find libjvm.so in a couple of the maps[]->l_initfini[]->l_name
>>>> arrays, yes.
>>>
>>> Okay, and of course there is an assumption that those make it to the
>>> maps. No wonder we run off the array.
>>>
>>>>> It must be present somewhere. I assume it's also on the main list,
>>>>> which starts off at _rtld_global._dl_ns[0]._ns_loaded.
>>>>
>>>> Hmm how do I iterate over that data structure ?
>>>>
>>>> See below:
>>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded[0]->l_name
>>>>> $186 = 0x7ffff7ff1d97 ""
>>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded[1]->l_name
>>>>> $187 = 0x0
>>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded[2]->l_name
>>>>> $188 = 0x0
>>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded->l_name
>>>>> $189 = 0x7ffff7ff1d97 ""
>>>>> (gdb) print _rtld_global._dl_ns[1]._ns_loaded->l_name
>>>>> Cannot access memory at address 0x8
>>>>> (gdb) print _rtld_global._dl_ns[2]._ns_loaded->l_name
>>>>> Cannot access memory at address 0x8
>>>
>>> It's a list chained by l_prev/l_next.
>>>
>>
>> Ok, yes "libjvm.so" is there, in multiple entries.
>>
>
> I managed to build glibc master, and yes it also crashes. Reverting the
> suspicious commit:
>
> commit 15a0c5730d1d5aeb95f50c9ec7470640084feae8
> Author: Chung-Lin Tang <cltang@codesourcery.com>
> Date: Thu Oct 21 21:41:22 2021 +0800
>
> elf: Fix slow DSO sorting behavior in dynamic loader (BZ #17645)
>
> fixes the crash. Adding a couple of more people.
>
And yes, using master (or host) glibc and running:
$ GLIBC_TUNABLES="glibc.rtld.dynamic_sort=1" ldd mylib.so
also works without crashing.
Jacob
next prev parent reply other threads:[~2022-02-07 13:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-04 13:45 Jacob Kroon
2022-02-04 13:58 ` Florian Weimer
2022-02-04 14:09 ` Jacob Kroon
2022-02-04 14:22 ` Florian Weimer
2022-02-04 14:27 ` Jacob Kroon
2022-02-04 16:09 ` Florian Weimer
2022-02-04 16:53 ` Jacob Kroon
2022-02-04 17:04 ` Florian Weimer
2022-02-04 17:11 ` Jacob Kroon
2022-02-04 17:15 ` Florian Weimer
2022-02-07 8:36 ` Jacob Kroon
2022-02-07 11:46 ` Jacob Kroon
2022-02-07 11:55 ` Florian Weimer
2022-02-07 12:15 ` Jacob Kroon
2022-02-07 12:27 ` Florian Weimer
2022-02-07 12:32 ` Jacob Kroon
2022-02-07 13:39 ` Jacob Kroon
2022-02-07 13:45 ` Jacob Kroon [this message]
2022-02-07 13:53 ` Adhemerval Zanella
2022-02-07 13:54 ` Jacob Kroon
2022-02-07 14:07 ` Florian Weimer
2022-02-07 16:28 ` Florian Weimer
2022-02-07 17:04 ` Jacob Kroon
2022-02-04 14:45 ` Jacob Kroon
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