From: Luis Machado <lgustavo@codesourcery.com>
To: Gary Benson <gbenson@redhat.com>
Cc: <gdb-patches@sourceware.org>, Pedro Alves <palves@redhat.com>
Subject: Re: [PATCH v2] Fix logic in exec_file_locate_attach
Date: Mon, 22 Feb 2016 22:00:00 -0000 [thread overview]
Message-ID: <56CB8506.3010602@codesourcery.com> (raw)
In-Reply-To: <20160222135109.GA2256@blade.nx>
On 02/22/2016 10:51 AM, Gary Benson wrote:
> Luis Machado wrote:
>> On 02/22/2016 07:40 AM, Gary Benson wrote:
>>> Luis Machado wrote:
>>>> On 02/19/2016 09:21 AM, Gary Benson wrote:
>>>>> This is an updated version of the patch I posted yesterday.
>>>>> It fails silently rather than throwing if the executable is
>>>>> not in the sysroot, which both fixes the sysroot-escape issue
>>>>> and results in a better GDB session for the user.
>>>>>
>>>>> Built and regtested on RHEL 6.6 x86_64.
>>>>>
>>>>> Luis, I think this patch will fix your connection drop without
>>>>> any further changes. Could you test it please?
>>>>
>>>> Unfortunately it doesn't completely solve the problem i saw, as
>>>> exec_file_find will still potentially throw errors and will
>>>> disrupt the connection attempt or stop execution of a custom
>>>> sequence of commands (as Pedro noted) when "attach" is part of
>>>> the sequence.
>>>>
>>>> define foo
>>>> attach <pid>
>>>>>>>> execution stops here if an error is thrown
>>>> info threads
>>>> info registers
>>>> end
>>>>
>>>> It still looks like a TRY/CATCH block is needed around at least
>>>> exec_file_find.
>>>
>>> What is throwing in exec_file_find? I'm just seeing lots of calls
>>> to gdb_open_cloexec and openp, and I don't think either of those
>>> should throw except for assertion failures or running out of
>>> memory.
>>
>> Not sure why i had exec_file_find in my mind. I meant to say
>> exec_file_attach still throws errors, when openp fails and
>> scratch_chan < 0. Sorry.
>
> You shouldn't get that now, the "if (full_exec_path == NULL) return"
> should have caught it. Are you still seeing thrown errors with your
> setup?
>
Yes. With your patch applied, i still see a case where we error out.
Suppose we have a test binary gdb/test, then:
- chmod -r gdb/test
- Fire up gdbserver with a test binary: ./gdb/gdbserver/gdbserver :2345
gdb/test
- Fire up GDB: ./gdb/gdb -ex "set sysroot" -ex "tar rem :2345"
You will see something similar to the following:
Sending packet: $qXfer:exec-file:read:3486:0,fff#5f...Packet received:
l/proc/13446/exe
/proc/13446/exe: Permission denied.
(gdb) i r
The program has no registers now.
(gdb)
This was the testcase suggested by Pedro and it proved to be a good one.
>> There is a symbol_file_add_main call right after calling
>> exec_file_attach in exec_file_locate_attach, but i didn't see any
>> errors being thrown from that one.
>
> You could probably race it (e.g. by deleting the file between the
> calls) but generally symbol_file_add_main won't fail because
> exec_file_attach would have failed if the file was missing or
> inaccessible.
My idea was to guard both exec_file_attach and symbol_file_add_main. We
can't have anything in that function throwing an error that won't be
caught, otherwise the above connection attempt will fail.
Luis
next prev parent reply other threads:[~2016-02-22 22:00 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-11 14:19 [PATCH] Remote debugging without a binary (regression) Luis Machado
2016-02-11 16:35 ` Gary Benson
2016-02-11 17:06 ` Luis Machado
2016-02-11 17:31 ` Pedro Alves
2016-02-11 17:42 ` Luis Machado
2016-02-12 10:31 ` Gary Benson
2016-02-12 10:59 ` Luis Machado
2016-02-12 15:24 ` Pedro Alves
2016-02-17 13:53 ` Gary Benson
2016-02-17 14:40 ` Pedro Alves
2016-02-17 17:02 ` [OB PATCH] Add missing cleanup in exec_file_locate_attach Gary Benson
2016-02-17 17:05 ` Gary Benson
2016-02-17 18:11 ` Luis Machado
2016-02-18 9:54 ` Gary Benson
2016-02-18 17:05 ` [PATCH] Fix logic " Gary Benson
2016-02-18 17:28 ` Pedro Alves
2016-02-19 10:24 ` Gary Benson
2016-02-19 10:33 ` Luis Machado
2016-02-19 11:21 ` [PATCH v2] " Gary Benson
2016-02-19 15:38 ` Luis Machado
2016-02-22 10:40 ` Gary Benson
2016-02-22 11:37 ` Luis Machado
2016-02-22 13:51 ` Gary Benson
2016-02-22 22:00 ` Luis Machado [this message]
2016-02-22 22:50 ` Luis Machado
2016-02-22 23:00 ` Pedro Alves
2016-02-23 0:04 ` Luis Machado
2016-02-23 0:13 ` Pedro Alves
2016-02-23 0:16 ` Luis Machado
2016-02-23 11:27 ` Gary Benson
2016-02-23 11:43 ` Pedro Alves
2016-02-23 12:15 ` Gary Benson
2016-02-23 12:20 ` Pedro Alves
2016-02-23 11:55 ` Pedro Alves
2016-02-24 11:56 ` Gary Benson
2016-02-12 15:29 ` [PATCH] Remote debugging without a binary (regression) Pedro Alves
2016-02-12 16:08 ` Luis Machado
2016-02-12 16:36 ` Pedro Alves
2016-02-12 17:31 ` Luis Machado
2016-02-17 11:46 ` Pedro Alves
2016-02-18 12:30 ` Gary Benson
2016-02-18 12:40 ` Luis Machado
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