[Lldb-commits] Patch for fixing FDE indexing when scan debug_info section

[Abid, Hafiz via lldb-commits]

?I will commit on your behalf.


Thanks,

Abid

________________________________
From: Tatyana Krasnukha <Tatyana.Krasnukha at synopsys.com>
Sent: Wednesday, May 24, 2017 6:30 PM
To: Abid, Hafiz; lldb-commits at lists.llvm.org
Subject: RE: [Lldb-commits] Patch for fixing FDE indexing when scan debug_info section

Formatting is done.
Created D33504, and it is accepted now, but what should I do next (I haven't commit access)?

Thanks,
Tatyana

From: Abid, Hafiz [mailto:Hafiz_Abid at mentor.com]
Sent: Wednesday, 24 May, 2017 12:37 PM
To: Tatyana Krasnukha <Tatyana.Krasnukha at synopsys.com>; lldb-commits at lists.llvm.org
Subject: Re: [Lldb-commits] Patch for fixing FDE indexing when scan debug_info section


Please put it as review in Phabricator so others can comment too. I am wondering how we can test this behaviour.

One can use -fno-asynchronous-unwind-tables with clang to disable generation of .eh_frame but the startup code

still brings in that section.



You also need to run clang-format to make sure formatting is right and I see some strange characters in the patch file.



> +      // Try to find .debug_frame section even if .eh_frame doesn't exist.

s/even if/if/



Thanks,

Abid

________________________________
From: Tatyana Krasnukha <Tatyana.Krasnukha at synopsys.com<mailto:Tatyana.Krasnukha at synopsys.com>>
Sent: Tuesday, May 23, 2017 6:20 PM
To: Abid, Hafiz; lldb-commits at lists.llvm.org<mailto:lldb-commits at lists.llvm.org>
Subject: RE: [Lldb-commits] Patch for fixing FDE indexing when scan debug_info section

Done. I have also added a little change which allow to use debug_info section when eh_frame is absent. This case really can take place on some platforms.

Thanks,
Tatyana

From: Abid, Hafiz [mailto:Hafiz_Abid at mentor.com]
Sent: Tuesday, 23 May, 2017 3:31 PM
To: Tatyana Krasnukha <Tatyana.Krasnukha at synopsys.com<mailto:Tatyana.Krasnukha at synopsys.com>>; lldb-commits at lists.llvm.org<mailto:lldb-commits at lists.llvm.org>
Subject: Re: [Lldb-commits] Patch for fixing FDE indexing when scan debug_info section

It looks ok to me. Please put the differences of .eh_frame and
.debug_frame that you described below in code comments too.?

Thanks,
Abid



________________________________
From: lldb-commits <lldb-commits-bounces at lists.llvm.org<mailto:lldb-commits-bounces at lists.llvm.org>> on behalf of Tatyana Krasnukha via lldb-commits <lldb-commits at lists.llvm.org<mailto:lldb-commits at lists.llvm.org>>
Sent: Thursday, May 18, 2017 9:37 PM
To: lldb-commits at lists.llvm.org<mailto:lldb-commits at lists.llvm.org>
Subject: [Lldb-commits] Patch for fixing FDE indexing when scan debug_info section

Fix FDE indexing while scan debug_info section.

There are some differences between eh_frame and debug_frame formats that are not considered by DWARFCallFrameInfo::GetFDEIndex.
An FDE entry contains CIE_pointer in debug_frame in same place as cie_id in eh_frame. As described in dwarf standard<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.dwarfstd.org_doc_dwarf-2D2.0.0.pdf&d=DwMFAw&c=DPL6_X_6JkXFx7AXWqB0tg&r=yfnu24japkhNGh-WqJObHXmH3mINtC_2FO828lrNpM0&m=6bXYUUYhGtSz4V-aPy_DuviU1kYtmn9rHUU-2aIGDzE&s=kMPV12z6OBKSq3lC8HgNgMkv23SamtORaFALS-I-Vts&e=> (section 6.4.1),
CIE_pointer is an "offset into the .debug_frame section". So, variable cie_offset should be equal cie_id for debug_frame.
FDE entries with zeroth CIE pointer (which is actually placed in cie_id variable) shouldn't be ignored also.

I had same issue as described here http://lists.llvm.org/pipermail/lldb-dev/2014-October/005520.html<https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.llvm.org_pipermail_lldb-2Ddev_2014-2DOctober_005520.html&d=DwMFAw&c=DPL6_X_6JkXFx7AXWqB0tg&r=yfnu24japkhNGh-WqJObHXmH3mINtC_2FO828lrNpM0&m=6bXYUUYhGtSz4V-aPy_DuviU1kYtmn9rHUU-2aIGDzE&s=7NGym3Cx6gVwlzBRE44Zm6Teee6tMi9Iq-BTRMjM6Pc&e=> , and these changes have fixed it for me (with "m_is_eh_frame" set to false, of course).

Tatyana Krasnukha
Software Engineer, Sr. I, Solutions Group, Synopsys Inc.
w +7.812.408.7463 | m +7 981 757-4491 | tatyana at synopsys.com<mailto:tatyana at synopsys.com>

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