[PATCH] LLVMSymbolizer: Use alternative method if no inlining frames found.

[Alexey Samsonov]

On Thu, Oct 17, 2013 at 11:56 AM, Will Dietz <w at wdtz.org> wrote:

> Ah, well after your DebugInfo change re:form classes lands,
> this patch is almost certainly going about this the wrong way.
>
> If you'd like I can update the patch, but since you just refactored
> things to support doing this properly it seems you should just
> go ahead and fix this yourself (compared to overhead of managing me doing
> it).
>
> The testcase is probably still useful regardless :).
>

Hi Will, I think I've fixed the problem in r193555.
Could you please commit your testcase with the following improvements:
* Add the original source code with descriptions of how to build the object
file (which compiler was used etc.)
See test/DebugInfo/Inputs/dwarfdump-test.cc for inspiration.
* Rewrite the test to use llvm-symbolizer (it will probably be shorter), or
just extend test/DebugInfo/llvm-symbolizer.test

Thanks!


>
> No worries, would rather see this done properly for sure.
> Thanks!
>
> ~Will
>
>
> On Thu, Oct 17, 2013 at 1:20 PM, Will Dietz <w at wdtz.org> wrote:
> > Great, thanks! You were absolutely right regarding the high_pc thing,
> > sorry for misdiagnosing the issue (and thanks for figuring this out!).
> >
> > Attached is a patch that attempts to address this issue,
> > with included test case (by far the larger time-sink after your
> > spot-on analysis).
> >
> > Thanks for taking a look and letting me take a crack at fixing this
> properly :).
> >
> > ~Will
> >
> >
> > On Thu, Oct 17, 2013 at 5:49 AM, Alexey Samsonov <samsonov at google.com>
> wrote:
> >> Hi Will,
> >>
> >> On Thu, Oct 17, 2013 at 12:51 AM, Will Dietz <w at wdtz.org> wrote:
> >>>
> >>> Fixes bug exposed by tsan lit tests where addresses fail to be
> >>> symbolized on my system (x86_64 linux).
> >>>
> >>> An example of this failure can be seen with this binary[1]:
> >>>
> >>> $ unxz ./thread_leak.3.c.tmp.xz
> >>>
> >>> Using llvm-symbolizer from ToT:
> >>>
> >>> $ echo ./thread_leak3.c.tmp 0x020560 | ~/llvm/build/bin/llvm-symbolizer
> >>> __interceptor_pthread_create
> >>> ??:0:0
> >>>
> >>> And after:
> >>>
> >>> $ echo ./thread_leak3.c.tmp 0x020560|~/llvm/build/bin/llvm-symbolizer
> >>> __interceptor_pthread_create
> >>>
> >>>
> /home/will/llvm/latest/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:876:0
> >>>
> >>> Proposed patch attached.
> >>
> >>
> >> Interesting. I agree that llvm-symbolizer should perform at least as
> good
> >> with --inlining=true
> >> than without it, but the fix should probably go the DWARF parser in
> >> DebugInfo library.
> >>
> >> Here's the DWARF entry for __interceptor_pthread_create in your binary:
> >>
> >> 0x0002c37a:   DW_TAG_subprogram [182] *
> >>                 DW_AT_external [DW_FORM_flag_present]   (true)
> >>                 DW_AT_name [DW_FORM_strp]       (
> .debug_str[0x00012957] =
> >> "__interceptor_pthread_create")
> >>                 DW_AT_decl_file [DW_FORM_data1] (0x01)
> >>                 DW_AT_decl_line [DW_FORM_data2] (0x036b)
> >>                 DW_AT_type [DW_FORM_ref4]       (cu + 0x49a0 =>
> >> {0x00014e6e})
> >>                 DW_AT_low_pc [DW_FORM_addr]     (0x0000000000020560)
> >>                 DW_AT_high_pc [DW_FORM_data8]   (0x000000000000015f)
> >> <-------------------- [1]
> >>                 DW_AT_frame_base [DW_FORM_exprloc]      (<0x1> 9c )
> >>                 DW_AT_Unknown_2117 [DW_FORM_flag_present]       (true)
> >>                 DW_AT_sibling [DW_FORM_ref4]    (cu + 0x1c267 =>
> >> {0x0002c735})
> >>
> >> [1] DW_AT_high_pc has different DW_FORM here and actually means the
> size of
> >> the functions, not its largest address.
> >> My guess is DWARF parser doesn't know about this and fails to build a
> >> correct address range for the function. I'm going
> >> to investigate this soon.
> >>
> >> Thanks for the reproducer!
> >>
> >>>
> >>> ~Will
> >>>
> >>> [1] http://wdtz.org/files/thread_leak3.c.tmp.xz
> >>>
> >>> _______________________________________________
> >>> llvm-commits mailing list
> >>> llvm-commits at cs.uiuc.edu
> >>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >>>
> >>
> >>
> >>
> >> --
> >> Alexey Samsonov, MSK
>



-- 
Alexey Samsonov, MSK
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