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Bug 2162495 - eu-addr2line -i option to display inlined functions doesn't work with LTO (-flto) and Dwarf5
Summary: eu-addr2line -i option to display inlined functions doesn't work with LTO (-f...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: elfutils
Version: 8.6
Hardware: All
OS: Linux
unspecified
medium
Target Milestone: rc
: ---
Assignee: Mark Wielaard
QA Contact: Martin Cermak
Petr Hybl
URL:
Whiteboard:
Depends On:
Blocks: 2182059
TreeView+ depends on / blocked
 
Reported: 2023-01-19 17:54 UTC by Vikramsingh Patil
Modified: 2024-04-04 15:49 UTC (History)
9 users (show)

Fixed In Version: elfutils-0.189-1.el8
Doc Type: Bug Fix
Doc Text:
.`eu-addr2line -i` now correctly handles code compiled with GCC link-time optimization Previously, the `dwarf_getscopes` function from the `libdw` library included in `elfutils` was unable to find an abstract origin definition of a function that was compiled with GCC link-time optimization. Consequently, when you used the `-i` argument in the `eu-addr2line` command, `eu-addr2line` was unable to show inline functions for code compiled with `gcc -flto`. With this update, the `libdw dwarf_getscopes` function looks in the correct compile unit for the inlined scope, and `eu-addr2line -i` works as expected.
Clone Of:
: 2182059 (view as bug list)
Environment:
Last Closed: 2023-11-14 15:47:35 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
reproducer code (1.02 KB, application/gzip)
2023-01-19 17:54 UTC, Vikramsingh Patil 		no flags Details
View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker RHELPLAN-145843 0 None None None 2023-01-19 17:57:55 UTC
Red Hat Knowledge Base (Solution) 7063134 0 None None None 2024-04-04 15:49:38 UTC
Red Hat Product Errata RHBA-2023:7089 0 None None None 2023-11-14 15:47:44 UTC

Description Vikramsingh Patil 2023-01-19 17:54:52 UTC 
Created attachment 1939208 [details]
reproducer code

Description of problem:
eu-addr2line -i option to display inlined functions doesn't work with LTO (-flto) and Dwarf5

Version-Release number of selected component (if applicable):
elfutils-0.187-4.el8.x86_64 
gcc-toolset-11-elfutils-0.185-5.el8.x86_64

How reproducible:
every time

Steps to Reproduce:
1.From repro.sh found in repro_inlines.tgz

scl enable gcc-toolset-11 'gcc -O2 -flto -gdwarf-5 -g sample.c'

2.scl enable gcc-toolset-11 'eu-addr2line  -fCi -e a.out 0x401055'


Actual results:

"main
/mnt/data/RTVs/testIK8/elfutils/repro_inlines/sample.c:6:5"

Expected results:

# "FunctionToInline1
# /mnt/data/repro_inlines/sample.c:6
# FunctionToInline2
# /mnt/data/repro_inlines/sample.c:34
# FunctionToInline3
# /mnt/data/repro_inlines/sample.c:39
# FunctionToInline4
# /mnt/data/elfutils/repro_inlines/sample.c:43
# FunctionToInline5
# /mnt/data/repro_inlines/sample.c:47
# FunctionToInline6
# /mnt/data/repro_inlines/sample.c:51
# main
# /mnt/data/repro_inlines/sample.c:57
# "

Additional info:
Comment 1 Mark Wielaard 2023-01-19 18:35:53 UTC 
This is indeed an issue with eu-addr2line -i, also in upstream.
It doesn't seem to rely on the DWARF version with both gcc -O2 -flto -gdwarf-4 and -gdwarf-5 you don't actually get inlined subroutines.

It seems to be caused by including the -C flag:
  -C, --demangle[=ARG]       Show demangled symbols (ARG is always ignored)

Without it:

$ eu-addr2line -fi -e a.out 0x0000000000401055
FunctionToInline1 inlined at /tmp/repro_inlines/sample.c:34:5 in main
/tmp/repro_inlines/sample.c:6:5
FunctionToInline2
/tmp/repro_inlines/sample.c:34:5
FunctionToInline3
/tmp/repro_inlines/sample.c:39:5
FunctionToInline4
/tmp/repro_inlines/sample.c:43:5
FunctionToInline5
/tmp/repro_inlines/sample.c:47:5
FunctionToInline6
/tmp/repro_inlines/sample.c:51:5
main
/tmp/repro_inlines/sample.c:57:5

I'll investigate, it shouldn't matter whether or not we are demangling the symbols, but apparently it does.

Note that as a workaround you can probably use binutils addr2line which seems to work correctly with -fCi (at least upstream, and tested against binutils version 2.38)
Comment 2 Mark Wielaard 2023-01-19 18:55:14 UTC 
(In reply to Mark Wielaard from comment #1)
> It seems to be caused by including the -C flag:
>   -C, --demangle[=ARG]       Show demangled symbols (ARG is always ignored)
> 
> Without it:
> 
> $ eu-addr2line -fi -e a.out 0x0000000000401055
> FunctionToInline1 inlined at /tmp/repro_inlines/sample.c:34:5 in main
> /tmp/repro_inlines/sample.c:6:5
> FunctionToInline2
> /tmp/repro_inlines/sample.c:34:5
> FunctionToInline3
> /tmp/repro_inlines/sample.c:39:5
> FunctionToInline4
> /tmp/repro_inlines/sample.c:43:5
> FunctionToInline5
> /tmp/repro_inlines/sample.c:47:5
> FunctionToInline6
> /tmp/repro_inlines/sample.c:51:5
> main
> /tmp/repro_inlines/sample.c:57:5
> 
> I'll investigate, it shouldn't matter whether or not we are demangling the
> symbols, but apparently it does.

This is really an embarrassing bug. The problem is that -C takes an argument (which is always ignored).
The code simply treats anything as an argument, so if you use eu-readelf -fCi ... it takes that 'i' as argument to -C and ignores it.
So you don't get -i inlines...

The workaround is putting -C last (-fiC):

$ eu-addr2line -fiC -e a.out 0x0000000000401052
FunctionToInline1 inlined at /tmp/repro_inlines/sample.c:34:5 in main
/tmp/repro_inlines/sample.c:6:5
FunctionToInline2
/tmp/repro_inlines/sample.c:34:5
FunctionToInline3
/tmp/repro_inlines/sample.c:39:5
FunctionToInline4
/tmp/repro_inlines/sample.c:43:5
FunctionToInline5
/tmp/repro_inlines/sample.c:47:5
FunctionToInline6
/tmp/repro_inlines/sample.c:51:5
main
/tmp/repro_inlines/sample.c:57:5
Comment 3 Carlos Santos 2023-01-20 13:43:57 UTC 
The customer(In reply to Mark Wielaard from comment #2)
> (In reply to Mark Wielaard from comment #1)
> > It seems to be caused by including the -C flag:
> >   -C, --demangle[=ARG]       Show demangled symbols (ARG is always ignored)
> > 
> > Without it:
> > 
> > $ eu-addr2line -fi -e a.out 0x0000000000401055
> > FunctionToInline1 inlined at /tmp/repro_inlines/sample.c:34:5 in main
> > /tmp/repro_inlines/sample.c:6:5
> > FunctionToInline2
> > /tmp/repro_inlines/sample.c:34:5
> > FunctionToInline3
> > /tmp/repro_inlines/sample.c:39:5
> > FunctionToInline4
> > /tmp/repro_inlines/sample.c:43:5
> > FunctionToInline5
> > /tmp/repro_inlines/sample.c:47:5
> > FunctionToInline6
> > /tmp/repro_inlines/sample.c:51:5
> > main
> > /tmp/repro_inlines/sample.c:57:5
> > 
> > I'll investigate, it shouldn't matter whether or not we are demangling the
> > symbols, but apparently it does.
> 
> This is really an embarrassing bug. The problem is that -C takes an argument
> (which is always ignored).
> The code simply treats anything as an argument, so if you use eu-readelf
> -fCi ... it takes that 'i' as argument to -C and ignores it.
> So you don't get -i inlines...
> 
> The workaround is putting -C last (-fiC):
> 
> $ eu-addr2line -fiC -e a.out 0x0000000000401052
> FunctionToInline1 inlined at /tmp/repro_inlines/sample.c:34:5 in main
> /tmp/repro_inlines/sample.c:6:5
> FunctionToInline2
> /tmp/repro_inlines/sample.c:34:5
> FunctionToInline3
> /tmp/repro_inlines/sample.c:39:5
> FunctionToInline4
> /tmp/repro_inlines/sample.c:43:5
> FunctionToInline5
> /tmp/repro_inlines/sample.c:47:5
> FunctionToInline6
> /tmp/repro_inlines/sample.c:51:5
> main
> /tmp/repro_inlines/sample.c:57:5

The customer for whom we opened the bugs replied that the workaround does not work and I confirmed it:

$ rpm -q gcc-toolset-11
gcc-toolset-11-11.1-1.el8.x86_64

$ rpm -qf /bin/eu-addr2line
elfutils-0.187-4.el8.x86_64

$ scl enable gcc-toolset-11 'gcc -O2 -flto -gdwarf-5 -g sample.c'

$ scl enable gcc-toolset-11 'eu-addr2line  -fiC -e a.out 0x0000000000401052'
main
/work/XXXXXXXX/repro_inlines/sample.c:6:5

$ /bin/eu-addr2line  -fiC -e a.out 0x0000000000401052
main
/work/XXXXXXXX/repro_inlines/sample.c:6:5
Comment 4 Mark Wielaard 2023-01-20 22:58:07 UTC 
(In reply to Carlos Santos from comment #3)
> The customer for whom we opened the bugs replied that the workaround does
> not work and I confirmed it:
> 
> $ rpm -q gcc-toolset-11
> gcc-toolset-11-11.1-1.el8.x86_64
> 
> $ rpm -qf /bin/eu-addr2line
> elfutils-0.187-4.el8.x86_64
> 
> $ scl enable gcc-toolset-11 'gcc -O2 -flto -gdwarf-5 -g sample.c'
> 
> $ scl enable gcc-toolset-11 'eu-addr2line  -fiC -e a.out 0x0000000000401052'
> main
> /work/XXXXXXXX/repro_inlines/sample.c:6:5
> 
> $ /bin/eu-addr2line  -fiC -e a.out 0x0000000000401052

You are right.
I apparently hadn't tested with the -flto option, thinking that wasn't it. Sorry.
If you do use -flto then it really doesn't work with or without -C or placing it last.

I go and try to figure out what goes wrong when the binary is produced with -flto.
Upstream acts the same, so it isn't a RHEL specific bug.
Comment 5 Mark Wielaard 2023-01-23 09:24:51 UTC 
So there are two issues:

1) The demangle option -C prevents -i to work when used before it.
   So -Ci won't show inlines, but -iC does. Submitted an upstream patch to fix that:
   https://patchwork.sourceware.org/project/elfutils/patch/20230123091128.687801-1-mark@klomp.org/

2) The -i inlines option doesn't work when using -flto. This has now easy
   workaround. The issue is that with -flto the abstract origin of an inlined subroutine
   is in a separate "compile unit", which confused the libdw dwarf_getscopes function.
   Patch to fix that submitted upstream:
   https://patchwork.sourceware.org/project/elfutils/patch/20230123091520.688326-1-mark@klomp.org/
Comment 14 errata-xmlrpc 2023-11-14 15:47:35 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (elfutils bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2023:7089
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