Re: [perf top] annotation doesn't work, libunwind doesn't seem to be working either

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Fri, Apr 04, 2025 at 03:13:12PM -0300, Arnaldo Carvalho de Melo wrote:
> On Fri, Apr 04, 2025 at 10:28:06AM -0700, Namhyung Kim wrote:
> > > I cannot get the libunwind build-feature failure to go away:
>  
> > > ...                               libcrypto: [ on  ]
> > > ...                               libunwind: [ OFF ]
> > > ...                             libcapstone: [ on  ]
> > > ...                               llvm-perf: [ on  ]
>  
> > > I do have libunwind-dev installed:
>  
> > > ii  libunwind-dev:amd64                                         1.6.2-3.1                                           amd64        library to determine the call-chain of a program - development
> > > ii  libunwind8:amd64                                            1.6.2-3.1                                           amd64        library to determine the call-chain of a program - runtime
>  
> > > but it fails to link:
>  
> > >  kepler:~/tip/tools/build/feature> cat test-libunwind.make.output
> > >  /usr/bin/ld: /tmp/cc2BfaNM.o: in function `main':
> > >  test-libunwind.c:(.text+0x1c): undefined reference to `_Ux86_64_create_addr_space'
> > >  /usr/bin/ld: test-libunwind.c:(.text+0x44): undefined reference to `_Ux86_64_init_remote'
> > >  /usr/bin/ld: test-libunwind.c:(.text+0x6b): undefined reference to `_Ux86_64_dwarf_search_unwind_table'
> > >  collect2: error: ld returned 1 exit status
>  
> > > I tried to install the libunwind-19-dev package, I tried to 
> > > uninstall/reinstall - no combination seems to work.
>  
> > > perf is also totally unhelpful about resolving such issues - it used to 
> > > issue tips about what packages to install, but those tips are not 
> > > present anymore, for this one at least.
>  
> > Since v6.13, we switched to disable libunwind by default and used
> > unwinding in libdw.
>  
> > commit 13e17c9ff491 ("perf build: Make libunwind opt-in rather than opt-out")
>  
> > You need to pass LIBUNWIND=1 to build with it.
> 
> But we should have that spelled out in the output of the build where it
> appears marked as not being enabled even with the usual devel libraries
> being available.
> 
> Its back to change in behaviour that is not clearly marked in the tool
> output.

I just tried but realized that I have the libunwind devel files
available...

so get:

Auto-detecting system features:
...                                   libdw: [ on  ]
...                                   glibc: [ on  ]
...                                  libbfd: [ on  ]
...                          libbfd-buildid: [ on  ]
...                                  libelf: [ on  ]
...                                 libnuma: [ on  ]
...                  numa_num_possible_cpus: [ on  ]
...                                 libperl: [ on  ]
...                               libpython: [ on  ]
...                               libcrypto: [ on  ]
...                               libunwind: [ on  ]
...                             libcapstone: [ on  ]
...                               llvm-perf: [ on  ]
...                                    zlib: [ on  ]
...                                    lzma: [ on  ]
...                               get_cpuid: [ on  ]
...                                     bpf: [ on  ]
...                                  libaio: [ on  ]
...                                 libzstd: [ on  ]



Nope, not really, I only have:

⬢ [acme@toolbox perf-tools-next]$ rpm -qa | grep unwind
libunwind-1.8.0-3.fc40.x86_64
⬢ [acme@toolbox perf-tools-next]$ rpm -e libunwind
error: Failed dependencies:
	libunwind.so.8()(64bit) is needed by (installed) gstreamer1-1.24.11-1.fc40.x86_64
⬢ [acme@toolbox perf-tools-next]$

So this is a bug...

There are no references to libunwind tools/build/feature/test-all.c and
it is building ok:

⬢ [acme@toolbox perf-tools-next]$ cat /tmp/build/perf-tools-next/feature/test-all.make.output 
⬢ [acme@toolbox perf-tools-next]$ 

and somehow libunwind devel files are being somehow detected as being present...

Investigating...

- Arnaldo