Re: Is there a way to override the symbol check for a specific file (or set)?

[Maynard J. <may...@us...>]

Randell Jesup wrote:
> I'm using Oprofile 0.9.6, running natively on an ARM under 2.6.10 with
> kernel support.
> 
> I'm trying to look at a profile on an embedded device (where the
> binaries are typically stripped and readonly/compressed).  I have access
> to vmlinux and the un-stripped binaries/libraries in a sub-tree (not a
> full filesystem image: --root doesn't work).
> 
> The problem is that even with --image-path, opreport seems to use the
> original file to fetch the symbols from.  Since the original location is
> read-only, I can't replace it with the with-symbols copy.  I've tried a
> number of variations on --image-path; --root doesn't work, and I've
> tried looking at the app, the library directly, etc.
> 
> Any way to override debug symbol reading and make image-path take
> precedence if the image is found?  (Or at least if no symbols are found
> in the canonical location)?
If opreport does not find symbol info in the sampled binary, it checks to see if 
it contains a gnu-debuglink that indicates a separate debuginfo file has been 
created.  If so, there are several standard locations opreport will look for the 
debuginfo file.  If you pass an image-path argument, it will look there, too. 
Most distros will provide separate debuginfo files for libraries.  If this is a 
distro-supplied library and there's a corresponding debuginfo rpm, then just 
install that rpm -- no need to use --image-path.  If you (or someone else) 
builds the library in question, then make sure a separate debuginfo file is 
created.  You can place the debuginfo file anywhere you want on the target 
system, and use the --image-path to tell opreport to look there.

For a binary 'foo' that initially contains debug info . . .
$ objcopy --only-keep-debug foo foo.debuginfo
$ objcopy --strip-debug foo
$ objcopy --add-gnu-debuglink=foo.debuginfo  foo


-Maynard

> 
> Note: I used the trick from the OLPC laptop debugging page to capture the
> data -- I had real problems trying to do it with --session-dir pointed
> to /usr/proj/whatever
> 
>       rm -rf /var/lib/oprofile
>       mkdir /var/lib/oprofile
>       mount -t ramfs none /var/lib/oprofile
>       opcontrol --setup --vmlinux=/boot/vmlinux --separate=library
>       opcontrol --start
>       opcontrol --shutdown
> 
> Thanks for any pointers or ideas!
> 
> 
> $ opreport --verbose=all --symbols --image-path=/usr/proj/xyzzy/target /usr/lib/libxyzzy.so.4 /usr/lib/libxyzzy.so.4
> 
> Archive: 
> Matched sample files: 1
> /var/lib/oprofile/samples/current/{root}/opt/bin/xyzzy/{dep}/{root}/usr/lib/lib/libxyzzy.so.4/TIMER.0.0.all.all.all
> profile_classes:
> event: 
> cpuinfo: CPU: CPU with timer interrupt, speed 0 MHz (estimated)
> class #0:
> name: TIMER:0
> longname: Profiling through timer interrupt
> ptemplate:
> event: TIMER
> count: 0
> unitmask: 0
> tgid: all
> tid: all
> cpu: all
> profiles_set #0:
> image: /opt/bin/xyzzy
> profile_dep_set #0:
> lib_image: /usr/lib/libxyzzy.so.4
> profile_sample_files #0:
> sample_filename: /var/lib/oprofile/samples/current/{root}/opt/bin/xyzzy/{dep}/{root}/usr/lib/libxyzzy.so.4/TIMER.0.0.all.all.all
> callgraph filenames:
> 
> CPU: CPU with timer interrupt, speed 0 MHz (estimated)
> Profiling through timer interrupt
> op_bfd ctor for /usr/lib/libxyzzy.so.4
> bfd_info::get_symbols() for /usr/lib/libxyzzy.so.4
> bfd_get_symtab_upper_bound: 4
> bfd_canonicalize_symtab: 0
> fetching .gnu_debuglink section
> failed to process separate debug file 
> number of symbols before filtering 1
> number of symbols now 1
> start_offset is now 0
> symbol /usr/lib/libxyzzy.so.4, value 0
> start 0, end 8609a0
> samples  %        image name               symbol name
> 2445     100.000  libxyzzy.so.4            /usr/lib/libxyzzy.so.4
>