Re: [PATCH 3/6] sysroot: debuginfo lookup with sysroot case do not remove sysroot from file_name

[David Smith <dsmith at redhat dot com>]

Hmm, the problem I have here is the code your patch wants to delete
was added to fix a sysroot problem in the following commit:

====
commit df932a3175284fa75a4c6bdb3aa7af1a34c15cd6
Author: Torsten Polle <Torsten.Polle@gmx.de>
Date:   Thu Mar 6 21:38:49 2014 +0100

    Fix: Debug links are not found if the sysroot is used.

    Signed-off-by: Torsten Polle <Torsten.Polle@gmx.de>
====

Torsten, have you tried using --sysroot recently?

On Mon, Mar 5, 2018 at 11:37 AM, Victor Kamensky <kamensky@cisco.com> wrote:
> If sysroot option is passed, and debug symbols reside in sysroot along
> with executable <foo> in <foo_dir>/.debug/<foo_file> directory, stap
> fails to find debuginfo because it strips out sysroot path from file_name
> so dwfl_standard_find_debuginfo ends up looking at host
> <foo_dir>/.debug/<foo_file> rather then checking
> <sysroot>/<foo_dir>/.debug/<foo_file>.
>
> Note in cross compile environment, it is good idea to set and export
> proper SYSTEMTAP_DEBUGINFO_PATH variable because usual built defaults that
> work for native distros very often not applicable to cross sysroot
> based environment. For example for yocto poky/OE build the following
> setting seems proper "+:.debug:build".
>
> Here are steps how to reproduce the issue. Note <sysroot> is produced by
> yocto poky build.
>
> [kamensky@coreos-lnx2 tests]$ ls /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/mkdir.coreutils
> /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/mkdir.coreutils
> [kamensky@coreos-lnx2 tests]$ ls /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/.debug/mkdir.coreutils
> /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/.debug/mkdir.coreutils
> [kamensky@coreos-lnx2 tests]$ /home/wd8/systemtap/20180208_2/packages/bin/stap --sysroot=/home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs -a x86_64 -r 4.9.78-yocto-standard -B CROSS_COMPILE=x86_64-poky-linux- --sysenv=PATH=/usr/bin:/bin:/usr/sbin:/sbin --sysenv=LD_LIBRARY_PATH=/lib:/usr/lib -v -l 'process("/bin/mkdir.coreutils").function("*")'
> Pass 1: parsed user script and 480 library scripts using 230184virt/93416res/5344shr/88612data kb, in 350usr/30sys/378real ms.
> process("/bin/mkdir.coreutils").function("_fini")
> process("/bin/mkdir.coreutils").function("_init")
> process("/bin/mkdir.coreutils").function("fts_children")
> process("/bin/mkdir.coreutils").function("fts_close")
> process("/bin/mkdir.coreutils").function("fts_open")
> process("/bin/mkdir.coreutils").function("fts_read")
> process("/bin/mkdir.coreutils").function("fts_set")
> Pass 2: analyzed script: 7 probes, 0 functions, 0 embeds, 0 globals using 233484virt/97928res/6212shr/91912data kb, in 20usr/0sys/26real ms.
>
> running above example under strace shows that stap tries to access
> /bin/.debug/mkdir.coreutils on host, rather then sysroot
>
> 13064 openat(AT_FDCWD, "/bin/mkdir.coreutils", O_RDONLY) = -1 ENOENT (No such file or directory)
> 13064 openat(AT_FDCWD, "/bin/.debug/mkdir.coreutils", O_RDONLY) = -1 ENOENT (No such file or directory)
> 13064 openat(AT_FDCWD, "/bin/mkdir.coreutils", O_RDONLY) = -1 ENOENT (No such file or directory)
> 13064 openat(AT_FDCWD, "/bin/build/mkdir.coreutils", O_RDONLY) = -1 ENOENT (No such file or directory)
> 13064 openat(AT_FDCWD, "/bin/mkdir.coreutils", O_RDONLY) = -1 ENOENT (No such file or directory)
>
> After fix applied stap is able to find /bin/.debug/mkdir.coreutils under
> sysroot:
>
> [kamensky@coreos-lnx2 tests]$ /home/wd8/systemtap/20180208_2/packages/bin/stap --sysroot=/home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs -a x86_64 -r 4.9.78-yocto-standard -B CROSS_COMPILE=x86_64-poky-linux- --sysenv=PATH=/usr/bin:/bin:/usr/sbin:/sbin --sysenv=LD_LIBRARY_PATH=/lib:/usr/lib -v -l 'process("/bin/mkdir.coreutils").function("*")' | wc
> Pass 1: parsed user script and 480 library scripts using 230184virt/93440res/5368shr/88612data kb, in 330usr/40sys/371real ms.
> Pass 2: analyzed script: 401 probes, 0 functions, 0 embeds, 0 globals using 235092virt/99484res/6256shr/93520data kb, in 30usr/0sys/35real ms.
>     249     249   29671
>
> Also verified on target that script like example below, once compiled
> against sysroot on host and copied back on target can trace 'mkdir'
> invocation functions:
>
> [kamensky@coreos-lnx2 tests]$ cat mkdir1.stp
> probe process("/bin/mkdir.coreutils").function("*").call {
>   printf ("%s -> %s\n", thread_indent(1), ppfunc())
> }
> probe process("/bin/mkdir.coreutils").function("*").return {
>   printf ("%s <- %s\n", thread_indent(-1), ppfunc())
> }
>
> Signed-off-by: Victor Kamensky <kamensky@cisco.com>
> ---
>  setupdwfl.cxx | 12 ------------
>  1 file changed, 12 deletions(-)
>
> diff --git a/setupdwfl.cxx b/setupdwfl.cxx
> index f00cf755b..e5bfa28f0 100644
> --- a/setupdwfl.cxx
> +++ b/setupdwfl.cxx
> @@ -637,18 +637,6 @@ internal_find_debuginfo (Dwfl_Module *mod,
>
>    call_dwfl_standard_find_debuginfo:
>
> -  if (current_session_for_find_debuginfo)
> -    {
> -      string sysroot = current_session_for_find_debuginfo->sysroot + "/*";
> -      int    found   = fnmatch(sysroot.c_str(), file_name, 0);
> -
> -      if (found)
> -       {
> -         file_name = file_name
> -           + current_session_for_find_debuginfo->sysroot.length() - 1;
> -       }
> -    }
> -
>    /* Call the original dwfl_standard_find_debuginfo */
>    return dwfl_standard_find_debuginfo(mod, userdata, modname, base,
>                file_name, debuglink_file,
> --
> 2.14.3
>



-- 
David Smith
Associate Manager
Red Hat