Re: [PATCH 2/6] sysroot: fix short release -r option handling in case of sysroot pass proper kernel modules

[David Smith <dsmith at redhat dot com>]

I tweaked this one. First, in commit 41efad047 I made sure that
sysroot paths don't end in a '/'. That then simplifies this patch,
since we don't have to special case sysroot == "/". I checked this in
as commit a9ce89bcd.

On Mon, Mar 5, 2018 at 11:37 AM, Victor Kamensky <kamensky@cisco.com> wrote:
> In case of -r option getting short release (opposite to full path of
> kernel build tree) stap passes short release name to
> dwfl_linux_kernel_report_offline function and this function tries to
> look up symbols in the host file system ignoring sysroot setting.
>
> Fix: in case of non empty, non "/" sysroot construct full path to
> kernel modules directory and store it into elfutils_kernel_path variable.
>
> Here are steps how to reproduce the issue. Note <sysroot> is produced by
> yocto poky build.
>
> [kamensky@coreos-lnx2 tests]$ cat meminfo.stp
> probe kernel.function("meminfo_proc_show") {
>         println("meminfo_proc_show called")
> }
> [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 -p4 -v -m meminfo meminfo.stp
> Pass 1: parsed user script and 480 library scripts using 230196virt/93452res/5364shr/88624data kb, in 340usr/30sys/375real ms.
> semantic error: while resolving probe point: identifier 'kernel' at meminfo.stp:1:7
>         source: probe kernel.function("meminfo_proc_show") {
>                       ^
>
> Running command under strace shows that stap is trying to open linux symbol file
> on host file system, instead of looking at sysroot location:
>
> 19517 openat(AT_FDCWD, "/boot/vmlinux-4.9.78-yocto-standard.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
> 19517 openat(AT_FDCWD, "/boot/vmlinux-4.9.78-yocto-standard", O_RDONLY) = -1 ENOENT (No such file or directory)
>
> Signed-off-by: Victor Kamensky <kamensky@cisco.com>
> ---
>  setupdwfl.cxx | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/setupdwfl.cxx b/setupdwfl.cxx
> index 11e0bb2af..f00cf755b 100644
> --- a/setupdwfl.cxx
> +++ b/setupdwfl.cxx
> @@ -359,9 +359,19 @@ setup_dwfl_kernel (unsigned *modules_found, systemtap_session &s)
>    // passs the plain kernel_release here.  So instead we have to
>    // hard-code this magic here.
>     string lib_path = "/lib/modules/" + s.kernel_release + "/build";
> -   if (s.kernel_build_tree == string(s.sysroot + lib_path) ||
> -       (s.kernel_build_tree == lib_path
> -       && s.sysroot == "/"))
> +   if (s.kernel_build_tree == string(s.sysroot + lib_path))
> +     {
> +       // If we have sysroot set does not make sense to pass
> +       // short release to dwfl, it won't take a sysroot into
> +       // account. Let's construct full path in such case.
> +       if (s.sysroot != "" && s.sysroot != "/")
> +        elfutils_kernel_path = string(s.sysroot + "/lib/modules/" + s.kernel_release);
> +       else
> +        elfutils_kernel_path = s.kernel_release;
> +     }
> +   else
> +     if (s.kernel_build_tree == lib_path
> +        && s.sysroot == "/")
>        elfutils_kernel_path = s.kernel_release;
>     else
>        elfutils_kernel_path = s.kernel_build_tree;
> --
> 2.14.3
>



-- 
David Smith
Associate Manager
Red Hat