Re: Location of vmlinux debuginfo file

[Mike Mason <mmlnx at us dot ibm dot com>]

Roland McGrath wrote:
> The flexible solution where systemtap can specify the details of what it
> wants more fully is something that comes naturally with the (coming) change
> to use "offline" style (aka relocatability, aka cross-debugging).  There
> systemtap can give an explicit directory name to elfutils (the function is
> dwfl_linux_kernel_report_offline).  
>
> /usr/lib/debug/boot/vmlinux-`uname -r` is already one of the files looked
> for by default.  So I am not sure why there is a problem on SLES.

I was wrong in my original email. SLES puts vmlinux-`uname -r`.debug in 
/usr/lib/debug/boot.  If I create a link from that file to 
/usr/lib/debug/boot/vmlinux-`uname -r` it works.

> It first looks for /boot/vmlinux-`uname -r` and if that does exist then
> it's used, and must either be the complete kernel with debuginfo itself,
> or else have a corresponding file /usr/lib/debug/boot/vmlinux-`uname -r`.debug
> (note the .debug suffix, /usr/lib/debug/PATH.debug is the standard
> transformation for any PATH).  

I'm not seeing where it ever tries to open a corresponding 
/usr/lib/debug/boot/vmlinux-`uname -r`.debug file. I put printf's next to 
every place an open is attempted and never saw an attempt to open that file. 
Had it attempted that, stap would have worked.  I can see in 
dwfl_standard_find_debuginfo() where this might be possible if it's called 
with debuglink_file == NULL, but it doesn't appear to ever be called that way. 
 What am I missing?

I also see various attempts to open files in a .debug subdirectory.  Is that a 
standard place for debuginfo files?

Thanks,
Mike