Re: Problem with vfs probe on Proxmox kernel

[Adam Guderski <a dot guderski at gmail dot com>]

On 26/01/17 22:34, David Smith wrote:
> On 01/26/2017 03:26 PM, Adam Guderski wrote:
> 
> ... stuff deleted ...
> 
>>> Based on the paths stored when compiling your kernel, systemtap is
>>> looking for the vmlinux file in '/lib/modules/4.4.35-2-pve/build/'.
>>> Obviously it isn't there. Can you search around and see if you can find
>>> it and link it to its proper place?
>>
>> I can't find it (find / -type f -name '*vmlinux*'). When I compiled from
>> source, I noticed this lines in Makefile for Proxmox VE kernel:
>>
>> # strip debug info
>> find tmp/lib/modules -name \*.ko -print | while read f ; do strip
>> --strip-debug "$$f"; done
>>
>> I thought that when I comment this out my kernel will have debug info
>> compiled into it.
> 
> That line you commented out is stripping debuginfo from kernel modules
> (*.ko), not the kernel itself.
> 
>> Interestingly, the config file for my kernel says that
>> CONFIG_DEBUG_INFO is enabled:
>>
>> # grep  DEBUG_INFO /boot/config-4.4.35-2-pve
>> CONFIG_DEBUG_INFO=y
>> # CONFIG_DEBUG_INFO_REDUCED is not set
>> # CONFIG_DEBUG_INFO_SPLIT is not set
>> CONFIG_DEBUG_INFO_DWARF4=y
> 
> I'd guess you missed another line in the Proxmox kernel Makefile where
> it strips debuginfo from the kernel itself.
> 
> What does "file" say on the kernel you built?
> 


It says:

# file /boot/vmlinuz-4.4.35-2-pve
/boot/vmlinuz-4.4.35-2-pve: Linux kernel x86 boot executable bzImage,
version 4.4.35-2-pve (root@pve-test) #1 SMP Sun Jan 22 00:59:19 CET 201,
RO-rootFS, swap_dev 0x6, Normal VGA

While looking for the vmlinux file, I found a script that (I think)
uncompresses a compressed kernel, so I did some testing:

# /usr/src/linux-headers-4.4.35-2-pve/scripts/extract-vmlinux
/boot/vmlinuz-4.4.35-2-pve > vmlinux
# file vmlinux
vmlinux: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically
linked, BuildID[sha1]=c23f97de3c8765073fbecf0b529383f1305c8e81, stripped

So yes, this appears that the kernel I compiled is still stripped, so I
missed something, I'll give it another look but the documentation is
sparse and I don't see another strip command in it. If you wonder how
this Makefile looks like, it's here:
https://git.proxmox.com/?p=pve-kernel.git;a=blob_plain;f=Makefile;hb=HEAD

Best regards and many thanks for your help.