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Date: Thu, 11 Jun 2020 19:59:03 +0200
From: Adam Zabrocki <pi3@....com.pl>
To: lkrg-users@...ts.openwall.com
Subject: Re: RE: ISRA optimized functions

On Thu, Jun 11, 2020 at 07:29:33PM +0200, Mikhail Morfikov wrote:
> On 11/06/2020 18:44, Adam Zabrocki wrote:
> > Hi,
> > 
> > On Wed, Jun 10, 2020 at 09:18:44AM +0200, Mikhail Morfikov wrote:
> >> I just tested and:
> >>
> >> # cat /proc/version
> >> Linux version 5.7.1-amd64 (morfik@...fikownia) (gcc version 10.1.0 (Debian 10.1.0-3), GNU ld (GNU Binutils for Debian) 2.34) #3 SMP PREEMPT Wed Jun 10 07:21:29 CEST 2020
> >>
> >> # dkms status
> >> lkrg, 0.7+git20200609, 5.7.1-amd64, x86_64: installed
> >>
> >> # modprobe -v p_lkrg
> >> insmod /lib/modules/5.7.1-amd64/updates/dkms/p_lkrg.ko
> >>
> >> # lsmod
> >> Module                  Size  Used by
> >> p_lkrg                225280  0
> >>
> >> In the syslog I have the following messages now:
> >>
> >> kernel: p_lkrg: loading out-of-tree module taints kernel.
> >> kernel: [p_lkrg] Loading LKRG...
> >> kernel: [p_lkrg] System does NOT support SMAP. LKRG can't enforce SMAP validation :(
> >> kernel: Freezing user space processes ... (elapsed 0.031 seconds) done.
> >> kernel: OOM killer disabled.
> >> kernel: [p_lkrg] 8/23 UMH paths were whitelisted...
> >> kernel: [p_lkrg] [kretprobe] register_kretprobe() for <lookup_fast> failed! [err=-22]
> >> kernel: [p_lkrg] Trying to find ISRA name for <lookup_fast>
> >> kernel: [p_lkrg] ISRA version not found!
> >> kernel: [p_lkrg] LKRG won't enforce pCFI validation on 'lookup_fast'
> >> kernel: [p_lkrg] LKRG initialized successfully!
> >> kernel: OOM killer enabled.
> >> kernel: Restarting tasks ... done.
> >>
> >> So what to do with this *lookup_fast* ?
> >>
> > 
> > It is not critical hook,  that's why LKRG continue initialization. If you have 
> > set log_level=3 then you should see an extra message printing such information.
> > However, can you please run the following command and provide the result?
> > 
> > # cat /proc/kallsyms|grep lookup_fast
> > 
> > I'm just curious
> 
> Here it is:
> 
> # cat /proc/kallsyms|grep lookup_fast
> ffffffffa16f05d0 t lookup_fast.constprop.0

You compiler enforced constprop optimization on that function. You can manually 
replace the name of lookup_fast to lookup_fast.constprop.0 and it will work 
fine. This function is ISRA safe and should CONSTPROP safe as well.


> ffffffffa2202580 t nft_hash_lookup_fast
> ffffffffc019a026 t p_pcfi_lookup_fast_entry.cold        [p_lkrg]
> ffffffffc01b3520 d p_pcfi_lookup_fast_kretprobe [p_lkrg]
> ffffffffc0191db0 t p_pcfi_lookup_fast_ret       [p_lkrg]
> ffffffffc0191fa0 t p_install_pcfi_lookup_fast_hook      [p_lkrg]
> ffffffffc0191dc0 t p_pcfi_lookup_fast_entry     [p_lkrg]
> ffffffffc0191fd0 t p_uninstall_pcfi_lookup_fast_hook    [p_lkrg]
> ffffffffc01bad74 b p_pcfi_lookup_fast_kretprobe_state   [p_lkrg]
> 




-- 
pi3 (pi3ki31ny) - pi3 (at) itsec pl
http://pi3.com.pl

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