linux-kernel - Re: [RFC] ftrace: Add support to keep some functions out of ftrace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Yv6wB4El4iueJtwX@krava>
Date:   Thu, 18 Aug 2022 23:32:55 +0200
From:   Jiri Olsa <olsajiri@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Jiri Olsa <olsajiri@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [RFC] ftrace: Add support to keep some functions out of ftrace

On Thu, Aug 18, 2022 at 02:00:21PM -0700, Alexei Starovoitov wrote:
> On Thu, Aug 18, 2022 at 1:50 PM Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > On Thu, 18 Aug 2022 22:27:07 +0200
> > Jiri Olsa <olsajiri@...il.com> wrote:
> >
> > > ok, so the problem with __attribute__((patchable_function_entry(5))) is that
> > > it puts function address into __patchable_function_entries section, which is
> > > one of ftrace locations source:
> > >
> > >   #define MCOUNT_REC()    . = ALIGN(8);     \
> > >     __start_mcount_loc = .;                 \
> > >     KEEP(*(__mcount_loc))                   \
> > >     KEEP(*(__patchable_function_entries))   \
> > >     __stop_mcount_loc = .;                  \
> > >    ...
> > >
> > >
> > > it looks like __patchable_function_entries is used for other than x86 archs,
> > > so we perhaps we could have x86 specific MCOUNT_REC macro just with
> > > __mcount_loc section?
> >
> > So something like this:
> >
> > #ifdef CONFIG_X86
> > # define NON_MCOUNT_PATCHABLE KEEP(*(__patchable_function_entries))
> > # define MCOUNT_PATCHABLE
> > #else
> > # define NON_MCOUNT_PATCHABLE
> > # define MCOUNT_PATCHABLE  KEEP(*(__patchable_function_entries))
> > #endif
> >
> >   #define MCOUNT_REC()    . = ALIGN(8);     \
> >     __start_mcount_loc = .;                 \
> >     KEEP(*(__mcount_loc))                   \
> >     MCOUNT_PATCHABLE                        \
> >     __stop_mcount_loc = .;                  \
> >     NON_MCOUNT_PATCHABLE                    \
> >    ...
> >
> > ??
> 
> That's what more or less Peter's patch is doing:
> Here it is again for reference:
> https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?id=8d075bdf11193f1d276bf19fa56b4b8dfe24df9e

ah nice, and discards the __patchable_function_entries section, great

jirka