linux-kernel - Re: [PATCH V4 3/3] x86: Add entry trampolines to kcore

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]

Date:   Wed, 6 Jun 2018 15:16:31 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, Jiri Olsa <jolsa@...hat.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH V4 3/3] x86: Add entry trampolines to kcore

On Wed, Jun 06, 2018 at 03:54:11PM +0300, Adrian Hunter wrote:
> Without program headers for PTI entry trampoline pages, the trampoline
> virtual addresses do not map to anything.
> 

> 
> In addition, entry trampolines all map to the same page.  Represent that by
> giving the corresponding program headers in kcore the same offset.
> 
> This has the benefit that, when perf tools uses /proc/kcore as a source for
> kernel object code, samples from different CPU trampolines are aggregated
> together.  Note, such aggregation is normal for profiling i.e. people want
> to profile the object code, not every different virtual address the object
> code might be mapped to (across different processes for example).
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> Acked-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  arch/x86/mm/cpu_entry_area.c | 10 ++++++++++
>  fs/proc/kcore.c              |  7 +++++--
>  include/linux/kcore.h        | 13 +++++++++++++
>  3 files changed, 28 insertions(+), 2 deletions(-)

This also adds the KCORE_REMAP functionality, but isn't mentioned at all
in the Changelog.

Still, looks OK I suppose,

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>