From: Ingo Molnar <mingo@kernel.org>
To: Nadav Amit <namit@vmware.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Damian Tometzki <linux_dti@icloud.com>,
linux-integrity <linux-integrity@vger.kernel.org>,
LSM List <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v7 08/14] x86/ftrace: Use text_poke_*() infrastructure
Date: Thu, 6 Dec 2018 17:28:57 +0100 [thread overview]
Message-ID: <20181206162857.GA119243@gmail.com> (raw)
In-Reply-To: <25B84F01-DB4C-4957-9703-769CCC9794BB@vmware.com>
* Nadav Amit <namit@vmware.com> wrote:
> > On Dec 4, 2018, at 5:34 PM, Nadav Amit <namit@vmware.com> wrote:
> >
> > A following patch is going to make module allocated memory
> > non-executable. This requires to modify ftrace and make the memory
> > executable again after it is configured.
> >
> > In addition, this patch makes ftrace use the general text poking
> > infrastructure instead ftrace's homegrown text patching. This provides
> > the advantages of having slightly "safer" code patching and avoiding
> > races with module removal or other mechanisms that patch the kernel
> > code.
> >
> > Cc: Steven Rostedt <rostedt@goodmis.org>
> > Signed-off-by: Nadav Amit <namit@vmware.com>
> > ---
> > arch/x86/kernel/ftrace.c | 74 +++++++++++++---------------------------
> > 1 file changed, 23 insertions(+), 51 deletions(-)
>
> Steven Rostedt pointed that using text_poke() instead of
> probe_kernel_write() would introduce considerable overheads. Running:
>
> # time { echo function > current_tracer; }
>
> takes 0.24s without this patch and 0.7s with. I don’t know whether to
> consider it “so bad”. Obviously we can introduce a batching mechanism and/or
> do some micro-optimization (the latter will not buy us much though).
This should definitely not regress, so can we try the batching approach?
Thanks,
Ingo
next prev parent reply other threads:[~2018-12-06 16:29 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-05 1:33 [PATCH v7 00/14] x86/alternative: text_poke() enhancements Nadav Amit
2018-12-05 1:33 ` [PATCH v7 01/14] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Nadav Amit
2018-12-05 1:33 ` [PATCH v7 02/14] x86/jump_label: Use text_poke_early() during early init Nadav Amit
2018-12-05 1:33 ` [PATCH v7 03/14] x86/mm: temporary mm struct Nadav Amit
2018-12-05 1:33 ` [PATCH v7 04/14] fork: provide a function for copying init_mm Nadav Amit
2018-12-05 1:33 ` [PATCH v7 05/14] x86/alternative: initializing temporary mm for patching Nadav Amit
2018-12-05 1:34 ` [PATCH v7 06/14] x86/alternative: use temporary mm for text poking Nadav Amit
2018-12-05 1:34 ` [PATCH v7 07/14] x86/kgdb: avoid redundant comparison of patched code Nadav Amit
2018-12-05 1:34 ` [PATCH v7 08/14] x86/ftrace: Use text_poke_*() infrastructure Nadav Amit
2018-12-06 0:06 ` Nadav Amit
2018-12-06 16:28 ` Ingo Molnar [this message]
2018-12-05 1:34 ` [PATCH v7 09/14] x86/kprobes: Instruction pages initialization enhancements Nadav Amit
2018-12-06 13:09 ` Masami Hiramatsu
2018-12-05 1:34 ` [PATCH v7 10/14] x86: avoid W^X being broken during modules loading Nadav Amit
2018-12-05 1:34 ` [PATCH v7 11/14] x86/jump-label: remove support for custom poker Nadav Amit
2018-12-05 1:34 ` [PATCH v7 12/14] x86/alternative: Remove the return value of text_poke_*() Nadav Amit
2018-12-05 1:34 ` [PATCH v7 13/14] module: Do not set nx for module memory before freeing Nadav Amit
2018-12-06 9:57 ` Peter Zijlstra
2018-12-06 17:28 ` Nadav Amit
2018-12-06 11:13 ` Andrea Parri
2018-12-06 18:52 ` Andy Lutomirski
2018-12-06 18:56 ` Nadav Amit
2018-12-06 20:21 ` Edgecombe, Rick P
2018-12-06 20:29 ` Nadav Amit
2018-12-13 14:10 ` Jessica Yu
2018-12-13 17:25 ` Nadav Amit
2018-12-05 1:34 ` [PATCH v7 14/14] module: Prevent module removal racing with text_poke() Nadav Amit
2018-12-06 10:01 ` Peter Zijlstra
2018-12-06 10:03 ` [PATCH v7 00/14] x86/alternative: text_poke() enhancements Peter Zijlstra
2018-12-10 1:06 ` Nadav Amit
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181206162857.GA119243@gmail.com \
--to=mingo@kernel.org \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=linux-integrity@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=linux_dti@icloud.com \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=namit@vmware.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).