Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le (ABIv2)

From	Torsten Duwe <duwe@lst.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le (ABIv2)
Date	2016-01-26 15:00 +0100
Message-ID	<qVck1-4Sm-3@gated-at.bofh.it> (permalink)
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On Tue, Jan 26, 2016 at 01:48:53PM +0100, Petr Mladek wrote:
> On Tue 2016-01-26 11:50:25, Miroslav Benes wrote:
> > 
> > We still need Petr's patch from [1] to make livepatch work, right? Could 
> > you, please, add it to this patch set to make it self-sufficient?

It's Petr's patch, I don't want to decide how to best tackle this, see below.
I think Michael is already aware that it is needed, too.

> > Second, what is the situation with mcount prologue between gcc < 6 and 
> > gcc-6? Are there only 12 bytes in gcc-6 prologue? If yes, we need to 

Precisely, it's commit e95d0248daced44 (in http://repo.or.cz/official-gcc.git)
or svn trunk change 222352 "No need for -mprofile-kernel to save LR to stack."
It's efficient, I like it.

> I am going to update the extra patch. There is an idea to detect the
> offset during build by scrips/recordmcount. This tool looks for the
> ftrace locations. The offset should always be a constant that depends
> on the used architecture, compiler, and compiler flags.

My first idea was to check for compiler version defines, but some vendors
are rumoured to patch their compilers ;-)

> The tool is called post build. We might need to pass the constant
> as a symbol added to the binary. The tool already adds some symbols.

That's even better.
Thanks!
	Torsten

Thread

[PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Torsten Duwe <duwe@lst.de> - 2016-01-25 18:10 +0100
  [PATCH v6 5/9] ppc64 ftrace_with_regs: spare early boot and low level Torsten Duwe <duwe@lst.de> - 2016-01-25 18:10 +0100
  [PATCH v6 8/9] Implement kernel live patching for ppc64le (ABIv2) Torsten Duwe <duwe@lst.de> - 2016-01-25 18:10 +0100
    Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le  (ABIv2) Miroslav Benes <mbenes@suse.cz> - 2016-01-26 12:00 +0100
      Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le (ABIv2) Petr Mladek <pmladek@suse.com> - 2016-01-26 13:50 +0100
        Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le  (ABIv2) Torsten Duwe <duwe@lst.de> - 2016-01-26 15:00 +0100
      Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le  (ABIv2) Torsten Duwe <duwe@lst.de> - 2016-01-26 15:10 +0100
        Re: [PATCH v6 8/9] Implement kernel live patching for ppc64le  (ABIv2) Miroslav Benes <mbenes@suse.cz> - 2016-01-26 15:20 +0100
          Re: Implement kernel live patching for ppc64le (ABIv2) Jessica Yu <jeyu@redhat.com> - 2016-01-27 03:00 +0100
  [PATCH v6 2/9] ppc64le FTRACE_WITH_REGS implementation Torsten Duwe <duwe@lst.de> - 2016-01-25 18:10 +0100
  [PATCH v6 7/9] ppc64 ftrace: disable profiling for some files Torsten Duwe <duwe@lst.de> - 2016-01-25 18:20 +0100
  Re: [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE  (ABI v2) Balbir Singh <bsingharora@gmail.com> - 2016-01-27 12:00 +0100
    Re: [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE  (ABI v2) Torsten Duwe <duwe@lst.de> - 2016-01-27 13:20 +0100

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