linux-kernel - Re: [PATCHv2 0/8] arm64: ftrace cleanup + FTRACE_WITH

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Message-ID: <20191104140440.GJ45140@lakrids.cambridge.arm.com>
Date:   Mon, 4 Nov 2019 14:04:40 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Amit Kachhap <Amit.Kachhap@....com>
Cc:     Will Deacon <will@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Catalin Marinas <Catalin.Marinas@....com>,
        "deller@....de" <deller@....de>, "duwe@...e.de" <duwe@...e.de>,
        "James.Bottomley@...senPartnership.com" 
        <James.Bottomley@...senPartnership.com>,
        James Morse <James.Morse@....com>,
        "jeyu@...nel.org" <jeyu@...nel.org>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "jthierry@...hat.com" <jthierry@...hat.com>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "svens@...ckframe.org" <svens@...ckframe.org>,
        "takahiro.akashi@...aro.org" <takahiro.akashi@...aro.org>
Subject: Re: [PATCHv2 0/8] arm64: ftrace cleanup + FTRACE_WITH_REGS

On Mon, Nov 04, 2019 at 01:03:51PM +0000, Amit Kachhap wrote:
> 
> 
> On 11/4/19 6:26 PM, Will Deacon wrote:
> > On Sat, Nov 02, 2019 at 05:42:25PM +0530, Amit Daniel Kachhap wrote:
> >> On 10/29/19 10:28 PM, Mark Rutland wrote:
> >>> This series is a reworked version of Torsten's FTRACE_WITH_REGS series
> >>> [1]. I've tried to rework the existing code in preparatory patches so
> >>> that the patchable-function-entry bits slot in with fewer surprises.
> >>> This version is based on v5.4-rc3, and can be found in my
> >>> arm64/ftrace-with-regs branch [2].
> >>>
> >>> Patch 1 adds an (optional) ftrace_init_nop(), which the core code uses
> >>> to initialize callsites. This allows us to avoid a synthetic MCOUNT_ADDR
> >>> symbol, and more cleanly separates the one-time initialization of the
> >>> callsite from dynamic NOP<->CALL modification. Architectures which don't
> >>> implement this get the existing ftrace_make_nop() with MCOUNT_ADDR.
> >>>
> >>> Recently parisc gained ftrace support using patchable-function-entry.
> >>> Patch 2 makes the handling of module callsite locations common in
> >>> kernel/module.c with a new FTRACE_CALLSITE_SECTION definition, and
> >>> removed the newly redundant bits from arch/parisc.
> >>>
> >>> Patches 3 and 4 move the module PLT initialization to module load time,
> >>> which simplifies runtime callsite modification. This also means that we
> >>> don't transitently mark the module text RW, and will allow for the
> >>> removal of module_disable_ro().
> >>>
> >>> Patches 5 and 6 add some trivial infrastructure, with patch 7 finally
> >>> adding FTRACE_WITH_REGS support. Additional work will be required for
> >>> livepatching (e.g. implementing reliable stack trace), which is
> >>> commented as part of patch 7.
> >>>
> >>> Patch 8 is a trivial cleanup atop of the rest of the series, making the
> >>> code easier to read and less susceptible to config-specific breakage.
> >> I tested the whole series with my latest in-kernel ptrauth patches [1]
> >> and graph_tracer/function_graph_tracer works fine, So for the whole series,
> >> Tested-by: Amit Daniel Kachhap <amit.kachhap@....com>
> >>
> >> Also I gave few minor comments in the individual patches. With those
> >> comments,
> >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
> Oops sorry I meant,
> Reviewed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>

Thanks!

I've added the Tested-by for the whole series, and the Reviewed-by for
patches 4 and 7. I haven't added it for patch 1 just yet; please reply
to my comment there if you'd still like to add a Reviewed-by.

Mark.