Re: [PATCHv2 0/8] arm64: ftrace cleanup + FTRACE_WITH_REGS

From: Sven Schnelle <svens@stackframe•org>
To: Mark Rutland <mark.rutland@arm•com>
Cc: jthierry@redhat•com, linux-parisc@vger•kernel.org,
	peterz@infradead•org, catalin.marinas@arm•com, deller@gmx•de,
	jpoimboe@redhat•com, linux-kernel@vger•kernel.org,
	rostedt@goodmis•org, James.Bottomley@HansenPartnership•com,
	takahiro.akashi@linaro•org, mingo@redhat•com,
	james.morse@arm•com, jeyu@kernel•org, amit.kachhap@arm•com,
	will@kernel•org, duwe@suse•de,
	linux-arm-kernel@lists•infradead.org
Subject: Re: [PATCHv2 0/8] arm64: ftrace cleanup + FTRACE_WITH_REGS
Date: Fri, 1 Nov 2019 16:39:30 +0100	[thread overview]
Message-ID: <20191101153929.GA9053@t470p.stackframe.org> (raw)
In-Reply-To: <20191029165832.33606-1-mark.rutland@arm.com>

Hi Mark,

On Tue, Oct 29, 2019 at 04:58:24PM +0000, Mark Rutland wrote:
> Hi,
> 
> 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.
> 
> Since v1 [3]:
> * Add a couple of people to Cc
> * Fold in Ard's Reviewed-by tag
> * Rename ftrace_code_init_disabled() to ftrace_nop_initialize()
> * Move ftrace_init_nop() to <linux/ftrace.h>, with kerneldoc
> * Update kerneldoc for rec parameters
[..]

I tested this series on parisc both with ftracing kernel internal functions and
module functions. Both are working fine, so feel free to add my

Tested-by: Sven Schnelle <svens@stackframe•org>

Regards
Sven

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