Re: [PATCH v3 1/5] jump_label: Don't warn on __exit jump entries

From: Andrew Murray <andrew.murray@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Will Deacon <will.deacon@arm.com>,
	Ard.Biesheuvel@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 1/5] jump_label: Don't warn on __exit jump entries
Date: Thu, 22 Aug 2019 19:41:02 +0100	[thread overview]
Message-ID: <20190822184101.GA14582@e119886-lin.cambridge.arm.com> (raw)
In-Reply-To: <20190822153237.GC33080@lakrids.cambridge.arm.com>

On Thu, Aug 22, 2019 at 04:32:37PM +0100, Mark Rutland wrote:
> On Mon, Aug 12, 2019 at 03:36:21PM +0100, Andrew Murray wrote:
> > On architectures that discard .exit.* sections at runtime, a
> > warning is printed for each jump label that is used within an
> > in-kernel __exit annotated function:
> > 
> > can't patch jump_label at ehci_hcd_cleanup+0x8/0x3c
> > WARNING: CPU: 0 PID: 1 at kernel/jump_label.c:410 __jump_label_update+0x12c/0x138
> > 
> > As these functions will never get executed (they are free'd along
> > with the rest of initmem) - we do not need to patch them and should
> > not display any warnings.
> > 
> > The warning is displayed because the test required to satisfy
> > jump_entry_is_init is based on init_section_contains (__init_begin to
> > __init_end) whereas the test in __jump_label_update is based on
> > init_kernel_text (_sinittext to _einittext) via kernel_text_address).
> > 
> > In addition to fixing this, we also remove an out-of-date comment
> > and use a WARN instead of a WARN_ONCE.
> 
> This last sentence is stale -- it was true in v1 but not since then.
> 
> With that droppped:
> 
> Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks.

Andrew Murray

> 
> Mark.
>  
> > Fixes: 19483677684b ("jump_label: Annotate entries that operate on __init code earlier")
> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> > Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> >  kernel/jump_label.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> > index df3008419a1d..cdb3ffab128b 100644
> > --- a/kernel/jump_label.c
> > +++ b/kernel/jump_label.c
> > @@ -407,7 +407,9 @@ static bool jump_label_can_update(struct jump_entry *entry, bool init)
> >  		return false;
> >  
> >  	if (!kernel_text_address(jump_entry_code(entry))) {
> > -		WARN_ONCE(1, "can't patch jump_label at %pS", (void *)jump_entry_code(entry));
> > +		WARN_ONCE(!jump_entry_is_init(entry),
> > +			  "can't patch jump_label at %pS",
> > +			  (void *)jump_entry_code(entry));
> >  		return false;
> >  	}
> >  
> > -- 
> > 2.21.0
> > 

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