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

From: Mark Rutland <mark.rutland@arm.com>
To: Andrew Murray <andrew.murray@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 16:32:37 +0100	[thread overview]
Message-ID: <20190822153237.GC33080@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20190812143625.42745-2-andrew.murray@arm.com>

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 In addition to fixing this, we also remove an out-of-date comment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>

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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