linux-kernel - Re: [PATCH 4.19 078/191] ia64: kprobes: Use generic kretprobe trampoline handler

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Date:   Thu, 5 Nov 2020 20:35:31 +0100
From:   Pavel Machek <pavel@....cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 078/191] ia64: kprobes: Use generic kretprobe
 trampoline handler

Hi!

> From: Masami Hiramatsu <mhiramat@...nel.org>
> 
> [ Upstream commit e792ff804f49720ce003b3e4c618b5d996256a18 ]
> 
> Use the generic kretprobe trampoline handler. Don't use
> framepointer verification.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Link: https://lore.kernel.org/r/159870606883.1229682.12331813108378725668.stgit@devnote2
> Signed-off-by: Sasha Levin <sashal@...nel.org>

There's no explanation here why this is good idea for -stable.

Plus, this seems to depend on commit
66ada2ccae4ed4dd07ba91df3b5fdb4c11335bd1 which is not present in
stable, so this will likely not build due to lack of
__kretprobe_trampoline_handler symbol. (I don't have ia64 to verify):

$ grep -ri __kretprobe_trampoline_handler .
./arch/ia64/kernel/kprobes.c:	regs->cr_iip = __kretprobe_trampoline_handler(regs, kretprobe_trampoline, NULL);
$

I believe it should be dropped.

Best regards,
									Pavel
...
> -	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
> -		hlist_del(&ri->hlist);
> -		kfree(ri);
> -	}
> +	regs->cr_iip = __kretprobe_trampoline_handler(regs, kretprobe_trampoline, NULL);

-- 
http://www.livejournal.com/~pavelmachek

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