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Date: Tue, 28 Apr 2026 10:13:08 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@kernel.org>
Cc: Mathias Stearn <mathias@mongodb.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Jinjie Ruan <ruanjinjie@huawei.com>, linux-man@vger.kernel.org,
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	Catalin Marinas <catalin.marinas@arm.com>,
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	"Paul E. McKenney" <paulmck@kernel.org>,
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Subject: Re: [REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64
 and tcmalloc everywhere
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In-Reply-To: <20260428073938.GH3126523@noisy.programming.kicks-ass.net>

On Tue, Apr 28, 2026 at 09:39:38AM +0200, Peter Zijlstra wrote:

> > +	return IS_ALIGNED((unsigned long)rseq, rseq_alloc_align()) &&
> > +		rseq_len >= offsetof(struct rseq, end);
> > +}
> 
> Given we really only differentiate between ORIG_RSEQ_SIZE (32) and
> sizeof(struct rseq), perhaps we should also add something like:
> 
> 	if (rseq_len != sizeof(struct rseq))
> 		return false;
> 

Wakeup juice, I need more wakeup juice :-) Its there, except written
weirdly with that offsetof thing.