[REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64 and tcmalloc everywhere

[Peter Zijlstra]

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.