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> > /* > - * struct rseq is aligned on 4 * 8 bytes to ensure it is always > - * contained within a single cache-line. > + * The alignment of struct rseq used by the kernel needs to be 32 bytes > + * so the kernel can interact with legacy userspace which allocate > + * struct rseq with its original alignment. > + * Userspace aligns struct rseq allocation on 32 bytes or more. I plan to send a v3 of this series to clarify this uapi comment with: /* * The original size and alignment of the allocation for struct rseq is * 32 bytes. * * The allocation size needs to be greater or equal to * max(getauxval(AT_RSEQ_FEATURE_SIZE), 32), and the allocation needs to * be aligned on max(getauxval(AT_RSEQ_ALIGN), 32). * * As an alternative, userspace is allowed to use both the original size * and alignment of 32 bytes for backward compatibility. * * A single active struct rseq registration per thread is allowed. */ Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com