Messages in this thread | | | Date | Mon, 24 Jan 2022 06:49:50 -0500 (EST) | From | Mathieu Desnoyers <> | Subject | Re: [RFC PATCH] rseq: Fix broken uapi field layout on 32-bit little endian |
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----- On Jan 24, 2022, at 2:42 AM, Linus Torvalds torvalds@linux-foundation.org wrote:
> On Sun, Jan 23, 2022 at 9:32 PM Mathieu Desnoyers > <mathieu.desnoyers@efficios.com> wrote: >> >> The rseq rseq_cs.ptr.{ptr32,padding} uapi endianness handling is >> entirely wrong on 32-bit little endian: a preprocessor logic mistake >> wrongly uses the big endian field layout on 32-bit little endian >> architectures. >> >> Fortunately, those ptr32 accessors were never used within the kernel, >> and only meant as a convenience for user-space. > > Please don't double down on something that was already broken once. > > Just remove the broken 32-bit one entirely that the kernel doesn't > even use, and make everybody use > > __u64 ptr64; > > and be done with it.
OK, should I just leave:
struct rseq { [...] union rseq_cs { __u64 ptr64; } rseq_cs; [...] };
and remove all the other content from the union, so users of rseq_abi->rseq_cs.ptr64 will continue to work as-is with either old and new headers ? This keeps a union in place with a single element, so I just want to confirm with you that is what you have in mind.
It does make tons of sense to just remove the broken convenience code and let user-space handle this based on the ptr64 field, so it will work fine with old and new headers.
Thanks for your feedback, and travel safe!
Mathieu
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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