Messages in this thread | | | Date | Tue, 25 Jan 2022 13:21:56 +0100 | From | Christian Brauner <> | Subject | Re: [RFC PATCH 02/15] rseq: Remove broken uapi field layout on 32-bit little endian |
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On Mon, Jan 24, 2022 at 12:12:40PM -0500, Mathieu Desnoyers 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. > > Remove those and only leave the "ptr64" union field, as this is the only > thing really needed to express the ABI. Document how 32-bit > architectures are meant to interact with this "ptr64" union field. > > Fixes: ec9c82e03a74 ("rseq: uapi: Declare rseq_cs field as union, update includes") > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > Cc: Florian Weimer <fw@deneb.enyo.de> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: linux-api@vger.kernel.org > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Andy Lutomirski <luto@amacapital.net> > Cc: Dave Watson <davejwatson@fb.com> > Cc: Paul Turner <pjt@google.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Russell King <linux@arm.linux.org.uk> > Cc: "H . Peter Anvin" <hpa@zytor.com> > Cc: Andi Kleen <andi@firstfloor.org> > Cc: Christian Brauner <christian.brauner@ubuntu.com> > Cc: Ben Maurer <bmaurer@fb.com> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Josh Triplett <josh@joshtriplett.org> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Michael Kerrisk <mtk.manpages@gmail.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Paul E. McKenney <paulmck@kernel.org> > --- > include/uapi/linux/rseq.h | 17 ++++------------- > 1 file changed, 4 insertions(+), 13 deletions(-) > > diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h > index 9a402fdb60e9..31290f2424a7 100644 > --- a/include/uapi/linux/rseq.h > +++ b/include/uapi/linux/rseq.h > @@ -105,22 +105,13 @@ struct rseq { > * Read and set by the kernel. Set by user-space with single-copy > * atomicity semantics. This field should only be updated by the > * thread which registered this data structure. Aligned on 64-bit. > + * > + * 32-bit architectures should update the low order bits of the > + * rseq_cs.ptr64 field, leaving the high order bits initialized > + * to 0. > */ > union {
A bit unfortunate we seem to have to keep the union around even though it's just one field now.
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