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.
A bit unfortunate we seem to have to keep the union around even though it's just one field now.