Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] m68k: Implement "current_stack_pointer" | Date | Thu, 24 Feb 2022 09:12:51 +0000 |
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From: Geert Uytterhoeven > Sent: 24 February 2022 08:59 ... > > +register unsigned long current_stack_pointer __asm__("sp"); > > I don't know what HARDENED_USERCOPY does, so I don't know if you need > "usp" (see rdusp()) or "sp"?
HARDENED_USERCOPY significantly slows down some systems calls (especially things like sendmsg()) by trying to run-time verify that the kernel buffer doesn't overrun a stack frame or kmalloc()ed buffer.
I've got measurable improvements by either using __copy_to/from_user() (which skips the tests) or user_access_begin() and __get_user().
At the moment the code for reading a compat iovec[] is actually faster than that for a native one!
David
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