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Wysocki" , Sakari Ailus , Sergey Senozhatsky , Stephen Rothwell , Steven Rostedt Subject: Re: [PATCH] rss_stat: Add support to detect RSS updates of external mm Message-ID: <20191106080037.GA59367@google.com> References: <20191106024452.81923-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191106024452.81923-1-joel@joelfernandes.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (19/11/05 21:44), Joel Fernandes (Google) wrote: [..] > +++ b/lib/vsprintf.c > @@ -761,11 +761,34 @@ static int __init initialize_ptr_random(void) > early_initcall(initialize_ptr_random); > > /* Maps a pointer to a 32 bit unique identifier. */ > +int ptr_to_hashval(const void *ptr, unsigned long *hashval_out) > +{ > + const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)"; > + unsigned long hashval; > + > + if (static_branch_unlikely(¬_filled_random_ptr_key)) > + return -EAGAIN; > + > +#ifdef CONFIG_64BIT > + hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key); > + /* > + * Mask off the first 32 bits, this makes explicit that we have > + * modified the address (and 32 bits is plenty for a unique ID). > + */ > + hashval = hashval & 0xffffffff; > +#else > + hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key); > +#endif > + *hashval_out = hashval; > + return 0; > +} Maybe we want to move this thing to more generic code - lib/siphash.c - since it's going to have several users. -ss