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McKenney" , Andy Lutomirski , Dave Watson , linux-kernel , linux-api , Paul Turner , Andrew Morton , Russell King , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andrew Hunter , Andi Kleen , Chris Lameter , Ben Maurer , rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk , Alexander Viro Message-ID: <991996685.2091.1522247499415.JavaMail.zimbra@efficios.com> In-Reply-To: <777590253.2016.1522245960189.JavaMail.zimbra@efficios.com> References: <20180327160542.28457-1-mathieu.desnoyers@efficios.com> <20180327160542.28457-3-mathieu.desnoyers@efficios.com> <20180328064703.56hsuicmikejg7np@tardis> <777590253.2016.1522245960189.JavaMail.zimbra@efficios.com> Subject: Re: [RFC PATCH for 4.17 02/21] rseq: Introduce restartable sequences system call (v12) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Originating-IP: [167.114.142.138] X-Mailer: Zimbra 8.8.7_GA_1964 (ZimbraWebClient - FF52 (Linux)/8.8.7_GA_1964) Thread-Topic: rseq: Introduce restartable sequences system call (v12) Thread-Index: giprJFg0sw1tC1sJYpw5uUx6Rdd1NHz1S5NN Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: ----- On Mar 28, 2018, at 10:06 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote: > ----- On Mar 28, 2018, at 2:47 AM, Boqun Feng boqun.feng@gmail.com wrote: > >> On Tue, Mar 27, 2018 at 12:05:23PM -0400, Mathieu Desnoyers wrote: >> [...] >>> Changes since v11: >>> >>> - Replace task struct rseq_preempt, rseq_signal, and rseq_migrate >>> bool by u32 rseq_event_mask. >> [...] >>> @@ -979,6 +980,17 @@ struct task_struct { >>> unsigned long numa_pages_migrated; >>> #endif /* CONFIG_NUMA_BALANCING */ >>> >>> +#ifdef CONFIG_RSEQ >>> + struct rseq __user *rseq; >>> + u32 rseq_len; >>> + u32 rseq_sig; >>> + /* >>> + * RmW on rseq_event_mask must be performed atomically >>> + * with respect to preemption. >>> + */ >>> + unsigned long rseq_event_mask; >> >> s/unsigned long/u32 > > good point, fixed. > Actually, by having a u32 instead of unsigned long here, it triggers those warnings: In file included from ./include/linux/bitops.h:38:0, from ./include/linux/kernel.h:11, from certs/system_keyring.c:13: ./arch/x86/include/asm/bitops.h:73:1: note: expected ‘volatile long unsigned int *’ but argument is of type ‘u32 *’ set_bit(long nr, volatile unsigned long *addr) ^ I suspect that casting the u32 * to a unsigned long * is not a safe approach, because the code can generate a load/store on unallocated memory (kasan might complain). Thoughts ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com