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McKenney" , Boqun Feng , 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: <49066300.2176.1522249413336.JavaMail.zimbra@efficios.com> In-Reply-To: <20180328125216.GF4129@hirez.programming.kicks-ass.net> References: <20180327160542.28457-1-mathieu.desnoyers@efficios.com> <20180327160542.28457-3-mathieu.desnoyers@efficios.com> <20180328122946.GU4043@hirez.programming.kicks-ass.net> <20180328125216.GF4129@hirez.programming.kicks-ass.net> 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: 7bit 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: 8pO+aFtj8q0XB7AMrsQCaF2stdX26A== 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 8:52 AM, Peter Zijlstra peterz@infradead.org wrote: > On Wed, Mar 28, 2018 at 02:29:46PM +0200, Peter Zijlstra wrote: >> > +static int rseq_get_rseq_cs(struct task_struct *t, >> > + unsigned long *start_ip, >> > + unsigned long *post_commit_offset, >> > + unsigned long *abort_ip, >> > + uint32_t *cs_flags) >> > +{ > >> >> > + >> > + *cs_flags = rseq_cs.flags; >> > + *start_ip = rseq_cs.start_ip; >> > + *post_commit_offset = rseq_cs.post_commit_offset; >> > + *abort_ip = rseq_cs.abort_ip; >> >> Then this becomes a straight struct assignment. > > I initially suggested passing a structure instead of many arguments, but > then recondidered, mostly because it will be inlined (due to having only > the one caller) anyway. Still, maybe a struct will work better, I dunno. I find the result of struct pointer argument cleaner indeed. I'll go for that approach. I'll memset rseq_cs to 0 in the following case though, because the caller expects the content of the structure to be set when rseq_get_rseq_cs() succeeds. static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) { struct rseq_cs __user *urseq_cs; unsigned long ptr; u32 __user *usig; u32 sig; int ret; ret = __get_user(ptr, &t->rseq->rseq_cs); if (ret) return ret; if (!ptr) { memset(rseq_cs, 0, sizeof(*rseq_cs)); return 0; } [...] Thanks! Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com