Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754878Ab2BCIfh (ORCPT ); Fri, 3 Feb 2012 03:35:37 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:63074 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754724Ab2BCIfg (ORCPT ); Fri, 3 Feb 2012 03:35:36 -0500 Date: Fri, 3 Feb 2012 12:35:30 +0400 From: Cyrill Gorcunov To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Andrew Morton , Pavel Emelyanov , Serge Hallyn , KAMEZAWA Hiroyuki , Kees Cook , Tejun Heo , Andrew Vagin , "Eric W. Biederman" , Alexey Dobriyan , Andi Kleen , KOSAKI Motohiro , "H. Peter Anvin" , Thomas Gleixner , Glauber Costa , Matt Helsley , Pekka Enberg , Eric Dumazet , Vasiliy Kulikov , Valdis.Kletnieks@vt.edu Subject: Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7 Message-ID: <20120203083530.GD1968@moon> References: <20120130140905.441199885@openvz.org> <20120130141852.309402052@openvz.org> <20120203074656.GC30543@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120203074656.GC30543@elte.hu> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4160 Lines: 160 On Fri, Feb 03, 2012 at 08:46:56AM +0100, Ingo Molnar wrote: > > * Cyrill Gorcunov wrote: > > > +/* Comparision type */ > > > + * We don't expose real in-memory order of objects for security > > + * reasons, still the comparision results should be suitable for > > + * sorting. Thus, we obfuscate kernel pointers values (using random > > + * cookies obtaned at early boot stage) and compare the production > > + * instead. > > > + * 0 - equal > > + * 1 - less than > > + * 2 - greater than > > + * 3 - not equal but ordering unavailable (reserved for future) > > Broken spelling in each of those comment blocks. Are these > comments write-only? No, they are not write-only. I've fixed typos in first comment block, though I don't understand what is wrong with 0,1,2,3 comments. > > > + /* > > + * Tasks are looked up in caller's > > + * PID namespace only. > > + */ > > Could be a single line. > Ok, will do so. > > + > > + task1 = find_task_by_vpid(pid1); > > + if (!task1) { > > + rcu_read_unlock(); > > + return -ESRCH; > > + } > > + > > + task2 = find_task_by_vpid(pid2); > > + if (!task2) { > > + put_task_struct(task1); > > + rcu_read_unlock(); > > + return -ESRCH; > > + } > > This is not the standard pattern of how we do error paths ... OK, I'll try to make it in standart way. > > > + /* > > + * Note for all cases but the KCMP_FILE we > > + * don't take any locks in a sake of speed. > > + */ > > Spelling. Not sure what you mean here, but I'll drop this comment to eliminate this problem. > > > + get_random_bytes(&cookies[i][j], > > + sizeof(cookies[i][j])); > > ugly line break. > Why? Looks pretty good to me. But sure I'll change it. > > +late_initcall(kcmp_cookie_init); > > any particular reason why this needs to be a late initcall? > Grr! The late_initcall remained here from versions where I've been playing with crypto hashes. Thanks, Ingo, I'll fix! > > + > > +clean: > > + $(E) " CLEAN" > > + $(Q) rm -fr ./run_test > > + $(Q) rm -fr ./test-file > > Needs buy-in from the kbuild guys. I took breakpoint test as example. Maybe I should send this test case code as a separate patch? > > > +#ifdef CONFIG_X86_64 > > +#include > > +#else > > +#include > > +#endif > > Why is asm/unistd.h not good? > With asm/unistd.h it fails to build because it requires the headers to be installed first (ie headers_install target) so I though this way would be more convenient, no? > > +static long sys_kcmp(int pid1, int pid2, int type, int fd1, int fd2) > > +{ > > + return syscall(__NR_kcmp, (long)pid1, (long)pid2, > > + (long)type, (long)fd1, (long)fd2); > > +} > > Why is a syscall that takes long arguments defined and called > with int and then cast over to long again? > Just a habit, the args will be converted to long anyway, so I don't see a problem here. Still I can drop them. > > + int pid2 = getpid(); > > + int ret; > > + > > + fd2 = open("test-file", O_RDWR, 0644); > > + if (fd2 < 0) { > > + perror("Can't open file"); > > + exit(1); > > + } > > + > > + /* An example of output and arguments */ > > + printf("pid1: %6d pid2: %6d FD: %2d FILES: %2d VM: %2d FS: %2d " > > + "SIGHAND: %2d IO: %2d SYSVSEM: %2d INV: %2d\n", > > Visibly stray whitespaces. > > > + /* This one should return same fd */ > > + ret = sys_kcmp(pid1, pid2, KCMP_FILE, fd1, fd1); > > + if (ret) { > > + printf("FAIL: 0 expected but %d returned\n", ret); > > + ret = -1; > > + } else > > + printf("PASS: 0 returned as expected\n"); > > + exit(ret); > > this is main(), what's wrong with the standard pattern of return > ret? > It's fork'ed children. > I don't know whether this code is correct, but the high amount > of basic cleanliness problems makes me worry about that. > Code is correct. I'll clean up the nits you pointed. Cyrill -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/