Messages in this thread | | | Date | Fri, 3 Feb 2012 12:35:30 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7 |
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On Fri, Feb 03, 2012 at 08:46:56AM +0100, Ingo Molnar wrote: > > * Cyrill Gorcunov <gorcunov@openvz.org> 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 <asm/unistd_64.h> > > +#else > > +#include <asm/unistd_32.h> > > +#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
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