On Sun 01-11-20 22:27:38, Paweł Jasiak wrote: > I am trying to run examples from man fanotify.7 but fanotify_mark always > fail with errno = EFAULT. > > fanotify_mark declaration is > > SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags, > __u64, mask, int, dfd, > const char __user *, pathname) > > When > > fanotify_mark(4, FAN_MARK_ADD | FAN_MARK_ONLYDIR, > FAN_CREATE | FAN_ONDIR, AT_FDCWD, 0xdeadc0de) > > is called on kernel side I can see in do_syscall_32_irqs_on that CPU > context is > bx = 0x4 = 4 > cx = 0x9 = FAN_MARK_ADD | FAN_MARK_ONLYDIR, > dx = 0x40000100 = FAN_CREATE | FAN_ONDIR > si = 0x0 > di = 0xffffff9c = AT_FDCWD > bp = 0xdeadc0de > ax = 0xffffffda > orix_ax = 0x153 > > I am not sure if it is ok because third argument is uint64_t so if I > understand correctly mask should be divided into two registers (dx and > si). > > But in fanotify_mark we get > fanotify_fd = 4 = bx > flags = 0x9 = cx > mask = 0x40000100 = dx > dfd = 0 = si > pathname = 0xffffff9c = di > > I believe that correct order is > fanotify_fd = 4 = bx > flags = 0x9 = cx > mask = 0x40000100 = (si << 32) | dx > dfd = 0xffffff9c = di > pathname = 0xdeadc0de = bp > > I think that we should call COMPAT version of fanotify_mark here > > COMPAT_SYSCALL_DEFINE6(fanotify_mark, > int, fanotify_fd, unsigned int, flags, > __u32, mask0, __u32, mask1, int, dfd, > const char __user *, pathname) > > or something wrong is with 64-bits arguments. > > I am running Linux 5.9.2 i686 on Pentium III (Coppermine). > For tests I am using Debian sid on qemu with 5.9.2 and default kernel > from repositories. > > Everything works fine on 5.5 and 5.4. Strange. Thanks for report. Looks like some issue got created / exposed somewhere between 5.5 and 5.9 (actually probably between 5.5 and 5.7 because the Linaro report you mentioned [1] is from 5.7-rc6). There were no changes in this area in fanotify, I think it must have been some x86 change that triggered this. Hum, looking into x86 changelog in that time range there was a series rewriting 32-bit ABI [2] that got merged into 5.7-rc1. Can you perhaps check whether 5.6 is good and 5.7-rc1 is bad? Brian, any idea whether your series could regress fanotify_mark(2) syscall? Do we have somewhere documented which syscalls need compat wrappers and how they should look like? Honza [1] https://lists.linux.it/pipermail/ltp/2020-June/017436.html [2] https://lore.kernel.org/lkml/20200313195144.164260-1-brgerst@xxxxxxxxx/ -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
