On Fri, Nov 27, 2020 at 2:30 PM Brian Gerst <brgerst@xxxxxxxxx> wrote: > > On Fri, Nov 27, 2020 at 1:13 PM Andy Lutomirski <luto@xxxxxxxxxx> wrote: > > > > On Thu, Nov 26, 2020 at 7:52 AM Jan Kara <jack@xxxxxxx> wrote: > > > > > > Commit converting syscalls taking 64-bit arguments to new scheme of compat > > > handlers omitted converting fanotify_mark(2) which then broke the > > > syscall for 32-bit x86 builds. Add missed conversion. It is somewhat > > > cumbersome since we need to keep the original compat handler for all the > > > other 32-bit archs. > > > > > > > This is stupendously ugly. I'm not really sure how this is supposed > > to work on any 32-bit arch. I'm also not sure whether we should > > expect the SYSCALL_DEFINE macros to figure this out by themselves. > > It works on 32-bit arches because the compiler implicitly uses > consecutive input registers or stack slots for 64-bit arguments, and > some arches have alignment requirements that result in hidden padding. > x86-32 is different now because parameters are passed in via pt_regs, > and the 64-bit value has to explicitly be reassembled from the high > and low 32-bit values, just like in the compat case. > That was my guess. > I think the simplest way to handle this is add a wrapper in > arch/x86/kernel/sys_ia32.c with the other fs syscalls that need 64-bit > args. That keeps this mess out of general code. Want to send a patch? I also wonder if there's a straightforward way to statically check this. Maybe the syscall wrapper macros could be rigged up to avoid emitting the ia32 stubs if there is a u64 or s64 arg, so the build would fail if someone tries to stick one in the syscall tables. I tried to do this, but I got a bit lost in the macro maze and my attempt didn't work. --Andy
