On Mon, Dec 10, 2018 at 04:30:25PM +0300, Dmitry V. Levin wrote: > On Mon, Dec 10, 2018 at 02:06:28PM +0100, Geert Uytterhoeven wrote: > > On Mon, Dec 10, 2018 at 1:41 PM Dmitry V. Levin <l...@altlinux.org> wrote: > > > On Mon, Dec 10, 2018 at 09:45:42AM +0100, Geert Uytterhoeven wrote: > > > > On Mon, Dec 10, 2018 at 5:30 AM Dmitry V. Levin <l...@altlinux.org> > > > > wrote: > > > > > syscall_get_* functions are required to be implemented on all > > > > > architectures in order to extend the generic ptrace API with > > > > > PTRACE_GET_SYSCALL_INFO request. > > > > > > > > > > This introduces asm/syscall.h on m68k implementing all 5 syscall_get_* > > > > > functions as documented in asm-generic/syscall.h: syscall_get_nr, > > > > > syscall_get_arguments, syscall_get_error, syscall_get_return_value, > > > > > and syscall_get_arch. > > > > > > > > > > Cc: Geert Uytterhoeven <ge...@linux-m68k.org> > > > > > Cc: Oleg Nesterov <o...@redhat.com> > > > > > Cc: Andy Lutomirski <l...@kernel.org> > > > > > Cc: Elvira Khabirova <lineprin...@altlinux.org> > > > > > Cc: Eugene Syromyatnikov <e...@redhat.com> > > > > > Cc: linux-m...@lists.linux-m68k.org > > > > > Signed-off-by: Dmitry V. Levin <l...@altlinux.org> > > > > > --- > > > > > > > > > > Notes: > > > > > v5: added syscall_get_nr, syscall_get_arguments, > > > > > syscall_get_error, > > > > > and syscall_get_return_value > > > > > v1: added syscall_get_arch > > > > > > > > > --- /dev/null > > > > > +++ b/arch/m68k/include/asm/syscall.h > > > > > @@ -0,0 +1,39 @@ > > > > > > > > > +static inline void > > > > > +syscall_get_arguments(struct task_struct *task, struct pt_regs *regs, > > > > > + unsigned int i, unsigned int n, unsigned long > > > > > *args) > > > > > +{ > > > > > + BUG_ON(i + n > 6); > > > > > > > > Does this have to crash the kernel? > > > > > > This is what most of other architectures do, but we could choose > > > a softer approach, e.g. use WARN_ON_ONCE instead. > > > > > > > Perhaps you can return an error code instead? > > > > > > That would be problematic given the signature of this function > > > and the nature of the potential bug which would most likely be a usage > > > error. > > > > Of course to handle that, the function's signature need to be changed. > > Changing it has the advantage that the error handling can be done at the > > caller, in common code, instead of duplicating it for all > > architectures, possibly > > leading to different semantics. > > Given that *all* current users of syscall_get_arguments specify i == 0 > (and there is an architecture that has BUG_ON(i)), > it should be really a usage error to get into situation where i + n > 6, > I wish a BUILD_BUG_ON could be used here instead. > > I don't think it worths pushing the change of API just to convert > a "cannot happen" assertion into an error that would have to be dealt with > on the caller side.
I suggest the following BUG_ON replacement for syscall_get_arguments: #define SYSCALL_MAX_ARGS 6 static inline void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs, unsigned int i, unsigned int n, unsigned long *args) { /* * Ideally there should have been * BUILD_BUG_ON(i + n > SYSCALL_MAX_ARGS); * instead of these checks. */ if (unlikely(i > SYSCALL_MAX_ARGS)) { WARN_ONCE(1, "i > SYSCALL_MAX_ARGS"); return; } if (unlikely(n > SYSCALL_MAX_ARGS - i)) { WARN_ONCE(1, "i + n > SYSCALL_MAX_ARGS"); n = SYSCALL_MAX_ARGS - i; } BUILD_BUG_ON(sizeof(regs->d1) != sizeof(args[0])); memcpy(args, ®s->d1 + i, n * sizeof(args[0])); } -- ldv
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