Re: [PATCH 1/3] sparc64: Add compile-time asserts for siginfo_t offsets

Marco Elver
2021-04-30T18:11:42Z

On Fri, 30 Apr 2021 at 19:42, Eric W. Biederman <ebiederm@xmission.com> wrote:
>
> Marco Elver <elver@google.com> writes:
>
> > To help catch ABI breaks at compile-time, add compile-time assertions to
> > verify the siginfo_t layout. Unlike other architectures, sparc64 is
> > special, because it is one of few architectures requiring si_trapno.
> > ABI breaks around that field would only be caught here.
>
> Arnd Bergman recently pointed out that we can move si_trapno into the
> union and make it specific to a handful of signals. Like we do other
> items in the union.
>
> Given that the code of perf_sigtrap is pretty much broken if si_trapno
> needs to be filled out. I think we should make that change before
> we set this ABI in stone like this.
>
> Otherwise this looks good.

Thanks, that's reasonable -- I'll reply to the other thread in a few minutes.

-- Marco

> Eric
>
> > Link: https://lkml.kernel.org/r/m11rat9f85.fsf@fess.ebiederm.org
> > Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
> > Signed-off-by: Marco Elver <elver@google.com>
> > ---
> > arch/sparc/kernel/signal32.c | 34 ++++++++++++++++++++++++++++++++++
> > arch/sparc/kernel/signal_64.c | 33 +++++++++++++++++++++++++++++++++
> > 2 files changed, 67 insertions(+)
> >
> > diff --git a/arch/sparc/kernel/signal32.c b/arch/sparc/kernel/signal32.c
> > index e9695a06492f..778ed5c26d4a 100644
> > --- a/arch/sparc/kernel/signal32.c
> > +++ b/arch/sparc/kernel/signal32.c
> > @@ -745,3 +745,37 @@ asmlinkage int do_sys32_sigstack(u32 u_ssptr, u32 u_ossptr, unsigned long sp)
> > out:
> > return ret;
> > }
> > +
> > +/*
> > + * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as
> > + * changes likely come with new fields that should be added below.
> > + */
> > +static_assert(NSIGILL == 11);
> > +static_assert(NSIGFPE == 15);
> > +static_assert(NSIGSEGV == 9);
> > +static_assert(NSIGBUS == 5);
> > +static_assert(NSIGTRAP == 6);
> > +static_assert(NSIGCHLD == 6);
> > +static_assert(NSIGSYS == 2);
> > +static_assert(offsetof(compat_siginfo_t, si_signo) == 0x00);
> > +static_assert(offsetof(compat_siginfo_t, si_errno) == 0x04);
> > +static_assert(offsetof(compat_siginfo_t, si_code) == 0x08);
> > +static_assert(offsetof(compat_siginfo_t, si_pid) == 0x0c);
> > +static_assert(offsetof(compat_siginfo_t, si_uid) == 0x10);
> > +static_assert(offsetof(compat_siginfo_t, si_tid) == 0x0c);
> > +static_assert(offsetof(compat_siginfo_t, si_overrun) == 0x10);
> > +static_assert(offsetof(compat_siginfo_t, si_status) == 0x14);
> > +static_assert(offsetof(compat_siginfo_t, si_utime) == 0x18);
> > +static_assert(offsetof(compat_siginfo_t, si_stime) == 0x1c);
> > +static_assert(offsetof(compat_siginfo_t, si_value) == 0x14);
> > +static_assert(offsetof(compat_siginfo_t, si_int) == 0x14);
> > +static_assert(offsetof(compat_siginfo_t, si_ptr) == 0x14);
> > +static_assert(offsetof(compat_siginfo_t, si_addr) == 0x0c);
> > +static_assert(offsetof(compat_siginfo_t, si_trapno) == 0x10);
> > +static_assert(offsetof(compat_siginfo_t, si_addr_lsb) == 0x14);
> > +static_assert(offsetof(compat_siginfo_t, si_lower) == 0x18);
> > +static_assert(offsetof(compat_siginfo_t, si_upper) == 0x1c);
> > +static_assert(offsetof(compat_siginfo_t, si_pkey) == 0x18);
> > +static_assert(offsetof(compat_siginfo_t, si_perf) == 0x14);
> > +static_assert(offsetof(compat_siginfo_t, si_band) == 0x0c);
> > +static_assert(offsetof(compat_siginfo_t, si_fd) == 0x10);
> > diff --git a/arch/sparc/kernel/signal_64.c b/arch/sparc/kernel/signal_64.c
> > index a0eec62c825d..c9bbf5f29078 100644
> > --- a/arch/sparc/kernel/signal_64.c
> > +++ b/arch/sparc/kernel/signal_64.c
> > @@ -556,3 +556,36 @@ void do_notify_resume(struct pt_regs *regs, unsigned long orig_i0, unsigned long
> > user_enter();
> > }
> >
> > +/*
> > + * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as
> > + * changes likely come with new fields that should be added below.
> > + */
> > +static_assert(NSIGILL == 11);
> > +static_assert(NSIGFPE == 15);
> > +static_assert(NSIGSEGV == 9);
> > +static_assert(NSIGBUS == 5);
> > +static_assert(NSIGTRAP == 6);
> > +static_assert(NSIGCHLD == 6);
> > +static_assert(NSIGSYS == 2);
> > +static_assert(offsetof(siginfo_t, si_signo) == 0x00);
> > +static_assert(offsetof(siginfo_t, si_errno) == 0x04);
> > +static_assert(offsetof(siginfo_t, si_code) == 0x08);
> > +static_assert(offsetof(siginfo_t, si_pid) == 0x10);
> > +static_assert(offsetof(siginfo_t, si_uid) == 0x14);
> > +static_assert(offsetof(siginfo_t, si_tid) == 0x10);
> > +static_assert(offsetof(siginfo_t, si_overrun) == 0x14);
> > +static_assert(offsetof(siginfo_t, si_status) == 0x18);
> > +static_assert(offsetof(siginfo_t, si_utime) == 0x20);
> > +static_assert(offsetof(siginfo_t, si_stime) == 0x28);
> > +static_assert(offsetof(siginfo_t, si_value) == 0x18);
> > +static_assert(offsetof(siginfo_t, si_int) == 0x18);
> > +static_assert(offsetof(siginfo_t, si_ptr) == 0x18);
> > +static_assert(offsetof(siginfo_t, si_addr) == 0x10);
> > +static_assert(offsetof(siginfo_t, si_trapno) == 0x18);
> > +static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x20);
> > +static_assert(offsetof(siginfo_t, si_lower) == 0x28);
> > +static_assert(offsetof(siginfo_t, si_upper) == 0x30);
> > +static_assert(offsetof(siginfo_t, si_pkey) == 0x28);
> > +static_assert(offsetof(siginfo_t, si_perf) == 0x20);
> > +static_assert(offsetof(siginfo_t, si_band) == 0x10);
> > +static_assert(offsetof(siginfo_t, si_fd) == 0x14);