linux-kernel - Re: [PATCH 1/3] sparc64: Add compile-time asserts for siginfo

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Date:   Fri, 30 Apr 2021 12:42:15 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Marco Elver <elver@...gle.com>
Cc:     linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org,
        davem@...emloft.net, mark.rutland@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        sparclinux@...r.kernel.org
Subject: Re: [PATCH 1/3] sparc64: Add compile-time asserts for siginfo_t offsets

Marco Elver <elver@...gle.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.

Eric

> Link: https://lkml.kernel.org/r/m11rat9f85.fsf@fess.ebiederm.org
> Suggested-by: Eric W. Biederman <ebiederm@...ssion.com>
> Signed-off-by: Marco Elver <elver@...gle.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);