Re: [PATCH 2/3] signal: Implement SIL_FAULT_TRAPNO

[Marco Elver <elver@google.com>]

On Sat, 1 May 2021 at 00:54, Eric W. Biederman <ebiederm@xmission.com> wrote:
>
> Now that si_trapno is part of the union in _si_fault and available on
> all architectures, add SIL_FAULT_TRAPNO and update siginfo_layout to
> return SIL_FAULT_TRAPNO when si_trapno is actually used.
>
> Update the code that uses siginfo_layout to deal with SIL_FAULT_TRAPNO
> and have the same code ignore si_trapno in in all other cases.
>
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---
>  fs/signalfd.c          |  7 ++-----
>  include/linux/signal.h |  1 +
>  kernel/signal.c        | 36 ++++++++++++++----------------------
>  3 files changed, 17 insertions(+), 27 deletions(-)
>
> diff --git a/fs/signalfd.c b/fs/signalfd.c
> index 040a1142915f..126c681a30e7 100644
> --- a/fs/signalfd.c
> +++ b/fs/signalfd.c
> @@ -123,15 +123,12 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
>                  */
>         case SIL_FAULT:
>                 new.ssi_addr = (long) kinfo->si_addr;
> -#ifdef __ARCH_SI_TRAPNO
> +       case SIL_FAULT_TRAPNO:
> +               new.ssi_addr = (long) kinfo->si_addr;
>                 new.ssi_trapno = kinfo->si_trapno;
> -#endif
>                 break;
>         case SIL_FAULT_MCEERR:
>                 new.ssi_addr = (long) kinfo->si_addr;
> -#ifdef __ARCH_SI_TRAPNO
> -               new.ssi_trapno = kinfo->si_trapno;
> -#endif
>                 new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
>                 break;
>         case SIL_PERF_EVENT:
> diff --git a/include/linux/signal.h b/include/linux/signal.h
> index 1e98548d7cf6..5160fd45e5ca 100644
> --- a/include/linux/signal.h
> +++ b/include/linux/signal.h
> @@ -40,6 +40,7 @@ enum siginfo_layout {
>         SIL_TIMER,
>         SIL_POLL,
>         SIL_FAULT,
> +       SIL_FAULT_TRAPNO,
>         SIL_FAULT_MCEERR,
>         SIL_FAULT_BNDERR,
>         SIL_FAULT_PKUERR,
> diff --git a/kernel/signal.c b/kernel/signal.c
> index c3017aa8024a..7b2d61cb7411 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1194,6 +1194,7 @@ static inline bool has_si_pid_and_uid(struct kernel_siginfo *info)
>         case SIL_TIMER:
>         case SIL_POLL:
>         case SIL_FAULT:
> +       case SIL_FAULT_TRAPNO:
>         case SIL_FAULT_MCEERR:
>         case SIL_FAULT_BNDERR:
>         case SIL_FAULT_PKUERR:
> @@ -2527,6 +2528,7 @@ static void hide_si_addr_tag_bits(struct ksignal *ksig)
>  {
>         switch (siginfo_layout(ksig->sig, ksig->info.si_code)) {
>         case SIL_FAULT:
> +       case SIL_FAULT_TRAPNO:
>         case SIL_FAULT_MCEERR:
>         case SIL_FAULT_BNDERR:
>         case SIL_FAULT_PKUERR:
> @@ -3206,6 +3208,12 @@ enum siginfo_layout siginfo_layout(unsigned sig, int si_code)
>                         if ((sig == SIGBUS) &&
>                             (si_code >= BUS_MCEERR_AR) && (si_code <= BUS_MCEERR_AO))
>                                 layout = SIL_FAULT_MCEERR;
> +                       else if (IS_ENABLED(ALPHA) &&
> +                                ((sig == SIGFPE) ||
> +                                 ((sig == SIGTRAP) && (si_code == TRAP_UNK))))
> +                               layout = SIL_FAULT_TRAPNO;
> +                       else if (IS_ENABLED(SPARC) && (sig == SIGILL) && (si_code == ILL_ILLTRP))
> +                               layout = SIL_FAULT_TRAPNO;

The breakage isn't apparent here, but in later patches. These need to
become CONFIG_SPARC and CONFIG_ALPHA.


>                         else if ((sig == SIGSEGV) && (si_code == SEGV_BNDERR))
>                                 layout = SIL_FAULT_BNDERR;
>  #ifdef SEGV_PKUERR
> @@ -3317,30 +3325,22 @@ void copy_siginfo_to_external32(struct compat_siginfo *to,
>                 break;
>         case SIL_FAULT:
>                 to->si_addr = ptr_to_compat(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> +               break;
> +       case SIL_FAULT_TRAPNO:
> +               to->si_addr = ptr_to_compat(from->si_addr);
>                 to->si_trapno = from->si_trapno;
> -#endif
>                 break;
>         case SIL_FAULT_MCEERR:
>                 to->si_addr = ptr_to_compat(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> -               to->si_trapno = from->si_trapno;
> -#endif
>                 to->si_addr_lsb = from->si_addr_lsb;
>                 break;
>         case SIL_FAULT_BNDERR:
>                 to->si_addr = ptr_to_compat(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> -               to->si_trapno = from->si_trapno;
> -#endif
>                 to->si_lower = ptr_to_compat(from->si_lower);
>                 to->si_upper = ptr_to_compat(from->si_upper);
>                 break;
>         case SIL_FAULT_PKUERR:
>                 to->si_addr = ptr_to_compat(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> -               to->si_trapno = from->si_trapno;
> -#endif
>                 to->si_pkey = from->si_pkey;
>                 break;
>         case SIL_PERF_EVENT:
> @@ -3401,30 +3401,22 @@ static int post_copy_siginfo_from_user32(kernel_siginfo_t *to,
>                 break;
>         case SIL_FAULT:
>                 to->si_addr = compat_ptr(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> +               break;
> +       case SIL_FAULT_TRAPNO:
> +               to->si_addr = compat_ptr(from->si_addr);
>                 to->si_trapno = from->si_trapno;
> -#endif
>                 break;
>         case SIL_FAULT_MCEERR:
>                 to->si_addr = compat_ptr(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> -               to->si_trapno = from->si_trapno;
> -#endif
>                 to->si_addr_lsb = from->si_addr_lsb;
>                 break;
>         case SIL_FAULT_BNDERR:
>                 to->si_addr = compat_ptr(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> -               to->si_trapno = from->si_trapno;
> -#endif
>                 to->si_lower = compat_ptr(from->si_lower);
>                 to->si_upper = compat_ptr(from->si_upper);
>                 break;
>         case SIL_FAULT_PKUERR:
>                 to->si_addr = compat_ptr(from->si_addr);
> -#ifdef __ARCH_SI_TRAPNO
> -               to->si_trapno = from->si_trapno;
> -#endif
>                 to->si_pkey = from->si_pkey;
>                 break;
>         case SIL_PERF_EVENT:
> --
> 2.30.1