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    Subject[PATCH v4 2/5] signal: Implement SIL_FAULT_TRAPNO
    From: "Eric W. Biederman" <ebiederm@xmission.com>

    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 the code assumes si_trapno is valid.

    There is room for future changes to reduce when si_trapno is valid but
    this is all that is needed to make si_trapno and the other members of
    the the union in _sigfault mutually exclusive.

    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.

    v1: https://lkml.kernel.org/r/m1o8dvs7s7.fsf_-_@fess.ebiederm.org
    v2: https://lkml.kernel.org/r/20210505141101.11519-6-ebiederm@xmission.com
    Reviewed-by: Marco Elver <elver@google.com>
    Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
    ---
    fs/signalfd.c | 8 +++-----
    include/linux/signal.h | 1 +
    kernel/signal.c | 34 ++++++++++++----------------------
    3 files changed, 16 insertions(+), 27 deletions(-)

    diff --git a/fs/signalfd.c b/fs/signalfd.c
    index 040a1142915f..e87e59581653 100644
    --- a/fs/signalfd.c
    +++ b/fs/signalfd.c
    @@ -123,15 +123,13 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
    */
    case SIL_FAULT:
    new.ssi_addr = (long) kinfo->si_addr;
    -#ifdef __ARCH_SI_TRAPNO
    + break;
    + 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 65888aec65a0..597594ee72de 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:
    @@ -3214,6 +3216,10 @@ enum siginfo_layout siginfo_layout(unsigned sig, int si_code)
    #endif
    else if ((sig == SIGTRAP) && (si_code == TRAP_PERF))
    layout = SIL_PERF_EVENT;
    +#ifdef __ARCH_SI_TRAPNO
    + else if (layout == SIL_FAULT)
    + layout = SIL_FAULT_TRAPNO;
    +#endif
    }
    else if (si_code <= NSIGPOLL)
    layout = SIL_POLL;
    @@ -3317,30 +3323,22 @@ 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 +3399,22 @@ 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
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