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    signal/parisc: Document a conflict with SI_USER with SIGFPE · b5daf2b9
    Eric W. Biederman 提交于
    Setting si_code to 0 results in a userspace seeing an si_code of 0.
    This is the same si_code as SI_USER.  Posix and common sense requires
    that SI_USER not be a signal specific si_code.  As such this use of 0
    for the si_code is a pretty horribly broken ABI.
    
    Further use of si_code == 0 guaranteed that copy_siginfo_to_user saw a
    value of __SI_KILL and now sees a value of SIL_KILL with the result
    that uid and pid fields are copied and which might copying the si_addr
    field by accident but certainly not by design.  Making this a very
    flakey implementation.
    
    Utilizing FPE_FIXME siginfo_layout will now return SIL_FAULT and the
    appropriate fields will reliably be copied.
    
    This bug is 13 years old and parsic machines are no longer being built
    so I don't know if it possible or worth fixing it.  But it is at least
    worth documenting this so other architectures don't make the same
    mistake.
    
    Possible ABI fixes includee:
      - Send the signal without siginfo
      - Don't generate a signal
      - Possibly assign and use an appropriate si_code
      - Don't handle cases which can't happen
    
    Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
    Cc: Helge Deller <deller@gmx.de>
    Cc: linux-parisc@vger.kernel.org
    Ref: 313c01d3e3fd ("[PATCH] PA-RISC update for 2.6.0")
    Histroy Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.gitSigned-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
    b5daf2b9
siginfo.h 356 字节