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    SubjectRe: [PATCH 2/2] coredump: add a new elf note with siginfo fields of the signal
    On 09/13, Denys Vlasenko wrote:
    >
    > This patch adds a new elf note, NT_SIGINFO, which contains
    > the remaining fields of siginfo_t.

    I can't really comment this patch, but...

    > +struct coredump_siginfo {
    > +/* int csi_signo; in prstatus.pr_info.si_signo instead */
    > +/* int csi_errno; in prstatus.pr_info.si_errno */
    > +/* int csi_code; in prstatus.pr_info.si_code */
    > + int csi_pid; /* PID of sending process */
    > + int csi_uid; /* Real UID of sending process */
    > +/* int csi_status; SIGCHLD never kills, field isn't meaningful */
    > +/* clock_t csi_utime; SIGCHLD never kills, field isn't meaningful */
    > +/* clock_t csi_stime; SIGCHLD never kills, field isn't meaningful */
    > + void *csi_ptr; /* union with si_int */
    > + int csi_tid; /* POSIX.1b timers */
    > + int csi_overrun; /* POSIX.1b timers */
    > + long csi_band; /* SIGIO/POLL: band event */
    > + int csi_fd; /* SIGIO/POLL: file descriptor */
    > + void *csi_addr; /* SEGV/BUS: address which caused fault */
    > + int csi_trapno; /* SEGV/BUS */
    > + int csi_addr_lsb; /* SEGV/BUS: least significant bit of address */
    > + /* Can be extended in the future, if siginfo_t is extended */
    > +};
    > +
    > +static void fill_siginfo_note(struct memelfnote *note, struct coredump_siginfo *data, siginfo_t *siginfo)
    > +{
    > + data->csi_pid = siginfo->si_pid;
    > + data->csi_uid = siginfo->si_uid;
    > + data->csi_ptr = siginfo->si_ptr;
    > + data->csi_overrun = siginfo->si_overrun;
    > + data->csi_tid = siginfo->si_tid;
    > + data->csi_band = siginfo->si_band;
    > + data->csi_fd = siginfo->si_fd;
    > + data->csi_addr = siginfo->si_addr;
    > +#ifdef __ARCH_SI_TRAPNO
    > + data->csi_trapno = siginfo->si_trapno;
    > +#endif
    > + /* Prevent signed short->int expansion: */
    > + data->csi_addr_lsb = (unsigned short)siginfo->si_addr_lsb;
    > +
    > + fill_note(note, "CORE", NT_SIGINFO, sizeof(*data), data);
    > +}

    I can't understand the layout. struct siginfo is union, for example
    si_overrun only makes sense if si_code = SI_TIMER.

    Not sure this is right. I think fill_siginfo_note() should either do
    memcpy() and let userspace to decode this (raw) info, or this layout
    should be unified with copy_siginfo_to_user().

    Note also that we do not expose the upper bits of si_code to user-space,
    probably coredump should do the same, I dunno.

    Oleg.



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