Hi Andi,
On Sat, Mar 20, 2010 at 5:29 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>
> Also clarify siginfo_t behaviour in signal.7 a bit with a new table.
>
> Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>
> Index: man-pages-3.24/man7/signal.7
> ===================================================================
> --- man-pages-3.24.orig/man7/signal.7
> +++ man-pages-3.24/man7/signal.7
> @@ -40,6 +40,7 @@
> .\" Added section on system call restarting (SA_RESTART)
> .\" Added section on stop/cont signals interrupting syscalls.
> .\" 2008-10-05, mtk: various additions
> +.\" 2009-10-03, Andi Kleen: add reference to implicit siginfo_t
> .\"
> .TH SIGNAL 7 2010-02-03 "Linux" "Linux Programmer's Manual"
> .SH NAME
> @@ -335,6 +336,29 @@ is synonymous with
> .\" parisc is the only exception: SIGSYS is 12, SIGUNUSED is 31
> .B SIGSYS
> on most architectures.
> +
> +Some of these signals, carry special additional information in a siginfo_t argument,
> +clarifying why they were sent.
> +.TS
> +l l
> +_____
> +lB l.
> +Signal siginfo_t fields
> +SIGKILL si_pid, si_uid
> +SIGCHLD si_pid, si_uid, si_status, si_utime, si_stime
> +SIGILL si_code, si_addr, si_trapno
> +SIGFPE si_code, si_addr, si_trapno
> +SIGSEGV si_code, si_addr, si_trapno
> +SIGBUS si_code, si_addr, si_trapno, si_addr_lsb
> +SIGTRAP si_code, si_addr, si_trapno
> +SIGPOLL si_band, si_fd
> +realtime signals > 32 si_pid, si_uid, si_value
> +posix timer si_tid, si_overrun, si_sigval
> +.TE
> +
> +Please see the
> +.I sigaction(2)
> +manpage for more details on the various fields
The information in this patch is rather incomplete, and is in any case
covered more completely in sigaction(2), so I haven't applied this
patch. On the other hand, it triggered me to make some improvements to
sigaction(2), as shown below.
Cheers,
Michael
--- a/man2/sigaction.2
+++ b/man2/sigaction.2
@@ -39,7 +39,8 @@
.\" 2004-12-09, mtk, added SI_TKILL + other minor changes
.\" 2005-09-15, mtk, split sigpending(), sigprocmask(), sigsuspend()
.\" out of this page into separate pages.
-+.\" 2010-06-10 Andi Kleen, add hwpoison signal extensions
+.\" 2010-06-11 Andi Kleen, add hwpoison signal extensions
+.\" 2010-06-11 mtk, improvements to discussion of various siginfo_t fields.
.\"
.TH SIGACTION 2 2010-06-11 "Linux" "Linux Programmer's Manual"
.SH NAME
@@ -174,7 +175,7 @@ or resume (i.e., they receive
This flag is only meaningful when establishing a handler for
.BR SIGCHLD .
.TP
-.BR SA_NOCLDWAIT " (Since Linux 2.6)"
+.BR SA_NOCLDWAIT " (since Linux 2.6)"
.\" To be precise: Linux 2.5.60 -- MTK
If
.I signum
@@ -270,9 +271,10 @@ siginfo_t {
int si_timerid; /* Timer ID; POSIX.1b timers */
.\" In the kernel: si_tid
void *si_addr; /* Memory location which caused fault */
- int si_band; /* Band event */
+ long si_band; /* Band event (was \fIint\fP in
+ glibc 2.3.2 and earlier) */
int si_fd; /* File descriptor */
- short si_addr_lsb; /* Least signifcant bit of address
+ short si_addr_lsb; /* Least significant bit of address
(since kernel 2.6.32) */
}
.fi
@@ -285,8 +287,10 @@ is generally unused on Linux.)
The rest of the struct may be a union, so that one should only
read the fields that are meaningful for the given signal:
.IP * 2
-POSIX.1b signals and
-.B SIGCHLD
+Signals sent with
+.BR kill (2)
+and
+.BR sigqueue (2)
fill in
.IR si_pid " and " si_uid .
.IP *
@@ -299,15 +303,35 @@ The
field is an internal ID used by the kernel to identify
the timer; it is not the same as the timer ID returned by
.BR timer_create (2).
+The
+.I si_overrun
+field is the timer overrun count;
+this is the same information as is obtained by a call to
+.BR timer_getoverrun (2).
+These fields are nonstandard Linux extensions.
.IP *
.B SIGCHLD
fills in
-.IR si_status ", " si_utime " and " si_stime .
+.IR si_pid ", " si_uid ", " si_status ", " si_utime " and " si_stime ,
+providing information about the child.
+The
+.I si_pid
+field is the process ID of the child;
+.I si_uid
+is the child's real user ID.
+The
+.I si_status
+field contains the exit status of the child (if
+.I si_code
+is
+.BR CLD_EXITED ),
+or the signal number that caused the process to change state.
The
.I si_utime
and
.I si_stime
-fields do not include the times used by waited-for children (unlike
+contain the user and system CPU time used by the child process;
+these fields do not include the times used by waited-for children (unlike
.BR getrusage (2)
and
.BR time (2)).
@@ -318,7 +342,7 @@ In 2.6 kernels before 2.6.27,
a bug meant that these fields reported time in units
of the (configurable) system jiffy (see
.BR time (7)).
-\" FIXME .
+.\" FIXME .
.\" When si_utime and si_stime where originally implemented, the
.\" measurement unit was HZ, which was the same as clock ticks
.\" (sysconf(_SC_CLK_TCK)). In 2.6, HZ became configurable, and
@@ -348,7 +372,7 @@ fill in
.I si_addr
with the address of the fault.
Some suberrors of
-.I SIGBUS,
+.BR SIGBUS ,
in particular
.B BUS_MCEERR_AO
and
@@ -365,9 +389,19 @@ contains
and
.I si_addr_lsb
are Linux-specific extensions.
-.B SIGPOLL
+.IP *
+.BR SIGPOLL / SIGIO
fills in
.IR si_band " and " si_fd .
+The
+.I si_band
+event is a bit mask containing the same values as are filled in the
+.I revents
+field by
+.BR poll (2).
+The
+.I si_fd
+field indicates the file descriptor for which the I/O event occurred.
.PP
.I si_code
is a value (not a bit mask)
--
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