manual: Update signal descriptions
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Commit Message
Based on auditing all the signals and source trees for Hurd and
Linux...
SIGSYS - This is not used for a bad system call (ENOSYS is used
for that). This is used by SECCOMP and some cases where an invalid
sub-function was requested.
SIGSTKFLT - Note it used to be a coprocessor stack fault but is now
obsolete and available for general user use.
SIGLOST - Hurd only now; note that its original purpose as an NFS
lock lost signal is obsolete.
SIGPWR - Note this is for power lost *and* power restored, and is
more a user-mode signal than a kernel-generated signal.
Comments
On 17/01/25 19:44, DJ Delorie wrote:
>
> Based on auditing all the signals and source trees for Hurd and
> Linux...
>
> SIGSYS - This is not used for a bad system call (ENOSYS is used
> for that). This is used by SECCOMP and some cases where an invalid
> sub-function was requested.
>
> SIGSTKFLT - Note it used to be a coprocessor stack fault but is now
> obsolete and available for general user use.
>
> SIGLOST - Hurd only now; note that its original purpose as an NFS
> lock lost signal is obsolete.
>
> SIGPWR - Note this is for power lost *and* power restored, and is
> more a user-mode signal than a kernel-generated signal.
>
> diff --git a/manual/signal.texi b/manual/signal.texi
> index 2012980efe..9d7f8667e5 100644
> --- a/manual/signal.texi
> +++ b/manual/signal.texi
> @@ -427,11 +427,21 @@ failure to properly emulate them.
>
> @deftypevr Macro int SIGSYS
> @standards{Unix, signal.h}
> -Bad system call; that is to say, the instruction to trap to the
> -operating system was executed, but the code number for the system call
> -to perform was invalid.
> +System call event. This signal may be generated by a valid system
> +call which requested an invalid sub-function, and also by the SECCOMP
> +filter when it filters a system call.
> +
> +If the system call itself is invalid or unsupported by the kernel, the
> +call will not raise this signal, but will return ENOSYS.
Maybe use @code{ENOSYS} here.
> +@end deftypevr
> +
> +@deftypevr Macro int SIGSTKFLT
> +Coprocessor stack fault. Obsolete, no longer generated. This signal
> +may be used by applications in much the way @code{SIGUSR1} and
> +@code{SIGUSR2} are.
> @end deftypevr
>
> +
Spurious new line maybe?
> @node Termination Signals
> @subsection Termination Signals
> @cindex program termination signals
> @@ -752,12 +762,11 @@ that isn't connected. @xref{Sending Data}.
> @deftypevr Macro int SIGLOST
> @standards{GNU, signal.h}
> @cindex lost resource signal
> -Resource lost. This signal is generated when you have an advisory lock
> -on an NFS file, and the NFS server reboots and forgets about your lock.
> -
> -On @gnuhurdsystems{}, @code{SIGLOST} is generated when any server program
> -dies unexpectedly. It is usually fine to ignore the signal; whatever
> -call was made to the server that died just returns an error.
> +Resource lost. On @gnuhurdsystems{}, @code{SIGLOST} is generated when
> +any server program dies unexpectedly. It is usually fine to ignore
> +the signal; whatever call was made to the server that died just
> +returns an error. This signal's original purpose of signalling a lost
> +NFS lock is obsolete.
> @end deftypevr
>
> @deftypevr Macro int SIGXCPU
> @@ -817,6 +826,17 @@ to print some status information about the system and what the process
> is doing. Otherwise the default is to do nothing.
> @end deftypevr
>
> +@deftypevr Macro int SIGPWR
> +@cindex power event signal
> +Power lost or restored. On s390x Linux systems, this signal is
> +generated when a machine check warning is issued, and is sent to the
> +process designated to receive ctrl-alt-del notificiations. Otherwise,
s/notificiations/notifications
> +it is up to userspace applications to generate this signal and manage
> +notifications as to the type of power event that happened.
> +
> +The default action is to terminate the process.
> +@end deftypevr
> +
> @node Signal Messages
> @subsection Signal Messages
> @cindex signal messages
>
Adhemerval Zanella Netto <adhemerval.zanella@linaro.org> writes:
>> +call will not raise this signal, but will return ENOSYS.
>
> Maybe use @code{ENOSYS} here.
Fixed.
>> @end deftypevr
>>
>> +
>
> Spurious new line maybe?
Fixed.
>> +process designated to receive ctrl-alt-del notificiations. Otherwise,
>
> s/notificiations/notifications
Fixed.
v2 shortly...
@@ -427,11 +427,21 @@ failure to properly emulate them.
@deftypevr Macro int SIGSYS
@standards{Unix, signal.h}
-Bad system call; that is to say, the instruction to trap to the
-operating system was executed, but the code number for the system call
-to perform was invalid.
+System call event. This signal may be generated by a valid system
+call which requested an invalid sub-function, and also by the SECCOMP
+filter when it filters a system call.
+
+If the system call itself is invalid or unsupported by the kernel, the
+call will not raise this signal, but will return ENOSYS.
+@end deftypevr
+
+@deftypevr Macro int SIGSTKFLT
+Coprocessor stack fault. Obsolete, no longer generated. This signal
+may be used by applications in much the way @code{SIGUSR1} and
+@code{SIGUSR2} are.
@end deftypevr
+
@node Termination Signals
@subsection Termination Signals
@cindex program termination signals
@@ -752,12 +762,11 @@ that isn't connected. @xref{Sending Data}.
@deftypevr Macro int SIGLOST
@standards{GNU, signal.h}
@cindex lost resource signal
-Resource lost. This signal is generated when you have an advisory lock
-on an NFS file, and the NFS server reboots and forgets about your lock.
-
-On @gnuhurdsystems{}, @code{SIGLOST} is generated when any server program
-dies unexpectedly. It is usually fine to ignore the signal; whatever
-call was made to the server that died just returns an error.
+Resource lost. On @gnuhurdsystems{}, @code{SIGLOST} is generated when
+any server program dies unexpectedly. It is usually fine to ignore
+the signal; whatever call was made to the server that died just
+returns an error. This signal's original purpose of signalling a lost
+NFS lock is obsolete.
@end deftypevr
@deftypevr Macro int SIGXCPU
@@ -817,6 +826,17 @@ to print some status information about the system and what the process
is doing. Otherwise the default is to do nothing.
@end deftypevr
+@deftypevr Macro int SIGPWR
+@cindex power event signal
+Power lost or restored. On s390x Linux systems, this signal is
+generated when a machine check warning is issued, and is sent to the
+process designated to receive ctrl-alt-del notificiations. Otherwise,
+it is up to userspace applications to generate this signal and manage
+notifications as to the type of power event that happened.
+
+The default action is to terminate the process.
+@end deftypevr
+
@node Signal Messages
@subsection Signal Messages
@cindex signal messages