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sigaltstack(2): document some modernizations:

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* un-document 'struct sigaltstack' tag for stack_t as this is BSD-specific;
  this doesn't seem useful enough to document as such
* alternate stacks are per thread, not per process
* update error codes to what the kernel does and POSIX requires

MFC after:	1 week
This commit is contained in:
jilles 2010-05-06 22:06:14 +00:00
parent c866f0bf58
commit b8933dba5f
1 changed files with 15 additions and 17 deletions
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32
lib/libc/sys/sigaltstack.2
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@ -28,7 +28,7 @@
.\" @(#)sigaltstack.2 8.2 (Berkeley) 5/1/95
.\" $FreeBSD$
.\"
.Dd May 1, 1995
.Dd May 6, 2010
.Dt SIGALTSTACK 2
.Os
.Sh NAME
@ -39,7 +39,7 @@
.Sh SYNOPSIS
.In signal.h
.Bd -literal
typedef struct sigaltstack {
typedef struct {
char *ss_sp;
size_t ss_size;
int ss_flags;
@ -51,25 +51,25 @@ typedef struct sigaltstack {
The
.Fn sigaltstack
system call
allows users to define an alternate stack on which signals
are to be processed.
allows defining an alternate stack on which signals
are to be processed for the current thread.
If
.Fa ss
is non-zero,
it specifies a pointer to and the size of a
.Em "signal stack"
on which to deliver signals,
and tells the system if the process is currently executing
on that stack.
on which to deliver signals.
When a signal's action indicates its handler
should execute on the signal stack (specified with a
.Xr sigaction 2
system call), the system checks to see
if the process is currently executing on that stack.
If the process is not currently executing on the signal stack,
if the thread is currently executing on that stack.
If the thread is not currently executing on the signal stack,
the system arranges a switch to the signal stack for the
duration of the signal handler's execution.
.Pp
An active stack cannot be modified.
.Pp
If
.Dv SS_DISABLE
is set in
@ -78,12 +78,6 @@ is set in
and
.Fa ss_size
are ignored and the signal stack will be disabled.
Trying to disable an active stack will cause
.Fn sigaltstack
to return -1 with
.Va errno
set to
.Er EINVAL .
A disabled stack will cause all signals to be
taken on the regular user stack.
If the stack is later re-enabled then all signals that were specified
@ -96,7 +90,7 @@ The
.Fa ss_flags
field will contain the value
.Dv SS_ONSTACK
if the process is currently on a signal stack and
if the thread is currently on a signal stack and
.Dv SS_DISABLE
if the signal stack is currently disabled.
.Sh NOTES
@ -146,8 +140,12 @@ or
.Fa oss
points to memory that is not a valid part of the process
address space.
.It Bq Er EPERM
An attempt was made to modify an active stack.
.It Bq Er EINVAL
An attempt was made to disable an active stack.
The
.Fa ss_flags
field was invalid.
.It Bq Er ENOMEM
Size of alternate stack area is less than or equal to
.Dv MINSIGSTKSZ .