diff options
author | jilles <jilles@FreeBSD.org> | 2010-05-06 22:06:14 +0000 |
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committer | jilles <jilles@FreeBSD.org> | 2010-05-06 22:06:14 +0000 |
commit | b8933dba5fbdeb54dfd1895700ff42ab0c5ce9ba (patch) | |
tree | a30d651e677a91f553ffc97821f348660add257d /lib/libc | |
parent | c866f0bf58897d1049847b73c521aa28c48f087f (diff) | |
download | FreeBSD-src-b8933dba5fbdeb54dfd1895700ff42ab0c5ce9ba.zip FreeBSD-src-b8933dba5fbdeb54dfd1895700ff42ab0c5ce9ba.tar.gz |
sigaltstack(2): document some modernizations:
* 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
Diffstat (limited to 'lib/libc')
-rw-r--r-- | lib/libc/sys/sigaltstack.2 | 32 |
1 files changed, 15 insertions, 17 deletions
diff --git a/lib/libc/sys/sigaltstack.2 b/lib/libc/sys/sigaltstack.2 index da6877e..6119c6a 100644 --- a/lib/libc/sys/sigaltstack.2 +++ b/lib/libc/sys/sigaltstack.2 @@ -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 . |