diff options
| -rw-r--r-- | lib/libc/sys/sigaltstack.2 | 26 |
1 files changed, 14 insertions, 12 deletions
diff --git a/lib/libc/sys/sigaltstack.2 b/lib/libc/sys/sigaltstack.2 index e830e51a758..58d6c4dcfa1 100644 --- a/lib/libc/sys/sigaltstack.2 +++ b/lib/libc/sys/sigaltstack.2 @@ -1,4 +1,4 @@ -.\" $OpenBSD: sigaltstack.2,v 1.21 2018/03/21 16:22:21 gsoares Exp $ +.\" $OpenBSD: sigaltstack.2,v 1.22 2018/04/22 12:55:11 deraadt Exp $ .\" $NetBSD: sigaltstack.2,v 1.3 1995/02/27 10:41:52 cgd Exp $ .\" .\" Copyright (c) 1983, 1991, 1992, 1993 @@ -30,7 +30,7 @@ .\" .\" @(#)sigaltstack.2 8.1 (Berkeley) 6/4/93 .\" -.Dd $Mdocdate: March 21 2018 $ +.Dd $Mdocdate: April 22 2018 $ .Dt SIGALTSTACK 2 .Os .Sh NAME @@ -93,14 +93,17 @@ if the thread is currently on a signal stack and .Dv SS_DISABLE if the signal stack is currently disabled. .Pp -The stack must be allocated using -.Xr mmap 2 -with -.Ar MAP_STACK -to inform the kernel that the memory is being used as a stack. -Otherwise, the first system call performed while operating on -that stack will deliver -.Dv SIGABRT . +To permit the space to operate as a stack, a page-aligned +inner region will be zeroed and have +.Dv MAP_STACK +(see +.Xr mmap 2 ) +enabled. +Once the sigaltstack is disabled, +.Dv MAP_STACK +remains on the memory, so it is best to deallocate the memory +via a method that results in +.Xr munmap 2 . .Sh NOTES The value .Dv SIGSTKSZ @@ -108,8 +111,7 @@ is defined to be the number of bytes/chars that would be used to cover the usual case when allocating an alternate stack area. The following code fragment is typically used to allocate an alternate stack. .Bd -literal -offset indent -if ((sigstk.ss_sp = mmap(NULL, SIGSTKSZ, PROT_WRITE | PROT_READ, - MAP_PRIVATE | MAP_ANON | MAP_STACK, -1, 0)) == MAP_FAILED) +if ((sigstk.ss_sp = malloc(SIGSTKSZ)) == NULL) /* error return */ sigstk.ss_size = SIGSTKSZ; sigstk.ss_flags = 0; |