[PATCH 3/3] prctl.2, proc.5: document arm alignment trap via /proc/apu/alignment

[Shawn Landden <shawnlandden-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

---
 man2/prctl.2 |    7 +++++--
 man5/proc.5  |   21 ++++++++++++++++++++-
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/man2/prctl.2 b/man2/prctl.2
index f4db191..b68bea2 100644
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -44,7 +44,7 @@
 .\" 2012-08-03 Shawn Landden, Document PR_SET_NO_NEW_PRIVS, PR_GET_NO_NEW_PRIVS,
 .\"       SECCOMP_MODE_STRICT, SECCOMP_MODE_FILTER
 .\"       (thx Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> 259e5e6c)
-.\"       PR_SET_TIMERSLACK, PR_GET_TIMESLACK
+.\"       PR_SET_TIMERSLACK, PR_GET_TIMESLACK, ARM alignment trap handler
 .\"
 .TH PRCTL 2 2012-08-03 "Linux" "Linux Programmer's Manual"
 .SH NAME
@@ -406,7 +406,10 @@ Pass
 \fBPR_UNALIGN_NOPRINT\fP to silently fix up unaligned user accesses,
 or \fBPR_UNALIGN_SIGBUS\fP to generate
 .B SIGBUS
-on unaligned user access.
+on unaligned user access. ARM is set system-wide via /proc/cpu/alignment (see
+.IR Documentation/arm/mem_alignment
+or
+.BR proc (5)).
 .TP
 .B PR_GET_UNALIGN
 (see
diff --git a/man5/proc.5 b/man5/proc.5
index 2ba1daa..e7ca611 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -58,7 +58,7 @@
 .\" to see what information could be imported from that file
 .\" into this file.
 .\"
-.TH PROC 5 2012-05-03 "Linux" "Linux Programmer's Manual"
+.TH PROC 5 2012-08-04 "Linux" "Linux Programmer's Manual"
 .SH NAME
 proc \- process information pseudo-file system
 .SH DESCRIPTION
@@ -1229,6 +1229,25 @@ cat /lib/modules/$(uname \-r)/build/.config
 is only provided if the kernel is configured with
 .BR CONFIG_IKCONFIG_PROC .
 .TP
+.IR /proc/cpu/alignment " (ARM only)"
+Set the behavior of the user-mode alignment trap handler. When writing, takes a
+number that is the sum of the fallowing: 1, print message to syslog; (signal) 2,
+fix up the user process performing the unaligned access; (fixup) 4, send a
+.BR SIGBUS
+signal (
+.BR SIGILL
+before 2.6.35) to the user process performing the unaligned access. (signal)
+Signal and fixup cannot be used together. On armv6+ either fixup or signal must
+be used, to prevent possible deadlock.
+
+Reading will provide statistics on fixups performed since boot in user and
+system mode, as well as the current user-mode trap behavior.
+
+Other architectures set this behavior on a per-process level, via
+.B prctl(PR_SET_UNALIGN).
+See
+.BR prctl (2).
+.TP
 .I /proc/cpuinfo
 This is a collection of CPU and system architecture dependent items,
 for each supported architecture a different list.
-- 
1.7.9.5

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