Testsuite docs: explain ptrace_scope and core_pattern requirements.

[Ciro Santilli <ciro.santilli@gmail.com>]

 From 526bde3e1716a13406f9343ff6a788da9e553e6d Mon Sep 17 00:00:00 2001
From: Ciro Santilli <ciro.santilli@gmail.com>
Date: Fri, 31 Jul 2015 10:05:53 +0200
Subject: [PATCH] Testsuite docs: explain ptrace_scope and core_pattern
  requirements.

ptrace_scope can break all attach related tests.

core_pattern can break bigcore.exp.

2015-07-31  Ciro Santilli  <ciro.santilli@gmail.com>

gdb:

	PR testsuite/18067
	PR testsuite/18704
	* README (GDB Testsuite): Explain ptrace_scope and core_pattern.
	Make section more succinct.
	Remove broken Red Hat DejaGNU FTP link.
---
  gdb/README | 35 ++++++++++++++++++++++++++---------
  1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/gdb/README b/gdb/README
index d485536..87a4a5f 100644
--- a/gdb/README
+++ b/gdb/README
@@ -595,15 +595,32 @@ think you will be ready to submit the patches.
  GDB Testsuite
  =============

-   Included with the GDB distribution is a DejaGNU based testsuite
-that can either be used to test your newly built GDB, or for
-regression testing a GDB with local modifications.
-
-   Running the testsuite requires the prior installation of DejaGNU,
-which is generally available via ftp.  The directory
-ftp://sources.redhat.com/pub/dejagnu/ will contain a recent snapshot.
-Once DejaGNU is installed, you can run the tests in one of the
-following ways:
+Requirements:
+
+*   DejaGNU
+
+*   Ability to attach to processes with the same UID.
+
+    In Linux, you need either to ensure that ptrace is allowed with:
+
+        echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
+
+    or sudo, which is a bad idea.
+
+*   Ability to generate big sparse core files.
+
+    In Linux, this is done by default, but it may be broken if your
+    distribution sets:
+
+        /proc/sys/kernel/core_pattern
+
+    to something starting with `|` to use a custom handler program.
+
+    You can fix that with:
+
+        echo | sudo tee /proc/sys/kernel/core_pattern
+
+Usage:

    (1)	cd gdb-VERSION
  	make check-gdb
-- 
1.9.1