Re: [PATCH] Cygwin: Improve FAQ on early breakpoint for ASLR

[Jon Turney <jon.turney@dronecode.org.uk>]

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On 04/11/2022 10:34, Corinna Vinschen wrote:
> On Nov  3 11:22, Jeremy Drake via Cygwin-patches wrote:
>> On Thu, 3 Nov 2022, Jon Turney wrote:
>>
>>> gdb supports 'set disable-randomization off' on Windows since [1]
>>> (included in gdb 13).
>>>
>>> https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=bcb9251f029da8dcf360a4f5acfa3b4211c87bb0;hp=8fea1a81c7d9279a6f91e49ebacfb61e0f8ce008
>>
>> Is it really *disable*-randomization *off*?  The double-negative seems to
>> suggest that in that case ASLR would be left *on*.
> 
> Yeah, sounds weird....

Yes, this is just stupidity.  Revised patch attached.

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From 9ffce0d6124933cf16aee3ad006e32858fe0754a Mon Sep 17 00:00:00 2001
From: Jon Turney <jon.turney@dronecode.org.uk>
Date: Tue, 1 Nov 2022 16:52:57 +0000
Subject: [PATCH] Cygwin: Improve FAQ on early breakpoint for ASLR

gdb supports the 'disable-randomization' setting on Windows since [1]
(included in gdb 13).

https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=bcb9251f029da8dcf360a4f5acfa3b4211c87bb0;hp=8fea1a81c7d9279a6f91e49ebacfb61e0f8ce008
---
 winsup/doc/faq-programming.xml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/winsup/doc/faq-programming.xml b/winsup/doc/faq-programming.xml
index 7945b6b88..36d0a401f 100644
--- a/winsup/doc/faq-programming.xml
+++ b/winsup/doc/faq-programming.xml
@@ -844,6 +844,12 @@ Guide here: <ulink url="https://cygwin.com/cygwin-ug-net/dll.html"/>.
   Note that the DllMain entrypoints for linked DLLs will have been executed
   before this breakpoint is hit.
 </para>
+
+<para>
+  (It may be necessary to use the <command>gdb</command> command <command>set
+  disable-randomization on</command> to turn off ASLR for the debugee to
+  prevent the base address getting randomized.)
+</para>
 </answer></qandaentry>
 
 <qandaentry id="faq.programming.debug">
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