Re: [PATCH 3/4] libbacktrace: work with aslr on windows

["Björn Schäpers" <gcc@hazardy.de>]

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An updated version, using neither A or W, but just the macro.

Am 21.01.2023 um 12:42 schrieb Eli Zaretskii:
>> Date: Sat, 21 Jan 2023 11:47:42 +0100
>> Cc: gcc@hazardy.de, gcc-patches@gcc.gnu.org, gcc@gcc.gnu.org
>> From: Gabriel Ravier <gabravier@gmail.com>
>>
>>
>> On 1/21/23 05:05, Eli Zaretskii wrote:
>>>> Date: Fri, 20 Jan 2023 21:39:56 +0100
>>>> Cc: gcc@hazardy.de, gcc-patches@gcc.gnu.org, gcc@gcc.gnu.org
>>>> From: Gabriel Ravier <gabravier@gmail.com>
>>>>
>>>>>> - using wide APIs with Windows is generally considered to be a best
>>>>>> practice, even when not strictly needed (and in this case I can't see
>>>>>> any problem with doing so, unless maybe we want to code to work with
>>>>>> Windows 95 or something like that...)
>>>>> There's no reason to forcibly break GDB on platforms where wide APIs
>>>>> are not available.
>>>> Are there even any platforms that have GetModuleHandleA but not
>>>> GetModuleHandleW ? MSDN states that Windows XP and Windows Server 2003
>>>> are the first versions to support both of the APIs, so if this is
>>>> supposed to work on Windows 98, for instance, whether we're using
>>>> GetModuleHandleA or GetModuleHandleW won't matter.
>>> I'm not sure I follow the logic.  A program that calls
>>> GetModuleHandleW will refuse to start on Windows that doesn't have
>>> that API.  So any version before XP is automatically excluded the
>>> moment you use code which calls that API directly (i.e. not through a
>>> function pointer or somesuch).
>> A program that calls GetModuleHandleA will also refuse to start on
>> Windows if it doesn't have that API. The set of Windows versions that do
>> not have GetModuleHandleA is, according to MSDN, the same as the set of
>> Windows versions that do not have GetModuleHandleW.
> 
> MSDN lies (because it wants to pretend that older versions don't
> exist).  Try this much more useful site:
> 
>    http://winapi.freetechsecrets.com/win32/WIN32GetModuleHandle.htm

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From 52cbe06b1c165172191f66ff7e55a49adecf661d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Sch=C3=A4pers?= <bjoern@hazardy.de>
Date: Sun, 30 Apr 2023 23:52:37 +0200
Subject: [PATCH 2/3] libbacktrace: work with aslr on windows
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Any underflow which might happen, will be countered by an overflow in
dwarf.c.

Tested on x86_64-linux and i686-w64-mingw32.

-- >8 --

Fixes https://github.com/ianlancetaylor/libbacktrace/issues/89 and
https://github.com/ianlancetaylor/libbacktrace/issues/82.

	* pecoff.c (coff_add): Set the base_address of the module, to
	find the debug information on moved applications.

Signed-off-by: Björn Schäpers <bjoern@hazardy.de>
---
 libbacktrace/pecoff.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/libbacktrace/pecoff.c b/libbacktrace/pecoff.c
index 56af4828e27..9cc13b47947 100644
--- a/libbacktrace/pecoff.c
+++ b/libbacktrace/pecoff.c
@@ -39,6 +39,18 @@ POSSIBILITY OF SUCH DAMAGE.  */
 #include "backtrace.h"
 #include "internal.h"
 
+#ifdef HAVE_WINDOWS_H
+#ifndef WIN32_MEAN_AND_LEAN
+#define WIN32_MEAN_AND_LEAN
+#endif
+
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif
+
+#include <windows.h>
+#endif
+
 /* Coff file header.  */
 
 typedef struct {
@@ -610,6 +622,8 @@ coff_add (struct backtrace_state *state, int descriptor,
   int debug_view_valid;
   int is_64;
   uintptr_t image_base;
+  uintptr_t base_address = 0;
+  uintptr_t module_handle;
   struct dwarf_sections dwarf_sections;
 
   *found_sym = 0;
@@ -856,7 +870,12 @@ coff_add (struct backtrace_state *state, int descriptor,
 				  + (sections[i].offset - min_offset));
     }
 
-  if (!backtrace_dwarf_add (state, /* base_address */ 0, &dwarf_sections,
+#ifdef HAVE_WINDOWS_H
+    module_handle = (uintptr_t) GetModuleHandle (NULL);
+    base_address = module_handle - image_base;
+#endif
+
+  if (!backtrace_dwarf_add (state, base_address, &dwarf_sections,
 			    0, /* FIXME: is_bigendian */
 			    NULL, /* altlink */
 			    error_callback, data, fileline_fn,
-- 
2.42.1