Re: [PATCH 6/4] libbacktrace: Add loaded dlls after initialize

["Björn Schäpers" <gcc@hazardy.de>]

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Am 07.01.2024 um 18:03 schrieb Eli Zaretskii:
>> Date: Sun, 7 Jan 2024 17:07:06 +0100
>> Cc: iant@google.com, gcc-patches@gcc.gnu.org, gcc@gcc.gnu.org
>> From: Björn Schäpers <gcc@hazardy.de>
>>
>>> That was about GetModuleHandle, not about GetModuleHandleEx.  For the
>>> latter, all Windows versions that support it also support "wide" APIs.
>>> So my suggestion is to use GetModuleHandleExW here.  However, you will
>>> need to make sure that notification_data->dll_base is declared as
>>> 'wchar_t *', not 'char *'.  If dll_base is declared as 'char *', then
>>> only GetModuleHandleExA will work, and you will lose the ability to
>>> support file names with non-ASCII characters outside of the current
>>> system codepage.
>>
>> The dll_base is a PVOID. With the GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS flag
>> GetModuleHandleEx does not look for a name, but uses an adress in the module to
>> get the HMODULE, so you cast it to char* or wchar_t* depending on which function
>> you call. Actually one could just cast the dll_base to HMODULE, at least in
>> win32 on x86 the HMODULE of a dll is always its base adress. But to make it
>> safer and future proof I went the way through GetModuleHandeEx.
> 
> In that case, you an call either GetModuleHandeExA or
> GetModuleHandeExW, the difference is minor.

Here an updated version without relying on TEXT or TCHAR, directly calling 
GetModuleHandleExW.

Kind regards,
Björn.

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From a8e1e64ccb56158ec8a7e5de0d5228f3f6f7e5c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Sch=C3=A4pers?= <bjoern@hazardy.de>
Date: Sat, 6 Jan 2024 22:53:54 +0100
Subject: [PATCH 3/3] libbacktrace: Add loaded dlls after initialize

libbacktrace/Changelog:

	* pecoff.c [HAVE_WINDOWS_H]:
	  (dll_notification_data): Added
	  (dll_notification_context): Added
	  (dll_notification): Added
	  (backtrace_initialize): Use LdrRegisterDllNotification to load
	                          debug information of later loaded
	                          dlls.
---
 libbacktrace/pecoff.c | 104 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 103 insertions(+), 1 deletion(-)

diff --git a/libbacktrace/pecoff.c b/libbacktrace/pecoff.c
index 647baa39640..d973a26f05a 100644
--- a/libbacktrace/pecoff.c
+++ b/libbacktrace/pecoff.c
@@ -62,6 +62,34 @@ POSSIBILITY OF SUCH DAMAGE.  */
 #undef Module32Next
 #endif
 #endif
+
+#if defined(_ARM_)
+#define NTAPI
+#else
+#define NTAPI __stdcall
+#endif
+
+/* This is a simplified (but binary compatible) version of what Microsoft
+   defines in their documentation. */
+struct dll_notifcation_data
+{
+  ULONG reserved;
+  /* The name as UNICODE_STRING struct. */
+  PVOID full_dll_name;
+  PVOID base_dll_name;
+  PVOID dll_base;
+  ULONG size_of_image;
+};
+
+#define LDR_DLL_NOTIFICATION_REASON_LOADED 1
+
+typedef LONG NTSTATUS;
+typedef VOID CALLBACK (*LDR_DLL_NOTIFICATION)(ULONG,
+					      struct dll_notifcation_data*,
+					      PVOID);
+typedef NTSTATUS NTAPI (*LDR_REGISTER_FUNCTION)(ULONG,
+						LDR_DLL_NOTIFICATION, PVOID,
+						PVOID*);
 #endif
 
 /* Coff file header.  */
@@ -912,7 +940,8 @@ coff_add (struct backtrace_state *state, int descriptor,
   return 0;
 }
 
-#if defined(HAVE_WINDOWS_H) && !defined(HAVE_TLHELP32_H)
+#ifdef HAVE_WINDOWS_H
+#ifndef HAVE_TLHELP32_H
 static void
 free_modules (struct backtrace_state *state,
 	      backtrace_error_callback error_callback, void *data,
@@ -958,6 +987,51 @@ get_all_modules (struct backtrace_state *state,
     }
 }
 #endif
+struct dll_notification_context
+{
+  struct backtrace_state *state;
+  backtrace_error_callback error_callback;
+  void *data;
+};
+
+VOID CALLBACK
+dll_notification (ULONG reason,
+struct dll_notifcation_data *notification_data,
+PVOID context)
+{
+  char module_name[MAX_PATH];
+  int descriptor;
+  struct dll_notification_context* dll_context =
+    (struct dll_notification_context*) context;
+  struct backtrace_state *state = dll_context->state;
+  void *data = dll_context->data;
+  backtrace_error_callback error_callback = dll_context->data;
+  fileline fileline;
+  int found_sym;
+  int found_dwarf;
+  HMODULE module_handle;
+
+  if (reason != LDR_DLL_NOTIFICATION_REASON_LOADED)
+    return;
+
+  if (!GetModuleHandleExW (GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS
+			   | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+			   (wchar_t*) notification_data->dll_base,
+			   &module_handle))
+    return;
+
+  if (!GetModuleFileNameA ((HMODULE) module_handle, module_name, MAX_PATH - 1))
+    return;
+
+  descriptor = backtrace_open (module_name, error_callback, data, NULL);
+
+  if (descriptor < 0)
+    return;
+
+  coff_add (state, descriptor, error_callback, data, &fileline, &found_sym,
+	    &found_dwarf, (uintptr_t) module_handle);
+}
+#endif
 
 /* Initialize the backtrace data we need from an ELF executable.  At
    the ELF level, all we need to do is find the debug info
@@ -978,6 +1052,7 @@ backtrace_initialize (struct backtrace_state *state,
 #ifdef HAVE_WINDOWS_H
   fileline module_fileline_fn;
   int module_found_sym;
+  HMODULE nt_dll_handle;
 
 #ifdef HAVE_TLHELP32_H
   HANDLE snapshot;
@@ -1065,6 +1140,33 @@ backtrace_initialize (struct backtrace_state *state,
   if (modules)
     free_modules (state, error_callback, data, &modules, bytes_allocated_for_modules);
 #endif
+
+  nt_dll_handle = GetModuleHandleW (L"ntdll.dll");
+  if (nt_dll_handle)
+    {
+      LDR_REGISTER_FUNCTION register_func;
+      const char register_name[] = "LdrRegisterDllNotification";
+      register_func = (LDR_REGISTER_FUNCTION) GetProcAddress (nt_dll_handle,
+							      register_name);
+
+      if (register_func)
+	{
+	  PVOID cookie;
+	  struct dll_notification_context *context
+	    = backtrace_alloc (state,
+			       sizeof(struct dll_notification_context),
+			       error_callback, data);
+
+	  if (context)
+	    {
+	      context->state = state;
+	      context->data = data;
+	      context->error_callback = error_callback;
+
+	      register_func (0, &dll_notification, context, &cookie);
+	    }
+	}
+    }
 #endif
 
   if (!state->threaded)
-- 
2.42.1