1 /* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5
6 #include "nsX11ErrorHandler.h"
7
8 #include "prenv.h"
9 #include "nsXULAppAPI.h"
10 #include "nsExceptionHandler.h"
11 #include "nsDebug.h"
12
13 #include "mozilla/X11Util.h"
14 #include <X11/Xlib.h>
15
16 #define BUFSIZE 2048 // What Xlib uses with XGetErrorDatabaseText
17
18 extern "C" {
X11Error(Display * display,XErrorEvent * event)19 int X11Error(Display* display, XErrorEvent* event) {
20 // Get an indication of how long ago the request that caused the error was
21 // made.
22 unsigned long age = NextRequest(display) - event->serial;
23
24 // Get a string to represent the request that caused the error.
25 nsAutoCString message;
26 if (event->request_code < 128) {
27 // Core protocol request
28 message.AppendInt(event->request_code);
29 } else {
30 // Extension request
31
32 // man XSetErrorHandler says "the error handler should not call any
33 // functions (directly or indirectly) on the display that will generate
34 // protocol requests or that will look for input events" so we use another
35 // temporary Display to request extension information. This assumes on
36 // the DISPLAY environment variable has been set and matches what was used
37 // to open |display|.
38 Display* tmpDisplay = XOpenDisplay(nullptr);
39 if (tmpDisplay) {
40 int nExts;
41 char** extNames = XListExtensions(tmpDisplay, &nExts);
42 int first_error;
43 if (extNames) {
44 for (int i = 0; i < nExts; ++i) {
45 int major_opcode, first_event;
46 if (XQueryExtension(tmpDisplay, extNames[i], &major_opcode,
47 &first_event, &first_error) &&
48 major_opcode == event->request_code) {
49 message.Append(extNames[i]);
50 message.Append('.');
51 message.AppendInt(event->minor_code);
52 break;
53 }
54 }
55
56 XFreeExtensionList(extNames);
57 }
58 XCloseDisplay(tmpDisplay);
59 }
60 }
61
62 char buffer[BUFSIZE];
63 if (message.IsEmpty()) {
64 buffer[0] = '\0';
65 } else {
66 XGetErrorDatabaseText(display, "XRequest", message.get(), "", buffer,
67 sizeof(buffer));
68 }
69
70 nsAutoCString notes;
71 if (buffer[0]) {
72 notes.Append(buffer);
73 } else {
74 notes.AppendLiteral("Request ");
75 notes.AppendInt(event->request_code);
76 notes.Append('.');
77 notes.AppendInt(event->minor_code);
78 }
79
80 notes.AppendLiteral(": ");
81
82 // Get a string to describe the error.
83 XGetErrorText(display, event->error_code, buffer, sizeof(buffer));
84 notes.Append(buffer);
85
86 // For requests where Xlib gets the reply synchronously, |age| will be 1
87 // and the stack will include the function making the request. For
88 // asynchronous requests, the current stack will often be unrelated to the
89 // point of making the request, even if |age| is 1, but sometimes this may
90 // help us count back to the point of the request. With XSynchronize on,
91 // the stack will include the function making the request, even though
92 // |age| will be 2 for asynchronous requests because XSynchronize is
93 // implemented by an empty request from an XSync, which has not yet been
94 // processed.
95 if (age > 1) {
96 // XSynchronize returns the previous "after function". If a second
97 // XSynchronize call returns the same function after an enable call then
98 // synchronization must have already been enabled.
99 if (XSynchronize(display, X11True) == XSynchronize(display, X11False)) {
100 notes.AppendLiteral("; sync");
101 } else {
102 notes.AppendLiteral("; ");
103 notes.AppendInt(uint32_t(age));
104 notes.AppendLiteral(" requests ago");
105 }
106 }
107
108 switch (XRE_GetProcessType()) {
109 case GeckoProcessType_Default:
110 case GeckoProcessType_Content:
111 CrashReporter::AppendAppNotesToCrashReport(notes);
112 break;
113 default:; // crash report notes not supported.
114 }
115
116 #ifdef DEBUG
117 // The resource id is unlikely to be useful in a crash report without
118 // context of other ids, but add it to the debug console output.
119 notes.AppendLiteral("; id=0x");
120 notes.AppendInt(uint32_t(event->resourceid), 16);
121 # ifdef MOZ_X11
122 // Actually, for requests where Xlib gets the reply synchronously,
123 // MOZ_X_SYNC=1 will not be necessary, but we don't have a table to tell us
124 // which requests get a synchronous reply.
125 if (!PR_GetEnv("MOZ_X_SYNC")) {
126 notes.AppendLiteral(
127 "\nRe-running with MOZ_X_SYNC=1 in the environment may give a more "
128 "helpful backtrace.");
129 }
130 # endif
131 #endif
132
133 MOZ_CRASH_UNSAFE(notes.get());
134 }
135 }
136
InstallX11ErrorHandler()137 void InstallX11ErrorHandler() {
138 XSetErrorHandler(X11Error);
139
140 Display* display = mozilla::DefaultXDisplay();
141 NS_ASSERTION(display, "No X display");
142 if (PR_GetEnv("MOZ_X_SYNC")) {
143 XSynchronize(display, X11True);
144 }
145 }
146