1# Using Crashpad to Collect Web Component Crash Information
2
3The **Web** component supports process crash information collection using Crashpad. Crashpad is a process crash information handling tool provided by the Chromium kernel. When a process (including the main process and web rendering process) crashes due to the use of a **Web** component, Crashpad writes the **minidump** file in the sandbox directory of the main process of the application. This file is in binary format and the filename extension is **.dmp**. It records crash causes, thread information, and register information. You can use this file to analyze process crashes related to **Web** components.
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5How to use
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71. When a process crashes because a **Web** component is used in the application, the corresponding **dmp** file is generated in the sandbox directory of the main process of the application. The sandbox path is as follows:
8
9   ```c
10   /data/storage/el2/log/crashpad
11   ```
12
132. Obtain the DMP file in the directory and then parse it. The procedure is as follows:
14
15   * Use the minidump_stackwalk tool to parse the DMP file, and then you can obtain the process crash information (crash cause, thread information, and register information). The example is as follows (Linux environment):
16
17     ```c
18     ./minidump_stackwalk b678e0b5-894b-4794-9ab3-fb5d6dda06a3.dmp > parsed_stacktrace.txt
19     ```
20
21     You can obtain minidump_stackwalk by compiling the source code of breakpad project. For details, see [Breakpad](https://chromium.googlesource.com/breakpad/breakpad).
22
23   * Sample of the parsed file is as follows:
24
25     ```c
26     Crash reason:  SIGSEGV /SEGV_MAPERR    The signal that causes the process crash, which is a segment error.
27     Crash address: 0x0
28     Process uptime: 12 seconds
29
30     Thread 0 (crashed)                     The Thread 0 crashes.
31      0 libweb_engine.so + 0x2e0b340        Call stack of layer 0. 0x2e0b340 is the offset address of the .so file, which can be used to decompile and parse the crash source code (depending on the unstripped .so file).
32          x0 = 0x00000006a5719ff8    x1 = 0x000000019a5a28c0
33          x2 = 0x0000000000020441    x3 = 0x00000000000001b6
34          x4 = 0x0000000000000018    x5 = 0x0000000000008065
35          x6 = 0x0000000000008065    x7 = 0x63ff686067666d60
36          x8 = 0x0000000000000000    x9 = 0x5f129cf9e7bf008c
37         x10 = 0x0000000000000001   x11 = 0x0000000000000000
38         x12 = 0x000000069bfcc6d8   x13 = 0x0000000009a1746e
39         x14 = 0x0000000000000000   x15 = 0x0000000000000000
40         x16 = 0x0000000690df4850   x17 = 0x000000010c0d47f8
41         x18 = 0x0000000000000000   x19 = 0x0000005eea827db8
42         x20 = 0x0000005eea827c38   x21 = 0x00000006a56b1000
43         x22 = 0x00000006a8b85020   x23 = 0x00000020002103c0
44         x24 = 0x00000006a56b8a70   x25 = 0x0000000000000000
45         x26 = 0x00000006a8b84e00   x27 = 0x0000000000000001
46         x28 = 0x0000000000000000    fp = 0x0000005eea827c10
47          lr = 0x000000069fa4b33c    sp = 0x0000005eea827c10
48          pc = 0x000000069fa4b340
49         Found by: given as instruction pointer in context
50      1  libweb_engine.so + 0x2e0b338
51          fp = 0x0000005eea827d80    lr = 0x000000069fa48d44
52          sp = 0x0000005eea827c20    pc = 0x000000069fa4b33c
53         Found by: previous frame's frame pointer
54      2  libweb_engine.so + 0x2e08d40
55          fp = 0x0000005eea827e50    lr = 0x00000006a385cef8
56          sp = 0x0000005eea827d90    pc = 0x000000069fa48d44
57         Found by: previous frame's frame pointer
58      3  libweb_engine.so + 0x6c1cef4
59          fp = 0x0000005eea828260    lr = 0x00000006a0f11298
60          sp = 0x0000005eea827e60    pc = 0x00000006a385cef8
61      ......
62     ```
63
64   * Use the llvm toolchain to parse the crash source code. The example is as follows (Linux environment):
65
66     ```c
67     ./llvm-addr2line -Cfpie libweb_engine.so 0x2e0b340
68     ```
69
70     The llvm-addr2line toolchain can be obtained in the SDK.
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