解释段错误消息

发布于 2024-08-27 08:11:11 字数 519 浏览 6 评论 0原文

以下段错误消息的正确解释是什么？

segfault at 10 ip 00007f9bebcca90d sp 00007fffb62705f0 error 4 in libQtWebKit.so.4.5.2[7f9beb83a000+f6f000]
segfault at 10 ip 00007fa44d78890d sp 00007fff43f6b720 error 4 in libQtWebKit.so.4.5.2[7fa44d2f8000+f6f000]
segfault at 11 ip 00007f2b0022acee sp 00007fff368ea610 error 4 in libQtWebKit.so.4.5.2[7f2aff9f7000+f6f000]
segfault at 11 ip 00007f24b21adcee sp 00007fff7379ded0 error 4 in libQtWebKit.so.4.5.2[7f24b197a000+f6f000]

原文

What is the correct interpretation of the following segfault messages?

segfault at 10 ip 00007f9bebcca90d sp 00007fffb62705f0 error 4 in libQtWebKit.so.4.5.2[7f9beb83a000+f6f000]
segfault at 10 ip 00007fa44d78890d sp 00007fff43f6b720 error 4 in libQtWebKit.so.4.5.2[7fa44d2f8000+f6f000]
segfault at 11 ip 00007f2b0022acee sp 00007fff368ea610 error 4 in libQtWebKit.so.4.5.2[7f2aff9f7000+f6f000]
segfault at 11 ip 00007f24b21adcee sp 00007fff7379ded0 error 4 in libQtWebKit.so.4.5.2[7f24b197a000+f6f000]

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苦笑流年记忆 2024-09-03 08:11:11

这是由于跟随空指针试图找到要运行的代码（即在取指令期间）而导致的段错误。

如果这是一个程序，而不是共享库，

请运行addr2line -e yourSegfaultingProgram 00007f9bebcca90d（并对给定的其他指令指针值重复）以查看错误发生的位置。更好的是，获得一个调试检测构建，并在 gdb 等调试器下重现问题。

不幸的是，由于它是一个共享库

，所以你已经被淹没了；事后不可能知道动态链接器将库放置在内存中的位置。在 gdb 下重现该问题。

错误的含义

如下是字段的细分：

address（在 at 之后） - 代码尝试访问的内存位置（很可能是 < code>10 和 11 是我们期望设置为有效值的指针的偏移量，但它指向 0）
ip - 指令指针，即。尝试执行此操作的代码所在的位置
sp - 堆栈指针
error - 页面错误的错误代码；请参阅下文了解这在 x86 上的含义（链接）。
<前><代码>/*
* 页面错误错误代码位：
*
* 位 0 == 0：未找到页面 1：保护故障
* 位 1 == 0：读访问 1：写访问
* bit 2 == 0：内核模式访问 1：用户模式访问
* 位 3 == 1：检测到保留位的使用
* 位 4 == 1：错误是指令获取
* 位 5 == 1：保护键阻止访问
* 位 15 == 1：SGX MMU 页面错误
*/

This is a segfault due to following a null pointer trying to find code to run (that is, during an instruction fetch).

If this were a program, not a shared library

Run addr2line -e yourSegfaultingProgram 00007f9bebcca90d (and repeat for the other instruction pointer values given) to see where the error is happening. Better, get a debug-instrumented build, and reproduce the problem under a debugger such as gdb.

Since it's a shared library

You're hosed, unfortunately; it's not possible to know where the libraries were placed in memory by the dynamic linker after-the-fact. Reproduce the problem under gdb.

What the error means

Here's the breakdown of the fields:

address (after the at) - the location in memory the code is trying to access (it's likely that 10 and 11 are offsets from a pointer we expect to be set to a valid value but which is instead pointing to 0)
ip - instruction pointer, ie. where the code which is trying to do this lives
sp - stack pointer

error - An error code for page faults; see below for what this means on x86 (link).

/*
 * Page fault error code bits:
 *
 *   bit 0 ==    0: no page found       1: protection fault
 *   bit 1 ==    0: read access         1: write access
 *   bit 2 ==    0: kernel-mode access  1: user-mode access
 *   bit 3 ==                           1: use of reserved bit detected
 *   bit 4 ==                           1: fault was an instruction fetch
 *   bit 5 ==                           1: protection keys block access
 *   bit 15 ==                          1: SGX MMU page-fault
 */

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梦幻的心爱 2024-09-03 08:11:11

错误 4 表示“原因是用户模式读取导致找不到页面。”。此处有一个工具可以对其进行解码。

这是内核的定义。请记住，4 表示设置了位 2，并且未设置其他位。如果将其转换为二进制，那就很清楚了。

/*
 * Page fault error code bits
 *      bit 0 == 0 means no page found, 1 means protection fault
 *      bit 1 == 0 means read, 1 means write
 *      bit 2 == 0 means kernel, 1 means user-mode
 *      bit 3 == 1 means use of reserved bit detected
 *      bit 4 == 1 means fault was an instruction fetch
 */
#define PF_PROT         (1<<0)
#define PF_WRITE        (1<<1)
#define PF_USER         (1<<2)
#define PF_RSVD         (1<<3)
#define PF_INSTR        (1<<4)

现在，“ip 00007f9bebcca90d”意味着发生段错误时指令指针位于0x00007f9bebcca90d。

“libQtWebKit.so.4.5.2[7f9beb83a000+f6f000]”告诉您：

崩溃所在的对象：“libQtWebKit.so.4.5.2”
该对象的基址“7f9beb83a000”
该对象有多大：“f6f000如果

你获取基地址并从 ip 中减去它，你就得到了该对象的偏移量：

0x00007f9bebcca90d - 0x7f9beb83a000 = 0x49090D

然后你可以在它上面运行 addr2line：

addr2line -e /usr/lib64/qt45/lib/libQtWebKit.so.4.5.2 -fCi 0x49090D
??
??:0

在我的例子中它不成功，要么我安装的副本与你的不同，或者被剥离。

Error 4 means "The cause was a user-mode read resulting in no page being found.". There's a tool that decodes it here.

Here's the definition from the kernel. Keep in mind that 4 means that bit 2 is set and no other bits are set. If you convert it to binary that becomes clear.

/*
 * Page fault error code bits
 *      bit 0 == 0 means no page found, 1 means protection fault
 *      bit 1 == 0 means read, 1 means write
 *      bit 2 == 0 means kernel, 1 means user-mode
 *      bit 3 == 1 means use of reserved bit detected
 *      bit 4 == 1 means fault was an instruction fetch
 */
#define PF_PROT         (1<<0)
#define PF_WRITE        (1<<1)
#define PF_USER         (1<<2)
#define PF_RSVD         (1<<3)
#define PF_INSTR        (1<<4)

Now then, "ip 00007f9bebcca90d" means the instruction pointer was at 0x00007f9bebcca90d when the segfault happened.

"libQtWebKit.so.4.5.2[7f9beb83a000+f6f000]" tells you:

The object the crash was in: "libQtWebKit.so.4.5.2"
The base address of that object "7f9beb83a000"
How big that object is: "f6f000"

If you take the base address and subtract it from the ip, you get the offset into that object:

0x00007f9bebcca90d - 0x7f9beb83a000 = 0x49090D

Then you can run addr2line on it:

addr2line -e /usr/lib64/qt45/lib/libQtWebKit.so.4.5.2 -fCi 0x49090D
??
??:0

In my case it wasn't successful, either the copy I installed isn't identical to yours, or it's stripped.

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给妤﹃绝世温柔 2024-09-03 08:11:11

让我们转到源代码 - 2.6.32，示例。如果设置了 show_unhandled_signals sysctl，则该消息由 arch/x86/mm/fault.c 中的 show_signal_msg() 函数打印。

“error”不是 errno 也不是信号号，它是“页面错误错误代码”——请参阅枚举 x86_pf_error_code 的定义。

“[7fa44d2f8000+f6f000]”是崩溃时映射违规对象的虚拟内存区域的起始地址和大小。 “ip”的值应适合该区域。有了这些信息，应该很容易在 gdb 中找到有问题的代码。

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浪漫人生路 2024-09-03 08:11:11

您可以通过以下步骤修复它：

dmesg

Ex：
[4970814.649014] upowerd[46459]：upowerd[55ce91248000+39000] 中 8 ip 000055ce91269328 sp 00007fff71b98480 错误 4 处出现段错误
[4970840.152464] upowerd[46512]: segfault at 8 ip 000055c18f8e5328 sp 00007fffa63df280 error 4 in upowerd[55c18f8c4000+39000]