“无法解释"；核心转储 [英] "Unexplainable" core dump

问题描述

我一生中看到过很多核心转储，但这一次让我很困惑.

I've seen many core dumps in my life, but this one has me stumped.

上下文:

在 AMD Barcelona CPU 的群集上运行的
• 多线程Linux/x86_64程序
• 崩溃的代码在很多
中执行
• 在负载下运行1000个程序实例(完全相同的优化二进制文件)，每小时会产生1-2次崩溃
• 崩溃发生在不同的计算机上(但是计算机本身是完全相同的)
• 所有崩溃看起来都是一样的(相同的地址，相同的调用堆栈)

• multi-threaded Linux/x86_64 program running on a cluster of AMD Barcelona CPUs
• the code that crashes is executed a lot
• running 1000 instances of the program (the exact same optimized binary) under load produces 1-2 crashes per hour
• the crashes happen on different machines (but the machines themselves are pretty identical)
• the crashes all look the same (same exact address, same call stack)

以下是崩溃的详细信息:

Here are the details of the crash:

Program terminated with signal 11, Segmentation fault.
#0  0x00000000017bd9fd in Foo()
(gdb) x/i $pc
=> 0x17bd9fd <_Z3Foov+349>: rex.RB orb $0x8d,(%r15)

(gdb) x/6i $pc-12
0x17bd9f1 <_Z3Foov+337>:    mov    (%rbx),%eax
0x17bd9f3 <_Z3Foov+339>:    mov    %rbx,%rdi
0x17bd9f6 <_Z3Foov+342>:    callq  *0x70(%rax)
0x17bd9f9 <_Z3Foov+345>:    cmp    %eax,%r12d
0x17bd9fc <_Z3Foov+348>:    mov    %eax,-0x80(%rbp)
0x17bd9ff <_Z3Foov+351>:    jge    0x17bd97e <_Z3Foov+222>

您会注意到，崩溃发生在指令的中间中，这是从0x17bd9f6处的调用返回到虚函数之后的.

You'll notice that the crash happened in the middle of instruction at 0x17bd9fc, which is after return from a call at 0x17bd9f6 to a virtual function.

当我检查虚拟表时，我发现它没有以任何方式损坏:

When I examine the virtual table, I see that it is not corrupted in any way:

(gdb) x/a $rbx
0x2ab094951f80: 0x3f8c550 <_ZTI4Foo1+16>
(gdb) x/a 0x3f8c550+0x70
0x3f8c5c0 <_ZTI4Foo1+128>:  0x2d3d7b0 <_ZN4Foo13GetEv>

，它指向这个琐碎的函数(通过查看源代码可以预期):

and that it points to this trivial function (as expected by looking at the source):

(gdb) disas 0x2d3d7b0
Dump of assembler code for function _ZN4Foo13GetEv:
   0x0000000002d3d7b0 <+0>: push   %rbp
   0x0000000002d3d7b1 <+1>: mov    0x70(%rdi),%eax
   0x0000000002d3d7b4 <+4>: mov    %rsp,%rbp
   0x0000000002d3d7b7 <+7>: leaveq 
   0x0000000002d3d7b8 <+8>: retq   
End of assembler dump.

此外，当我查看Foo1::Get()应该返回的寄信人地址时:

Further, when I look at the return address that Foo1::Get() should have returned to:

(gdb) x/a $rsp-8
0x2afa55602048: 0x17bd9f9 <_Z3Foov+345>

我看到它指向了正确的指令，所以好像在从Foo1::Get()返回时，出现了一些小怪兽，并将%rip递增了4.

I see that it points to the right instruction, so it's as if during the return from Foo1::Get(), some gremlin came along and incremented %rip by 4.

合理的解释?

推荐答案

因此，看起来不太可能，我们似乎已经遇到了真正的CPU错误.

So, unlikely as it may seem, we appear to have hit an actual bona-fide CPU bug.

http://support.amd.com/us/Processor_TechDocs/41322_10h_Rev_Gd.pdf 具有erratum#721:

http://support.amd.com/us/Processor_TechDocs/41322_10h_Rev_Gd.pdf has erratum #721:

721处理器可能不正确地更新堆栈指针

说明

Under a highly specific and detailed set of internal timing conditions,
the processor may incorrectly update the stack pointer after a long series
of push and/or near-call instructions, or a long series of pop 
and/or near-return instructions. The processor must be in 64-bit mode for
this erratum to occur.

对系统的潜在影响

Potential Effect on System

The stack pointer value jumps by a value of approximately 1024, either in
the positive or negative direction.
This incorrect stack pointer causes unpredictable program or system behavior,
usually observed as a program exception or crash (for example, a #GP or #UD).

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