c++ - 程序在调试器外正常，步进时调试器下的 SIGILL？

Question

我正在尝试在 BeagleBone Black 上调试程序。在调试器之外，它会产生不正确的结果，但不会产生 SIGILL。它在调试器下也运行正常，没有断点。但是，它会在单步执行时生成带有断点设置的 SIGILL。该程序和库不使用基于 SIGILL 的 cpu 功能探测器。但是，我不知道GDB在做什么。

在我看到的调试器下:

(gdb) b main
Breakpoint 1 at 0x26f20: file test.cxx, line 22.
(gdb) r
Starting program: /home/cryptopp/test.exe

Breakpoint 1, main (argc=0x1, argv=0xbeffea54) at test.cxx:22
22          byte key[16] = {0};
(gdb) n
23          byte iv[12] = {0};
(gdb)
25          GCM<AES>::Encryption enc;
(gdb)
26          enc.SetKeyWithIV(key, 16, iv, 12);
(gdb)
28          std::string plain(0x00, 16);
(gdb)

Program received signal SIGILL, Illegal instruction.
0x00026d5c in std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)
    ()
(gdb) n
Single stepping until exit from function _ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_,
which has no line number information.

Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.

和:

(gdb) shell echo _ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_ | c++filt
std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)

我尝试搜索此问题，但未能找到匹配项。我的噪音太大了。

当 GDB 设置断点时，为什么我遇到 SIGILL，我该如何解决？

---

NEON 是我要研究的问题。这是用于程序和库的命令行:

$ echo $CXXFLAGS
-DDEBUG -g3 -O0 -march=armv7-a -mtune=cortex-a8 -mfpu=neon -mfloat-abi=hard
$ g++ $CXXFLAGS test.cxx ./libcryptopp.a -o test.exe

和:

$ gdb --version
GNU gdb (Debian 7.7.1+dfsg-5) 7.7.1

$ uname -a
Linux beaglebone 4.1.15-ti-rt-r40 #1 SMP PREEMPT RT Thu Jan 7 23:32:08 UTC 2016 armv7l GNU/Linux

$ cat /proc/cpuinfo
processor       : 0
model name      : ARMv7 Processor rev 2 (v7l)
BogoMIPS        : 996.14
Features        : half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpd32
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x3
CPU part        : 0xc08
CPU revision    : 2

Hardware        : Generic AM33XX (Flattened Device Tree)
Revision        : 0000
Serial          : 0000000000000000

和:

Breakpoint 1, main (argc=0x1, argv=0xbeffea54) at test.cxx:22
22          byte key[16] = {0};
(gdb) n
23          byte iv[12] = {0};
(gdb)
25          GCM<AES>::Encryption enc;
(gdb)
26          enc.SetKeyWithIV(key, 16, iv, 12);
(gdb)
28          std::string plain(0x00, 16);
(gdb)

Program received signal SIGILL, Illegal instruction.
0x00026d5c in std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)
    ()

(gdb) up
#1  0x00026f82 in main (argc=0x1, argv=0xbeffea54) at test.cxx:28
28          std::string plain(0x00, 16);
(gdb) disass
Dump of assembler code for function main(int, char**):
   0x00026f10 <+0>:     push    {r4, r7, lr}
   0x00026f12 <+2>:     sub.w   sp, sp, #916    ; 0x394
   0x00026f16 <+6>:     add     r7, sp, #16
   0x00026f18 <+8>:     adds    r3, r7, #4
   0x00026f1a <+10>:    str     r0, [r3, #0]
   0x00026f1c <+12>:    mov     r3, r7
   0x00026f1e <+14>:    str     r1, [r3, #0]
   0x00026f20 <+16>:    add.w   r3, r7, #692    ; 0x2b4
   0x00026f24 <+20>:    movs    r2, #0
   0x00026f26 <+22>:    str     r2, [r3, #0]
   0x00026f28 <+24>:    adds    r3, #4
   0x00026f2a <+26>:    movs    r2, #0
   0x00026f2c <+28>:    str     r2, [r3, #0]
   0x00026f2e <+30>:    adds    r3, #4
   0x00026f30 <+32>:    movs    r2, #0
   0x00026f32 <+34>:    str     r2, [r3, #0]
   0x00026f34 <+36>:    adds    r3, #4
   0x00026f36 <+38>:    movs    r2, #0
   0x00026f38 <+40>:    str     r2, [r3, #0]
   0x00026f3a <+42>:    adds    r3, #4
   0x00026f3c <+44>:    add.w   r3, r7, #680    ; 0x2a8
   0x00026f40 <+48>:    movs    r2, #0
---Type <return> to continue, or q <return> to quit---
   0x00026f42 <+50>:    str     r2, [r3, #0]
   0x00026f44 <+52>:    adds    r3, #4
   0x00026f46 <+54>:    movs    r2, #0
   0x00026f48 <+56>:    str     r2, [r3, #0]
   0x00026f4a <+58>:    adds    r3, #4
   0x00026f4c <+60>:    movs    r2, #0
   0x00026f4e <+62>:    str     r2, [r3, #0]
   0x00026f50 <+64>:    adds    r3, #4
   0x00026f52 <+66>:    add.w   r3, r7, #240    ; 0xf0
   0x00026f56 <+70>:    mov     r0, r3
   0x00026f58 <+72>:    bl      0x2a804 <CryptoPP::GCM_Final<CryptoPP::Rijndael, (CryptoPP::GCM_TablesOption)0, true>::GCM_Final()>
   0x00026f5c <+76>:    add.w   r1, r7, #240    ; 0xf0
   0x00026f60 <+80>:    add.w   r2, r7, #692    ; 0x2b4
   0x00026f64 <+84>:    add.w   r4, r7, #680    ; 0x2a8
   0x00026f68 <+88>:    movs    r3, #12
   0x00026f6a <+90>:    str     r3, [sp, #0]
   0x00026f6c <+92>:    mov     r0, r1
   0x00026f6e <+94>:    mov     r1, r2
   0x00026f70 <+96>:    movs    r2, #16
   0x00026f72 <+98>:    mov     r3, r4
   0x00026f74 <+100>:   bl      0x2da0c <CryptoPP::SimpleKeyingInterface::SetKeyWithIV(unsigned char const*, unsigned int, unsigned char const*, unsigned int)>
---Type <return> to continue, or q <return> to quit---
   0x00026f78 <+104>:   add.w   r3, r7, #708    ; 0x2c4
   0x00026f7c <+108>:   mov     r0, r3
   0x00026f7e <+110>:   blx     0x26d58 <_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_+852>
=> 0x00026f82 <+114>:   add.w   r2, r7, #676    ; 0x2a4
   0x00026f86 <+118>:   add.w   r3, r7, #708    ; 0x2c4
   0x00026f8a <+122>:   mov     r0, r2
   0x00026f8c <+124>:   movs    r1, #0
   0x00026f8e <+126>:   movs    r2, #16
   ...

Answer 1

感谢@ks1322，这是一个已知的 GDB/内核错误。参见 GDB crashes on debugging multithreaded program on ARM SMP dual core system在 GDB 问题跟踪器中。

根据 Debian BTS，这也是一个已知问题。参见 SIGILL when stepping through application on armhf在 Debian BTS 中。

该错误已被重新填写，希望它可能会在未来一两年的某个时候真正得到修复。参见 GDB Crash due to GDB/Kernel generated SIGILL

这就是我鄙视 Debian 的错误报告系统的原因。东西被报道，然后它就腐烂了。没有什么是固定的。