Valgrind reports error disInstr(arm): unhandled instruction: 0xEC510F1E

Directory title

  • Problem background
  • specific reason
  • The principle behind
  • Conclusion

Problem background

When using cross-compiled Valgrind on the arm platform to monitor your own process, you will find that processes that rely on libcrypto will report an error.
Roughly as follows

==20393== Memcheck, a memory error detector
==20393== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==20393== Using Valgrind-3.20.0 and LibVEX; rerun with -h for copyright info
==20393== Command: ./my_process
==20393==
==20393==
disInstr(arm): unhandled instruction: 0xEC510F1E
                 cond=14(0xE) 27:20=197(0xC5) 4:4=1 3:0=14(0xE)
==20393== valgrind: Unrecognized instruction at address 0x4d32848.
==20393== at 0x4D32848: ? (in /usr/lib/libcrypto.so.1.0.2)
==20393== Your program just tried to execute an instruction that Valgrind
==20393== did not recognize. There are two possible reasons for this.
==20393== 1. Your program has a bug and erroneously jumped to a non-code
==20393== location. If you are running Memcheck and you just saw a
==20393== warning about a bad jump, it's probably your program's fault.
==20393== 2. The instruction is legitimate but Valgrind doesn't handle it,
==20393== i.e. it's Valgrind's fault. If you think this is the case or
==20393== you are not sure, please let us know and we'll try to fix it.
==20393== Either way, Valgrind will now raise a SIGILL signal which will
==20393== probably kill your program.

Specific reasons

When dealing with issues related to Valgrind on the ARM platform, especially when encountering unrecognized instructions in the libcrypto library after cross-compiling, there are several factors and potential solutions to consider:

  1. Configuration adjustments for ARM: When cross-compiling Valgrind for ARM, specific configuration changes may be required. For example, it is crucial to modify the configuration file to correctly target the ARM architecture. A suggested command for this kind of adjustment is sed -i -e "s#armv7#arm#g" configure[16?source].

  2. Cross-compilation environment: It is crucial to ensure that the cross-compilation environment is set up correctly. This includes using the correct cross-compiler and settings for the target ARM platform. For example, if you use Fedora VM to cross-compile for ARM Cortex M4 CPU, please ensure that the compilation environment (such as QT IDE) is correctly configured for the ARM platform [17?source].

  3. Valgrind’s Intermediate Language (VEX): Valgrind uses an intermediate language (VEX) to simulate your program and check for memory violations. This language captures instructions from various assemblers such as i386, amd64 and ARM. However, it may sometimes miss some special instructions, which may be related to problems you are encountering in the libcrypto library [18?source].

  4. Valgrind Compatibility with ARM: Valgrind is designed to work with multiple platforms, including ARM, but maintaining compatibility with each platform is challenging due to the low-level nature of the tool. Some features may not be fully supported on all platforms, which may cause problems with commands not being recognized [19? source] [20? source].

In summary, solving the problem may require:

  • Adjust configuration to target ARM architecture.
  • Make sure the cross-compilation environment is set up correctly.
  • Understand the limitations of the Valgrind intermediate language and its compatibility with ARM.

If these steps do not resolve the issue, you may need to further investigate the specific directive or library function that Valgrind does not recognize. It may also be helpful to consult Valgrind’s documentation or community forums for more specific advice on the ARM platform and libcrypto library.

Principle behind

While dealing with Valgrind’s inability to handle a specific instruction on the ARM platform, specifically the instruction 0xEC510F1E, I found some relevant information. This issue was reported on the KDE Bugtracking System, describing a situation similar to the issue you are experiencing.

The problem mentioned in the report is that Valgrind cannot recognize the instruction 0xEC510F1E when processing the _armv7_tick function located in the libcrypto.so.1.0.0 library. . This instruction is mrrc p15, #1, r0, r1, c14, which is used to read the CP15 CNTVCT register (virtual timer). The binary representation of this instruction is as follows:

cond const Rt2 Rt copr opc1 CRm
1110 11000101 0001 0000 1111 0001 1110

This code can always reproduce this problem [32?source].

This issue indicates that Valgrind may not support certain specialized ARM instructions, specifically those related to hardware timer operation. This can cause Valgrind to crash or behave unexpectedly when trying to run code that uses these instructions. Solving such problems may require updating the version of Valgrind, or modifying the relevant code to avoid using instructions that Valgrind does not recognize. Also consider reporting this issue to Valgrind’s development team so it can be fixed in a future version.

The reason why Valgrind doesn’t recognize reading the CP15 CNTVCT register (virtual timer) may have to do with how it emulates code execution on an ARM processor. Valgrind uses an intermediate language (VEX) to simulate program execution so that it can detect memory violations and other errors. This simulation process requires Valgrind to understand and translate every instruction of the processor.

However, since Valgrind emulates processor instructions at a high level, it may not fully support all processor-specific instructions, especially those that are closely related to hardware features. On ARM processors, some special hardware operation instructions (such as reading hardware timer registers) may not be within the scope of Valgrind’s simulation.

In addition, the development and maintenance of Valgrind is an ongoing process, and new processor features and instruction sets may emerge before Valgrind supports them. Therefore, when new or uncommon processor instructions appear, Valgrind may not be able to correctly recognize and emulate these instructions, causing it to be unable to process code that involves these instructions.

Conclusion

In our programming learning journey, understanding is an important step for us to move to a higher level. However, mastering new skills and ideas always requires time and persistence. From a psychological point of view, learning is often accompanied by constant trial and error and adjustment, which is like our brain gradually optimizing its “algorithm” for solving problems.

This is why when we encounter mistakes, we should view them as opportunities to learn and improve, rather than More than just an obsession. By understanding and solving these problems, we can not only fix the current code, but also improve our programming skills and prevent making the same mistakes in future projects.

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