coredump: implement host parser

[etiaro]

Description

Implement parser for phoenix-rtos/phoenix-rtos-utils#242 that allows post-mortem debugging of crashed process using GDB.

Motivation and Context

RTOS-1043 Research core dump and backtrace techniques
RTOS-1049 Implement core dump on MMU targets
RTOS-1062 Implement core dump on NOMMU targets

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: (list targets here).

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[gemini-code-assist]

Hello @etiaro, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

Hello! Gemini here, providing a summary of this pull request.

This PR introduces a new host-side utility, coredump_parser, designed to process coredump data generated by the Phoenix RTOS kernel (specifically the format implemented in the linked PR #649). The primary goal is to enable post-mortem debugging of crashed processes on the target system using standard host tools like GDB.

The parser reads encoded coredump data from standard input, which is expected to be in a specific format including start/end markers, process information, Base64 encoding, and Run-Length Encoding (RLE). It decodes the data, performs a CRC32 validation to ensure integrity, and then writes the raw memory dump to a file in a specified output directory. The utility is designed to handle multiple coredumps streamed via stdin and generates unique filenames for each dump.

Highlights

• New Host Utility: Adds a new executable coredump_parser to the project, intended to run on the host machine.
• Coredump Parsing Logic: Implements the core logic for reading, decoding (Base64 and RLE), and validating (CRC32) Phoenix RTOS coredump data streamed via stdin.
• File Output for Debugging: Writes the decoded raw memory data to a file in a user-specified directory, formatted for use with debuggers like GDB.
• Handles Multiple Dumps: The parser can process multiple coredumps from a single input stream, generating unique output files for each.

Changelog

Click here to see the changelog

• coredump_parser/Makefile
  • Added a new Makefile to build the coredump_parser executable.
• coredump_parser/parser.cpp
  • Added the main C++ source file for the coredump parser.
  • Includes functions for Base64 decoding (b64_index, read_b64).
  • Includes function for Run-Length Encoding (RLE) decoding (decode_rle).
  • Includes function for CRC32 validation (check_crc).
  • Implements logic to read from stdin, detect coredump markers (_COREDUMP_START_, _COREDUMP_END_), extract process info, and call decoding/validation functions (watch_stdin, read_decode).
  • Includes function to write the decoded memory data to a file (parse_dump).
  • Includes function to generate unique output filenames based on process name, CRC, and index (get_output_path).
  • Contains the main function for argument parsing and the main processing loop.
• coredump_parser/readme.md
  • Added a README file explaining how to use the coredump_parser utility.
  • Provides instructions for debugging using gdb-multiarch.

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---

Core dump arrives,
Base64, RLE unwinds,
Debug begins now.

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[gemini-code-assist]

Code Review

This pull request introduces a parser for Phoenix coredumps, enabling post-mortem debugging with GDB. This is a valuable addition for diagnostics.

The implementation covers base64 decoding, RLE decoding, and CRC checking. The overall structure is logical. However, I've identified a few issues, including some critical and high-severity ones related to potential out-of-bounds memory access and error handling, that should be addressed before merging. There are also some medium-severity suggestions for improving code robustness and clarity.

No explicit style guide was provided, so feedback is based on common C++ best practices focusing on correctness, maintainability, and safety.

Summary of Findings

• Critical: Out-of-Bounds Read in CRC Check Debug Message: A debug print statement in check_crc (parser.cpp:121) attempts an unsafe memory access by trying to read the CRC from a data buffer that has already had the CRC removed. This will lead to an out-of-bounds read and likely crash if the remaining data size is less than 4 bytes.
• High: Potential Out-of-Bounds Read During CRC Extraction: In read_decode (parser.cpp:141), the CRC is extracted from the decoded data. If the decoded data is shorter than 4 bytes, this operation will read out of bounds, causing a crash or undefined behavior. A size check is needed.
• High: Shadowed Loop Variable: In check_crc (parser.cpp:113), an inner loop variable i shadows an outer loop variable i. This is poor practice and can lead to confusion or bugs.
• Medium: Type Punning for CRC Extraction: In read_decode (parser.cpp:141), type punning is used to convert bytes to uint32_t for CRC extraction. Using memcpy is a safer and more standards-compliant approach.
• Medium: Ambiguous EOF Return Code: The watch_stdin function (parser.cpp:172) returns EOF. It would be clearer to use a custom status code (perhaps from an enum) to distinguish clean end-of-file from other error conditions.
• Medium: Integer Error Codes vs. Enum Class: Error codes (parser.cpp:8-11) are defined as const int. Using an enum class would provide better type safety and semantic grouping.
• Low: Copyright Year in Makefile (Not Commented): The Makefile (coredump_parser/Makefile:4) has a copyright year of 2025, which is likely a typo. (Severity: low, not commented due to review settings)
• Low: Use of C Headers (Not Commented): The C header <stdio.h> is used (parser.cpp:5). In C++, <cstdio> is generally preferred for C standard library headers. (Severity: low, not commented due to review settings)
• Low: Error Messages Stream (Not Commented): Error messages are printed to std::cout. std::cerr is the standard stream for error messages. (Severity: low, not commented due to review settings)
• Low: C-style Typedef Struct (Not Commented): The C-style typedef struct { ... } additional_info; (parser.cpp:14-18) is used. In C++, struct additional_info { ... }; is sufficient. (Severity: low, not commented due to review settings)

Merge Readiness

This pull request introduces a significant and useful feature. However, due to the presence of critical and high-severity issues, particularly those related to potential out-of-bounds memory access which could lead to crashes, I recommend that these issues be addressed before the pull request is merged. The medium-severity suggestions should also be considered for improving the overall quality and robustness of the code.

I am not authorized to approve pull requests, but based on this review, changes are requested.

Changes implemented