[PATCH 00/10] vmcore-tasks: lightweight task and backtrace extractor for vmcore files

[Pnina Feder]

Hi,

Did you have a chance to look at it?
I got a response from Linux kernel saying the kernel patch looks ok and they want to know if you are interested in it.
https://lore.kernel.org/all/20260622211430.4008899-1-pnina.feder@mobileye.com/

Thanks,
Pnina

> This series adds vmcore-tasks, a new userspace tool for extracting per-task debugging information from Linux vmcore (kdump) files. It is designed as a lightweight tool, targeting embedded systems where crash-utility may not be available.
> 
> Motivation
> ----------
> 
> After a kernel panic, kdump produces a vmcore containing a full memory snapshot. Existing post-mortem tools like crash-utility are powerful but heavyweight — they require vmlinux with DWARF debug info and a matching kernel symbol table. On embedded targets with limited storage, stripped kernels, or unsupported architectures, this is often not practical.
> 
> vmcore-tasks takes a different approach: it requires no vmlinux or DWARF data. Instead, a kernel-side component exports the  necessary struct offsets, sizes, and symbol addresses into the standard vmcoreinfo note section. This data, already embedded in the vmcore by kdump, is sufficient to navigate kernel data structures, allowing it to run directly from crash-kernel, and only solving bt addresses later with tools like addr2line.
> 
> vmcore-tasks extract:
> 
>   - Per-task register state (pt_regs) and user-space backtraces
>   - VMA memory maps with filename resolution via dentry walk
>   - Per-thread state for multi-threaded processes
>   - Kernel dmesg log (reuses existing vmcore-dmesg infrastructure)
> 
> Architecture
> ------------
> 
> The tool is structured in layers:
> 
>   util_lib/          Foundation: vmcoreinfo parser, memory reader,
>                      maple tree walker (reuses existing elf_info.c
>                      and adds new shared utilities)
> 
>   vmcore_tasks/      Core logic: task enumeration, VMA collection,
>                      generic stack unwinder with arch callbacks
> 
>   vmcore_tasks/arch/ Architecture backends: page table translation
>                      and instruction decode (RISC-V 64, MIPS64)
> 
> The generic unwinder in unwind.c drives frame recovery using arch-provided callbacks (detect SP adjustment, RA save, signal trampolines), so adding a new architecture requires only implementing the instruction decode — not the unwinding state machine.
> 
> VMA enumeration auto-selects between the legacy mm_struct->mmap linked list (kernels < 6.1) and maple tree walk (kernels >= 6.1) based on vmcoreinfo content.
> 
> Integration with kexec-tools
> ----------------------------
> 
> The new files are placed in vmcore_tasks/ and util_lib/.
> The util_lib additions (vmcore_info.c, memory.c, maple_tree.c) are currently built only by the vmcore_tasks Makefile.
> Integration into the main kexec-tools build system can follow once the tool matures.
> 
> The tool reuses elf_info.c from util_lib for ELF parsing and
> paddr_to_offset() for physical-to-file-offset mapping, and reuses
> dump_dmesg() from vmcore-dmesg for kernel log extraction.
> 
> Depends on kernel-side patch to export the needed vmcoreinfo values.
> Will update with a link to this patch later.
> 
> Testing
> -------
> 
> Validated against vmcore files from controlled kernel panic scenarios on RISC-V 64-bit (SV39) and MIPS64 platforms, covering multi-frame backtraces, leaf functions, and signal frame unwinding. Tested both natively and cross-architecture (x86_64 host processing RISC-V/MIPS64 vmcores).
> 
> Pnina Feder (10):
>   util_lib: add paddr_to_offset function and expose raw vmcoreinfo data
>   util_lib: Add vmcoreinfo parser and memory reader
>   util_lib: Add maple tree walker for VMA enumeration
>   vmcore_tasks: Add common definitions and project infrastructure
>   vmcore_tasks: arch: Add RISC-V 64-bit architecture support
>   vmcore_tasks: arch: Add MIPS64 architecture support
>   vmcore_tasks: Add generic user-space stack unwinder
>   vmcore_tasks: Add VMA utilities and task enumeration
>   vmcore_tasks: Add main entry point and backtrace parser
>   vmcore_tasks: Add README with project documentation