[PATCH 0/4] vmcore-tasks: export per-task metadata to vmcoreinfo

[Pnina Feder]

This series extends vmcoreinfo with struct offsets and sizes needed by
the vmcore-tasks userspace tool to extract per-task state from a vmcore
dump without requiring kernel debug symbols (DWARF/BTF).

The vmcore-tasks tool reads /proc/vmcore (or a saved vmcore file) and
reconstructs, for each task:
  - task name, pid, state, flags
  - VMA list (start, end, flags, backing file)
  - user register state (saved on the kernel stack at kernel entry)
  - user-space backtrace with VMA/filename mapping
  - kernel dmesg buffer

This provides a lightweight post-mortem crash analysis capability for
production environments where full debug info (DWARF/BTF) is not
available.

The companion userspace tool is submitted to kexec-tools:
  https://lore.kernel.org/all/20260622205550.1087163-1-pnina.feder@xxxxxxxxxxxx/

The series is structured as follows:

  Patch 1: Increase vmcoreinfo buffer from PAGE_SIZE to a fixed SZ_8K,
           decoupled from page size to avoid waste on large-page
           architectures (MIPS 16KB, arm64 64KB).

  Patch 2: Export generic struct offsets (task_struct, mm_struct,
           vm_area_struct, maple_tree, file/dentry/path, pt_regs,
           signal_struct) needed to walk task lists and VMAs.

  Patch 3: Export RISC-V arch-specific offsets (signal frame layouts,
           register context structures) for user register extraction.

  Patch 4: Export MIPS arch-specific offsets (signal frame layouts,
           register context structures) for user register extraction.

Additional architecture support (arm64, x86, etc.) can follow the
same pattern established by patches 3 and 4.

Tested on MIPS64 (QEMU Malta) and RISC-V with full kdump pipeline:
primary kernel -> kexec panic -> crash kernel -> vmcore-tasks analysis.

Pnina Feder (4):
  vmcoreinfo: increase vmcoreinfo buffer to 8KB
  vmcoreinfo: export task and mm struct offsets to vmcoreinfo
  riscv: vmcore_info: export riscv arch-specific struct offsets to
    vmcoreinfo
  mips: vmcore_info: export mips arch-specific struct offsets to
    vmcoreinfo

 .../admin-guide/kdump/vmcoreinfo.rst          | 137 ++++++++++++++++++
 arch/mips/kernel/Makefile                     |   1 +
 arch/mips/kernel/signal.c                     |   8 +
 arch/mips/kernel/vmcore_info.c                |  22 +++
 arch/riscv/kernel/signal.c                    |   8 +
 arch/riscv/kernel/vmcore_info.c               |  11 ++
 include/linux/vmcore_info.h                   |   3 +-
 kernel/vmcore_info.c                          |  60 ++++++++
 8 files changed, 249 insertions(+), 1 deletion(-)
 create mode 100644 arch/mips/kernel/vmcore_info.c

-- 
2.43.0