[PATCH 0/2] kallsyms: show typed function parameters in oops/WARN dumps

[Sasha Levin <sashal@kernel.org>]

Building on the lineinfo series, this adds typed function parameter
display to oops and WARN dumps.  A build-time tool extracts parameter
names and types from DWARF, and the kernel maps pt_regs to the calling
convention at crash time.  When BTF is available, struct pointer
parameters are dereferenced and their members displayed.

Example output from a WARN in a function receiving struct new_utsname *
(kernel version info) and struct file * parameters:

 ------------[ cut here ]------------
 WARNING: drivers/tty/sysrq.c:1209 at demo_crash+0xf/0x20 (drivers/tty/sysrq.c:1209)
 CPU: 2 UID: 0 PID: 323 Comm: bash
 RIP: 0010:demo_crash+0xf/0x20 (drivers/tty/sysrq.c:1209)
 ...
 RDI: ffffffffb8ca8d00
 RSI: ffffa0a3c250acc0
 ...
 Function parameters (paraminfo_demo_crash):
  uts      (struct new_utsname *) = 0xffffffffb8ca8d00
   .sysname = "Linux"                        .nodename = "localhost"
   .release = "7.0.0-rc2-00006-g3190..."     .version = "#45 SMP PRE"
  file     (struct file *       ) = 0xffffa0a3c250acc0
   .f_mode = (fmode_t)67993630               .f_op = (struct file_operations *)0xffffffffb7237620
   .f_flags = (unsigned int)32769            .f_cred = (struct cred *)0xffffa0a3c2e06a80
   .dentry = (struct dentry *)0xffffa0a3c0978cc0
   .prev_pos = (loff_t)-1
 Call Trace:
  <TASK>
  write_sysrq_trigger+0x96/0xb0 (drivers/tty/sysrq.c:1222)
  proc_reg_write+0x54/0xa0 (fs/proc/inode.c:330)
  vfs_write+0xc9/0x480 (fs/read_write.c:686)
  ksys_write+0x6e/0xe0 (fs/read_write.c:738)
  do_syscall_64+0xe2/0x570 (arch/x86/entry/syscall_64.c:62)
  entry_SYSCALL_64_after_hwframe+0x77/0x7f (arch/x86/entry/entry_64.S:121)

Patch 1 adds the core paraminfo infrastructure (DWARF extraction,
kernel-side lookup, register-to-parameter mapping, ~1-2 MB overhead).
Patch 2 adds optional BTF-based struct rendering, gated behind
CONFIG_KALLSYMS_PARAMINFO_BTF.

Sasha Levin (2):
  kallsyms: show function parameter info in oops/WARN dumps
  kallsyms: add BTF-based deep parameter rendering in oops dumps

 .../admin-guide/kallsyms-lineinfo.rst         |  31 +
 arch/x86/kernel/dumpstack.c                   |   6 +-
 include/linux/kallsyms.h                      |   9 +
 init/Kconfig                                  |  40 ++
 kernel/Makefile                               |   1 +
 kernel/kallsyms.c                             | 182 ++++++
 kernel/kallsyms_internal.h                    |   6 +
 kernel/kallsyms_paraminfo_btf.c               | 199 ++++++
 lib/Kconfig.debug                             |  11 +
 lib/tests/Makefile                            |   3 +
 lib/tests/paraminfo_kunit.c                   | 249 ++++++++
 scripts/Makefile                              |   3 +
 scripts/empty_paraminfo.S                     |  18 +
 scripts/gen_paraminfo.c                       | 597 ++++++++++++++++++
 scripts/link-vmlinux.sh                       |  44 +-
 15 files changed, 1393 insertions(+), 6 deletions(-)
 create mode 100644 kernel/kallsyms_paraminfo_btf.c
 create mode 100644 lib/tests/paraminfo_kunit.c
 create mode 100644 scripts/empty_paraminfo.S
 create mode 100644 scripts/gen_paraminfo.c

--
2.51.0