On Tue, Mar 24, 2026 at 9:00 AM Sasha Levin <[email protected]> wrote: > > On Tue, Mar 24, 2026 at 08:03:30AM -0700, Alexei Starovoitov wrote: > >On Mon, Mar 23, 2026 at 9:49 AM Sasha Levin <[email protected]> wrote: > >> > >> Embed DWARF-derived function parameter name and type information in the > >> kernel image so that oops and WARN dumps display the crashing function's > >> register-passed arguments with their names, types, and values. > >> > >> A new build-time tool (scripts/gen_paraminfo.c) parses DW_TAG_subprogram > >> and DW_TAG_formal_parameter entries from DWARF .debug_info, extracting > >> parameter names and human-readable type strings. The resulting tables are > >> stored in .rodata using the same two-phase link approach as lineinfo. > >> > >> At runtime, kallsyms_show_paraminfo() performs a binary search on the > >> paraminfo tables, maps parameters to x86-64 calling convention registers > >> (RDI, RSI, RDX, RCX, R8, R9), and prints each parameter's name, type, > >> and value from pt_regs. If a parameter value matches the page fault > >> address (CR2), it is highlighted with "<-- fault address". > >> > >> Integration at show_regs() means this works for both oops and WARN() > >> automatically, since both paths provide full pt_regs at the exception > >> point. > >> > >> Example output: > >> > >> Function parameters (ext4_readdir): > >> file (struct file *) = 0xffff888123456000 > >> ctx (struct dir_context *) = 0x0000000000001234 <-- fault > >> address > >> > >> Gated behind CONFIG_KALLSYMS_PARAMINFO (depends on > >> CONFIG_KALLSYMS_LINEINFO). > >> Adds approximately 1-2 MB to the kernel image for ~58K functions. > >> > >> Assisted-by: Claude:claude-opus-4-6 > >> Signed-off-by: Sasha Levin <[email protected]> > > > >Nack. > > > >You asked claude to reinvent pahole and BTF and it did it > >completely missing years of fine tuning that pahole does. > > Let's keep this on the technical side please. > > >dwarf cannot be trusted as-is. pahole converts it carefully > >by analyzing optimized out arguments and dropping signatures > > Fair point about pahole and optimized-out args. The problem is that BTF > depends > on BPF_SYSCALL, and the environments I care about can't enable either.
This is trivially fixable without reinventing pahole.
