Re: [PATCH] perf riscv: fix register name strings

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Jun 08, 2026 at 05:27:03PM -0300, Arnaldo Carvalho de Melo wrote:
> On Mon, Jun 08, 2026 at 01:08:28PM -0700, Ian Rogers wrote:
> > On Mon, Jun 8, 2026 at 12:27 PM Martin Kaiser <martin@kaiser.cx> wrote:
> > >
> > > On risc-v, pref probe generates an invalid syntax for a named register in
> > > a kprobe.
> > >
> > > $ perf probe --debug verbose --add "n_tty_write tty"
> > > ...
> > > Writing event: p:probe/n_tty_write _text+8922528 tty=%"%a0":x64
> > > Failed to write event: Invalid argument
> > >
> > > The problem is the combination of
> > >
> > >    #define REG_DWARFNUM_NAME(reg, idx) [idx] = "%" #reg
> > >
> > > and entries such as
> > >
> > >    REG_DWARFNUM_NAME("%a0", 10)
> > >
> > > where #reg will escape the quotes of the first macro parameter.
> > >
> > > Update the macro definition to produce the correct syntax for a named
> > > register in a kprobe, i.e. the unquoted register name with only one
> > > leading %.
> > >
> > > Fixes: a90c4519186d ("perf riscv: Remove dwarf-regs.c and add dwarf-regs-table.h")
> > > Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> > 
> > Reviewed-by: Ian Rogers <irogers@google.com>
> > 
> > Thanks for catching this! Sashiko is also green for this change:
> > https://sashiko.dev/#/patchset/20260608192731.708606-1-martin%40kaiser.cx
> 
> Strange,
> 
>   LD      /tmp/build/perf-tools-next/tests/perf-test-in.o
>   LD      /tmp/build/perf-tools-next/perf-test-in.o
> In file included from util/dwarf-regs.c:23:
> util/../arch/riscv/include/dwarf-regs-table.h:5:9: error: ‘REG_DWARFNUM_NAME’ redefined [-Werror]
>     5 | #define REG_DWARFNUM_NAME(reg, idx)     [idx] = reg
>       |         ^~~~~~~~~~~~~~~~~
> In file included from util/dwarf-regs.c:22:
> util/../arch/powerpc/include/dwarf-regs-table.h:10:9: note: this is the location of the previous definition
>    10 | #define REG_DWARFNUM_NAME(reg, idx)     [idx] = "%" #reg
>       |         ^~~~~~~~~~~~~~~~~
> In file included from util/dwarf-regs.c:24:
> util/../arch/s390/include/dwarf-regs-table.h:5:9: error: ‘REG_DWARFNUM_NAME’ redefined [-Werror]
>     5 | #define REG_DWARFNUM_NAME(reg, idx)     [idx] = "%" #reg
>       |         ^~~~~~~~~~~~~~~~~
> util/../arch/riscv/include/dwarf-regs-table.h:5:9: note: this is the location of the previous definition
>     5 | #define REG_DWARFNUM_NAME(reg, idx)     [idx] = reg
>       |         ^~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[4]: *** [/home/acme/git/perf-tools-next/tools/build/Makefile.build:96: /tmp/build/perf-tools-next/util/dwarf-regs.o] Error 1
> 
> 
> Trying to figure out why Sashiko is green on it but it doesn't build
> here...

C preprocessor benign redefinition rule kicked in, this is a preexisting
problem, the headers need to undef that REG_DWARFNUM_NAME that now is
different in one of the headers, Risc-V's.

I'll cook up a patch to merge before this one.

- Arnaldo