Re: [PATCH -next] modpost: move some defines to the file head

[Palmer Dabbelt]

On Wed, 12 Jul 2023 08:55:23 PDT (-0700), masahiroy@xxxxxxxxxx wrote:
> +To: Luis Chamberlain, the commiter of the breakage
>
>
>
> On Wed, Jul 12, 2023 at 10:44 AM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > with "module: Ignore RISC-V mapping symbols too", build error occurs,
> >
> > scripts/mod/modpost.c: In function ‘is_valid_name’:
> > scripts/mod/modpost.c:1055:57: error: ‘EM_RISCV’ undeclared (first use in this function)
> >   return !is_mapping_symbol(name, elf->hdr->e_machine == EM_RISCV);
> >
> > Fix it by moving the EM_RISCV to the file head, also some other
> > defines in case of similar problem in the future.
>
>
>
> BTW, why is the flag 'is_riscv' needed?
>
>
> All symbols starting with '$' look special to me.
>
>
>
> Why not like this?
>
>
>        if (str[0] == '$')
>                  return true;
>
>        return false;

There's a bit of commentary in the v1 
<https://lore.kernel.org/all/20230707054007.32591-1-palmer@xxxxxxxxxxxx/>, 
but essentially it's not necessary.  I just wanted to play things safe 
and avoid changing the mapping symbol detection elsewhere in order to 
deal with RISC-V.

IIRC we decided $ was special in RISC-V because there were some other 
ports that behaved that way, but it wasn't universal.  If folks are OK 
treating $-prefixed symbols as special everywhere that's fine with me, I 
just wasn't sure what the right answer was.  

There's also some similar arch-specific-ness with the labels and such in 
here.

> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > ---
> >  scripts/mod/modpost.c | 32 ++++++++++++++++----------------
> >  1 file changed, 16 insertions(+), 16 deletions(-)
> >
> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index 7c71429d6502..885cca272eb8 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -60,6 +60,22 @@ static unsigned int nr_unresolved;
> >
> >  #define MODULE_NAME_LEN (64 - sizeof(Elf_Addr))
> >
> > +#ifndef EM_RISCV
> > +#define EM_RISCV               243
> > +#endif
> > +
> > +#ifndef R_RISCV_SUB32
> > +#define R_RISCV_SUB32          39
> > +#endif
> > +
> > +#ifndef EM_LOONGARCH
> > +#define EM_LOONGARCH           258
> > +#endif
> > +
> > +#ifndef R_LARCH_SUB32
> > +#define R_LARCH_SUB32          55
> > +#endif
> > +
> >  void __attribute__((format(printf, 2, 3)))
> >  modpost_log(enum loglevel loglevel, const char *fmt, ...)
> >  {
> > @@ -1428,22 +1444,6 @@ static int addend_mips_rel(uint32_t *location, Elf_Rela *r)
> >         return 0;
> >  }
> >
> > -#ifndef EM_RISCV
> > -#define EM_RISCV               243
> > -#endif
> > -
> > -#ifndef R_RISCV_SUB32
> > -#define R_RISCV_SUB32          39
> > -#endif
> > -
> > -#ifndef EM_LOONGARCH
> > -#define EM_LOONGARCH           258
> > -#endif
> > -
> > -#ifndef R_LARCH_SUB32
> > -#define R_LARCH_SUB32          55
> > -#endif
> > -
> >  static void section_rela(struct module *mod, struct elf_info *elf,
> >                          Elf_Shdr *sechdr)
> >  {
> > --
> > 2.41.0