Re: [PATCH] riscv: Fixup compile error BUILD_BUG_ON failed

[Guo Ren <guoren@kernel.org>]

On Sun, Jun 28, 2020 at 10:52 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> On Sun, 28 Jun 2020 14:12:07 +0800
> Guo Ren <guoren@kernel.org> wrote:
>
> > On Sun, Jun 28, 2020 at 10:59 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
> > >
> > > On Sat, 27 Jun 2020 16:20:02 +0000
> > > guoren@kernel.org wrote:
> > >
> > > > From: Guo Ren <guoren@linux.alibaba.com>
> > > >
> > > > Unfortunately, the current code couldn't be compiled, because
> > > > BUILD_BUG_ON needs a static defined value, not a dynamic
> > > > variable with a0 regs. Just use it inline as a solution.
> > > >
> > > >   CC      arch/riscv/kernel/patch.o
> > > > In file included from ./include/linux/kernel.h:11,
> > > >                  from ./include/linux/list.h:9,
> > > >                  from ./include/linux/preempt.h:11,
> > > >                  from ./include/linux/spinlock.h:51,
> > > >                  from arch/riscv/kernel/patch.c:6:
> > > > In function ‘fix_to_virt’,
> > > >     inlined from ‘patch_map’ at arch/riscv/kernel/patch.c:37:17:
> > > > ./include/linux/compiler.h:392:38: error: call to ‘__compiletime_assert_205’ declared with attribute error: BUILD_BUG_ON failed: idx >= __end_of_fixed_addresses
> > > >   _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > > >                                       ^
> > > > ./include/linux/compiler.h:373:4: note: in definition of macro ‘__compiletime_assert’
> > > >     prefix ## suffix();    \
> > > >     ^~~~~~
> > > > ./include/linux/compiler.h:392:2: note: in expansion of macro ‘_compiletime_assert’
> > > >   _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > > >   ^~~~~~~~~~~~~~~~~~~
> > > > ./include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’
> > > >  #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> > > >                                      ^~~~~~~~~~~~~~~~~~
> > > > ./include/linux/build_bug.h:50:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
> > > >   BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> > > >   ^~~~~~~~~~~~~~~~
> > > > ./include/asm-generic/fixmap.h:32:2: note: in expansion of macro ‘BUILD_BUG_ON’
> > > >   BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
> > > >   ^~~~~~~~~~~~
> > > >
> > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > > > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > > > Cc: Zong Li <zong.li@sifive.com>
> > > > ---
> > > >  arch/riscv/kernel/patch.c | 3 +--
> > > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > > >
> > > > diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> > > > index d4a64df..f8e84f2 100644
> > > > --- a/arch/riscv/kernel/patch.c
> > > > +++ b/arch/riscv/kernel/patch.c
> > > > @@ -20,7 +20,7 @@ struct patch_insn {
> > > >  };
> > > >
> > > >  #ifdef CONFIG_MMU
> > > > -static void *patch_map(void *addr, int fixmap)
> > > > +static inline void *patch_map(void *addr, int fixmap)
> > >
> > > Would we be better to use "__always_inline" as same as fix_to_virt?
> > Ok
> >
> > > And also, could you add a comment why we need to make it inline?
> > I've mentioned in comment:
> > > > BUILD_BUG_ON needs a static defined value, not a dynamic
> > > > variable with a0 regs.
> >
> > idx must be a const unsigned int or it will cause compile error with
> > BUILD_BUG_ON.
>
> Ah, sorry for the confusion. I meant the comment line in the code.
Ok.

> BTW, can we also use "const unsigned int" for the fixmap index so that
> no one miss it anymore?
Sure, actually I've done it in my patch V2. Thx for mention.

-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/