linux-kernel - Re: [PATCH V2] riscv: Fixup compile error BUILD_BUG

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Message-Id: <20200629012524.c941a5f18aa7f312d325f714@kernel.org>
Date:   Mon, 29 Jun 2020 01:25:24 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     guoren@...nel.org
Cc:     greentime.hu@...ive.com, palmerdabbelt@...gle.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        paul.walmsley@...ive.com, anup@...infault.org,
        linux-csky@...r.kernel.org, zong.li@...ive.com,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V2] riscv: Fixup compile error BUILD_BUG_ON failed

On Sun, 28 Jun 2020 16:07:37 +0000
guoren@...nel.org wrote:

> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> Unfortunately, the current code couldn't be compiled:
> 
>   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);
>   ^~~~~~~~~~~~
> 
> Because fix_to_virt(, idx) needs a const value, not a dynamic variable of
> reg-a0 or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".

Looks good to me :)

Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks!

> 
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Zong Li <zong.li@...ive.com>
> ---
> Changelog V2:
>  - Use __always_inline as same as fix_to_virt
>  - Use const "const unsigned int" for 2th param
> 
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> ---
>  arch/riscv/kernel/patch.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> index d4a64df..3179a4e 100644
> --- a/arch/riscv/kernel/patch.c
> +++ b/arch/riscv/kernel/patch.c
> @@ -20,7 +20,12 @@ struct patch_insn {
>  };
>  
>  #ifdef CONFIG_MMU
> -static void *patch_map(void *addr, int fixmap)
> +/*
> + * The fix_to_virt(, idx) needs a const value (not a dynamic variable of
> + * reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
> + * So use '__always_inline' and 'const unsigned int fixmap' here.
> + */
> +static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
>  {
>  	uintptr_t uintaddr = (uintptr_t) addr;
>  	struct page *page;
> @@ -37,7 +42,6 @@ static void *patch_map(void *addr, int fixmap)
>  	return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
>  					 (uintaddr & ~PAGE_MASK));
>  }
> -NOKPROBE_SYMBOL(patch_map);
>  
>  static void patch_unmap(int fixmap)
>  {
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>