I'm looking to enable -Wmissing-variable-declarations behind W=1. 0day
bot spotted the following instance in ARCH=riscv builds:

  arch/riscv/mm/init.c:276:7: warning: no previous extern declaration
  for non-static variable 'trampoline_pg_dir'
  [-Wmissing-variable-declarations]
  276 | pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
      |       ^
  arch/riscv/mm/init.c:276:1: note: declare 'static' if the variable is
  not intended to be used outside of this translation unit
  276 | pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
      | ^
  arch/riscv/mm/init.c:279:7: warning: no previous extern declaration
  for non-static variable 'early_pg_dir'
  [-Wmissing-variable-declarations]
  279 | pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
      |       ^
  arch/riscv/mm/init.c:279:1: note: declare 'static' if the variable is
  not intended to be used outside of this translation unit
  279 | pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
      | ^

These symbols are referenced by more than one translation unit, so make
sure they're both declared and include the correct header for their
declarations. Finally, sort the list of includes to help keep them tidy.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/llvm/202308081000.tTL1ElTr-lkp@intel.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/riscv/include/asm/pgtable.h | 1 +
 arch/riscv/mm/init.c             | 9 +++++----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 75970ee2bda2..4c8c0f83a974 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -188,6 +188,7 @@ extern struct pt_alloc_ops pt_ops __initdata;
 #define PAGE_KERNEL_IO		__pgprot(_PAGE_IOREMAP)
 
 extern pgd_t swapper_pg_dir[];
+extern pgd_t trampoline_pg_dir[];
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline int pmd_present(pmd_t pmd)
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 9ce504737d18..cc0e06b4f223 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -26,12 +26,13 @@
 #include <linux/kfence.h>
 
 #include <asm/fixmap.h>
-#include <asm/tlbflush.h>
-#include <asm/sections.h>
-#include <asm/soc.h>
 #include <asm/io.h>
-#include <asm/ptdump.h>
 #include <asm/numa.h>
+#include <asm/pgtable.h>
+#include <asm/ptdump.h>
+#include <asm/sections.h>
+#include <asm/soc.h>
+#include <asm/tlbflush.h>
 
 #include "../kernel/head.h"
 

---
base-commit: 14f9643dc90adea074a0ffb7a17d337eafc6a5cc
change-id: 20230808-riscv_static-348036edcae7

Best regards,
-- 
Nick Desaulniers <ndesaulniers@google.com>

On Tue, Aug 08, 2023 at 09:15:41AM -0700, Nick Desaulniers wrote:
> I'm looking to enable -Wmissing-variable-declarations behind W=1. 0day
> bot spotted the following instance in ARCH=riscv builds:
> 
>   arch/riscv/mm/init.c:276:7: warning: no previous extern declaration
>   for non-static variable 'trampoline_pg_dir'
>   [-Wmissing-variable-declarations]
>   276 | pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>       |       ^
>   arch/riscv/mm/init.c:276:1: note: declare 'static' if the variable is
>   not intended to be used outside of this translation unit
>   276 | pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>       | ^
>   arch/riscv/mm/init.c:279:7: warning: no previous extern declaration
>   for non-static variable 'early_pg_dir'
>   [-Wmissing-variable-declarations]
>   279 | pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>       |       ^
>   arch/riscv/mm/init.c:279:1: note: declare 'static' if the variable is
>   not intended to be used outside of this translation unit
>   279 | pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>       | ^
> 
> These symbols are referenced by more than one translation unit, so make
> sure they're both declared and include the correct header for their
> declarations. Finally, sort the list of includes to help keep them tidy.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/llvm/202308081000.tTL1ElTr-lkp@intel.com/
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
>  arch/riscv/include/asm/pgtable.h | 1 +
>  arch/riscv/mm/init.c             | 9 +++++----
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 75970ee2bda2..4c8c0f83a974 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -188,6 +188,7 @@ extern struct pt_alloc_ops pt_ops __initdata;
>  #define PAGE_KERNEL_IO		__pgprot(_PAGE_IOREMAP)
>  
>  extern pgd_t swapper_pg_dir[];
> +extern pgd_t trampoline_pg_dir[];

Missing early_pg_dir too? It looks like there is already a declaration
in arch/riscv/mm/kasan_init.c that could be hoisted here?

>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  static inline int pmd_present(pmd_t pmd)
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 9ce504737d18..cc0e06b4f223 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -26,12 +26,13 @@
>  #include <linux/kfence.h>
>  
>  #include <asm/fixmap.h>
> -#include <asm/tlbflush.h>
> -#include <asm/sections.h>
> -#include <asm/soc.h>
>  #include <asm/io.h>
> -#include <asm/ptdump.h>
>  #include <asm/numa.h>
> +#include <asm/pgtable.h>
> +#include <asm/ptdump.h>
> +#include <asm/sections.h>
> +#include <asm/soc.h>
> +#include <asm/tlbflush.h>
>  
>  #include "../kernel/head.h"
>  
> 
> ---
> base-commit: 14f9643dc90adea074a0ffb7a17d337eafc6a5cc
> change-id: 20230808-riscv_static-348036edcae7
> 
> Best regards,
> -- 
> Nick Desaulniers <ndesaulniers@google.com>
>

On Tue, Aug 8, 2023 at 9:24 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Tue, Aug 08, 2023 at 09:15:41AM -0700, Nick Desaulniers wrote:
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index 75970ee2bda2..4c8c0f83a974 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -188,6 +188,7 @@ extern struct pt_alloc_ops pt_ops __initdata;
> >  #define PAGE_KERNEL_IO               __pgprot(_PAGE_IOREMAP)
> >
> >  extern pgd_t swapper_pg_dir[];
> > +extern pgd_t trampoline_pg_dir[];
>
> Missing early_pg_dir too? It looks like there is already a declaration
> in arch/riscv/mm/kasan_init.c that could be hoisted here?

Yep, will respin. Good catch!

-- 
Thanks,
~Nick Desaulniers