diff mbox series

[RFC,1/1] riscv: Improve arch_get_mmap_end() macro

Message ID 20231222082711.454374-1-leobras@redhat.com
State New
Headers
Series [RFC,1/1] riscv: Improve arch_get_mmap_end() macro |

Commit Message

Leonardo Bras Soares Passos Dec. 22, 2023, 8:27 a.m. UTC 
  This macro caused me some confusion, which took some reviewer's time to
make it clear, so I propose adding a short comment in code to avoid
confusion in the future.

Also, added some improvements to the macro, such as removing the
assumption of VA_USER_SV57 being the largest address space.

Signed-off-by: Leonardo Bras <leobras@redhat.com>
---
 arch/riscv/include/asm/processor.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Comments

Guo Ren Dec. 22, 2023, 11:48 a.m. UTC | #1 
On Fri, Dec 22, 2023 at 4:27 PM Leonardo Bras <leobras@redhat.com> wrote:
>
> This macro caused me some confusion, which took some reviewer's time to
> make it clear, so I propose adding a short comment in code to avoid
> confusion in the future.
>
> Also, added some improvements to the macro, such as removing the
> assumption of VA_USER_SV57 being the largest address space.
>
> Signed-off-by: Leonardo Bras <leobras@redhat.com>
> ---
>  arch/riscv/include/asm/processor.h | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index f19f861cda549..2278e2a8362af 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -18,15 +18,21 @@
>  #define DEFAULT_MAP_WINDOW     (UL(1) << (MMAP_VA_BITS - 1))
>  #define STACK_TOP_MAX          TASK_SIZE_64
>
> +/*
> + * addr is a hint to the maximum userspace address that mmap should provide, so
> + * this macro needs to return the largest address space available so that
> + * mmap_end < addr, being mmap_end the top of that address space.
> + * See Documentation/arch/riscv/vm-layout.rst for more details.
> + */
>  #define arch_get_mmap_end(addr, len, flags)                    \
>  ({                                                             \
>         unsigned long mmap_end;                                 \
>         typeof(addr) _addr = (addr);                            \
>         if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \
>                 mmap_end = STACK_TOP_MAX;                       \
> -       else if ((_addr) >= VA_USER_SV57)                       \
> -               mmap_end = STACK_TOP_MAX;                       \
> -       else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \
> +       else if (((_addr) >= VA_USER_SV57) && (VA_BITS >= VA_BITS_SV57)) \
> +               mmap_end = VA_USER_SV57;                        \
It's clearer.

LGTM.
Reviewed-by: Guo Ren <guoren@kernel.org>

> +       else if (((_addr) >= VA_USER_SV48) && (VA_BITS >= VA_BITS_SV48)) \
>                 mmap_end = VA_USER_SV48;                        \
>         else                                                    \
>                 mmap_end = VA_USER_SV39;                        \
> --
> 2.43.0
>
Leonardo Bras Soares Passos Dec. 22, 2023, 5:15 p.m. UTC | #2 
On Fri, Dec 22, 2023 at 07:48:36PM +0800, Guo Ren wrote:
> On Fri, Dec 22, 2023 at 4:27 PM Leonardo Bras <leobras@redhat.com> wrote:
> >
> > This macro caused me some confusion, which took some reviewer's time to
> > make it clear, so I propose adding a short comment in code to avoid
> > confusion in the future.
> >
> > Also, added some improvements to the macro, such as removing the
> > assumption of VA_USER_SV57 being the largest address space.
> >
> > Signed-off-by: Leonardo Bras <leobras@redhat.com>
> > ---
> >  arch/riscv/include/asm/processor.h | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> > index f19f861cda549..2278e2a8362af 100644
> > --- a/arch/riscv/include/asm/processor.h
> > +++ b/arch/riscv/include/asm/processor.h
> > @@ -18,15 +18,21 @@
> >  #define DEFAULT_MAP_WINDOW     (UL(1) << (MMAP_VA_BITS - 1))
> >  #define STACK_TOP_MAX          TASK_SIZE_64
> >
> > +/*
> > + * addr is a hint to the maximum userspace address that mmap should provide, so
> > + * this macro needs to return the largest address space available so that
> > + * mmap_end < addr, being mmap_end the top of that address space.
> > + * See Documentation/arch/riscv/vm-layout.rst for more details.
> > + */
> >  #define arch_get_mmap_end(addr, len, flags)                    \
> >  ({                                                             \
> >         unsigned long mmap_end;                                 \
> >         typeof(addr) _addr = (addr);                            \
> >         if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \
> >                 mmap_end = STACK_TOP_MAX;                       \
> > -       else if ((_addr) >= VA_USER_SV57)                       \
> > -               mmap_end = STACK_TOP_MAX;                       \
> > -       else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \
> > +       else if (((_addr) >= VA_USER_SV57) && (VA_BITS >= VA_BITS_SV57)) \
> > +               mmap_end = VA_USER_SV57;                        \
> It's clearer.
> 
> LGTM.
> Reviewed-by: Guo Ren <guoren@kernel.org>

Thanks!
Leo

> 
> > +       else if (((_addr) >= VA_USER_SV48) && (VA_BITS >= VA_BITS_SV48)) \
> >                 mmap_end = VA_USER_SV48;                        \
> >         else                                                    \
> >                 mmap_end = VA_USER_SV39;                        \
> > --
> > 2.43.0
> >
> 
> 
> -- 
> Best Regards
>  Guo Ren
>
diff mbox series

Patch

diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index f19f861cda549..2278e2a8362af 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -18,15 +18,21 @@ 
 #define DEFAULT_MAP_WINDOW	(UL(1) << (MMAP_VA_BITS - 1))
 #define STACK_TOP_MAX		TASK_SIZE_64
 
+/*
+ * addr is a hint to the maximum userspace address that mmap should provide, so
+ * this macro needs to return the largest address space available so that
+ * mmap_end < addr, being mmap_end the top of that address space.
+ * See Documentation/arch/riscv/vm-layout.rst for more details.
+ */
 #define arch_get_mmap_end(addr, len, flags)			\
 ({								\
 	unsigned long mmap_end;					\
 	typeof(addr) _addr = (addr);				\
 	if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \
 		mmap_end = STACK_TOP_MAX;			\
-	else if ((_addr) >= VA_USER_SV57)			\
-		mmap_end = STACK_TOP_MAX;			\
-	else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \
+	else if (((_addr) >= VA_USER_SV57) && (VA_BITS >= VA_BITS_SV57)) \
+		mmap_end = VA_USER_SV57;			\
+	else if (((_addr) >= VA_USER_SV48) && (VA_BITS >= VA_BITS_SV48)) \
 		mmap_end = VA_USER_SV48;			\
 	else							\
 		mmap_end = VA_USER_SV39;			\