linux-kernel - Re: [PATCH 07/16] powerpc: mm: Support MAP_BELOW

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Message-ID: <Zs9ek1Cr1SaQzSqg@ghost>
Date: Wed, 28 Aug 2024 10:29:55 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Arnd Bergmann <arnd@...db.de>, Paul Walmsley <paul.walmsley@...ive.com>,
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Subject: Re: [PATCH 07/16] powerpc: mm: Support MAP_BELOW_HINT

On Wed, Aug 28, 2024 at 08:34:49AM +0200, Christophe Leroy wrote:
> Hi Charlie,
> 
> Le 28/08/2024 à 07:49, Charlie Jenkins a écrit :
> > Add support for MAP_BELOW_HINT to arch_get_mmap_base() and
> > arch_get_mmap_end().
> > 
> > Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> > ---
> >   arch/powerpc/include/asm/task_size_64.h | 36 +++++++++++++++++++++++++++------
> >   1 file changed, 30 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/task_size_64.h b/arch/powerpc/include/asm/task_size_64.h
> > index 239b363841aa..a37a5a81365d 100644
> > --- a/arch/powerpc/include/asm/task_size_64.h
> > +++ b/arch/powerpc/include/asm/task_size_64.h
> > @@ -72,12 +72,36 @@
> >   #define STACK_TOP_MAX TASK_SIZE_USER64
> >   #define STACK_TOP (is_32bit_task() ? STACK_TOP_USER32 : STACK_TOP_USER64)
> > -#define arch_get_mmap_base(addr, len, base, flags) \
> > -	(((addr) > DEFAULT_MAP_WINDOW) ? (base) + TASK_SIZE - DEFAULT_MAP_WINDOW : (base))
> > +#define arch_get_mmap_base(addr, len, base, flags)					\
> 
> This macro looks quite big for a macro, can it be a static inline function
> instead ? Same for the other macro below.
> 

I had overlooked that possibility, I think that's a great solution, I
will change that.

> > +({											\
> > +	unsigned long mmap_base;							\
> > +	typeof(flags) _flags = (flags);							\
> > +	typeof(addr) _addr = (addr);							\
> > +	typeof(base) _base = (base);							\
> > +	typeof(len) _len = (len);							\
> > +	unsigned long rnd_gap = DEFAULT_MAP_WINDOW - (_base);				\
> > +	if (_flags & MAP_BELOW_HINT && _addr != 0 && ((_addr + _len) > BIT(VA_BITS - 1)))\
> > +		mmap_base = (_addr + _len) - rnd_gap;					\
> > +	else										\
> > +		mmap_end = ((_addr > DEFAULT_MAP_WINDOW) ?				\
> > +				_base + TASK_SIZE - DEFAULT_MAP_WINDOW :		\
> > +				_base);							\
> > +	mmap_end;									\
> 
> mmap_end doesn't exist, did you mean mmap_base ?

Oh whoops, thank you!

- Charlie

> 
> > +})
> > -#define arch_get_mmap_end(addr, len, flags) \
> > -	(((addr) > DEFAULT_MAP_WINDOW) || \
> > -	 (((flags) & MAP_FIXED) && ((addr) + (len) > DEFAULT_MAP_WINDOW)) ? TASK_SIZE : \
> > -									    DEFAULT_MAP_WINDOW)
> > +#define arch_get_mmap_end(addr, len, flags)							\
> > +({												\
> > +	unsigned long mmap_end;									\
> > +	typeof(flags) _flags = (flags);								\
> > +	typeof(addr) _addr = (addr);								\
> > +	typeof(len) _len = (len);								\
> > +	if (_flags & MAP_BELOW_HINT && _addr != 0 && ((_addr + _len) > BIT(VA_BITS - 1)))	\
> > +		mmap_end = (_addr + _len);							\
> > +	else											\
> > +		mmap_end = (((_addr) > DEFAULT_MAP_WINDOW) ||					\
> > +				(((_flags) & MAP_FIXED) && ((_addr) + (_len) > DEFAULT_MAP_WINDOW))\
> > +				? TASK_SIZE : DEFAULT_MAP_WINDOW)				\
> > +	mmap_end;										\
> > +})
> >   #endif /* _ASM_POWERPC_TASK_SIZE_64_H */
> >