linux-kernel - Re: [PATCH 2/2] efi: Fix warning of int-to-pointer-cast on x86 32-bit builds

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Date:	Fri, 23 Oct 2015 12:30:23 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	linux-efi@...r.kernel.org, izumi.taku@...fujitsu.com,
	matt.fleming@...el.com, linux-kernel@...r.kernel.org,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [PATCH 2/2] efi: Fix warning of int-to-pointer-cast on x86
 32-bit builds


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> 
> > From: Taku Izumi <izumi.taku@...fujitsu.com>
> > 
> > Commit 0f96a99dab36 ("efi: Add "efi_fake_mem" boot option")
> > introduces the following warning message:
> > 
> >   drivers/firmware/efi/fake_mem.c:186:20: warning: cast to pointer
> >   from integer of different size [-Wint-to-pointer-cast]
> > 
> > new_memmap_phy was defined as a u64 value and cast to void*, causing
> > a int-to-pointer-cast warning on x86 32-bit builds.
> > However, since the void* type is inappropriate for a physical
> > address, the definition of struct efi_memory_map::phys_map has been
> > changed to phys_addr_t in the previous patch, and so the cast can be
> > dropped entirely.
> > 
> > This patch also changes the type of the "new_memmap_phy" variable
> > from "u64" to "phys_addr_t" to align with the types of
> > memblock_alloc() and struct efi_memory_map::phys_map.
> > 
> > Reported-by: Ingo Molnar <mingo@...nel.org>
> > Signed-off-by: Taku Izumi <izumi.taku@...fujitsu.com>
> > [ard.biesheuvel: removed void* cast, updated commit log]
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > ---
> >  drivers/firmware/efi/fake_mem.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/firmware/efi/fake_mem.c b/drivers/firmware/efi/fake_mem.c
> > index 32bcb14df2c8..ed3a854950cc 100644
> > --- a/drivers/firmware/efi/fake_mem.c
> > +++ b/drivers/firmware/efi/fake_mem.c
> > @@ -59,7 +59,7 @@ void __init efi_fake_memmap(void)
> >  	u64 start, end, m_start, m_end, m_attr;
> >  	int new_nr_map = memmap.nr_map;
> >  	efi_memory_desc_t *md;
> > -	u64 new_memmap_phy;
> > +	phys_addr_t new_memmap_phy;
> >  	void *new_memmap;
> >  	void *old, *new;
> >  	int i;
> > @@ -183,7 +183,7 @@ void __init efi_fake_memmap(void)
> >  	/* swap into new EFI memmap */
> >  	efi_unmap_memmap();
> >  	memmap.map = new_memmap;
> > -	memmap.phys_map = (void *)new_memmap_phy;
> > +	memmap.phys_map = new_memmap_phy;
> >  	memmap.nr_map = new_nr_map;
> >  	memmap.map_end = memmap.map + memmap.nr_map * memmap.desc_size;
> 
> Please guys, think for a change!
> 
> How is this supposed to work with:
> 
>    include/linux/efi.h:    void *phys_map;
> 
> ?

Ah, I take that back, now I see your patch 1/2 that changes it to phys_addr_t.

That's the right solution, and it also cleans up the code:

  Reviewed-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo
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