Hi Ricardo,
On Mon, Feb 2, 2015 at 1:49 PM, Ricardo Ribalda Delgado
<ricardo.ribalda@xxxxxxxxx> wrote:
> Regarding ioread8 et al.
>
> On include/asm-generic/io.h is defined as:
> extern unsigned int ioread8(void __iomem *);
>
> On include/asm-generic/io.h:
> static inline u8 ioread8(const volatile void __iomem *addr)
>
> Please ignore the qualifiers right now. The first function returns an
> unsigned integer, the second a u8.
>
> Through #ifdefs, different arches uses the first or the second definitions.
>
> If we consider this code:
>
> u8 varA;
> u8 varB;
> u8 varC;
> void * pvar=varB;
... = &varB;
> *pvar = ioread8(valid_memory);
>
> Depending if ioread8 returns a u8 or a unsigned int, aren't we also
> accessing varC?
>
> Could not this be a problem?
Please try to compile the above.
The compiler will tell you you cannot dereference a void pointer.
Now, replace "void *" by "unsigned int *".
After that, varC will indeed be overwritten. But the compiler will still have
warned you that you assigned the address of an u8 variable to an
unsigned int pointer.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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