lkml.org 
[lkml]   [2017]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC v6 19/62] powerpc: ability to create execute-disabled pkeys
On Thu, Jul 27, 2017 at 11:54:31AM -0300, Thiago Jung Bauermann wrote:
>
> Ram Pai <linuxram@us.ibm.com> writes:
>
> > --- a/arch/powerpc/include/asm/pkeys.h
> > +++ b/arch/powerpc/include/asm/pkeys.h
> > @@ -2,6 +2,18 @@
> > #define _ASM_PPC64_PKEYS_H
> >
> > extern bool pkey_inited;
> > +/* override any generic PKEY Permission defines */
> > +#undef PKEY_DISABLE_ACCESS
> > +#define PKEY_DISABLE_ACCESS 0x1
> > +#undef PKEY_DISABLE_WRITE
> > +#define PKEY_DISABLE_WRITE 0x2
> > +#undef PKEY_DISABLE_EXECUTE
> > +#define PKEY_DISABLE_EXECUTE 0x4
> > +#undef PKEY_ACCESS_MASK
> > +#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
> > + PKEY_DISABLE_WRITE |\
> > + PKEY_DISABLE_EXECUTE)
> > +
>
> Is it ok to #undef macros from another header? Especially since said
> header is in uapi (include/uapi/asm-generic/mman-common.h).
>
> Also, it's unnecessary to undef the _ACCESS and _WRITE macros since they
> are identical to the original definition. And since these macros are
> originally defined in an uapi header, the powerpc-specific ones should
> be in an uapi header as well, if I understand it correctly.

The architectural neutral code allows the implementation to define the
macros to its taste. powerpc headers due to legacy reason includes the
include/uapi/asm-generic/mman-common.h header. That header includes the
generic definitions of only PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE.
Unfortunately we end up importing them. I dont want to depend on them.
Any changes there could effect us. Example if the generic uapi header
changed PKEY_DISABLE_ACCESS to 0x4, we will have a conflict with
PKEY_DISABLE_EXECUTE. Hence I undef them and define the it my way.

>
> An alternative solution is to define only PKEY_DISABLE_EXECUTE in
> arch/powerpc/include/uapi/asm/mman.h and then test for its existence to
> properly define PKEY_ACCESS_MASK in
> include/uapi/asm-generic/mman-common.h. What do you think of the code
> below?
>
> diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
> index e31f5ee8e81f..67e6a3a343ae 100644
> --- a/arch/powerpc/include/asm/pkeys.h
> +++ b/arch/powerpc/include/asm/pkeys.h
> @@ -4,17 +4,6 @@
> #include <asm/firmware.h>
>
> extern bool pkey_inited;
> -/* override any generic PKEY Permission defines */
> -#undef PKEY_DISABLE_ACCESS
> -#define PKEY_DISABLE_ACCESS 0x1
> -#undef PKEY_DISABLE_WRITE
> -#define PKEY_DISABLE_WRITE 0x2
> -#undef PKEY_DISABLE_EXECUTE
> -#define PKEY_DISABLE_EXECUTE 0x4
> -#undef PKEY_ACCESS_MASK
> -#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
> - PKEY_DISABLE_WRITE |\
> - PKEY_DISABLE_EXECUTE)
>
> #define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \
> VM_PKEY_BIT3 | VM_PKEY_BIT4)
> diff --git a/arch/powerpc/include/uapi/asm/mman.h b/arch/powerpc/include/uapi/asm/mman.h
> index ab45cc2f3101..dee43feb7c53 100644
> --- a/arch/powerpc/include/uapi/asm/mman.h
> +++ b/arch/powerpc/include/uapi/asm/mman.h
> @@ -45,4 +45,6 @@
> #define MAP_HUGE_1GB (30 << MAP_HUGE_SHIFT) /* 1GB HugeTLB Page */
> #define MAP_HUGE_16GB (34 << MAP_HUGE_SHIFT) /* 16GB HugeTLB Page */
>
> +#define PKEY_DISABLE_EXECUTE 0x4
> +
> #endif /* _UAPI_ASM_POWERPC_MMAN_H */
> diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
> index 72eb9a1bde79..777f8f8dff47 100644
> --- a/arch/powerpc/mm/pkeys.c
> +++ b/arch/powerpc/mm/pkeys.c
> @@ -12,7 +12,7 @@
> * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> * more details.
> */
> -#include <uapi/asm-generic/mman-common.h>
> +#include <asm/mman.h>
> #include <linux/pkeys.h> /* PKEY_* */
>
> bool pkey_inited;
> diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
> index 8c27db0c5c08..93e3841d9ada 100644
> --- a/include/uapi/asm-generic/mman-common.h
> +++ b/include/uapi/asm-generic/mman-common.h
> @@ -74,7 +74,15 @@
>
> #define PKEY_DISABLE_ACCESS 0x1
> #define PKEY_DISABLE_WRITE 0x2
> +
> +/* The arch-specific code may define PKEY_DISABLE_EXECUTE */
> +#ifdef PKEY_DISABLE_EXECUTE
> +#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS | \
> + PKEY_DISABLE_WRITE | \
> + PKEY_DISABLE_EXECUTE)
> +#else
> #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
> PKEY_DISABLE_WRITE)
> +#endif
>
> #endif /* __ASM_GENERIC_MMAN_COMMON_H */

I suppose we can do it this way aswell. but dont like the way it is
spreading the defines accross multiple files.

>
>
> > diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
> > index 98d0391..b9ad98d 100644
> > --- a/arch/powerpc/mm/pkeys.c
> > +++ b/arch/powerpc/mm/pkeys.c
> > @@ -73,6 +73,7 @@ int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
> > unsigned long init_val)
> > {
> > u64 new_amr_bits = 0x0ul;
> > + u64 new_iamr_bits = 0x0ul;
> >
> > if (!is_pkey_enabled(pkey))
> > return -1;
> > @@ -85,5 +86,14 @@ int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
> >
> > init_amr(pkey, new_amr_bits);
> >
> > + /*
> > + * By default execute is disabled.
> > + * To enable execute, PKEY_ENABLE_EXECUTE
> > + * needs to be specified.
> > + */
> > + if ((init_val & PKEY_DISABLE_EXECUTE))
> > + new_iamr_bits |= IAMR_EX_BIT;
> > +
> > + init_iamr(pkey, new_iamr_bits);
> > return 0;
> > }
>
> The comment seems to be from an earlier version which has the logic
> inverted, and there is no PKEY_ENABLE_EXECUTE. Should the comment be
> updated to the following?
>
> By default execute is enabled.
> To disable execute, PKEY_DISABLE_EXECUTE needs to be specified.

yes. the comment is misleading. I just took it out.

RP

>
> --
> Thiago Jung Bauermann
> IBM Linux Technology Center

--
Ram Pai

\
 
 \ /
  Last update: 2017-07-30 01:26    [W:0.099 / U:14.940 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site