On Mon, Jun 19, 2017 at 10:18:01PM +1000, Michael Ellerman wrote:
> Hi Ram,
>
> Ram Pai <linux...@us.ibm.com> writes:
> > Sys_pkey_alloc() allocates and returns available pkey
> > Sys_pkey_free() frees up the pkey.
> >
> > Total 32 keys are supported on powerpc. However pkey 0,1 and 31
> > are reserved. So effectively we have 29 pkeys.
> >
> > Signed-off-by: Ram Pai <linux...@us.ibm.com>
> > ---
> > include/linux/mm.h | 31 ++++---
> > include/uapi/asm-generic/mman-common.h | 2 +-
>
> Those changes need to be split out and acked by mm folks.
>
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 7cb17c6..34ddac7 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -204,26 +204,35 @@ extern int overcommit_kbytes_handler(struct ctl_table
> > *, int, void __user *,
> > #define VM_MERGEABLE 0x80000000 /* KSM may merge identical
> > pages */
> >
> > #ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS
> > -#define VM_HIGH_ARCH_BIT_0 32 /* bit only usable on 64-bit
> > architectures */
> > -#define VM_HIGH_ARCH_BIT_1 33 /* bit only usable on 64-bit
> > architectures */
> > -#define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit
> > architectures */
> > -#define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit
> > architectures */
> > +#define VM_HIGH_ARCH_BIT_0 32 /* bit only usable on 64-bit arch */
> > +#define VM_HIGH_ARCH_BIT_1 33 /* bit only usable on 64-bit arch */
> > +#define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit arch */
> > +#define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit arch */
>
> Please don't change the comments, it makes the diff harder to read.
The lines were surpassing 80 columns. tried to compress the comments
without loosing meaning. will restore.
>
> You're actually just adding this AFAICS:
>
> > +#define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit arch */
>
> > #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0)
> > #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1)
> > #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2)
> > #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3)
> > +#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
> > #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
> >
> > #if defined(CONFIG_X86)
> ^
> > # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at
> > once (x86) */
> > -#if defined (CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)
> > -# define VM_PKEY_SHIFT VM_HIGH_ARCH_BIT_0
> > -# define VM_PKEY_BIT0 VM_HIGH_ARCH_0 /* A protection key is a 4-bit
> > value */
> > -# define VM_PKEY_BIT1 VM_HIGH_ARCH_1
> > -# define VM_PKEY_BIT2 VM_HIGH_ARCH_2
> > -# define VM_PKEY_BIT3 VM_HIGH_ARCH_3
> > -#endif
> > +#if defined(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) \
> > + || defined(CONFIG_PPC64_MEMORY_PROTECTION_KEYS)
> > +#define VM_PKEY_SHIFT VM_HIGH_ARCH_BIT_0
> > +#define VM_PKEY_BIT0 VM_HIGH_ARCH_0 /* A protection key is a 5-bit
> > value */
> ^ 4?
> > +#define VM_PKEY_BIT1 VM_HIGH_ARCH_1
> > +#define VM_PKEY_BIT2 VM_HIGH_ARCH_2
> > +#define VM_PKEY_BIT3 VM_HIGH_ARCH_3
> > +#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
>
> That appears to be inside an #if defined(CONFIG_X86) ?
>
> > #elif defined(CONFIG_PPC)
> ^
> Should be CONFIG_PPC64_MEMORY_PROTECTION_KEYS no?
Its a little garbled. Will fix it.
>
> > +#define VM_PKEY_BIT0 VM_HIGH_ARCH_0 /* A protection key is a 5-bit
> > value */
> > +#define VM_PKEY_BIT1 VM_HIGH_ARCH_1
> > +#define VM_PKEY_BIT2 VM_HIGH_ARCH_2
> > +#define VM_PKEY_BIT3 VM_HIGH_ARCH_3
> > +#define VM_PKEY_BIT4 VM_HIGH_ARCH_4 /* intel does not use this bit
> > */
> > + /* but reserved for future expansion */
>
> But this hunk is for PPC ?
>
> Is it OK for the other arches & generic code to add another VM_PKEY_BIT4 ?
No. it has to be PPC specific.
>
> Do you need to update show_smap_vma_flags() ?
>
> > # define VM_SAO VM_ARCH_1 /* Strong Access Ordering
> > (powerpc) */
> > #elif defined(CONFIG_PARISC)
> > # define VM_GROWSUP VM_ARCH_1
>
> > diff --git a/include/uapi/asm-generic/mman-common.h
> > b/include/uapi/asm-generic/mman-common.h
> > index 8c27db0..b13ecc6 100644
> > --- a/include/uapi/asm-generic/mman-common.h
> > +++ b/include/uapi/asm-generic/mman-common.h
> > @@ -76,5 +76,5 @@
> > #define PKEY_DISABLE_WRITE 0x2
> > #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
> > PKEY_DISABLE_WRITE)
> > -
> > +#define PKEY_DISABLE_EXECUTE 0x4
>
> How you can set that if it's not in PKEY_ACCESS_MASK?
I was wondering how to handle this. x86 does not support this flag.
However powerpc has the ability to enable/disable execute permission
on a key. It cannot be done from userspace, but can be done through
the sys_mprotect_pkey() sys call. Initially I was thinking of not
enabling it in powerpc aswell, but than i think we should be not block
the hardware feature from being used. I will make
PKEY_DISABLE_EXECUTE as part of the PKEY_ACCESS_MASK, and have powerpc
handle it. Also will x86 patch that return error if the flag is
provided.
makes sense?
Thanks for your comments,
RP
>
> See:
>
> SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
> {
> int pkey;
> int ret;
>
> /* No flags supported yet. */
> if (flags)
> return -EINVAL;
> /* check for unsupported init values */
> if (init_val & ~PKEY_ACCESS_MASK)
> return -EINVAL;
>
>
> cheers
--
Ram Pai
