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author | Dave Hansen <dave.hansen@linux.intel.com> | 2016-02-12 13:02:36 -0800 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2016-02-18 19:46:32 +0100 |
commit | 8459429693395ca9e8d18101300b120ad9171795 (patch) | |
tree | 56a67afee6292c137696a31dabe873777304adb8 /arch/x86/include/asm/pgtable.h | |
parent | b8b9b6ba9dec3f155c7555cb208ba4078e97aedb (diff) | |
download | linux-next-8459429693395ca9e8d18101300b120ad9171795.tar.gz |
x86/mm/pkeys: Allow kernel to modify user pkey rights register
The Protection Key Rights for User memory (PKRU) is a 32-bit
user-accessible register. It contains two bits for each
protection key: one to write-disable (WD) access to memory
covered by the key and another to access-disable (AD).
Userspace can read/write the register with the RDPKRU and WRPKRU
instructions. But, the register is saved and restored with the
XSAVE family of instructions, which means we have to treat it
like a floating point register.
The kernel needs to write to the register if it wants to
implement execute-only memory or if it implements a system call
to change PKRU.
To do this, we need to create a 'pkru_state' buffer, read the old
contents in to it, modify it, and then tell the FPU code that
there is modified data in there so it can (possibly) move the
buffer back in to the registers.
This uses the fpu__xfeature_set_state() function that we defined
in the previous patch.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210236.0BE13217@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/pgtable.h')
-rw-r--r-- | arch/x86/include/asm/pgtable.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 3cbfae80abb2..1ff49ec29ece 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -921,16 +921,17 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) #define PKRU_AD_BIT 0x1 #define PKRU_WD_BIT 0x2 +#define PKRU_BITS_PER_PKEY 2 static inline bool __pkru_allows_read(u32 pkru, u16 pkey) { - int pkru_pkey_bits = pkey * 2; + int pkru_pkey_bits = pkey * PKRU_BITS_PER_PKEY; return !(pkru & (PKRU_AD_BIT << pkru_pkey_bits)); } static inline bool __pkru_allows_write(u32 pkru, u16 pkey) { - int pkru_pkey_bits = pkey * 2; + int pkru_pkey_bits = pkey * PKRU_BITS_PER_PKEY; /* * Access-disable disables writes too so we need to check * both bits here. |