[RFC PATCH 02/15] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support

ira.weiny
2020-07-14T07:04:07Z

From: Fenghua Yu <fenghua.yu@intel.com>

Define a helper, get_new_pkr(), which will be used to support both
Protection Key User (PKU) and the new Protection Key for Supervisor
(PKS) in subsequent patches.

Co-developed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
arch/x86/include/asm/pkeys.h | 2 ++
arch/x86/kernel/fpu/xstate.c | 17 +++--------------
arch/x86/mm/pkeys.c | 28 ++++++++++++++++++++++++++++
3 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index be8b3e448f76..34cef29fed20 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -136,4 +136,6 @@ static inline int vma_pkey(struct vm_area_struct *vma)
return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
}

+u32 get_new_pkr(u32 old_pkr, int pkey, unsigned long init_val);
+
#endif /*_ASM_X86_PKEYS_H */
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index fc1ec2986e03..1def71dc8105 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -954,9 +954,7 @@ const void *get_xsave_field_ptr(int xfeature_nr)
int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val)
{
- u32 old_pkru;
- int pkey_shift = (pkey * PKR_BITS_PER_PKEY);
- u32 new_pkru_bits = 0;
+ u32 old_pkru, new_pkru;

/*
* This check implies XSAVE support. OSPKE only gets
@@ -972,21 +970,12 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
*/
WARN_ON_ONCE(pkey >= arch_max_pkey());

- /* Set the bits we need in PKRU: */
- if (init_val & PKEY_DISABLE_ACCESS)
- new_pkru_bits |= PKR_AD_BIT;
- if (init_val & PKEY_DISABLE_WRITE)
- new_pkru_bits |= PKR_WD_BIT;
-
- /* Shift the bits in to the correct place in PKRU for pkey: */
- new_pkru_bits <<= pkey_shift;
-
/* Get old PKRU and mask off any old bits in place: */
old_pkru = read_pkru();
- old_pkru &= ~((PKR_AD_BIT|PKR_WD_BIT) << pkey_shift);
+ new_pkru = get_new_pkr(old_pkru, pkey, init_val);

/* Write old part along with new part: */
- write_pkru(old_pkru | new_pkru_bits);
+ write_pkru(new_pkru);

return 0;
}
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index f5efb4007e74..a5c680d32930 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -208,3 +208,31 @@ static __init int setup_init_pkru(char *opt)
return 1;
}
__setup("init_pkru=", setup_init_pkru);
+
+/*
+ * Get a new pkey register value from the user values specified.
+ *
+ * Kernel users use the same flags as user space:
+ * PKEY_DISABLE_ACCESS
+ * PKEY_DISABLE_WRITE
+ */
+u32 get_new_pkr(u32 old_pkr, int pkey, unsigned long init_val)
+{
+ int pkey_shift = (pkey * PKR_BITS_PER_PKEY);
+ u32 new_pkr_bits = 0;
+
+ /* Set the bits we need in the register: */
+ if (init_val & PKEY_DISABLE_ACCESS)
+ new_pkr_bits |= PKR_AD_BIT;
+ if (init_val & PKEY_DISABLE_WRITE)
+ new_pkr_bits |= PKR_WD_BIT;
+
+ /* Shift the bits in to the correct place: */
+ new_pkr_bits <<= pkey_shift;
+
+ /* Mask off any old bits in place: */
+ old_pkr &= ~((PKR_AD_BIT | PKR_WD_BIT) << pkey_shift);
+
+ /* Return the old part along with the new part: */
+ return old_pkr | new_pkr_bits;
+}