[PATCH V8 05/44] x86/fpu: Refactor arch_set_user_pkey_access()

ira.weiny
2022-01-27T17:55:48Z

From: Ira Weiny <ira.weiny@intel.com>

Both PKU and PKS update their register values in the same way. They can
therefore share the update code.

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

pkey_update_pkval() contributed by Thomas

Co-developed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Update for V8:
Replace the code Peter provided in update_pkey_reg() for
Thomas' pkey_update_pkval()
-- https://lore.kernel.org/lkml/20200717085442.GX10769@hirez.programming.kicks-ass.net/
---
arch/x86/include/asm/pkeys.h | 2 ++
arch/x86/kernel/fpu/xstate.c | 22 ++++------------------
arch/x86/mm/pkeys.c | 16 ++++++++++++++++
3 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index 1d5f14aff5f6..cc4d4f552f9d 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -131,4 +131,6 @@ static inline int vma_pkey(struct vm_area_struct *vma)
return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
}

+u32 pkey_update_pkval(u32 pkval, int pkey, u32 accessbits);
+
#endif /*_ASM_X86_PKEYS_H */
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index d8ddd306d225..00d059db4106 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1071,8 +1071,7 @@ void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val)
{
- u32 old_pkru, new_pkru_bits = 0;
- int pkey_shift;
+ u32 pkru;

/*
* This check implies XSAVE support. OSPKE only gets
@@ -1089,22 +1088,9 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
if (WARN_ON_ONCE(pkey >= arch_max_pkey()))
return -EINVAL;

- /* Set the bits needed 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: */
- pkey_shift = pkey * PKR_BITS_PER_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);
-
- /* Write old part along with new part: */
- write_pkru(old_pkru | new_pkru_bits);
+ pkru = read_pkru();
+ pkru = pkey_update_pkval(pkru, pkey, init_val);
+ write_pkru(pkru);

return 0;
}
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index aa7042f272fb..cf12d8bf122b 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -190,3 +190,19 @@ static __init int setup_init_pkru(char *opt)
return 1;
}
__setup("init_pkru=", setup_init_pkru);
+
+/*
+ * Kernel users use the same flags as user space:
+ * PKEY_DISABLE_ACCESS
+ * PKEY_DISABLE_WRITE
+ */
+u32 pkey_update_pkval(u32 pkval, int pkey, u32 accessbits)
+{
+ int shift = pkey * PKR_BITS_PER_PKEY;
+
+ if (WARN_ON_ONCE(accessbits & ~PKEY_ACCESS_MASK))
+ accessbits &= PKEY_ACCESS_MASK;
+
+ pkval &= ~(PKEY_ACCESS_MASK << shift);
+ return pkval | accessbits << shift;
+}
--
2.31.1