From: Ira Weiny <[email protected]>
Both PKU and PKS update their register values in the same way. They can
therefore share the update code.
Define a helper, update_pkey_val(), which will be used to support both
Protection Key User (PKU) and the new Protection Key for Supervisor
(PKS) in subsequent patches.
Use that helper in arch_set_user_pkey_access().
Co-developed-by: Peter Zijlstra <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>
---
arch/x86/include/asm/pkeys.h | 2 ++
arch/x86/kernel/fpu/xstate.c | 22 ++++------------------
arch/x86/mm/pkeys.c | 23 +++++++++++++++++++++++
3 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index 5c7bcaa79623..597f19e4525b 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -133,4 +133,6 @@ static inline int vma_pkey(struct vm_area_struct *vma)
return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
}
+u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags);
+
#endif /*_ASM_X86_PKEYS_H */
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 6af0c80ad425..4f95ab38a23c 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -915,8 +915,7 @@ EXPORT_SYMBOL_GPL(get_xsave_addr);
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
@@ -933,22 +932,9 @@ 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 * PKRU_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 = update_pkey_val(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..ca2e20b18645 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -190,3 +190,26 @@ static __init int setup_init_pkru(char *opt)
return 1;
}
__setup("init_pkru=", setup_init_pkru);
+
+/*
+ * Replace disable bits for @pkey with values from @flags
+ *
+ * Kernel users use the same flags as user space:
+ * PKEY_DISABLE_ACCESS
+ * PKEY_DISABLE_WRITE
+ */
+u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags)
+{
+ int pkey_shift = pkey * PKR_BITS_PER_PKEY;
+
+ /* Mask out old bit values */
+ pk_reg &= ~(((1 << PKR_BITS_PER_PKEY) - 1) << pkey_shift);
+
+ /* Or in new values */
+ if (flags & PKEY_DISABLE_ACCESS)
+ pk_reg |= PKR_AD_BIT << pkey_shift;
+ if (flags & PKEY_DISABLE_WRITE)
+ pk_reg |= PKR_WD_BIT << pkey_shift;
+
+ return pk_reg;
+}
--
2.28.0.rc0.12.gb6a658bd00c9
On Tue, Aug 03 2021 at 21:32, ira weiny wrote:
> +/*
> + * Replace disable bits for @pkey with values from @flags
> + *
> + * Kernel users use the same flags as user space:
> + * PKEY_DISABLE_ACCESS
> + * PKEY_DISABLE_WRITE
> + */
> +u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags)
pkey_.... please.
> +{
> + int pkey_shift = pkey * PKR_BITS_PER_PKEY;
> +
> + /* Mask out old bit values */
> + pk_reg &= ~(((1 << PKR_BITS_PER_PKEY) - 1) << pkey_shift);
> +
> + /* Or in new values */
> + if (flags & PKEY_DISABLE_ACCESS)
> + pk_reg |= PKR_AD_BIT << pkey_shift;
> + if (flags & PKEY_DISABLE_WRITE)
> + pk_reg |= PKR_WD_BIT << pkey_shift;
> +
> + return pk_reg;
Also this code is silly.
#define PKEY_ACCESS_MASK (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 | accessbit << pkey_shift;
}
See? It does not even need comments because it's self explaining and
uses sensible argument names matching the function name.