On 7/6/20 12:34 PM, Michael Ellerman wrote:
"Aneesh Kumar K.V" <aneesh.ku...@linux.ibm.com> writes:
max_pkey now represents max key value that userspace can allocate.
I guess commit message is confusing.
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
arch/powerpc/include/asm/pkeys.h | 7 +++++--
arch/powerpc/mm/book3s64/pkeys.c | 14 +++++++-------
2 files changed, 12 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index 75d2a2c19c04..652bad7334f3 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -12,7 +12,7 @@
#include <asm/firmware.h>
DECLARE_STATIC_KEY_FALSE(pkey_disabled);
-extern int pkeys_total; /* total pkeys as per device tree */
+extern int max_pkey;
extern u32 initial_allocation_mask; /* bits set for the initially allocated
keys */
extern u32 reserved_allocation_mask; /* bits set for reserved keys */
@@ -44,7 +44,10 @@ static inline int vma_pkey(struct vm_area_struct *vma)
return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT;
}
-#define arch_max_pkey() pkeys_total
+static inline int arch_max_pkey(void)
+{
+ return max_pkey;
+}
If pkeys_total = 32 then max_pkey = 31.
we have
#ifdef CONFIG_PPC_4K_PAGES
/*
* The OS can manage only 8 pkeys due to its inability to represent them
* in the Linux 4K PTE. Mark all other keys reserved.
*/
max_pkey = min(8, pkeys_total);
#else
max_pkey = pkeys_total;
#endif
so it is 32.
So we can't just substitute one for the other. ie. arch_max_pkey() must
have been wrong, or it is wrong now.
diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 87d882a9aaf2..a4d7287082a8 100644
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -14,7 +14,7 @@
DEFINE_STATIC_KEY_FALSE(pkey_disabled);
DEFINE_STATIC_KEY_FALSE(execute_pkey_disabled);
-int pkeys_total; /* Total pkeys as per device tree */
+int max_pkey; /* Maximum key value supported */
u32 initial_allocation_mask; /* Bits set for the initially allocated keys
*/
/*
* Keys marked in the reservation list cannot be allocated by userspace
@@ -84,7 +84,7 @@ static int scan_pkey_feature(void)
static int pkey_initialize(void)
{
- int os_reserved, i;
+ int pkeys_total, i;
/*
* We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral
@@ -122,12 +122,12 @@ static int pkey_initialize(void)
* The OS can manage only 8 pkeys due to its inability to represent them
* in the Linux 4K PTE. Mark all other keys reserved.
*/
- os_reserved = pkeys_total - 8;
+ max_pkey = min(8, pkeys_total);
Shouldn't it be 7 ?
#else
- os_reserved = 0;
+ max_pkey = pkeys_total;
#endif
- if (unlikely((pkeys_total - os_reserved) <= execute_only_key)) {
+ if (unlikely(max_pkey <= execute_only_key)) {
Isn't that an off-by-one now?
This is one-off boot time code, there's no need to clutter it with
unlikely.
/*
* Insufficient number of keys to support
* execute only key. Mark it unavailable.
@@ -174,10 +174,10 @@ static int pkey_initialize(void)
default_uamor &= ~(0x3ul << pkeyshift(1));
/*
- * Prevent the usage of OS reserved the keys. Update UAMOR
+ * Prevent the usage of OS reserved keys. Update UAMOR
* for those keys.
*/
- for (i = (pkeys_total - os_reserved); i < pkeys_total; i++) {
+ for (i = max_pkey; i < pkeys_total; i++) {
Another off-by-one? Shouldn't we start from max_pkey + 1 ?
reserved_allocation_mask |= (0x1 << i);
default_uamor &= ~(0x3ul << pkeyshift(i));
}
It is the commit message. It is max pkey such that userspace can
allocate 0 - maxp_pkey -1.
-aneesh
