powerpc: track allocation status of all pkeys

Total 32 keys are available on power7 and above. However
pkey 0,1 are reserved. So effectively we  have  30 pkeys.

On 4K kernels, we do not  have  5  bits  in  the  PTE to
represent  all the keys; we only have 3bits. Two of those
keys are reserved; pkey 0 and pkey 1. So effectively  we
have 6 pkeys.

This patch keeps track of reserved keys, allocated  keys
and keys that are currently free.

Also it  adds  skeletal  functions  and macros, that the
architecture-independent code expects to be available.

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index c9448e19847a3ef5eba44ffe1d813d37e3ba5e39..37ef23cc1136d188199dc05f33264b1a0b61202f 100644 (file)
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -108,6 +108,15 @@ typedef struct {
 #ifdef CONFIG_SPAPR_TCE_IOMMU
        struct list_head iommu_group_mem_list;
 #endif
+
+#ifdef CONFIG_PPC_MEM_KEYS
+       /*
+        * Each bit represents one protection key.
+        * bit set   -> key allocated
+        * bit unset -> key available for allocation
+        */
+       u32 pkey_allocation_map;
+#endif
 } mm_context_t;
 
 /*

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index fb5e6a3ce12709a1a8ce1c90111e5b4d7999b752..7d0f2d05189b4415acd76a6e9d6fbf4cc3616a3b 100644 (file)
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -193,5 +193,9 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
        return true;
 }
 
+#ifndef CONFIG_PPC_MEM_KEYS
+#define pkey_mm_init(mm)
+#endif /* CONFIG_PPC_MEM_KEYS */
+
 #endif /* __KERNEL__ */
 #endif /* __ASM_POWERPC_MMU_CONTEXT_H */

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index dadea7d4324df8452cb806ec5af05e5ed5e89828..79b105d1ff7369f121511d487b34e976fa3ef8ed 100644 (file)
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -11,21 +11,94 @@
 #include <linux/jump_label.h>
 
 DECLARE_STATIC_KEY_TRUE(pkey_disabled);
-#define ARCH_VM_PKEY_FLAGS 0
+extern int pkeys_total; /* total pkeys as per device tree */
+extern u32 initial_allocation_mask; /* bits set for reserved keys */
+
+/*
+ * Define these here temporarily so we're not dependent on patching linux/mm.h.
+ * Once it's updated we can drop these.
+ */
+#ifndef VM_PKEY_BIT0
+# define VM_PKEY_SHIFT VM_HIGH_ARCH_BIT_0
+# define VM_PKEY_BIT0  VM_HIGH_ARCH_0
+# define VM_PKEY_BIT1  VM_HIGH_ARCH_1
+# define VM_PKEY_BIT2  VM_HIGH_ARCH_2
+# define VM_PKEY_BIT3  VM_HIGH_ARCH_3
+# define VM_PKEY_BIT4  VM_HIGH_ARCH_4
+#endif
+
+#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \
+                           VM_PKEY_BIT3 | VM_PKEY_BIT4)
+
+#define arch_max_pkey() pkeys_total
+
+#define pkey_alloc_mask(pkey) (0x1 << pkey)
+
+#define mm_pkey_allocation_map(mm) (mm->context.pkey_allocation_map)
+
+#define __mm_pkey_allocated(mm, pkey) {        \
+       mm_pkey_allocation_map(mm) |= pkey_alloc_mask(pkey); \
+}
+
+#define __mm_pkey_free(mm, pkey) {     \
+       mm_pkey_allocation_map(mm) &= ~pkey_alloc_mask(pkey);   \
+}
+
+#define __mm_pkey_is_allocated(mm, pkey)       \
+       (mm_pkey_allocation_map(mm) & pkey_alloc_mask(pkey))
+
+#define __mm_pkey_is_reserved(pkey) (initial_allocation_mask & \
+                                      pkey_alloc_mask(pkey))
 
 static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
 {
-       return false;
+       /* A reserved key is never considered as 'explicitly allocated' */
+       return ((pkey < arch_max_pkey()) &&
+               !__mm_pkey_is_reserved(pkey) &&
+               __mm_pkey_is_allocated(mm, pkey));
 }
 
+/*
+ * Returns a positive, 5-bit key on success, or -1 on failure.
+ * Relies on the mmap_sem to protect against concurrency in mm_pkey_alloc() and
+ * mm_pkey_free().
+ */
 static inline int mm_pkey_alloc(struct mm_struct *mm)
 {
-       return -1;
+       /*
+        * Note: this is the one and only place we make sure that the pkey is
+        * valid as far as the hardware is concerned. The rest of the kernel
+        * trusts that only good, valid pkeys come out of here.
+        */
+       u32 all_pkeys_mask = (u32)(~(0x0));
+       int ret;
+
+       if (static_branch_likely(&pkey_disabled))
+               return -1;
+
+       /*
+        * Are we out of pkeys? We must handle this specially because ffz()
+        * behavior is undefined if there are no zeros.
+        */
+       if (mm_pkey_allocation_map(mm) == all_pkeys_mask)
+               return -1;
+
+       ret = ffz((u32)mm_pkey_allocation_map(mm));
+       __mm_pkey_allocated(mm, ret);
+       return ret;
 }
 
 static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
 {
-       return -EINVAL;
+       if (static_branch_likely(&pkey_disabled))
+               return -1;
+
+       if (!mm_pkey_is_allocated(mm, pkey))
+               return -EINVAL;
+
+       __mm_pkey_free(mm, pkey);
+
+       return 0;
 }
 
 /*
@@ -48,4 +121,6 @@ static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 {
        return 0;
 }
+
+extern void pkey_mm_init(struct mm_struct *mm);
 #endif /*_ASM_POWERPC_KEYS_H */

diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
index 59c0766ae4e04d024cd33dad8faf577b7001c25c..929d9ef7083f1ac85155f349788713eafbd1ea09 100644 (file)
--- a/arch/powerpc/mm/mmu_context_book3s64.c
+++ b/arch/powerpc/mm/mmu_context_book3s64.c
@@ -16,6 +16,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/mm.h>
+#include <linux/pkeys.h>
 #include <linux/spinlock.h>
 #include <linux/idr.h>
 #include <linux/export.h>
@@ -118,6 +119,7 @@ static int hash__init_new_context(struct mm_struct *mm)
 
        subpage_prot_init_new_context(mm);
 
+       pkey_mm_init(mm);
        return index;
 }
 

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index a11afba584b9759f0501f1d0c2104602890df7a2..e68e367dcdd7828ba59d4ffa3228936aa7ee3437 100644 (file)
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -9,21 +9,61 @@
 
 DEFINE_STATIC_KEY_TRUE(pkey_disabled);
 bool pkey_execute_disable_supported;
+int  pkeys_total;              /* Total pkeys as per device tree */
+u32  initial_allocation_mask;  /* Bits set for reserved keys */
 
 int pkey_initialize(void)
 {
+       int os_reserved, i;
+
        /*
         * Disable the pkey system till everything is in place. A subsequent
         * patch will enable it.
         */
        static_branch_enable(&pkey_disabled);
 
+       /* Lets assume 32 keys */
+       pkeys_total = 32;
+
+       /*
+        * Adjust the upper limit, based on the number of bits supported by
+        * arch-neutral code.
+        */
+       pkeys_total = min_t(int, pkeys_total,
+                       (ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT));
+
        /*
         * Disable execute_disable support for now. A subsequent patch will
         * enable it.
         */
        pkey_execute_disable_supported = false;
+
+#ifdef CONFIG_PPC_4K_PAGES
+       /*
+        * The OS can manage only 8 pkeys due to its inability to represent them
+        * in the Linux 4K PTE.
+        */
+       os_reserved = pkeys_total - 8;
+#else
+       os_reserved = 0;
+#endif
+       /*
+        * Bits are in LE format. NOTE: 1, 0 are reserved.
+        * key 0 is the default key, which allows read/write/execute.
+        * key 1 is recommended not to be used. PowerISA(3.0) page 1015,
+        * programming note.
+        */
+       initial_allocation_mask = ~0x0;
+       for (i = 2; i < (pkeys_total - os_reserved); i++)
+               initial_allocation_mask &= ~(0x1 << i);
        return 0;
 }
 
 arch_initcall(pkey_initialize);
+
+void pkey_mm_init(struct mm_struct *mm)
+{
+       if (static_branch_likely(&pkey_disabled))
+               return;
+       mm_pkey_allocation_map(mm) = initial_allocation_mask;
+}