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Subject[PATCH v9 04/51] powerpc: track allocation status of all pkeys
Date
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>
---
arch/powerpc/include/asm/book3s/64/mmu.h | 9 +++
arch/powerpc/include/asm/mmu_context.h | 1 +
arch/powerpc/include/asm/pkeys.h | 95 ++++++++++++++++++++++++++++-
arch/powerpc/mm/mmu_context_book3s64.c | 2 +
arch/powerpc/mm/pkeys.c | 33 ++++++++++
5 files changed, 136 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index 37fdede..df17fbc 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -108,6 +108,15 @@ struct patb_entry {
#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 2c24447..6d7c4f1 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -145,6 +145,7 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,

#ifndef CONFIG_PPC_MEM_KEYS
#define pkey_initialize()
+#define pkey_mm_init(mm)
#endif /* CONFIG_PPC_MEM_KEYS */

#endif /* __KERNEL__ */
diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index a54cb39..e5deac7 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -15,21 +15,101 @@
#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 */
+
+/*
+ * powerpc needs VM_PKEY_BIT* bit to enable pkey system.
+ * Without them, at least compilation needs to succeed.
+ */
+#ifndef VM_PKEY_BIT0
+#define VM_PKEY_SHIFT 0
+#define VM_PKEY_BIT0 0
+#define VM_PKEY_BIT1 0
+#define VM_PKEY_BIT2 0
+#define VM_PKEY_BIT3 0
+#endif
+
+/*
+ * powerpc needs an additional vma bit to support 32 keys. Till the additional
+ * vma bit lands in include/linux/mm.h we can only support 16 keys.
+ */
+#ifndef VM_PKEY_BIT4
+#define VM_PKEY_BIT4 0
+#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;
}

/*
@@ -53,5 +133,12 @@ static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
return 0;
}

+static inline void pkey_mm_init(struct mm_struct *mm)
+{
+ if (static_branch_likely(&pkey_disabled))
+ return;
+ mm_pkey_allocation_map(mm) = initial_allocation_mask;
+}
+
extern void pkey_initialize(void);
#endif /*_ASM_POWERPC_KEYS_H */
diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
index 05e1538..5df223a 100644
--- 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 c97a7a0..512bdf2 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -13,18 +13,51 @@

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 */

void __init 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);
}
--
1.7.1
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