[PATCH v9 04/51] powerpc: track allocation status of all pkeys
Ram Pai
linuxram at us.ibm.com
Mon Nov 6 19:56:56 AEDT 2017
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 at linux.vnet.ibm.com>
Signed-off-by: Ram Pai <linuxram at 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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