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 | 4 + arch/powerpc/include/asm/pkeys.h | 90 ++++++++++++++++++++++++++++- arch/powerpc/mm/mmu_context_book3s64.c | 2 + arch/powerpc/mm/pkeys.c | 40 +++++++++++++ 5 files changed, 141 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h index c9448e1..37ef23c 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 fb5e6a3..7d0f2d0 100644 --- 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 1280b35..1e8cef2 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; }
/* @@ -52,4 +132,6 @@ 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 59c0766..929d9ef 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 de7dc48..e2f3992 100644 --- a/arch/powerpc/mm/pkeys.c +++ b/arch/powerpc/mm/pkeys.c @@ -13,21 +13,61 @@
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; +}