blob: e6f500fabf5eac8b2c6b25ebe2e5c47b52783023 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0+
/*
* PowerPC Memory Protection Keys management
*
* Copyright 2017, Ram Pai, IBM Corporation.
*/
#include <asm/mman.h>
#include <asm/setup.h>
#include <linux/pkeys.h>
#include <linux/of_device.h>
DEFINE_STATIC_KEY_TRUE(pkey_disabled);
bool pkey_execute_disable_supported;
int pkeys_total; /* Total pkeys as per device tree */
bool pkeys_devtree_defined; /* pkey property exported by device tree */
u32 initial_allocation_mask; /* Bits set for reserved keys */
u64 pkey_amr_uamor_mask; /* Bits in AMR/UMOR not to be touched */
u64 pkey_iamr_mask; /* Bits in AMR not to be touched */
#define AMR_BITS_PER_PKEY 2
#define AMR_RD_BIT 0x1UL
#define AMR_WR_BIT 0x2UL
#define IAMR_EX_BIT 0x1UL
#define PKEY_REG_BITS (sizeof(u64)*8)
#define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY))
static void scan_pkey_feature(void)
{
u32 vals[2];
struct device_node *cpu;
cpu = of_find_node_by_type(NULL, "cpu");
if (!cpu)
return;
if (of_property_read_u32_array(cpu,
"ibm,processor-storage-keys", vals, 2))
return;
/*
* Since any pkey can be used for data or execute, we will just treat
* all keys as equal and track them as one entity.
*/
pkeys_total = be32_to_cpu(vals[0]);
pkeys_devtree_defined = true;
}
static inline bool pkey_mmu_enabled(void)
{
if (firmware_has_feature(FW_FEATURE_LPAR))
return pkeys_total;
else
return cpu_has_feature(CPU_FTR_PKEY);
}
int pkey_initialize(void)
{
int os_reserved, i;
/*
* We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral
* generic defines for PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE.
* Ensure that the bits a distinct.
*/
BUILD_BUG_ON(PKEY_DISABLE_EXECUTE &
(PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
/*
* pkey_to_vmflag_bits() assumes that the pkey bits are contiguous
* in the vmaflag. Make sure that is really the case.
*/
BUILD_BUG_ON(__builtin_clzl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) +
__builtin_popcountl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)
!= (sizeof(u64) * BITS_PER_BYTE));
/* scan the device tree for pkey feature */
scan_pkey_feature();
/*
* Let's assume 32 pkeys on P8 bare metal, if its not defined by device
* tree. We make this exception since skiboot forgot to expose this
* property on power8.
*/
if (!pkeys_devtree_defined && !firmware_has_feature(FW_FEATURE_LPAR) &&
cpu_has_feature(CPU_FTRS_POWER8))
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));
if (!pkey_mmu_enabled() || radix_enabled() || !pkeys_total)
static_branch_enable(&pkey_disabled);
else
static_branch_disable(&pkey_disabled);
if (static_branch_likely(&pkey_disabled))
return 0;
/*
* The device tree cannot be relied to indicate support for
* execute_disable support. Instead we use a PVR check.
*/
if (pvr_version_is(PVR_POWER7) || pvr_version_is(PVR_POWER7p))
pkey_execute_disable_supported = false;
else
pkey_execute_disable_supported = true;
#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
initial_allocation_mask = ~0x0;
pkey_amr_uamor_mask = ~0x0ul;
pkey_iamr_mask = ~0x0ul;
/*
* key 0, 1 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.
*/
for (i = 2; i < (pkeys_total - os_reserved); i++) {
initial_allocation_mask &= ~(0x1 << i);
pkey_amr_uamor_mask &= ~(0x3ul << pkeyshift(i));
pkey_iamr_mask &= ~(0x1ul << pkeyshift(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;
/* -1 means unallocated or invalid */
mm->context.execute_only_pkey = -1;
}
static inline u64 read_amr(void)
{
return mfspr(SPRN_AMR);
}
static inline void write_amr(u64 value)
{
mtspr(SPRN_AMR, value);
}
static inline u64 read_iamr(void)
{
if (!likely(pkey_execute_disable_supported))
return 0x0UL;
return mfspr(SPRN_IAMR);
}
static inline void write_iamr(u64 value)
{
if (!likely(pkey_execute_disable_supported))
return;
mtspr(SPRN_IAMR, value);
}
static inline u64 read_uamor(void)
{
return mfspr(SPRN_UAMOR);
}
static inline void write_uamor(u64 value)
{
mtspr(SPRN_UAMOR, value);
}
static bool is_pkey_enabled(int pkey)
{
u64 uamor = read_uamor();
u64 pkey_bits = 0x3ul << pkeyshift(pkey);
u64 uamor_pkey_bits = (uamor & pkey_bits);
/*
* Both the bits in UAMOR corresponding to the key should be set or
* reset.
*/
WARN_ON(uamor_pkey_bits && (uamor_pkey_bits != pkey_bits));
return !!(uamor_pkey_bits);
}
static inline void init_amr(int pkey, u8 init_bits)
{
u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey));
u64 old_amr = read_amr() & ~((u64)(0x3ul) << pkeyshift(pkey));
write_amr(old_amr | new_amr_bits);
}
static inline void init_iamr(int pkey, u8 init_bits)
{
u64 new_iamr_bits = (((u64)init_bits & 0x1UL) << pkeyshift(pkey));
u64 old_iamr = read_iamr() & ~((u64)(0x1ul) << pkeyshift(pkey));
write_iamr(old_iamr | new_iamr_bits);
}
static void pkey_status_change(int pkey, bool enable)
{
u64 old_uamor;
/* Reset the AMR and IAMR bits for this key */
init_amr(pkey, 0x0);
init_iamr(pkey, 0x0);
/* Enable/disable key */
old_uamor = read_uamor();
if (enable)
old_uamor |= (0x3ul << pkeyshift(pkey));
else
old_uamor &= ~(0x3ul << pkeyshift(pkey));
write_uamor(old_uamor);
}
void __arch_activate_pkey(int pkey)
{
pkey_status_change(pkey, true);
}
void __arch_deactivate_pkey(int pkey)
{
pkey_status_change(pkey, false);
}
/*
* Set the access rights in AMR IAMR and UAMOR registers for @pkey to that
* specified in @init_val.
*/
int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val)
{
u64 new_amr_bits = 0x0ul;
u64 new_iamr_bits = 0x0ul;
if (!is_pkey_enabled(pkey))
return -EINVAL;
if (init_val & PKEY_DISABLE_EXECUTE) {
if (!pkey_execute_disable_supported)
return -EINVAL;
new_iamr_bits |= IAMR_EX_BIT;
}
init_iamr(pkey, new_iamr_bits);
/* Set the bits we need in AMR: */
if (init_val & PKEY_DISABLE_ACCESS)
new_amr_bits |= AMR_RD_BIT | AMR_WR_BIT;
else if (init_val & PKEY_DISABLE_WRITE)
new_amr_bits |= AMR_WR_BIT;
init_amr(pkey, new_amr_bits);
return 0;
}
void thread_pkey_regs_save(struct thread_struct *thread)
{
if (static_branch_likely(&pkey_disabled))
return;
/*
* TODO: Skip saving registers if @thread hasn't used any keys yet.
*/
thread->amr = read_amr();
thread->iamr = read_iamr();
thread->uamor = read_uamor();
}
void thread_pkey_regs_restore(struct thread_struct *new_thread,
struct thread_struct *old_thread)
{
if (static_branch_likely(&pkey_disabled))
return;
/*
* TODO: Just set UAMOR to zero if @new_thread hasn't used any keys yet.
*/
if (old_thread->amr != new_thread->amr)
write_amr(new_thread->amr);
if (old_thread->iamr != new_thread->iamr)
write_iamr(new_thread->iamr);
if (old_thread->uamor != new_thread->uamor)
write_uamor(new_thread->uamor);
}
void thread_pkey_regs_init(struct thread_struct *thread)
{
if (static_branch_likely(&pkey_disabled))
return;
thread->amr = read_amr() & pkey_amr_uamor_mask;
thread->iamr = read_iamr() & pkey_iamr_mask;
thread->uamor = read_uamor() & pkey_amr_uamor_mask;
}
static inline bool pkey_allows_readwrite(int pkey)
{
int pkey_shift = pkeyshift(pkey);
if (!is_pkey_enabled(pkey))
return true;
return !(read_amr() & ((AMR_RD_BIT|AMR_WR_BIT) << pkey_shift));
}
int __execute_only_pkey(struct mm_struct *mm)
{
bool need_to_set_mm_pkey = false;
int execute_only_pkey = mm->context.execute_only_pkey;
int ret;
/* Do we need to assign a pkey for mm's execute-only maps? */
if (execute_only_pkey == -1) {
/* Go allocate one to use, which might fail */
execute_only_pkey = mm_pkey_alloc(mm);
if (execute_only_pkey < 0)
return -1;
need_to_set_mm_pkey = true;
}
/*
* We do not want to go through the relatively costly dance to set AMR
* if we do not need to. Check it first and assume that if the
* execute-only pkey is readwrite-disabled than we do not have to set it
* ourselves.
*/
if (!need_to_set_mm_pkey && !pkey_allows_readwrite(execute_only_pkey))
return execute_only_pkey;
/*
* Set up AMR so that it denies access for everything other than
* execution.
*/
ret = __arch_set_user_pkey_access(current, execute_only_pkey,
PKEY_DISABLE_ACCESS |
PKEY_DISABLE_WRITE);
/*
* If the AMR-set operation failed somehow, just return 0 and
* effectively disable execute-only support.
*/
if (ret) {
mm_pkey_free(mm, execute_only_pkey);
return -1;
}
/* We got one, store it and use it from here on out */
if (need_to_set_mm_pkey)
mm->context.execute_only_pkey = execute_only_pkey;
return execute_only_pkey;
}
static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
{
/* Do this check first since the vm_flags should be hot */
if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
return false;
return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
}
/*
* This should only be called for *plain* mprotect calls.
*/
int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
int pkey)
{
/*
* If the currently associated pkey is execute-only, but the requested
* protection is not execute-only, move it back to the default pkey.
*/
if (vma_is_pkey_exec_only(vma) && (prot != PROT_EXEC))
return 0;
/*
* The requested protection is execute-only. Hence let's use an
* execute-only pkey.
*/
if (prot == PROT_EXEC) {
pkey = execute_only_pkey(vma->vm_mm);
if (pkey > 0)
return pkey;
}
/* Nothing to override. */
return vma_pkey(vma);
}
static bool pkey_access_permitted(int pkey, bool write, bool execute)
{
int pkey_shift;
u64 amr;
if (!pkey)
return true;
if (!is_pkey_enabled(pkey))
return true;
pkey_shift = pkeyshift(pkey);
if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift)))
return true;
amr = read_amr(); /* Delay reading amr until absolutely needed */
return ((!write && !(amr & (AMR_RD_BIT << pkey_shift))) ||
(write && !(amr & (AMR_WR_BIT << pkey_shift))));
}
bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
{
if (static_branch_likely(&pkey_disabled))
return true;
return pkey_access_permitted(pte_to_pkey_bits(pte), write, execute);
}
/*
* We only want to enforce protection keys on the current thread because we
* effectively have no access to AMR/IAMR for other threads or any way to tell
* which AMR/IAMR in a threaded process we could use.
*
* So do not enforce things if the VMA is not from the current mm, or if we are
* in a kernel thread.
*/
static inline bool vma_is_foreign(struct vm_area_struct *vma)
{
if (!current->mm)
return true;
/* if it is not our ->mm, it has to be foreign */
if (current->mm != vma->vm_mm)
return true;
return false;
}
bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
bool execute, bool foreign)
{
if (static_branch_likely(&pkey_disabled))
return true;
/*
* Do not enforce our key-permissions on a foreign vma.
*/
if (foreign || vma_is_foreign(vma))
return true;
return pkey_access_permitted(vma_pkey(vma), write, execute);
}