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-rw-r--r--arch/powerpc/mm/book3s64/pkeys.c470
1 files changed, 470 insertions, 0 deletions
diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
new file mode 100644
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+++ b/arch/powerpc/mm/book3s64/pkeys.c
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+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * PowerPC Memory Protection Keys management
+ *
+ * Copyright 2017, Ram Pai, IBM Corporation.
+ */
+
+#include <asm/mman.h>
+#include <asm/mmu_context.h>
+#include <asm/mmu.h>
+#include <asm/setup.h>
+#include <asm/smp.h>
+#include <asm/firmware.h>
+
+#include <linux/pkeys.h>
+#include <linux/of_fdt.h>
+
+
+int num_pkey; /* Max number of pkeys supported */
+/*
+ * Keys marked in the reservation list cannot be allocated by userspace
+ */
+u32 reserved_allocation_mask __ro_after_init;
+
+/* Bits set for the initially allocated keys */
+static u32 initial_allocation_mask __ro_after_init;
+
+/*
+ * Even if we allocate keys with sys_pkey_alloc(), we need to make sure
+ * other thread still find the access denied using the same keys.
+ */
+u64 default_amr __ro_after_init = ~0x0UL;
+u64 default_iamr __ro_after_init = 0x5555555555555555UL;
+u64 default_uamor __ro_after_init;
+EXPORT_SYMBOL(default_amr);
+/*
+ * Key used to implement PROT_EXEC mmap. Denies READ/WRITE
+ * We pick key 2 because 0 is special key and 1 is reserved as per ISA.
+ */
+static int execute_only_key = 2;
+static bool pkey_execute_disable_supported;
+
+
+#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 int __init dt_scan_storage_keys(unsigned long node,
+ const char *uname, int depth,
+ void *data)
+{
+ const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
+ const __be32 *prop;
+ int *pkeys_total = (int *) data;
+
+ /* We are scanning "cpu" nodes only */
+ if (type == NULL || strcmp(type, "cpu") != 0)
+ return 0;
+
+ prop = of_get_flat_dt_prop(node, "ibm,processor-storage-keys", NULL);
+ if (!prop)
+ return 0;
+ *pkeys_total = be32_to_cpu(prop[0]);
+ return 1;
+}
+
+static int __init scan_pkey_feature(void)
+{
+ int ret;
+ int pkeys_total = 0;
+
+ /*
+ * Pkey is not supported with Radix translation.
+ */
+ if (early_radix_enabled())
+ return 0;
+
+ ret = of_scan_flat_dt(dt_scan_storage_keys, &pkeys_total);
+ if (ret == 0) {
+ /*
+ * Let's assume 32 pkeys on P8/P9 bare metal, if its not defined by device
+ * tree. We make this exception since some version of skiboot forgot to
+ * expose this property on power8/9.
+ */
+ if (!firmware_has_feature(FW_FEATURE_LPAR)) {
+ unsigned long pvr = mfspr(SPRN_PVR);
+
+ if (PVR_VER(pvr) == PVR_POWER8 || PVR_VER(pvr) == PVR_POWER8E ||
+ PVR_VER(pvr) == PVR_POWER8NVL || PVR_VER(pvr) == PVR_POWER9)
+ pkeys_total = 32;
+ }
+ }
+
+#ifdef CONFIG_PPC_MEM_KEYS
+ /*
+ * 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) + 1));
+#endif
+ return pkeys_total;
+}
+
+void __init pkey_early_init_devtree(void)
+{
+ int pkeys_total, i;
+
+#ifdef CONFIG_PPC_MEM_KEYS
+ /*
+ * 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));
+#endif
+ /*
+ * Only P7 and above supports SPRN_AMR update with MSR[PR] = 1
+ */
+ if (!early_cpu_has_feature(CPU_FTR_ARCH_206))
+ return;
+
+ /* scan the device tree for pkey feature */
+ pkeys_total = scan_pkey_feature();
+ if (!pkeys_total)
+ goto out;
+
+ /* Allow all keys to be modified by default */
+ default_uamor = ~0x0UL;
+
+ cur_cpu_spec->mmu_features |= MMU_FTR_PKEY;
+
+ /*
+ * 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. Mark all other keys reserved.
+ */
+ num_pkey = min(8, pkeys_total);
+#else
+ num_pkey = pkeys_total;
+#endif
+
+ if (unlikely(num_pkey <= execute_only_key) || !pkey_execute_disable_supported) {
+ /*
+ * Insufficient number of keys to support
+ * execute only key. Mark it unavailable.
+ */
+ execute_only_key = -1;
+ } else {
+ /*
+ * Mark the execute_only_pkey as not available for
+ * user allocation via pkey_alloc.
+ */
+ reserved_allocation_mask |= (0x1 << execute_only_key);
+
+ /*
+ * Deny READ/WRITE for execute_only_key.
+ * Allow execute in IAMR.
+ */
+ default_amr |= (0x3ul << pkeyshift(execute_only_key));
+ default_iamr &= ~(0x1ul << pkeyshift(execute_only_key));
+
+ /*
+ * Clear the uamor bits for this key.
+ */
+ default_uamor &= ~(0x3ul << pkeyshift(execute_only_key));
+ }
+
+ if (unlikely(num_pkey <= 3)) {
+ /*
+ * Insufficient number of keys to support
+ * KUAP/KUEP feature.
+ */
+ disable_kuep = true;
+ disable_kuap = true;
+ WARN(1, "Disabling kernel user protection due to low (%d) max supported keys\n", num_pkey);
+ } else {
+ /* handle key which is used by kernel for KAUP */
+ reserved_allocation_mask |= (0x1 << 3);
+ /*
+ * Mark access for kup_key in default amr so that
+ * we continue to operate with that AMR in
+ * copy_to/from_user().
+ */
+ default_amr &= ~(0x3ul << pkeyshift(3));
+ default_iamr &= ~(0x1ul << pkeyshift(3));
+ default_uamor &= ~(0x3ul << pkeyshift(3));
+ }
+
+ /*
+ * Allow access for only key 0. And prevent any other modification.
+ */
+ default_amr &= ~(0x3ul << pkeyshift(0));
+ default_iamr &= ~(0x1ul << pkeyshift(0));
+ default_uamor &= ~(0x3ul << pkeyshift(0));
+ /*
+ * key 0 is special in that we want to consider it an allocated
+ * key which is preallocated. We don't allow changing AMR bits
+ * w.r.t key 0. But one can pkey_free(key0)
+ */
+ initial_allocation_mask |= (0x1 << 0);
+
+ /*
+ * key 1 is recommended not to be used. PowerISA(3.0) page 1015,
+ * programming note.
+ */
+ reserved_allocation_mask |= (0x1 << 1);
+ default_uamor &= ~(0x3ul << pkeyshift(1));
+
+ /*
+ * Prevent the usage of OS reserved keys. Update UAMOR
+ * for those keys. Also mark the rest of the bits in the
+ * 32 bit mask as reserved.
+ */
+ for (i = num_pkey; i < 32 ; i++) {
+ reserved_allocation_mask |= (0x1 << i);
+ default_uamor &= ~(0x3ul << pkeyshift(i));
+ }
+ /*
+ * Prevent the allocation of reserved keys too.
+ */
+ initial_allocation_mask |= reserved_allocation_mask;
+
+ pr_info("Enabling pkeys with max key count %d\n", num_pkey);
+out:
+ /*
+ * Setup uamor on boot cpu
+ */
+ mtspr(SPRN_UAMOR, default_uamor);
+
+ return;
+}
+
+#ifdef CONFIG_PPC_KUEP
+void setup_kuep(bool disabled)
+{
+ if (disabled)
+ return;
+ /*
+ * On hash if PKEY feature is not enabled, disable KUAP too.
+ */
+ if (!early_radix_enabled() && !early_mmu_has_feature(MMU_FTR_PKEY))
+ return;
+
+ if (smp_processor_id() == boot_cpuid) {
+ pr_info("Activating Kernel Userspace Execution Prevention\n");
+ cur_cpu_spec->mmu_features |= MMU_FTR_BOOK3S_KUEP;
+ }
+
+ /*
+ * Radix always uses key0 of the IAMR to determine if an access is
+ * allowed. We set bit 0 (IBM bit 1) of key0, to prevent instruction
+ * fetch.
+ */
+ mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED);
+ isync();
+}
+#endif
+
+#ifdef CONFIG_PPC_KUAP
+void setup_kuap(bool disabled)
+{
+ if (disabled)
+ return;
+ /*
+ * On hash if PKEY feature is not enabled, disable KUAP too.
+ */
+ if (!early_radix_enabled() && !early_mmu_has_feature(MMU_FTR_PKEY))
+ return;
+
+ if (smp_processor_id() == boot_cpuid) {
+ pr_info("Activating Kernel Userspace Access Prevention\n");
+ cur_cpu_spec->mmu_features |= MMU_FTR_KUAP;
+ }
+
+ /*
+ * Set the default kernel AMR values on all cpus.
+ */
+ mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
+ isync();
+}
+#endif
+
+#ifdef CONFIG_PPC_MEM_KEYS
+void pkey_mm_init(struct mm_struct *mm)
+{
+ if (!mmu_has_feature(MMU_FTR_PKEY))
+ return;
+ mm_pkey_allocation_map(mm) = initial_allocation_mask;
+ mm->context.execute_only_pkey = execute_only_key;
+}
+
+static inline void init_amr(int pkey, u8 init_bits)
+{
+ u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey));
+ u64 old_amr = current_thread_amr() & ~((u64)(0x3ul) << pkeyshift(pkey));
+
+ current->thread.regs->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 = current_thread_iamr() & ~((u64)(0x1ul) << pkeyshift(pkey));
+
+ if (!likely(pkey_execute_disable_supported))
+ return;
+
+ current->thread.regs->iamr = old_iamr | new_iamr_bits;
+}
+
+/*
+ * 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;
+ u64 pkey_bits, uamor_pkey_bits;
+
+ /*
+ * Check whether the key is disabled by UAMOR.
+ */
+ pkey_bits = 0x3ul << pkeyshift(pkey);
+ uamor_pkey_bits = (default_uamor & pkey_bits);
+
+ /*
+ * Both the bits in UAMOR corresponding to the key should be set
+ */
+ if (uamor_pkey_bits != pkey_bits)
+ 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;
+}
+
+int execute_only_pkey(struct mm_struct *mm)
+{
+ return mm->context.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_ACCESS_FLAGS) != 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;
+
+ pkey_shift = pkeyshift(pkey);
+ if (execute)
+ return !(current_thread_iamr() & (IAMR_EX_BIT << pkey_shift));
+
+ amr = current_thread_amr();
+ if (write)
+ return !(amr & (AMR_WR_BIT << pkey_shift));
+
+ return !(amr & (AMR_RD_BIT << pkey_shift));
+}
+
+bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
+{
+ if (!mmu_has_feature(MMU_FTR_PKEY))
+ 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.
+ */
+bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
+ bool execute, bool foreign)
+{
+ if (!mmu_has_feature(MMU_FTR_PKEY))
+ 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);
+}
+
+void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm)
+{
+ if (!mmu_has_feature(MMU_FTR_PKEY))
+ return;
+
+ /* Duplicate the oldmm pkey state in mm: */
+ mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm);
+ mm->context.execute_only_pkey = oldmm->context.execute_only_pkey;
+}
+
+#endif /* CONFIG_PPC_MEM_KEYS */