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Subject[PATCH v9 10/51] powerpc: store and restore the pkey state across context switches
Date
Store and restore the AMR, IAMR and UAMOR register state of the task
before scheduling out and after scheduling in, respectively.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
arch/powerpc/include/asm/mmu_context.h | 3 ++
arch/powerpc/include/asm/pkeys.h | 4 ++
arch/powerpc/include/asm/processor.h | 5 +++
arch/powerpc/kernel/process.c | 7 ++++
arch/powerpc/mm/pkeys.c | 49 +++++++++++++++++++++++++++++++-
5 files changed, 67 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 6d7c4f1..4eccc2f 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -146,6 +146,9 @@ 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)
+#define thread_pkey_regs_save(thread)
+#define thread_pkey_regs_restore(new_thread, old_thread)
+#define thread_pkey_regs_init(thread)
#endif /* CONFIG_PPC_MEM_KEYS */

#endif /* __KERNEL__ */
diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index 652c750..0b2d9f0 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -156,5 +156,9 @@ static inline void pkey_mm_init(struct mm_struct *mm)
mm_pkey_allocation_map(mm) = initial_allocation_mask;
}

+extern void thread_pkey_regs_save(struct thread_struct *thread);
+extern void thread_pkey_regs_restore(struct thread_struct *new_thread,
+ struct thread_struct *old_thread);
+extern void thread_pkey_regs_init(struct thread_struct *thread);
extern void pkey_initialize(void);
#endif /*_ASM_POWERPC_KEYS_H */
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index fab7ff8..e3c417c 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -309,6 +309,11 @@ struct thread_struct {
struct thread_vr_state ckvr_state; /* Checkpointed VR state */
unsigned long ckvrsave; /* Checkpointed VRSAVE */
#endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
+#ifdef CONFIG_PPC_MEM_KEYS
+ unsigned long amr;
+ unsigned long iamr;
+ unsigned long uamor;
+#endif
#ifdef CONFIG_KVM_BOOK3S_32_HANDLER
void* kvm_shadow_vcpu; /* KVM internal data */
#endif /* CONFIG_KVM_BOOK3S_32_HANDLER */
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index a0c74bb..148b934 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -42,6 +42,7 @@
#include <linux/hw_breakpoint.h>
#include <linux/uaccess.h>
#include <linux/elf-randomize.h>
+#include <linux/pkeys.h>

#include <asm/pgtable.h>
#include <asm/io.h>
@@ -1085,6 +1086,8 @@ static inline void save_sprs(struct thread_struct *t)
t->tar = mfspr(SPRN_TAR);
}
#endif
+
+ thread_pkey_regs_save(t);
}

static inline void restore_sprs(struct thread_struct *old_thread,
@@ -1120,6 +1123,8 @@ static inline void restore_sprs(struct thread_struct *old_thread,
mtspr(SPRN_TAR, new_thread->tar);
}
#endif
+
+ thread_pkey_regs_restore(new_thread, old_thread);
}

#ifdef CONFIG_PPC_BOOK3S_64
@@ -1705,6 +1710,8 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
current->thread.tm_tfiar = 0;
current->thread.load_tm = 0;
#endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
+
+ thread_pkey_regs_init(&current->thread);
}
EXPORT_SYMBOL(start_thread);

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index 3ddc13a..469f370 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -16,6 +16,8 @@
bool pkey_execute_disable_supported;
int pkeys_total; /* Total pkeys as per 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
@@ -74,8 +76,16 @@ void __init pkey_initialize(void)
* programming note.
*/
initial_allocation_mask = ~0x0;
- for (i = 2; i < (pkeys_total - os_reserved); i++)
+
+ /* register mask is in BE format */
+ pkey_amr_uamor_mask = ~0x0ul;
+ pkey_iamr_mask = ~0x0ul;
+
+ 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));
+ }
}

static inline u64 read_amr(void)
@@ -200,3 +210,40 @@ int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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)
+{
+ write_amr(read_amr() & pkey_amr_uamor_mask);
+ write_iamr(read_iamr() & pkey_iamr_mask);
+ write_uamor(read_uamor() & pkey_amr_uamor_mask);
+}
--
1.7.1
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