linux-kernel - [RFC v6 20/62] powerpc: store and restore the pkey state across context switches

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Date:   Sat, 15 Jul 2017 20:56:22 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, dave.hansen@...el.com, hbabu@...ibm.com,
        linuxram@...ibm.com, arnd@...db.de, akpm@...ux-foundation.org,
        corbet@....net, mingo@...hat.com, mhocko@...nel.org
Subject: [RFC v6 20/62] powerpc: store and restore the pkey state across context switches

Store and restore the AMR, IAMR and UMOR register state of the task
before scheduling out and after scheduling in, respectively.

Signed-off-by: Ram Pai <linuxram@...ibm.com>
---
 arch/powerpc/include/asm/processor.h |    5 +++++
 arch/powerpc/kernel/process.c        |   18 ++++++++++++++++++
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 1189d04..dcb1cf0 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_PPC64_MEMORY_PROTECTION_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 2ad725e..9429361 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1096,6 +1096,11 @@ static inline void save_sprs(struct thread_struct *t)
 		t->tar = mfspr(SPRN_TAR);
 	}
 #endif
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+	t->amr = mfspr(SPRN_AMR);
+	t->iamr = mfspr(SPRN_IAMR);
+	t->uamor = mfspr(SPRN_UAMOR);
+#endif
 }
 
 static inline void restore_sprs(struct thread_struct *old_thread,
@@ -1131,6 +1136,14 @@ static inline void restore_sprs(struct thread_struct *old_thread,
 			mtspr(SPRN_TAR, new_thread->tar);
 	}
 #endif
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+	if (old_thread->amr != new_thread->amr)
+		mtspr(SPRN_AMR, new_thread->amr);
+	if (old_thread->iamr != new_thread->iamr)
+		mtspr(SPRN_IAMR, new_thread->iamr);
+	if (old_thread->uamor != new_thread->uamor)
+		mtspr(SPRN_UAMOR, new_thread->uamor);
+#endif
 }
 
 struct task_struct *__switch_to(struct task_struct *prev,
@@ -1689,6 +1702,11 @@ 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 */
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+	current->thread.amr   = 0x0ul;
+	current->thread.iamr  = 0x0ul;
+	current->thread.uamor = 0x0ul;
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
 }
 EXPORT_SYMBOL(start_thread);
 
-- 
1.7.1