Subject: [RFC PATCH 16/25] powerpc/book3s64/pkeys: Reset userspace AMR correctly on exec

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 27 Apr 2020 13:34:57 +0530

On fork, we inherit from the parent and on exec, we should switch to default_amr values.

Also, avoid changing the AMR register value within the kernel. The kernel now runs with
different AMR values.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 arch/powerpc/include/asm/pkeys.h |  1 +
 arch/powerpc/kernel/process.c    |  3 ++-
 arch/powerpc/mm/book3s64/pkeys.c | 16 +---------------
 3 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index 6e8157f78b52..cd1a03044814 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -13,6 +13,7 @@
 
 extern int max_pkey;
 extern u64 default_uamor;
+extern u64 default_amr;
 extern u32 reserved_allocation_mask; /* bits set for reserved keys */
 
 #define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index fc4cc32d4726..9660bab1d99d 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1473,6 +1473,8 @@ void arch_setup_new_exec(void)
 		current->thread.regs = regs - 1;
 	}
 
+	current->thread.regs->kuap  = default_amr;
+	current->thread.regs->kuep  = default_iamr;
 }
 #endif
 
@@ -1827,7 +1829,6 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
 	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/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index d0d781876c20..42ca7aa09d5b 100644
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -20,7 +20,7 @@ int  max_pkey;			/* Maximum key value supported */
  */
 u32  reserved_allocation_mask;
 static u32  initial_allocation_mask;   /* Bits set for the initially allocated keys */
-static u64 default_amr;
+u64 default_amr;
 static u64 default_iamr;
 /* Allow all keys to be modified by default */
 u64 default_uamor = ~0x0UL;
@@ -387,20 +387,6 @@ void thread_pkey_regs_restore(struct thread_struct *new_thread,
 		write_uamor(new_thread->uamor);
 }
 
-void thread_pkey_regs_init(struct thread_struct *thread)
-{
-	if (!mmu_has_feature(MMU_FTR_PKEY))
-		return;
-
-	thread->amr   = default_amr;
-	thread->iamr  = default_iamr;
-	thread->uamor = default_uamor;
-
-	write_amr(default_amr);
-	write_iamr(default_iamr);
-	write_uamor(default_uamor);
-}
-
 int execute_only_pkey(struct mm_struct *mm)
 {
 	if (static_branch_likely(&execute_pkey_disabled))
-- 
2.25.3