Subject: [PATCH 09/14] powerpc/64: treat low kernel text as irqs soft-masked

From: Nicholas Piggin <[email-masked]>
Date: Tue, 16 Mar 2021 08:03:57 +1000

Treat code below __end_soft_masked as soft-masked for the purpose
of alternate return. 64s already mostly does this for scv entry.

This will be used to exit from interrupts without disabling MSR[EE].

Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/include/asm/interrupt.h |  8 ++++++++
 arch/powerpc/kernel/exceptions-64e.S | 12 +++++++++++-
 arch/powerpc/kernel/exceptions-64s.S |  3 ++-
 arch/powerpc/kernel/interrupt_64.S   |  6 +++++-
 4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 5cdbd3630254..8796eb4630c9 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -72,6 +72,10 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup
 		 */
 		if (TRAP(regs) != 0x700)
 			CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
+		BUG_ON(regs->nip < (unsigned long)__end_soft_masked);
+		/* Move this under a debugging check */
+		if (arch_irq_disabled_regs(regs))
+			BUG_ON(search_kernel_restart_table(regs->nip));
 	}
 #endif
 
@@ -147,6 +151,10 @@ static inline bool nmi_disables_ftrace(struct pt_regs *regs)
 static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct interrupt_nmi_state *state)
 {
 #ifdef CONFIG_PPC64
+	/* Ensure arch_irq_disabled_regs(regs) looks right. */
+	if (!(regs->msr & MSR_PR) && regs->nip < (unsigned long)__end_soft_masked)
+		regs->softe = IRQS_ALL_DISABLED;
+
 	state->irq_soft_mask = local_paca->irq_soft_mask;
 	state->irq_happened = local_paca->irq_happened;
 
diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 69d0d63cee85..87fe307b4da8 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -342,7 +342,17 @@ ret_from_mc_except:
 #define PROLOG_ADDITION_MASKABLE_GEN(n)					    \
 	lbz	r10,PACAIRQSOFTMASK(r13);	/* are irqs soft-masked? */ \
 	andi.	r10,r10,IRQS_DISABLED;	/* yes -> go out of line */ \
-	bne	masked_interrupt_book3e_##n
+	bne	masked_interrupt_book3e_##n;				    \
+	/* Kernel code below __end_soft_masked is implicitly masked */	    \
+	andi.	r10,r11,MSR_PR;						    \
+	bne	1f;			/* user -> not masked */	    \
+	std	r14,PACA_EXGEN+EX_R14(r13);				    \
+	LOAD_REG_IMMEDIATE_SYM(r14, r10, __end_soft_masked);		    \
+	mfspr	r10,SPRN_SRR0;						    \
+	cmpld	r10,r14;						    \
+	ld	r14,PACA_EXGEN+EX_R14(r13);				    \
+	blt	masked_interrupt_book3e_##n;				    \
+1:
 
 #define PROLOG_ADDITION_2REGS_GEN(n)					    \
 	std	r14,PACA_EXGEN+EX_R14(r13);				    \
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 32b11431ac4a..bd0c82ac9de5 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -514,8 +514,9 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real)
 
 		/* Kernel code running below __end_interrupts is implicitly
 		 * soft-masked */
-		LOAD_HANDLER(r10, __end_interrupts)
+		LOAD_HANDLER(r10, __end_soft_masked)
 		cmpld	r11,r10
+
 		li	r10,IMASK
 		blt-	1f
 
diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index 8a2b8188108b..c6a0349dde59 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -642,4 +642,8 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 interrupt_return_macro srr
 #ifdef CONFIG_PPC_BOOK3S
 interrupt_return_macro hsrr
-#endif
+#endif /* CONFIG_PPC_BOOK3S */
+
+	.globl __end_soft_masked
+__end_soft_masked:
+DEFINE_FIXED_SYMBOL(__end_soft_masked)
-- 
2.23.0