[PATCH v2 15/19] arm64: entry: split bad stack entry

[Mark Rutland]

We'd like to keep all the entry sequencing in entry-common.c, as this
will allow us to ensure this is all consistent, and free from any
unsound instrumentation.

Currently handle_bad_stack() performs the NMI entry sequence in traps.c.
Let's split the low-level entry sequence from the reporting, moving the
former to entry-common.c and keeping the latter in traps.c. To make it
clear that reporting function never returns, it is renamed to
panic_bad_stack().

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: James Morse <james.morse at arm.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Will Deacon <will at kernel.org>
---
 arch/arm64/include/asm/exception.h | 4 ++++
 arch/arm64/kernel/entry-common.c   | 9 +++++++++
 arch/arm64/kernel/traps.c          | 6 +-----
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h
index 40a3a20dca1c..952402ca9533 100644
--- a/arch/arm64/include/asm/exception.h
+++ b/arch/arm64/include/asm/exception.h
@@ -31,6 +31,8 @@ static inline u32 disr_to_esr(u64 disr)
 	return esr;
 }
 
+asmlinkage void handle_bad_stack(struct pt_regs *regs);
+
 asmlinkage void el1t_64_sync_handler(struct pt_regs *regs);
 asmlinkage void el1t_64_irq_handler(struct pt_regs *regs);
 asmlinkage void el1t_64_fiq_handler(struct pt_regs *regs);
@@ -74,4 +76,6 @@ void do_el0_svc(struct pt_regs *regs);
 void do_el0_svc_compat(struct pt_regs *regs);
 void do_ptrauth_fault(struct pt_regs *regs, unsigned int esr);
 void do_serror(struct pt_regs *regs, unsigned int esr);
+
+void panic_bad_stack(struct pt_regs *regs, unsigned int esr, unsigned long far);
 #endif	/* __ASM_EXCEPTION_H */
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 6f1caec913a9..801c7d479d47 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -104,6 +104,15 @@ void noinstr arm64_exit_nmi(struct pt_regs *regs)
 	__nmi_exit();
 }
 
+asmlinkage void noinstr handle_bad_stack(struct pt_regs *regs)
+{
+	unsigned int esr = read_sysreg(esr_el1);
+	unsigned long far = read_sysreg(far_el1);
+
+	arm64_enter_nmi(regs);
+	panic_bad_stack(regs, esr, far);
+}
+
 static void noinstr enter_el1_irq_or_nmi(struct pt_regs *regs)
 {
 	if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && !interrupts_enabled(regs))
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 7def18ff02e2..4d157d2d8f67 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -763,15 +763,11 @@ void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr)
 DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)
 	__aligned(16);
 
-asmlinkage void noinstr handle_bad_stack(struct pt_regs *regs)
+void panic_bad_stack(struct pt_regs *regs, unsigned int esr, unsigned long far)
 {
 	unsigned long tsk_stk = (unsigned long)current->stack;
 	unsigned long irq_stk = (unsigned long)this_cpu_read(irq_stack_ptr);
 	unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);
-	unsigned int esr = read_sysreg(esr_el1);
-	unsigned long far = read_sysreg(far_el1);
-
-	arm64_enter_nmi(regs);
 
 	console_verbose();
 	pr_emerg("Insufficient stack space to handle exception!");
-- 
2.11.0