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

Mark Rutland
2021-05-19T13:11:02Z

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@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@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!");