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-rw-r--r--arch/riscv/kernel/traps.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index f3e96d60a2ff..7abd8e4c4df6 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -221,11 +221,29 @@ asmlinkage unsigned long get_overflow_stack(void)
OVERFLOW_STACK_SIZE;
}
+/*
+ * A pseudo spinlock to protect the shadow stack from being used by multiple
+ * harts concurrently. This isn't a real spinlock because the lock side must
+ * be taken without a valid stack and only a single register, it's only taken
+ * while in the process of panicing anyway so the performance and error
+ * checking a proper spinlock gives us doesn't matter.
+ */
+unsigned long spin_shadow_stack;
+
asmlinkage void handle_bad_stack(struct pt_regs *regs)
{
unsigned long tsk_stk = (unsigned long)current->stack;
unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);
+ /*
+ * We're done with the shadow stack by this point, as we're on the
+ * overflow stack. Tell any other concurrent overflowing harts that
+ * they can proceed with panicing by releasing the pseudo-spinlock.
+ *
+ * This pairs with an amoswap.aq in handle_kernel_stack_overflow.
+ */
+ smp_store_release(&spin_shadow_stack, 0);
+
console_verbose();
pr_emerg("Insufficient stack space to handle exception!\n");