[RFC PATCH V2 6/7] x86/entry: is_debug_stack() don't check of DB1 stack

Lai Jiangshan
2020-05-26T01:42:43Z

IST-shift code is removed from entry code, #DB will not
at DB1 stack. So we remove the check of DB1 stack in
is_debug_stack().

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/kernel/nmi.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 1c58454ac5fb..2f463f5880c6 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -500,15 +500,10 @@ static noinstr bool is_debug_stack(unsigned long addr)
{
struct cea_exception_stacks *cs = __this_cpu_read(cea_exception_stacks);
unsigned long top = CEA_ESTACK_TOP(cs, DB);
- unsigned long bot = CEA_ESTACK_BOT(cs, DB1);
+ unsigned long bot = CEA_ESTACK_BOT(cs, DB);

if (__this_cpu_read(debug_stack_usage))
return true;
- /*
- * Note, this covers the guard page between DB and DB1 as well to
- * avoid two checks. But by all means @addr can never point into
- * the guard page.
- */
return addr >= bot && addr < top;
}
#endif
--
2.20.1