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Subject[PATCH] x86: Increase exception stack sizes
On Wed, Sep 15, 2021 at 03:34:20PM +0800, 王贇 wrote:
> Hi, Dave, Peter
>
> What if we just increase the stack size when ftrace enabled?

I think we can do an unconditional increase. But please first test that
guard page patch :-)

---
Subject: x86: Increase exception stack sizes
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed Sep 15 16:19:46 CEST 2021

It turns out that a single page of stack is trivial to overflow with
all the tracing gunk enabled. Raise the exception stacks to 2 pages,
which is still half the interrupt stacks, which are at 4 pages.

Reported-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/page_64_types.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -15,7 +15,7 @@
#define THREAD_SIZE_ORDER (2 + KASAN_STACK_ORDER)
#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)

-#define EXCEPTION_STACK_ORDER (0 + KASAN_STACK_ORDER)
+#define EXCEPTION_STACK_ORDER (1 + KASAN_STACK_ORDER)
#define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)

#define IRQ_STACK_ORDER (2 + KASAN_STACK_ORDER)
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