On Thursday 11 May 2006 13:17, Andrew Morton wrote:-"bibo,mao" <bibo.mao@xxxxxxxxx> wrote:Hi,So.... why not do it this way?
In x86_64 platform, INT1 and INT3 trap stack is IST stack called DEBUG_STACK,
when INT1/INT3 trap happens, system will switch to DEBUG_STACK by hardware. Current DEBUG_STACK size is 4K, when int1/int3 trap happens, kernel will minus current DEBUG_STACK IST value by 4k. But if int3/int1 trap is nested, it will destroy other vector's IST stack. This patch modifies this, it sets DEBUG_STACK size as 8K and allows two level of nested int1/int3 trap.
Kprobe DEBUG_STACK may be nested, because kprobe hanlder may be probed by other kprobes. This patch is against 2.6.17-rc3. Thanks jbeulich for pointing out error in the first patch.
Signed-Off-By: bibo, mao <bibo.mao@xxxxxxxxx>
--- 2.6.17-rc3.org/include/asm-x86_64/page.h 2006-05-10 12:07:18.000000000 +0800
+++ 2.6.17-rc3/include/asm-x86_64/page.h 2006-05-10 12:19:24.000000000 +0800
@@ -20,7 +20,7 @@
#define EXCEPTION_STACK_ORDER 0
#define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
-#define DEBUG_STACK_ORDER EXCEPTION_STACK_ORDER
+#define DEBUG_STACK_ORDER (EXCEPTION_STACK_ORDER + 1)
#define DEBUG_STKSZ (PAGE_SIZE << DEBUG_STACK_ORDER)
#define IRQSTACK_ORDER 2
Last time we discussed this I was told it could nest upto 3 or 4 times
So that still wouldn't work.
If anything they should decrease the int3/debug stack to 2K, then 8K might be enough.
Or even better would be to fix kprobes to not do that.
I think paranoidentry would need to be fixed for that too.
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