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Subject[PATCH -tip v8 05/26] [BUGFIX] kprobes/x86: Prohibit probing on debug_stack_*
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Prohibit probing on debug_stack_reset and debug_stack_set_zero.
Since the both functions are called from TRACE_IRQS_ON/OFF_DEBUG
macros which run in int3 ist entry, probing it may cause a soft
lockup.

This happens when the kernel built with CONFIG_DYNAMIC_FTRACE=y
and CONFIG_TRACE_IRQFLAGS=y.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
---
arch/x86/kernel/cpu/common.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index cca53d8..cddee83 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -8,6 +8,7 @@
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/init.h>
+#include <linux/kprobes.h>
#include <linux/kgdb.h>
#include <linux/smp.h>
#include <linux/io.h>
@@ -1160,6 +1161,7 @@ int is_debug_stack(unsigned long addr)
(addr <= __get_cpu_var(debug_stack_addr) &&
addr > (__get_cpu_var(debug_stack_addr) - DEBUG_STKSZ));
}
+NOKPROBE_SYMBOL(is_debug_stack);

DEFINE_PER_CPU(u32, debug_idt_ctr);

@@ -1168,6 +1170,7 @@ void debug_stack_set_zero(void)
this_cpu_inc(debug_idt_ctr);
load_current_idt();
}
+NOKPROBE_SYMBOL(debug_stack_set_zero);

void debug_stack_reset(void)
{
@@ -1176,6 +1179,7 @@ void debug_stack_reset(void)
if (this_cpu_dec_return(debug_idt_ctr) == 0)
load_current_idt();
}
+NOKPROBE_SYMBOL(debug_stack_reset);

#else /* CONFIG_X86_64 */




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