There are some users that would like the ability of a temporary
per-cpu deactivation of the debugger trap.
More specifically, we have seen that when kvm-unit-tests runs with
kgdb enabled, the kernel halts on the debugger during the KVM x86
instruction emulation that performs a test of a division by zero,
and also during fwait.
A second patch depending on this one addresses that issue.
Signed-off-by: Dan Aloni <alonid@xxxxxxxxxxxxxxx>
Signed-off-by: Muli Ben-Yehuda <muli@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/kgdb.h | 8 ++++++++
arch/x86/kernel/kgdb.c | 21 +++++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/arch/x86/include/asm/kgdb.h b/arch/x86/include/asm/kgdb.h
index 332f98c..35bec81 100644
--- a/arch/x86/include/asm/kgdb.h
+++ b/arch/x86/include/asm/kgdb.h
@@ -86,4 +86,12 @@ static inline void arch_kgdb_breakpoint(void)
extern int kgdb_ll_trap(int cmd, const char *str,
struct pt_regs *regs, long err, int trap, int sig);
+#ifdef CONFIG_KGDB
+extern void kgdb_ll_local_disable(void);
+extern void kgdb_ll_local_enable(void);
+#else
+#define kgdb_ll_local_disable() do {} while (0)
+#define kgdb_ll_local_enable() do {} while (0)
+#endif
+
#endif /* _ASM_X86_KGDB_H */
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 836f832..c269ad8 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -587,6 +587,22 @@ int kgdb_ll_trap(int cmd, const char *str,
return __kgdb_notify(&args, cmd);
}
+static DEFINE_PER_CPU(bool, kgdb_swallow_traps);
+
+void kgdb_ll_local_disable(void)
+{
+ __this_cpu_write(kgdb_swallow_traps, true);
+}
+
+EXPORT_SYMBOL(kgdb_ll_local_disable);
+
+void kgdb_ll_local_enable(void)
+{
+ __this_cpu_write(kgdb_swallow_traps, false);
+}
+
+EXPORT_SYMBOL(kgdb_ll_local_enable);
+
static int
kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
{
@@ -594,6 +610,11 @@ kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
int ret;
local_irq_save(flags);
+ if (__this_cpu_read(kgdb_swallow_traps) && cmd == DIE_TRAP) {
+ local_irq_restore(flags);
+ return NOTIFY_DONE;
+ }
+
ret = __kgdb_notify(ptr, cmd);
local_irq_restore(flags);
--
1.8.3.1
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