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-rw-r--r--drivers/lguest/interrupts_and_traps.c6
-rw-r--r--drivers/lguest/lg.h1
-rw-r--r--drivers/lguest/x86/core.c6
3 files changed, 11 insertions, 2 deletions
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index eb934b024..67392b6ab 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -331,7 +331,7 @@ void set_interrupt(struct lg_cpu *cpu, unsigned int irq)
* Actually now I think of it, it's possible that Ron *is* half the Plan 9
* userbase. Oh well.
*/
-static bool could_be_syscall(unsigned int num)
+bool could_be_syscall(unsigned int num)
{
/* Normal Linux IA32_SYSCALL_VECTOR or reserved vector? */
return num == IA32_SYSCALL_VECTOR || num == syscall_vector;
@@ -416,6 +416,10 @@ bool deliver_trap(struct lg_cpu *cpu, unsigned int num)
*
* This routine indicates if a particular trap number could be delivered
* directly.
+ *
+ * Unfortunately, Linux 4.6 started using an interrupt gate instead of a
+ * trap gate for syscalls, so this trick is ineffective. See Mastery for
+ * how we could do this anyway...
*/
static bool direct_trap(unsigned int num)
{
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index ac8ad0461..69b3814af 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -167,6 +167,7 @@ void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta);
bool send_notify_to_eventfd(struct lg_cpu *cpu);
void init_clockdev(struct lg_cpu *cpu);
bool check_syscall_vector(struct lguest *lg);
+bool could_be_syscall(unsigned int num);
int init_interrupts(void);
void free_interrupts(void);
diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index 6a4cd771a..adc162c70 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -429,8 +429,12 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
return;
break;
case 32 ... 255:
+ /* This might be a syscall. */
+ if (could_be_syscall(cpu->regs->trapnum))
+ break;
+
/*
- * These values mean a real interrupt occurred, in which case
+ * Other values mean a real interrupt occurred, in which case
* the Host handler has already been run. We just do a
* friendly check if another process should now be run, then
* return to run the Guest again.