Add SMI detection accuracy improvements

Signed-off-by: Carles Pey <[email protected]>

chipsec/modules/tools/smm/smm_ptr.py

@@ -148,6 +148,9 @@
 # be long-running
 OUTLIER_THRESHOLD = 33.3
 
+# Scan mode delay before retry
+SCAN_MODE_RETRY_DELAY = 0.01
+
 # SMI count MSR
 MSR_SMI_COUNT = 0x00000034
 
@@ -262,7 +265,7 @@ def add(self, duration, code, data, gprs, confirmed=False):
                 self.max.update(duration, code, data, gprs.copy())
             elif duration < self.min.duration:
                 self.min.update(duration, code, data, gprs.copy())
-        else:
+        elif self.is_slow_outlier(duration):
             self.outliers += 1
             self.outliers_hist += 1
             self.outlier.update(duration, code, data, gprs.copy())
@@ -277,15 +280,31 @@ def avg(self):
             self.acc_smi_duration = 0
             self.acc_smi_num = 0
 
-    def is_outlier(self, value):
-        self.avg()
+    def is_slow_outlier(self, value):
         ret = False
         if self.avg_smi_duration and value > self.avg_smi_duration * (1 + OUTLIER_THRESHOLD / 100):
             ret = True
         if self.hist_smi_duration and value > self.hist_smi_duration * (1 + OUTLIER_THRESHOLD / 100):
             ret = True
         return ret
 
+    def is_fast_outlier(self, value):
+        ret = False
+        if self.avg_smi_duration and value < self.avg_smi_duration * (1 - OUTLIER_THRESHOLD / 100):
+            ret = True
+        if self.hist_smi_duration and value < self.hist_smi_duration * (1 - OUTLIER_THRESHOLD / 100):
+            ret = True
+        return ret
+
+    def is_outlier(self, value):
+        self.avg()
+        ret = False
+        if self.is_slow_outlier(value):
+            ret = True
+        if self.is_fast_outlier(value):
+            ret = True
+        return ret
+
     def skip(self):
         return self.outliers or self.confirmed
 
@@ -487,6 +506,7 @@ def smi_fuzz_iter(self, thread_id, _addr, _smi_desc, fill_contents=True, restore
             # Re-do the call if it was identified as an outlier, due to periodic SMI delays
             #
             if scan.is_outlier(duration):
+                time.sleep(SCAN_MODE_RETRY_DELAY)
                 while True:
                     _, duration = self.send_smi_timed(thread_id, _smi_desc.smi_code, _smi_desc.smi_data, _smi_desc.name, _smi_desc.desc, _rax, _rbx, _rcx, _rdx, _rsi, _rdi)
                     if scan.valid_smi_count():

drivers/linux/amd64/cpu.asm

@@ -40,7 +40,6 @@
  global __cpuid__
  global __swsmi__
  global __swsmi_timed__
- global __swsmi_timed_test__
 
  section .text
 
@@ -463,6 +462,8 @@ __swsmi_timed__:
     ror ax, 8
     out 0B3h, al
 
+    wbinvd
+    mfence
     ; read time-stamp counter
     mov r9, rax
     mov r11, rdx

drivers/linux/chipsec_km.c

@@ -1114,9 +1114,12 @@ static long d_ioctl(struct file *file, unsigned int ioctl_num, unsigned long ioc
             break;
         }
 
+        unsigned long flags;
         unsigned long m_time;
         preempt_disable();
+        local_irq_save(flags);
         __swsmi_timed__((SMI_CTX *)ptr, &m_time);
+        local_irq_restore(flags);
         preempt_enable();
         ptrbuf[numargs] = m_time;