2 files changed, 19 insertions, 0 deletions
diff --git a/asm/asm_x86.h b/asm/asm_x86.h
index ec9ebd0..0781fc7 100644
--- a/asm/asm_x86.h
+++ b/asm/asm_x86.h
@@ -100,4 +100,6 @@ static inline void x86_paging_enable()    {x86_set_cr(0,x86_get_cr(0)| 0x8000000
 /** Disable paging */
 static inline void x86_paging_disable()   {x86_set_cr(0,x86_get_cr(0)&~0x80000000);}
 
+/** Read Time Stamp Counter */
+uint64_t x86_rdtscp();
 #endif
diff --git a/asm/asm_x86.s b/asm/asm_x86.s
index 3481ec2..7f0f56b 100644
--- a/asm/asm_x86.s
+++ b/asm/asm_x86.s
@@ -24,6 +24,9 @@
 .global x86_get_cr
 .global x86_set_cr
 
+// timer
+.global x86_rdtscp
+
 x86_outb:
     mov 4(%esp), %edx
     mov 8(%esp), %eax
@@ -132,3 +135,17 @@ x86_invlpg:
     mov 4(%esp), %eax // addr
     invlpg (%eax)
     ret
+
+#x86_rdtscp:
+#    rdtscp
+#    ret
+# https://stackoverflow.com/questions/12631856/difference-between-rdtscp-rdtsc-memory-and-cpuid-rdtsc
+x86_rdtscp:
+    lfence #intel
+    rdtsc
+    ret
+
+#x86_rdtscp:
+#    mfence #amd
+#    rdtsc
+#    ret