diff --git a/src/globals.h b/src/globals.h
index 0cf4260..4ec6dcb 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -43,19 +43,14 @@
 // Required object alignment
 const int kObjectAlignment = 8;
 
-// Required ARM instruction alignment
+// ARM instruction alignment. ARM processors require code to be 4-byte aligned.
 const int kArmAlignment = 4;
 
-// Required X86 instruction alignment
+// X86 instruction alignment. This is the recommended alignment for maximum performance.
 const int kX86Alignment = 16;
 
-// System page size.  Normally you're expected to get this from
-// sysconf(_SC_PAGESIZE) or some system-specific define (usually
-// PAGESIZE or PAGE_SIZE).  If we use a simple compile-time constant
-// the compiler can generate appropriate masks directly, so we define
-// it here and verify it as the runtime is starting up.
-//
-// Must be a power of 2.
+// System page size. We check this against sysconf(_SC_PAGE_SIZE) at runtime, but use a simple
+// compile-time constant so the compiler can generate better code.
 const int kPageSize = 4096;
 
 }  // namespace art
diff --git a/src/thread_x86.cc b/src/thread_x86.cc
index 30caaec..73b0465 100644
--- a/src/thread_x86.cc
+++ b/src/thread_x86.cc
@@ -30,11 +30,6 @@
 #include <asm/ldt.h>
 #endif
 
-// TODO: add SYS_modify_ldt definition to bionic
-#ifndef SYS_modify_ldt
-#define SYS_modify_ldt __NR_modify_ldt
-#endif
-
 namespace art {
 
 void Thread::InitCpu() {
@@ -49,7 +44,7 @@
   std::vector<uint64_t> ldt(LDT_ENTRIES);
   size_t ldt_size(sizeof(uint64_t) * ldt.size());
   memset(&ldt[0], 0, ldt_size);
-  syscall(SYS_modify_ldt, 0, &ldt[0], ldt_size);
+  syscall(__NR_modify_ldt, 0, &ldt[0], ldt_size);
   // Create empty slot to point at current Thread*
   user_desc ldt_entry;
   memset(&ldt_entry, 0, sizeof(ldt_entry));
@@ -72,7 +67,7 @@
     LOG(FATAL) << "Failed to find available LDT slot";
   }
   // Update LDT
-  CHECK_EQ(0, syscall(SYS_modify_ldt, 1, &ldt_entry, sizeof(ldt_entry)));
+  CHECK_EQ(0, syscall(__NR_modify_ldt, 1, &ldt_entry, sizeof(ldt_entry)));
   // Change FS to be new LDT entry
   uint16_t table_indicator = 1 << 2;  // LDT
   uint16_t rpl = 3;  // Requested privilege level