diff --git a/libc/kernel/uapi/asm-arm/asm/swab.h b/libc/kernel/uapi/asm-arm/asm/swab.h
index 7684c22..3fff953 100644
--- a/libc/kernel/uapi/asm-arm/asm/swab.h
+++ b/libc/kernel/uapi/asm-arm/asm/swab.h
@@ -11,7 +11,18 @@
 #ifndef __STRICT_ANSI__
 #define __SWAB_64_THRU_32__
 #endif
+static inline __attribute__((__const__)) __u32 __arch_swab32(__u32 x) {
+  __u32 t;
 #ifndef __thumb__
+  if(! __builtin_constant_p(x)) {
+    asm("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
+  } else
 #endif
+  t = x ^ ((x << 16) | (x >> 16));
+  x = (x << 24) | (x >> 8);
+  t &= ~0x00FF0000;
+  x ^= (t >> 8);
+  return x;
+}
 #define __arch_swab32 __arch_swab32
 #endif
diff --git a/libc/kernel/uapi/asm-x86/asm/swab.h b/libc/kernel/uapi/asm-x86/asm/swab.h
index 31c850d..ce43658 100644
--- a/libc/kernel/uapi/asm-x86/asm/swab.h
+++ b/libc/kernel/uapi/asm-x86/asm/swab.h
@@ -8,9 +8,27 @@
 #define _ASM_X86_SWAB_H
 #include <linux/types.h>
 #include <linux/compiler.h>
+static inline __attribute__((__const__)) __u32 __arch_swab32(__u32 val) {
+  asm("bswapl %0" : "=r" (val) : "0" (val));
+  return val;
+}
 #define __arch_swab32 __arch_swab32
+static inline __attribute__((__const__)) __u64 __arch_swab64(__u64 val) {
 #ifdef __i386__
+  union {
+    struct {
+      __u32 a;
+      __u32 b;
+    } s;
+    __u64 u;
+  } v;
+  v.u = val;
+  asm("bswapl %0; bswapl %1; xchgl %0,%1" : "=r" (v.s.a), "=r" (v.s.b) : "0" (v.s.a), "1" (v.s.b));
+  return v.u;
 #else
+  asm("bswapq %0" : "=r" (val) : "0" (val));
+  return val;
 #endif
+}
 #define __arch_swab64 __arch_swab64
 #endif