diff --git a/libc/arch-arm/bionic/strlen.c b/libc/arch-arm/bionic/strlen.c
new file mode 100644
index 0000000..01632e3
--- /dev/null
+++ b/libc/arch-arm/bionic/strlen.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <string.h>
+#include <stdint.h>
+#include <machine/cpu-features.h>
+
+size_t strlen(const char *s)
+{
+    __builtin_prefetch(s);
+    __builtin_prefetch(s+32);
+    
+    union {
+        const char      *b;
+        const uint32_t  *w;
+        uintptr_t       i;
+    } u;
+    
+    // these are some scratch variables for the asm code below
+    uint32_t v, t;
+    
+    // initialize the string length to zero
+    size_t l = 0;
+
+    // align the pointer to a 32-bit word boundary
+    u.b = s;
+    while (u.i & 0x3)  {
+        if (__builtin_expect(*u.b++ == 0, 0)) {
+            goto done;
+        }
+        l++;
+    }
+
+    // loop for each word, testing if it contains a zero byte
+    // if so, exit the loop and update the length.
+    // We need to process 32 bytes per loop to schedule PLD properly
+    // and achieve the maximum bus speed.
+    asm(
+        "ldr     %[v], [ %[s] ], #4         \n"
+        "sub     %[l], %[l], %[s]           \n"
+        "0:                                 \n"
+#if __ARM_HAVE_PLD
+        "pld     [ %[s], #64 ]              \n"
+#endif
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+#if !defined(__OPTIMIZE_SIZE__)
+        "bne     1f                         \n"
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+        "bne     1f                         \n"
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+        "bne     1f                         \n"
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+        "bne     1f                         \n"
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+        "bne     1f                         \n"
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+        "bne     1f                         \n"
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+        "bne     1f                         \n"
+        "sub     %[t], %[v], %[mask], lsr #7\n"
+        "and     %[t], %[t], %[mask]        \n"
+        "bics    %[t], %[t], %[v]           \n"
+        "ldreq   %[v], [ %[s] ], #4         \n"
+#endif
+        "beq     0b                         \n"
+        "1:                                 \n"
+        "add     %[l], %[l], %[s]           \n"
+        "tst     %[v], #0xFF                \n"
+        "beq     2f                         \n"
+        "add     %[l], %[l], #1             \n"
+        "tst     %[v], #0xFF00              \n"
+        "beq     2f                         \n"
+        "add     %[l], %[l], #1             \n"
+        "tst     %[v], #0xFF0000            \n"
+        "addne   %[l], %[l], #1             \n"
+        "2:                                 \n"
+        : [l]"=&r"(l), [v]"=&r"(v), [t]"=&r"(t), [s]"=&r"(u.b)
+        : "%[l]"(l), "%[s]"(u.b), [mask]"r"(0x80808080UL)
+        : "cc"
+    );
+    
+done:
+    return l;
+}