diff --git a/liba/Makefile b/liba/Makefile
index db13011f5..92111d16f 100644
--- a/liba/Makefile
+++ b/liba/Makefile
@@ -7,4 +7,7 @@ tests += $(addprefix liba/test/, stdint.c)
 
 # The use of aeabi-rt could be made conditional to an AEABI target.
 # In practice we're always using liba on such a target.
-objs += $(addprefix liba/src/aeabi-rt/, memcpy.o)
+objs += $(addprefix liba/src/aeabi-rt/, \
+  memclr.o \
+  memcpy.o \
+)
diff --git a/liba/src/aeabi-rt/README.txt b/liba/src/aeabi-rt/README.txt
index be3109f12..37691aaf5 100644
--- a/liba/src/aeabi-rt/README.txt
+++ b/liba/src/aeabi-rt/README.txt
@@ -9,6 +9,7 @@ memory copying/clearing/setting, etc...
 Since we're telling our compiler to build an AEABI binary, it may decide to use
 those symbols, and so we have to provide an implementation for them. Refer to
 the "Run-time ABI for the ARM Architecture" for a full list of functions.
+http://infocenter.arm.com/help/topic/com.arm.doc.ihi0043d/IHI0043D_rtabi.pdf
 
 Note that this is not formally the job of a libc implementation. Similar code is
 often shipped alongside a compiler (LLVM calls it compiler-rt, GCC libgcc). But
diff --git a/liba/src/aeabi-rt/memclr.c b/liba/src/aeabi-rt/memclr.c
new file mode 100644
index 000000000..d777c7e65
--- /dev/null
+++ b/liba/src/aeabi-rt/memclr.c
@@ -0,0 +1,8 @@
+#include <stddef.h>
+#include <string.h>
+
+/* See the "Run-time ABI for the ARM Architecture", Section 4.3.3 */
+
+void __aeabi_memclr4(void * dest, size_t n) {
+  memset(dest, 0, n);
+}