diff --git a/src/arch/i386/include/bits/errfile.h b/src/arch/i386/include/bits/errfile.h
index 99927c28..70c78eaf 100644
--- a/src/arch/i386/include/bits/errfile.h
+++ b/src/arch/i386/include/bits/errfile.h
@@ -6,7 +6,7 @@
  * @{
  */
 
-#define ERRFILE_umalloc		( ERRFILE_ARCH | ERRFILE_CORE | 0x00000000 )
+#define ERRFILE_memtop_umalloc	( ERRFILE_ARCH | ERRFILE_CORE | 0x00000000 )
 #define ERRFILE_memmap		( ERRFILE_ARCH | ERRFILE_CORE | 0x00010000 )
 #define ERRFILE_pnpbios		( ERRFILE_ARCH | ERRFILE_CORE | 0x00020000 )
 #define ERRFILE_smbios		( ERRFILE_ARCH | ERRFILE_CORE | 0x00030000 )
diff --git a/src/arch/i386/include/bits/umalloc.h b/src/arch/i386/include/bits/umalloc.h
new file mode 100644
index 00000000..dcbd0a6b
--- /dev/null
+++ b/src/arch/i386/include/bits/umalloc.h
@@ -0,0 +1,12 @@
+#ifndef _BITS_UMALLOC_H
+#define _BITS_UMALLOC_H
+
+/** @file
+ *
+ * i386-specific user memory allocation API implementations
+ *
+ */
+
+#include <gpxe/memtop_umalloc.h>
+
+#endif /* _BITS_UMALLOC_H */
diff --git a/src/arch/i386/include/gpxe/memtop_umalloc.h b/src/arch/i386/include/gpxe/memtop_umalloc.h
new file mode 100644
index 00000000..a3cd2c01
--- /dev/null
+++ b/src/arch/i386/include/gpxe/memtop_umalloc.h
@@ -0,0 +1,16 @@
+#ifndef _GPXE_MEMTOP_UMALLOC_H
+#define _GPXE_MEMTOP_UMALLOC_H
+
+/** @file
+ *
+ * External memory allocation
+ *
+ */
+
+#ifdef UMALLOC_MEMTOP
+#define UMALLOC_PREFIX_memtop
+#else
+#define UMALLOC_PREFIX_memtop __memtop_
+#endif
+
+#endif /* _GPXE_MEMTOP_UMALLOC_H */
diff --git a/src/arch/i386/core/umalloc.c b/src/arch/i386/interface/pcbios/memtop_umalloc.c
similarity index 90%
rename from src/arch/i386/core/umalloc.c
rename to src/arch/i386/interface/pcbios/memtop_umalloc.c
index 3990488c..2eb7f76d 100644
--- a/src/arch/i386/core/umalloc.c
+++ b/src/arch/i386/interface/pcbios/memtop_umalloc.c
@@ -36,9 +36,6 @@
 /** Equivalent of NOWHERE for user pointers */
 #define UNOWHERE ( ~UNULL )
 
-/** Start of Etherboot text, as defined by the linker */
-extern char _text[];
-
 /** An external memory block */
 struct external_memory {
 	/** Size of this memory block (excluding this header) */
@@ -135,7 +132,7 @@ static void ecollect_free ( void ) {
  * Calling realloc() with a new size of zero is a valid way to free a
  * memory block.
  */
-userptr_t urealloc ( userptr_t ptr, size_t new_size ) {
+static userptr_t memtop_urealloc ( userptr_t ptr, size_t new_size ) {
 	struct external_memory extmem;
 	userptr_t new = ptr;
 	size_t align;
@@ -200,25 +197,4 @@ userptr_t urealloc ( userptr_t ptr, size_t new_size ) {
 	return ( new_size ? new : UNOWHERE );
 }
 
-/**
- * Allocate external memory
- *
- * @v size		Requested size
- * @ret ptr		Memory, or UNULL
- *
- * Memory is guaranteed to be aligned to a page boundary.
- */
-userptr_t umalloc ( size_t size ) {
-	return urealloc ( UNULL, size );
-}
-
-/**
- * Free external memory
- *
- * @v ptr		Memory allocated by umalloc(), or UNULL
- *
- * If @c ptr is UNULL, no action is taken.
- */
-void ufree ( userptr_t ptr ) {
-	urealloc ( ptr, 0 );
-}
+PROVIDE_UMALLOC ( memtop, urealloc, memtop_urealloc );
diff --git a/src/config/defaults/pcbios.h b/src/config/defaults/pcbios.h
index 211f28cf..b782647c 100644
--- a/src/config/defaults/pcbios.h
+++ b/src/config/defaults/pcbios.h
@@ -13,5 +13,6 @@
 #define TIMER_PCBIOS
 #define CONSOLE_PCBIOS
 #define NAP_PCBIOS
+#define UMALLOC_MEMTOP
 
 #endif /* CONFIG_DEFAULTS_PCBIOS_H */
diff --git a/src/config/umalloc.h b/src/config/umalloc.h
new file mode 100644
index 00000000..de4019e5
--- /dev/null
+++ b/src/config/umalloc.h
@@ -0,0 +1,12 @@
+#ifndef CONFIG_UMALLOC_H
+#define CONFIG_UMALLOC_H
+
+/** @file
+ *
+ * User memory allocation API configuration
+ *
+ */
+
+#include <config/defaults.h>
+
+#endif /* CONFIG_UMALLOC_H */
diff --git a/src/include/gpxe/umalloc.h b/src/include/gpxe/umalloc.h
index 49ec22b4..ffa0c0c4 100644
--- a/src/include/gpxe/umalloc.h
+++ b/src/include/gpxe/umalloc.h
@@ -8,10 +8,58 @@
  *
  */
 
+#include <gpxe/api.h>
+#include <config/umalloc.h>
 #include <gpxe/uaccess.h>
 
-extern userptr_t umalloc ( size_t size );
-extern userptr_t urealloc ( userptr_t ptr, size_t new_size );
-extern void ufree ( userptr_t ptr );
+/**
+ * Provide a user memory allocation API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @v _func		Implementing function
+ */
+#define PROVIDE_UMALLOC( _subsys, _api_func, _func ) \
+	PROVIDE_SINGLE_API ( UMALLOC_PREFIX_ ## _subsys, _api_func, _func )
+
+/* Include all architecture-independent I/O API headers */
+
+/* Include all architecture-dependent I/O API headers */
+#include <bits/umalloc.h>
+
+/**
+ * Reallocate external memory
+ *
+ * @v userptr		Memory previously allocated by umalloc(), or UNULL
+ * @v new_size		Requested size
+ * @ret userptr		Allocated memory, or UNULL
+ *
+ * Calling realloc() with a new size of zero is a valid way to free a
+ * memory block.
+ */
+userptr_t urealloc ( userptr_t userptr, size_t new_size );
+
+/**
+ * Allocate external memory
+ *
+ * @v size		Requested size
+ * @ret userptr		Memory, or UNULL
+ *
+ * Memory is guaranteed to be aligned to a page boundary.
+ */
+static inline __always_inline userptr_t umalloc ( size_t size ) {
+	return urealloc ( UNULL, size );
+}
+
+/**
+ * Free external memory
+ *
+ * @v userptr		Memory allocated by umalloc(), or UNULL
+ *
+ * If @c ptr is UNULL, no action is taken.
+ */
+static inline __always_inline void ufree ( userptr_t userptr ) {
+	urealloc ( userptr, 0 );
+}
 
 #endif /* _GPXE_UMALLOC_H */