diff --git a/ape/ape.S b/ape/ape.S
index 13eba1c7e..aada551aa 100644
--- a/ape/ape.S
+++ b/ape/ape.S
@@ -235,8 +235,9 @@ pc:	cld
 #endif
 	ljmp	$0,$REAL(1f)
 1:	mov	%cx,%ds
-	mov	$IMAGE_BASE_REAL-0x0500,%cx	# clears bss
-	mov	$0x0500>>4,%ax			# struct mman
+	.set	mm,0x0500			# struct mman
+	mov	$IMAGE_BASE_REAL-mm,%cx		# clears bss
+	mov	$mm>>4,%ax
 	mov	%ax,%es
 	xor	%ax,%ax
 	xor	%di,%di
@@ -328,7 +329,7 @@ dsknfo:	push	%bx
 	movpp	%es,%ds
 	xor	%si,%si
 	mov	%si,%es
-	mov	$0x1d10,%si		# mman::pc_drive_base_table
+	mov	$mm+"struct mman::pc_drive_base_table",%si
 	xchg	%si,%di
 	movsw	#→ headunloadtime, headloadtime
 	movsw	#→ shutofftime, bytespersector
@@ -381,11 +382,11 @@ pcread:	push	%ax
 	add	$512>>4,%si
 	mov	%si,%es
 	inc	%al			# ++sector
-	cmp	0x1d1c,%al		# mman::pc_drive_last_sector
+	cmp	mm+"struct mman::pc_drive_last_sector",%al
 	jbe	2f
 	mov	$1,%al
 	inc	%dh			# ++head
-	cmp	0x1d20,%dh		# mman::pc_drive_last_head
+	cmp	mm+"struct mman::pc_drive_last_head",%dh
 	jbe	2f
 	xor	%dh,%dh
 	inc	%cx			# ++cylinder
@@ -1288,10 +1289,9 @@ lcheck:	pushf				# check for i8086 / i8088 / i80186
 	.endfn	lcheck
 
 //	Gets memory map from BIOS.
-e820:	mov	$0x0510>>4,%di		# mman::e820
-	mov	%di,%es
-	xor	%di,%di			# es:di is destination buffer
-	xor	%ebx,%ebx		# ebx is an api state tracker
+e820:	xor	%ebx,%ebx		# %ebx is an api state tracker
+	mov	%bx,%es
+	mov	$mm+"struct mman::e820",%di # es:di is destination buffer
 1:	mov	$0xE820,%eax		# magic
 	mov	$8+8+4+4,%ecx		# sizeof(struct SmapEntry)
 	mov	$0x534d4150,%edx	# magic number
@@ -1315,7 +1315,7 @@ e820:	mov	$0x0510>>4,%di		# mman::e820
 4:	add	$8+8+4+4,%di		# keep entry
 5:	test	%ebx,%ebx		# last entry?
 	jz	8f
-	cmp	$(256-1)*(8+8+4+4),%di
+	cmp	$mm+"struct mman::e820_end"-(8+8+4+4),%di
 	jb	1b
 8:	xor	%ax,%ax			# add a blank sentinel entry
 	mov	$(8+8)/2,%cx
@@ -1425,7 +1425,7 @@ pinit:	push	%ds
 //
 //	@see	Intel Manual V3A §4.1.2
 golong:	cli
-	lidt	0x1d22					# mman::bad_idt
+	lidt	mm+"struct mman::bad_idt"
 	mov	%cr4,%eax
 	or	$CR4_PAE|CR4_PGE|CR4_OSFXSR,%eax
 	mov	%eax,%cr4
@@ -1458,7 +1458,7 @@ long:	xor	%eax,%eax
 	xor	%ebx,%ebx
 	xor	%ebp,%ebp
 	push	%rbp
-	mov	$0x0500,%rdi			# mman
+	mov	$mm,%rdi
 	mov	%cr3,%rsi
 	mov	$IMAGE_BASE_REAL,%edx
 	call	__map_phdrs
diff --git a/libc/intrin/mman.greg.c b/libc/intrin/mman.greg.c
index 12cb3dc7e..e85eb9784 100644
--- a/libc/intrin/mman.greg.c
+++ b/libc/intrin/mman.greg.c
@@ -128,7 +128,26 @@ static noasan textreal void __invert_memory(struct mman *mm, uint64_t *pml4t) {
   }
 }
 
+/**
+ * Exports information about the offset of a field within a structure type,
+ * so that assembly language routines can use it.  This macro can be invoked
+ * from inside a function whose code is known to be emitted.
+ */
+#define export_offsetof(type, member)                       \
+    do {                                                    \
+      asm volatile(".globl \"" #type "::" #member "\"\n\t"  \
+                   ".set \"" #type "::" #member "\",%c0"    \
+                   : /* no outputs */                       \
+                   : "i" (offsetof(type, member)));         \
+    } while (0)
+
 noasan textreal void __setup_mman(struct mman *mm, uint64_t *pml4t) {
+  export_offsetof(struct mman, pc_drive_base_table);
+  export_offsetof(struct mman, pc_drive_last_sector);
+  export_offsetof(struct mman, pc_drive_last_head);
+  export_offsetof(struct mman, e820);
+  export_offsetof(struct mman, e820_end);
+  export_offsetof(struct mman, bad_idt);
   __normalize_e820(mm);
   __invert_memory(mm, pml4t);
 }
diff --git a/libc/runtime/mman.internal.h b/libc/runtime/mman.internal.h
index 8c582a52d..5a9e2b642 100644
--- a/libc/runtime/mman.internal.h
+++ b/libc/runtime/mman.internal.h
@@ -9,14 +9,15 @@ struct mman {
   int32_t pdpi;                          /* 0x0508 */
   int32_t e820n;                         /* 0x050c */
   struct SmapEntry e820[256];            /* 0x0510 */
+  struct SmapEntry e820_end[0];          /* 0x1d10 */
   char pc_drive_base_table[11];          /* 0x1d10 */
   unsigned char pc_drive_type;           /* 0x1d1b */
   unsigned char pc_drive_last_sector;    /* 0x1d1c */
-  unsigned short pc_drive_last_cylinder; /* 0x1d1d */
-  unsigned char pc_drives_attached;      /* 0x1d1f */
-  unsigned char pc_drive_last_head;      /* 0x1d20 */
-  unsigned char pc_drive;                /* 0x1d21 */
-  char bad_idt[6];                       /* 0x1d22 */
+  unsigned short pc_drive_last_cylinder; /* 0x1d1e */
+  unsigned char pc_drives_attached;      /* 0x1d20 */
+  unsigned char pc_drive_last_head;      /* 0x1d21 */
+  unsigned char pc_drive;                /* 0x1d22 */
+  char bad_idt[6];                       /* 0x1d23 */
 };
 
 COSMOPOLITAN_C_END_