diff --git a/executer/user/arch/arm64/arch-eclair.c b/executer/user/arch/arm64/arch-eclair.c
index 93be202e..47c8cbda 100644
--- a/executer/user/arch/arm64/arch-eclair.c
+++ b/executer/user/arch/arm64/arch-eclair.c
@@ -98,8 +98,8 @@ uintptr_t virt_to_phys(uintptr_t va)
 		return (va - MAP_ST + PHYS_OFFSET);
 	}
 
-	if (va >= MAP_KERNEL) {
-		return (va - MAP_KERNEL + kernel_base);
+	if (va >= MAP_KERNEL_START) {
+		return (va - MAP_KERNEL_START + kernel_base);
 	}
 
 	return NOPHYS;
@@ -107,7 +107,13 @@ uintptr_t virt_to_phys(uintptr_t va)
 
 int arch_setup_constants(void)
 {
-	/* Nothing here */
+	MAP_KERNEL_START = lookup_symbol("_head");
+	if (MAP_KERNEL_START == NOSYMBOL) {
+		fprintf(stderr, "error: obtaining MAP_KERNEL_START\n");
+		return 1;
+	}
+	printf("arm64 MAP_KERNEL_START 0x%lx\n", MAP_KERNEL_START);
+
 	return 0;
 }
 
diff --git a/executer/user/arch/arm64/include/arch-eclair.h b/executer/user/arch/arm64/include/arch-eclair.h
index 9140788b..891aec54 100644
--- a/executer/user/arch/arm64/include/arch-eclair.h
+++ b/executer/user/arch/arm64/include/arch-eclair.h
@@ -9,15 +9,11 @@
 #
 # if (CONFIG_ARM64_VA_BITS == 42)
 #  /* VA_BITS=42, 64K_PAGE address */
-#  define MAP_KERNEL		0xfffffc0007800000
 #  define MAP_ST		0xfffffe0000000000
-#  define MAP_KERNEL_TEXT	"0xfffffc0007800000"
 #
 # elif (CONFIG_ARM64_VA_BITS == 48)
 #  /* VA_BITS=48, 64K_PAGE address */
-#  define MAP_KERNEL		0xffff000007800000
 #  define MAP_ST		0xffff800000000000
-#  define MAP_KERNEL_TEXT	"0xffff000007800000"
 #
 # else
 #
@@ -29,15 +25,11 @@
 #
 # if (CONFIG_ARM64_VA_BITS == 39)
 #  /* VA_BITS=39, 4K_PAGE address */
-#  define MAP_KERNEL		0xffffff8007800000
 #  define MAP_ST		0xffffffc000000000
-#  define MAP_KERNEL_TEXT	"0xffffff8007800000"
 #
 # elif (CONFIG_ARM64_VA_BITS == 48)
 #  /* VA_BITS=48, 4K_PAGE address */
-#  define MAP_KERNEL		0xffff000007800000
 #  define MAP_ST		0xffff800000000000
-#  define MAP_KERNEL_TEXT	"0xffff000007800000"
 #
 # else
 #
diff --git a/executer/user/arch/x86_64/arch-eclair.c b/executer/user/arch/x86_64/arch-eclair.c
index f8620a7f..2a5ba4e0 100644
--- a/executer/user/arch/x86_64/arch-eclair.c
+++ b/executer/user/arch/x86_64/arch-eclair.c
@@ -124,6 +124,16 @@ uintptr_t virt_to_phys(uintptr_t va)
 
 int arch_setup_constants(void)
 {
+	MAP_KERNEL_START = lookup_symbol("_head");
+	if (MAP_KERNEL_START == NOSYMBOL) {
+		fprintf(stderr, "error: obtaining MAP_KERNEL_START\n");
+		return 1;
+	}
+
+	/* One page extra head, see smp-x86.lds */
+	MAP_KERNEL_START -= 0x1000;
+	printf("x86 MAP_KERNEL_START 0x%lx\n", MAP_KERNEL_START);
+
 	if (read_symbol_64("linux_page_offset_base",
 				&linux_page_offset) != 0) {
 		fprintf(stderr, "error: obtaining Linux page offset\n");
diff --git a/executer/user/arch/x86_64/include/arch-eclair.h b/executer/user/arch/x86_64/include/arch-eclair.h
index cc466d15..1a0f056b 100644
--- a/executer/user/arch/x86_64/include/arch-eclair.h
+++ b/executer/user/arch/x86_64/include/arch-eclair.h
@@ -4,7 +4,6 @@
 
 #define MAP_ST_START       0xffff800000000000UL
 #define MAP_FIXED_START    0xffff860000000000UL
-#define MAP_KERNEL_START   0xFFFFFFFFFE800000UL
 extern unsigned long linux_page_offset;
 #define ARCH_CLV_SPAN	"x86_cpu_local_variables_span"
 
diff --git a/executer/user/eclair.c b/executer/user/eclair.c
index 69ece3c2..f7c752c8 100644
--- a/executer/user/eclair.c
+++ b/executer/user/eclair.c
@@ -60,6 +60,9 @@ struct thread_info {
 	uintptr_t arch_clv;
 }; /* struct thread_info */
 
+/* Virtual address where McKernel is mapped to */
+unsigned long MAP_KERNEL_START;
+
 static struct options opt;
 static volatile int f_done = 0;
 static bfd *symbfd = NULL;
@@ -83,7 +86,6 @@ uintptr_t lookup_symbol(char *name)
 			return (symtab[i]->section->vma + symtab[i]->value);
 		}
 	}
-#define NOSYMBOL ((uintptr_t)-1)
 	return NOSYMBOL;
 } /* lookup_symbol() */
 
@@ -794,10 +796,11 @@ static void command(const char *cmd, char *res, size_t res_size) {
 			rbp += sprintf(rbp, "T0;tnotrun:0");
 		}
 		else if (!strncmp(p, "qXfer:memory-map:read::", 23)) {
-			char *str =
-				"<memory-map>"
-				"<memory type=\"rom\" start=\""MAP_KERNEL_TEXT"\" length=\"0x27000\"/>"
-				"</memory-map>";
+			char str[1024];
+			sprintf(str, "<memory-map>"
+					"<memory type=\"rom\" start=\"0x%lx\" length=\"0x27000\"/>"
+					"</memory-map>", MAP_KERNEL_START);
+
 			rbp += sprintf(rbp, "l");
 			if (0)
 			rbp += print_hex(rbp, res_size, str);
diff --git a/executer/user/eclair.h b/executer/user/eclair.h
index 9542253c..8f9f24b7 100644
--- a/executer/user/eclair.h
+++ b/executer/user/eclair.h
@@ -8,6 +8,8 @@
 #include <inttypes.h>
 #include <arch-eclair.h>
 
+extern unsigned long MAP_KERNEL_START;
+
 /* common */
 int read_mem(uintptr_t va, void *buf, size_t size);
 #define NOSYMBOL ((uintptr_t)-1)