diff --git a/src/ftracetool.c b/src/ftracetool.c
index d29a29c..1a7dbd1 100644
--- a/src/ftracetool.c
+++ b/src/ftracetool.c
@@ -17,6 +17,71 @@
 
 #define CLEANUP(f) __attribute__((cleanup(f)))
 
+struct ftt_mapping
+{
+    char *key;
+    char *value;
+    struct ftt_mapping *next;
+};
+
+static struct ftt_mapping *gs_mappings;
+
+static struct ftt_mapping *parse_mapping(const char *const raw_str)
+{
+    struct ftt_mapping *mapping = NULL;
+    char *const s = strchr(raw_str, '=');
+    if (s)
+    {
+        const size_t len = strlen(raw_str);
+        const size_t key_len = s - raw_str + 1; // including 0-terminator
+        const size_t value_len = len - key_len + 1;
+        if (key_len == 0 || value_len == 0)
+        {
+            return NULL;
+        }
+        mapping = calloc(1, sizeof(*mapping));
+        if (!mapping)
+        {
+            return NULL;
+        }
+        mapping->key = calloc(key_len, sizeof(char));
+        mapping->value = calloc(value_len, sizeof(char));
+        if (!mapping->key || !mapping->value)
+        {
+            free(mapping->key);
+            free(mapping->value);
+            free(mapping);
+            return NULL;
+        }
+
+        memcpy(mapping->key, raw_str, key_len - 1);
+        memcpy(mapping->value, s + 1, value_len - 1);
+    }
+
+    return mapping;
+}
+
+static int embed_mappings(sexp ctx)
+{
+    sexp_gc_var2(s_mapping, mapping_name);
+    sexp_gc_preserve2(ctx, mapping_name, s_mapping);
+    mapping_name = sexp_intern(ctx, "*ftt-mappings*", -1);
+    s_mapping = SEXP_NULL;
+    for (struct ftt_mapping const *mapping = gs_mappings; mapping;
+         mapping = mapping->next)
+    {
+        sexp_gc_var3(key, value, cell);
+        sexp_gc_preserve3(ctx, key, value, cell);
+        key = sexp_c_string(ctx, mapping->key, -1);
+        value = sexp_c_string(ctx, mapping->value, -1);
+        cell = sexp_cons(ctx, key, value);
+        s_mapping = sexp_cons(ctx, cell, s_mapping);
+        sexp_gc_release3(ctx);
+    }
+    sexp_env_define(ctx, sexp_context_env(ctx), mapping_name, s_mapping);
+    sexp_gc_release2(ctx);
+}
+
 static void show_version()
 {
     printf("ftracetool v%s\n", VERSION_STRING);
@@ -25,6 +90,7 @@ static void show_version()
 static void show_usage()
 {
     printf("ftracetool v%s\n \
+  -m key=value Set mapping\n \
   -e Execute script\n \
   -s Show symbols in elf file\n \
   -v Show version\n \
@@ -248,6 +314,7 @@ static int do_execute_script(const char *const filename)
     ctx = sexp_make_eval_context(NULL, NULL, NULL, 0, 0);
     sexp_load_standard_env(ctx, NULL, SEXP_SEVEN);
     sexp_load_standard_ports(ctx, NULL, stdin, stdout, stderr, 1);
+    embed_mappings(ctx);
 
     sexp_gc_var1(filename_obj);
 
@@ -279,7 +346,7 @@ int main(int argc, char **argv)
     char filename[NAME_MAX] = {};
     bool execute_script = false;
     bool show_symbols_in_file = false;
-    while ((opt = getopt(argc, argv, "vhs:e:")) != -1)
+    while ((opt = getopt(argc, argv, "vhs:e:m:")) != -1)
     {
         switch (opt)
         {
@@ -305,6 +372,16 @@ int main(int argc, char **argv)
             show_symbols_in_file = true;
             break;
         }
+        case 'm':
+        {
+            struct ftt_mapping *const mapping = parse_mapping(optarg);
+            if (mapping)
+            {
+                mapping->next = gs_mappings;
+                gs_mappings = mapping;
+            }
+            break;
+        }
         default:
         {
             show_usage();