diff --git a/libr/core/cconfig.c b/libr/core/cconfig.c
index 707b6a8d19b2c..3ecd70567c356 100644
--- a/libr/core/cconfig.c
+++ b/libr/core/cconfig.c
@@ -1826,6 +1826,7 @@ R_API int r_core_config_init(RCore *core) {
 	SETPREF("asm.hints", "false", "Show hints for magic numbers in disasm");
 	SETPREF("asm.marks", "true", "Show marks before the disassembly");
 	SETPREF("asm.cmtrefs", "false", "Show flag and comments from refs in disasm");
+	SETPREF("asm.cmtpatch", "false", "Show patch comments in disasm");
 	SETCB("bin.strpurge", "false", &cb_strpurge, "Try to purge false positive strings");
 	SETPREF("bin.libs", "false", "Try to load libraries after loading main binary");
 	SETCB("bin.strfilter", "", &cb_strfilter, "Filter strings (?:help, a:scii, e:mail, p:ath, u:rl, 8:utf8)");
diff --git a/libr/core/core.c b/libr/core/core.c
index 9d0c1a05b9685..57d24e227596e 100644
--- a/libr/core/core.c
+++ b/libr/core/core.c
@@ -222,9 +222,36 @@ R_API RCore *r_core_cast(void *p) {
 	return (RCore*)p;
 }
 
-static int core_cmd_callback (void *user, const char *cmd) {
+static void core_post_write_callback(void *user, ut64 maddr, ut8 *bytes, int cnt) {
 	RCore *core = (RCore *)user;
-	return r_core_cmd0 (core, cmd);
+
+	if (!r_config_get_i (core->config, "asm.cmtpatch")) {
+		return;
+	}
+
+	char *hex_pairs = r_hex_bin2strdup (bytes, cnt);
+	if (!hex_pairs) {
+		eprintf ("core_post_write_callback: Cannot obtain hex pairs\n");
+		return;
+	}
+
+	char *comment = r_str_newf ("patch: %d bytes (%s)", cnt, hex_pairs);
+	free (hex_pairs);
+	if (!comment) {
+		eprintf ("core_post_write_callback: Cannot create comment\n");
+		return;
+	}
+
+	ut64 vaddr = r_io_section_maddr_to_vaddr (core->io, maddr);
+	vaddr = (vaddr == UT64_MAX) ? maddr : vaddr;
+
+	r_meta_add (core->anal, R_META_TYPE_COMMENT, vaddr, vaddr, comment);
+	free (comment);
+}
+
+static int core_cmd_callback (void *user, const char *cmd) {
+    RCore *core = (RCore *)user;
+    return r_core_cmd0 (core, cmd);
 }
 
 static char *core_cmdstr_callback (void *user, const char *cmd) {
@@ -1509,6 +1536,7 @@ R_API int r_core_init(RCore *core) {
 	core->io->user = (void *)core;
 	core->io->cb_core_cmd = core_cmd_callback;
 	core->io->cb_core_cmdstr = core_cmdstr_callback;
+	core->io->cb_core_post_write = core_post_write_callback;
 	core->sign = r_sign_new ();
 	core->search = r_search_new (R_SEARCH_KEYWORD);
 	r_io_undo_enable (core->io, 1, 0); // TODO: configurable via eval
diff --git a/libr/include/r_io.h b/libr/include/r_io.h
index 682cb8f8fe33a..78aca2c467183 100644
--- a/libr/include/r_io.h
+++ b/libr/include/r_io.h
@@ -161,6 +161,8 @@ typedef struct r_io_t {
 	void *user;
 	int (*cb_core_cmd)(void *user, const char *str);
 	char* (*cb_core_cmdstr)(void *user, const char *str);
+	/* Used for comment generation */
+	void (*cb_core_post_write)(void *user, ut64 maddr, ut8 *orig_bytes, int orig_len);
 	struct r_io_plugin_t *plugin_default;
 } RIO;
 
diff --git a/libr/io/io.c b/libr/io/io.c
index 951e856df937a..4a1fffa8e8d7e 100644
--- a/libr/io/io.c
+++ b/libr/io/io.c
@@ -576,6 +576,15 @@ R_API ut64 r_io_read_i(RIO *io, ut64 addr, int sz) {
 	return ret;
 }
 
+/* Same as r_io_read_at, but not consume bytes */
+R_API int r_io_peek_at(RIO *io, const ut64 addr, ut8 *buf, const int sz) {
+	int ret = -1;
+	r_io_seek (io, addr, R_IO_SEEK_SET);
+	ret = r_io_read (io, buf, sz);
+	r_io_seek (io, addr, R_IO_SEEK_SET);
+	return ret;
+}
+
 // TODO. this is a physical resize
 R_API bool r_io_resize(RIO *io, ut64 newsize) {
 	if (io->plugin) {
@@ -649,20 +658,34 @@ R_API int r_io_set_write_mask(RIO *io, const ut8 *buf, int len) {
 }
 
 R_API int r_io_write(RIO *io, const ut8 *buf, int len) {
-	int i, ret = -1;
-	ut8 *data = NULL;
+	ut64 maddr = io->off;
+	int i, ret = -1, orig_len = 0;
+	ut8 *data = NULL, *orig_bytes = NULL;
 
 	/* check section permissions */
 	if (io->enforce_rwx & R_IO_WRITE) {
 		if (!(r_io_section_get_rwx (io, io->off) & R_IO_WRITE)) {
-			return -1;
+			ret = -1;
+			goto cleanup;
 		}
 	}
 
+	orig_bytes = malloc (len);
+	if (!orig_bytes) {
+		eprintf ("Cannot allocate %d bytes", len);
+		ret = -1;
+		goto cleanup;
+	}
+
+	orig_len = r_io_peek_at (io, io->off, orig_bytes, len);
+
 	if (io->cached) {
 		ret = r_io_cache_write (io, io->off, buf, len);
 		if (ret == len) {
-			return len;
+			if (orig_len > 0 && io->cb_core_post_write) {
+				io->cb_core_post_write (io->user, maddr, orig_bytes, orig_len);
+			}
+			goto cleanup;
 		}
 		if (ret > 0) {
 			len -= ret;
@@ -677,12 +700,11 @@ R_API int r_io_write(RIO *io, const ut8 *buf, int len) {
 		data = (len > 0)? malloc (len): NULL;
 		if (!data) {
 			eprintf ("malloc failed in write_mask_fd");
-			return -1;
+			ret = -1;
+			goto cleanup;
 		}
 		// memset (data, io->Oxff, len);
-		r_io_seek (io, io->off, R_IO_SEEK_SET);
-		r_io_read (io, data, len);
-		r_io_seek (io, io->off, R_IO_SEEK_SET);
+		r_io_peek_at (io, io->off, data, len);
 		for (i = 0; i < len; i++) {
 			data[i] = buf[i] &
 				io->write_mask_buf[i % io->write_mask_len];
@@ -733,7 +755,15 @@ R_API int r_io_write(RIO *io, const ut8 *buf, int len) {
 			io->off += ret;
 		}
 	}
+
+	if (ret > 0 && orig_len > 0 && io->cb_core_post_write) {
+		io->cb_core_post_write (io->user, maddr, orig_bytes, orig_len);
+	}
+
+cleanup:
 	free (data);
+	free (orig_bytes);
+
 	return ret;
 }