Merge branch 'contrib/github_pr_17464' into 'master'

Update the QEMU instructions for the security_features_app example (GitHub PR)

Closes IDFGH-16318 and IDFGH-16311

See merge request espressif/esp-idf!41438

Author: AdityaHPatwardhan

examples/security/security_features_app/README.md

@@ -67,6 +67,14 @@ If you want to enable the security features on a target which has been virtually
 
 The detailed instructions on how to use QEMU can be found in the [QEMU documentation](https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/tools/qemu.html).
 
+For QEMU emulation, the eFuses are emulated and are saved in a file. The default location for this file is `build/qemu_efuse.bin`. 
+
+It is possible to save the eFuses in a different location by specifying the `--efuse-file` option when running QEMU commands. This is useful as the build directory may get modified and the flashed eFuse context may get reset.
+
+```sh
+idf.py qemu --efuse-file <path_to_efuse.bin>
+```
+
 <details>
 <summary>Target specific documentation</summary>
 
@@ -121,7 +129,7 @@ Please follow below steps to enable Secure Boot V2:
 	For QEMU emulation, the above command can be updated as follows:
 
 	```
-	idf.py qemu efuse-burn-key BLOCK_KEY0 digest.bin SECURE_BOOT_DIGEST0
+	idf.py qemu --efuse-file qemu_efuse.bin efuse-burn-key BLOCK_KEY0 digest.bin SECURE_BOOT_DIGEST0
 	```
 	</details>
 
@@ -141,7 +149,7 @@ Please follow below steps to enable Secure Boot V2:
 	For QEMU emulation, the above command can be updated as follows:
 
 	```
-	idf.py qemu efuse-burn SECURE_BOOT_EN
+	idf.py qemu --efuse-file qemu_efuse.bin efuse-burn SECURE_BOOT_EN
 	```
 	</details>
 
@@ -202,7 +210,7 @@ Follow below steps to enable Flash Encryption:
 	For QEMU emulation, the above command can be updated as follows:
 
 	```
-	idf.py qemu efuse-burn-key BLOCK_KEY1 my_flash_encryption_key.bin XTS_AES_128_KEY
+	idf.py qemu --efuse-file qemu_efuse.bin efuse-burn-key BLOCK_KEY1 my_flash_encryption_key.bin XTS_AES_128_KEY
 	```
 	</details>
 
@@ -220,7 +228,7 @@ Follow below steps to enable Flash Encryption:
 	For QEMU emulation, the above command can be updated as follows:
 
 	```
-	idf.py qemu efuse-burn SPI_BOOT_CRYPT_CNT 7
+	idf.py qemu --efuse-file qemu_efuse.bin efuse-burn SPI_BOOT_CRYPT_CNT 7
 	```
 	</details>
 
@@ -306,7 +314,7 @@ We shall use the [nvs_partition_gen.py](../../../components/nvs_flash/nvs_partit
 	For QEMU emulation, the above command can be updated as follows:
 
 	```
-	idf.py qemu efuse-burn-key BLOCK_KEY2 keys/hmac_key.bin HMAC_UP
+	idf.py qemu --efuse-file qemu_efuse.bin efuse-burn-key BLOCK_KEY2 keys/hmac_key.bin HMAC_UP
 	```
 	</details>
 
@@ -371,7 +379,7 @@ The target provides an ability to disable JTAG access in the device for the soft
 	For QEMU emulation, the above command can be updated as follows:
 
     ```shell
-    idf.py qemu efuse-burn-key BLOCK_KEY3 secure_jtag_hmac_key.bin HMAC_DOWN_JTAG
+    idf.py qemu --efuse-file qemu_efuse.bin efuse-burn-key BLOCK_KEY3 secure_jtag_hmac_key.bin HMAC_DOWN_JTAG
     ```
 
 	</details>
@@ -389,7 +397,7 @@ The target provides an ability to disable JTAG access in the device for the soft
 	For QEMU emulation, the above command can be updated as follows:
 
     ```shell
-    idf.py qemu efuse-burn SOFT_DIS_JTAG 7
+    idf.py qemu --efuse-file qemu_efuse.bin efuse-burn SOFT_DIS_JTAG 7
     ```
 
 	</details>
@@ -599,20 +607,26 @@ Below are the commands that can be used to to emulate the target device on host
 
 2. Build qemu image
 
+	First create a directory to store the merged binary
+
+	```sh
+	mkdir -p build/qemu
+	```
+
     The qemu image can be built with following command
 
     ```sh
-	idf.py merge-bin --merge-args ../qemu/qemu_flash_args -o qemu/security_features_flash_image.bin
+	idf.py merge-bin -o qemu/security_features_flash_image.bin --fill-flash-size 4MB @qemu/qemu_flash_args 
     ```
 
-**NOTE: The `idf.py merge-bin` command runs with `build` as the working directory. Make sure the relative path provided are relative to the `build` directory
+	**NOTE: The `idf.py merge-bin` command runs with `build` as the working directory. Make sure the relative path provided are relative to the `build` directory**
 
 ### Run example on QEMU
 
 The following command can be used to run example on qemu
 
 ```sh
-idf.py qemu --flash-file build/qemu/security_features_flash_image.bin monitor
+idf.py qemu --efuse-file qemu_efuse.bin --flash-file build/qemu/security_features_flash_image.bin monitor
 ```
 
 The qemu session can be closed by pressing `CTRL+ ]`.