Merge pull request #1381 from antonio-nino-diaz-arm/an/kernel-boot

plat/arm: Introduce ARM_LINUX_KERNEL_AS_BL33 build option

docs/user-guide.rst

@@ -695,6 +695,15 @@ Arm development platform specific build options
    Trusted Watchdog may be disabled at build time for testing or development
    purposes.
 
+-  ``ARM_LINUX_KERNEL_AS_BL33``: The Linux kernel expects registers x0-x3 to
+   have specific values at boot. This boolean option allows the Trusted Firmware
+   to have a Linux kernel image as BL33 by preparing the registers to these
+   values before jumping to BL33. This option defaults to 0 (disabled). For now,
+   it  only supports AArch64 kernels. ``RESET_TO_BL31`` must be 1 when using it.
+   If this option is set to 1, ``ARM_PRELOADED_DTB_BASE`` must be set to the
+   location of a device tree blob (DTB) already loaded in memory.  The Linux
+   Image address must be specified using the ``PRELOADED_BL33_BASE`` option.
+
 -  ``ARM_RECOM_STATE_ID_ENC``: The PSCI1.0 specification recommends an encoding
    for the construction of composite state-ID in the power-state parameter.
    The existing PSCI clients currently do not support this encoding of
@@ -1492,41 +1501,92 @@ without a BL33 and prepare to jump to a BL33 image loaded at address
 
     make PRELOADED_BL33_BASE=0x80000000 PLAT=fvp all fip
 
-Boot of a preloaded bootwrapped kernel image on Base FVP
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Boot of a preloaded kernel image on Base FVP
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The following example uses a simplified boot flow by directly jumping from the
+TF-A to the Linux kernel, which will use a ramdisk as filesystem. This can be
+useful if both the kernel and the device tree blob (DTB) are already present in
+memory (like in FVP).
 
-The following example uses the AArch64 boot wrapper. This simplifies normal
-world booting while also making use of TF-A features. It can be obtained from
-its repository with:
+For example, if the kernel is loaded at ``0x80080000`` and the DTB is loaded at
+address ``0x82000000``, the firmware can be built like this:
 
 ::
 
-    git clone git://git.kernel.org/pub/scm/linux/kernel/git/mark/boot-wrapper-aarch64.git
+    CROSS_COMPILE=aarch64-linux-gnu-  \
+    make PLAT=fvp DEBUG=1             \
+    RESET_TO_BL31=1                   \
+    ARM_LINUX_KERNEL_AS_BL33=1        \
+    PRELOADED_BL33_BASE=0x80080000    \
+    ARM_PRELOADED_DTB_BASE=0x82000000 \
+    all fip
+
+Now, it is needed to modify the DTB so that the kernel knows the address of the
+ramdisk. The following script generates a patched DTB from the provided one,
+assuming that the ramdisk is loaded at address ``0x84000000``. Note that this
+script assumes that the user is using a ramdisk image prepared for U-Boot, like
+the ones provided by Linaro. If using a ramdisk without this header,the ``0x40``
+offset in ``INITRD_START`` has to be removed.
+
+.. code:: bash
+
+    #!/bin/bash
+
+    # Path to the input DTB
+    KERNEL_DTB=<path-to>/<fdt>
+    # Path to the output DTB
+    PATCHED_KERNEL_DTB=<path-to>/<patched-fdt>
+    # Base address of the ramdisk
+    INITRD_BASE=0x84000000
+    # Path to the ramdisk
+    INITRD=<path-to>/<ramdisk.img>
 
-After compiling it, an ELF file is generated. It can be loaded with the
-following command:
+    # Skip uboot header (64 bytes)
+    INITRD_START=$(printf "0x%x" $((${INITRD_BASE} + 0x40)) )
+    INITRD_SIZE=$(stat -Lc %s ${INITRD})
+    INITRD_END=$(printf "0x%x" $((${INITRD_BASE} + ${INITRD_SIZE})) )
+
+    CHOSEN_NODE=$(echo                                        \
+    "/ {                                                      \
+            chosen {                                          \
+                    linux,initrd-start = <${INITRD_START}>;   \
+                    linux,initrd-end = <${INITRD_END}>;       \
+            };                                                \
+    };")
+
+    echo $(dtc -O dts -I dtb ${KERNEL_DTB}) ${CHOSEN_NODE} |  \
+            dtc -O dtb -o ${PATCHED_KERNEL_DTB} -
+
+And the FVP binary can be run with the following command:
 
 ::
 
     <path-to>/FVP_Base_AEMv8A-AEMv8A                            \
-        -C bp.secureflashloader.fname=bl1.bin     \
-        -C bp.flashloader0.fname=fip.bin          \
-        -a cluster0.cpu0=<bootwrapped-kernel.elf> \
-        --start cluster0.cpu0=0x0
-
-The ``-a cluster0.cpu0=<bootwrapped-kernel.elf>`` option loads the ELF file. It
-also sets the PC register to the ELF entry point address, which is not the
-desired behaviour, so the ``--start cluster0.cpu0=0x0`` option forces the PC back
-to 0x0 (the BL1 entry point address) on CPU #0. The ``PRELOADED_BL33_BASE`` define
-used when compiling the FIP must match the ELF entry point.
-
-Boot of a preloaded bootwrapped kernel image on Juno
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The procedure to obtain and compile the boot wrapper is very similar to the case
-of the FVP. The execution must be stopped at the end of bl2\_main(), and the
-loading method explained above in the EL3 payload boot flow section may be used
-to load the ELF file over JTAG on Juno.
+    -C pctl.startup=0.0.0.0                                     \
+    -C bp.secure_memory=1                                       \
+    -C cluster0.NUM_CORES=4                                     \
+    -C cluster1.NUM_CORES=4                                     \
+    -C cache_state_modelled=1                                   \
+    -C cluster0.cpu0.RVBAR=0x04020000                           \
+    -C cluster0.cpu1.RVBAR=0x04020000                           \
+    -C cluster0.cpu2.RVBAR=0x04020000                           \
+    -C cluster0.cpu3.RVBAR=0x04020000                           \
+    -C cluster1.cpu0.RVBAR=0x04020000                           \
+    -C cluster1.cpu1.RVBAR=0x04020000                           \
+    -C cluster1.cpu2.RVBAR=0x04020000                           \
+    -C cluster1.cpu3.RVBAR=0x04020000                           \
+    --data cluster0.cpu0="<path-to>/bl31.bin"@0x04020000        \
+    --data cluster0.cpu0="<path-to>/<patched-fdt>"@0x82000000   \
+    --data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
+    --data cluster0.cpu0="<path-to>/<ramdisk.img>"@0x84000000
+
+Boot of a preloaded kernel image on Juno
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The Trusted Firmware must be compiled in a similar way as for FVP explained
+above. The process to load binaries to memory is the one explained in
+`Booting an EL3 payload on Juno`_.
 
 Running the software on FVP
 ---------------------------

plat/arm/common/arm_bl31_setup.c

@@ -81,7 +81,7 @@ void arm_bl31_early_platform_setup(bl31_params_t *from_bl2, uintptr_t soc_fw_con
 	assert(from_bl2 == NULL);
 	assert(plat_params_from_bl2 == NULL);
 
-#ifdef BL32_BASE
+# ifdef BL32_BASE
 	/* Populate entry point information for BL32 */
 	SET_PARAM_HEAD(&bl32_image_ep_info,
 				PARAM_EP,
@@ -90,7 +90,7 @@ void arm_bl31_early_platform_setup(bl31_params_t *from_bl2, uintptr_t soc_fw_con
 	SET_SECURITY_STATE(bl32_image_ep_info.h.attr, SECURE);
 	bl32_image_ep_info.pc = BL32_BASE;
 	bl32_image_ep_info.spsr = arm_get_spsr_for_bl32_entry();
-#endif /* BL32_BASE */
+# endif /* BL32_BASE */
 
 	/* Populate entry point information for BL33 */
 	SET_PARAM_HEAD(&bl33_image_ep_info,
@@ -106,6 +106,19 @@ void arm_bl31_early_platform_setup(bl31_params_t *from_bl2, uintptr_t soc_fw_con
 	bl33_image_ep_info.spsr = arm_get_spsr_for_bl33_entry();
 	SET_SECURITY_STATE(bl33_image_ep_info.h.attr, NON_SECURE);
 
+# if ARM_LINUX_KERNEL_AS_BL33
+	/*
+	 * According to the file ``Documentation/arm64/booting.txt`` of the
+	 * Linux kernel tree, Linux expects the physical address of the device
+	 * tree blob (DTB) in x0, while x1-x3 are reserved for future use and
+	 * must be 0.
+	 */
+	bl33_image_ep_info.args.arg0 = (u_register_t)ARM_PRELOADED_DTB_BASE;
+	bl33_image_ep_info.args.arg1 = 0U;
+	bl33_image_ep_info.args.arg2 = 0U;
+	bl33_image_ep_info.args.arg3 = 0U;
+# endif
+
 #else /* RESET_TO_BL31 */
 
 	/*

plat/arm/common/arm_common.mk

@@ -80,6 +80,27 @@ ARM_XLAT_TABLES_LIB_V1		:=	0
 $(eval $(call assert_boolean,ARM_XLAT_TABLES_LIB_V1))
 $(eval $(call add_define,ARM_XLAT_TABLES_LIB_V1))
 
+# Don't have the Linux kernel as a BL33 image by default
+ARM_LINUX_KERNEL_AS_BL33	:=	0
+$(eval $(call assert_boolean,ARM_LINUX_KERNEL_AS_BL33))
+$(eval $(call add_define,ARM_LINUX_KERNEL_AS_BL33))
+
+ifeq (${ARM_LINUX_KERNEL_AS_BL33},1)
+  ifneq (${ARCH},aarch64)
+    $(error "ARM_LINUX_KERNEL_AS_BL33 is only available in AArch64.")
+  endif
+  ifneq (${RESET_TO_BL31},1)
+    $(error "ARM_LINUX_KERNEL_AS_BL33 is only available if RESET_TO_BL31=1.")
+  endif
+  ifndef PRELOADED_BL33_BASE
+    $(error "PRELOADED_BL33_BASE must be set if ARM_LINUX_KERNEL_AS_BL33 is used.")
+  endif
+  ifndef ARM_PRELOADED_DTB_BASE
+    $(error "ARM_PRELOADED_DTB_BASE must be set if ARM_LINUX_KERNEL_AS_BL33 is used.")
+  endif
+  $(eval $(call add_define,ARM_PRELOADED_DTB_BASE))
+endif
+
 # Use an implementation of SHA-256 with a smaller memory footprint but reduced
 # speed.
 $(eval $(call add_define,MBEDTLS_SHA256_SMALLER))