CSS: Enable booting of EL3 payloads
This patch adds support for booting EL3 payloads on CSS platforms,
for example Juno. In this scenario, the Trusted Firmware follows
its normal boot flow up to the point where it would normally pass
control to the BL31 image. At this point, it jumps to the EL3
payload entry point address instead.
Before handing over to the EL3 payload, the data SCP writes for AP
at the beginning of the Trusted SRAM is restored, i.e. we zero the
first 128 bytes and restore the SCP Boot configuration. The latter
is saved before transferring the BL30 image to SCP and is restored
just after the transfer (in BL2). The goal is to make it appear that
the EL3 payload is the first piece of software to run on the target.
The BL31 entrypoint info structure is updated to make the primary
CPU jump to the EL3 payload instead of the BL31 image.
The mailbox is populated with the EL3 payload entrypoint address,
which releases the secondary CPUs out of their holding pen (if the
SCP has powered them on). The arm_program_trusted_mailbox() function
has been exported for this purpose.
The TZC-400 configuration in BL2 is simplified: it grants secure
access only to the whole DRAM. Other security initialization is
unchanged.
This alternative boot flow is disabled by default. A new build option
EL3_PAYLOAD_BASE has been introduced to enable it and provide the EL3
payload's entry point address. The build system has been modified
such that BL31 and BL33 are not compiled and/or not put in the FIP in
this case, as those images are not used in this boot flow.
Change-Id: Id2e26fa57988bbc32323a0effd022ab42f5b5077
diff --git a/bl2/bl2_main.c b/bl2/bl2_main.c
index f8a2372..a3f016f 100644
--- a/bl2/bl2_main.c
+++ b/bl2/bl2_main.c
@@ -83,6 +83,7 @@
return e;
}
+#ifndef EL3_PAYLOAD_BASE
/*******************************************************************************
* Load the BL3-1 image.
* The bl2_to_bl31_params and bl31_ep_info params will be updated with the
@@ -190,6 +191,7 @@
return e;
}
+#endif /* EL3_PAYLOAD_BASE */
/*******************************************************************************
* The only thing to do in BL2 is to load further images and pass control to
@@ -232,6 +234,22 @@
bl2_to_bl31_params = bl2_plat_get_bl31_params();
bl31_ep_info = bl2_plat_get_bl31_ep_info();
+#ifdef EL3_PAYLOAD_BASE
+ /*
+ * In the case of an EL3 payload, we don't need to load any further
+ * images. Just update the BL31 entrypoint info structure to make BL1
+ * jump to the EL3 payload.
+ * The pointer to the memory the platform has set aside to pass
+ * information to BL3-1 in the normal boot flow is reused here, even
+ * though only a fraction of the information contained in the
+ * bl31_params_t structure makes sense in the context of EL3 payloads.
+ * This will be refined in the future.
+ */
+ VERBOSE("BL2: Populating the entrypoint info for the EL3 payload\n");
+ bl31_ep_info->pc = EL3_PAYLOAD_BASE;
+ bl31_ep_info->args.arg0 = (unsigned long) bl2_to_bl31_params;
+ bl2_plat_set_bl31_ep_info(NULL, bl31_ep_info);
+#else
e = load_bl31(bl2_to_bl31_params, bl31_ep_info);
if (e) {
ERROR("Failed to load BL3-1 (%i)\n", e);
@@ -253,6 +271,7 @@
ERROR("Failed to load BL3-3 (%i)\n", e);
plat_error_handler(e);
}
+#endif /* EL3_PAYLOAD_BASE */
/* Flush the params to be passed to memory */
bl2_plat_flush_bl31_params();