aarch32: use lr as bl32 boot argument on aarch32 only systems

Add 'lr_svc' as a boot parameter in AArch32 bl1. This is used by Optee
and Trusty to get the non-secure entry point on AArch32 platforms.

This change is not ported in AArch64 mode where the BL31, not BL32,
is in charge of booting the non secure image (BL33).
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>

bl1/aarch32/bl1_exceptions.S

@@ -73,6 +73,11 @@ debug_loop:
 	ldr	r1, [r8, #(ENTRY_POINT_INFO_PC_OFFSET + 4)]
 	msr	spsr, r1
 
+	/* Some BL32 stages expect lr_svc to provide the BL33 entry address */
+	cps	#MODE32_svc
+	ldr	lr, [r8, #ENTRY_POINT_INFO_LR_SVC_OFFSET]
+	cps	#MODE32_mon
+
 	add	r8, r8, #ENTRY_POINT_INFO_ARGS_OFFSET
 	ldm	r8, {r0, r1, r2, r3}
 	eret

include/common/ep_info.h

@@ -20,7 +20,8 @@
  ******************************************************************************/
 #define ENTRY_POINT_INFO_PC_OFFSET	U(0x08)
 #ifdef AARCH32
-#define ENTRY_POINT_INFO_ARGS_OFFSET	U(0x10)
+#define ENTRY_POINT_INFO_LR_SVC_OFFSET	U(0x10)
+#define ENTRY_POINT_INFO_ARGS_OFFSET	U(0x14)
 #else
 #define ENTRY_POINT_INFO_ARGS_OFFSET	U(0x18)
 #endif
@@ -93,6 +94,7 @@ typedef struct entry_point_info {
 	uintptr_t pc;
 	uint32_t spsr;
 #ifdef AARCH32
+	uintptr_t lr_svc;
 	aapcs32_params_t args;
 #else
 	aapcs64_params_t args;
@@ -108,6 +110,12 @@ CASSERT(ENTRY_POINT_INFO_PC_OFFSET ==
 		__builtin_offsetof(entry_point_info_t, pc), \
 		assert_BL31_pc_offset_mismatch);
 
+#ifdef AARCH32
+CASSERT(ENTRY_POINT_INFO_LR_SVC_OFFSET ==
+		__builtin_offsetof(entry_point_info_t, lr_svc),
+		assert_entrypoint_lr_offset_error);
+#endif
+
 CASSERT(ENTRY_POINT_INFO_ARGS_OFFSET == \
 		__builtin_offsetof(entry_point_info_t, args), \
 		assert_BL31_args_offset_mismatch);