Remove all non-configurable dead loops

Added a new platform porting function plat_panic_handler, to allow
platforms to handle unexpected error situations. It must be
implemented in assembly as it may be called before the C environment
is initialized. A default implementation is provided, which simply
spins.

Corrected all dead loops in generic code to call this function
instead. This includes the dead loop that occurs at the end of the
call to panic().

All unnecesary wfis from bl32/tsp/aarch64/tsp_exceptions.S have
been removed.

Change-Id: I67cb85f6112fa8e77bd62f5718efcef4173d8134

12 files changed, 92 insertions, 59 deletions

diff --git a/bl2/aarch64/bl2_entrypoint.S b/bl2/aarch64/bl2_entrypoint.S
index 75eb02a9..476efe85 100644
--- a/bl2/aarch64/bl2_entrypoint.S
+++ b/bl2/aarch64/bl2_entrypoint.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -43,8 +43,8 @@ func bl2_entrypoint
 	 * available to BL2 for future use.
 	 * x0 is not currently used.
 	 * ---------------------------------------------
- 	 */
- 	mov	x20, x1
+	 */
+	mov	x20, x1
 
 	/* ---------------------------------------------
 	 * Set the exception vector to something sane.
@@ -126,6 +126,11 @@ func bl2_entrypoint
 	 * ---------------------------------------------
 	 */
 	bl	bl2_main
-_panic:
-	b	_panic
+
+	/* ---------------------------------------------
+	 * Should never reach this point.
+	 * ---------------------------------------------
+	 */
+	bl	plat_panic_handler
+
 endfunc bl2_entrypoint
diff --git a/bl2u/aarch64/bl2u_entrypoint.S b/bl2u/aarch64/bl2u_entrypoint.S
index c9aad81f..ef3db926 100644
--- a/bl2u/aarch64/bl2u_entrypoint.S
+++ b/bl2u/aarch64/bl2u_entrypoint.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -122,6 +122,10 @@ func bl2u_entrypoint
 	 */
 	bl	bl2u_main
 
-_panic:
-	b	_panic
+	/* ---------------------------------------------
+	 * Should never reach this point.
+	 * ---------------------------------------------
+	 */
+	bl	plat_panic_handler
+
 endfunc bl2u_entrypoint
diff --git a/bl31/aarch64/crash_reporting.S b/bl31/aarch64/crash_reporting.S
index 1d1e60d8..ff915728 100644
--- a/bl31/aarch64/crash_reporting.S
+++ b/bl31/aarch64/crash_reporting.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -351,17 +351,17 @@ func do_crash_reporting
 	plat_print_interconnect_regs
 
 	/* Done reporting */
-	b	crash_panic
+	bl	plat_panic_handler
 endfunc do_crash_reporting
 
 #else	/* CRASH_REPORTING */
 func report_unhandled_exception
 report_unhandled_interrupt:
-	b	crash_panic
+	bl	plat_panic_handler
 endfunc report_unhandled_exception
 #endif	/* CRASH_REPORTING */
 
 
 func crash_panic
-	b	crash_panic
-endfunc crash_panic
\ No newline at end of file
+	bl	plat_panic_handler
+endfunc crash_panic
diff --git a/bl32/tsp/aarch64/tsp_entrypoint.S b/bl32/tsp/aarch64/tsp_entrypoint.S
index 531ab9bf..453d2c14 100644
--- a/bl32/tsp/aarch64/tsp_entrypoint.S
+++ b/bl32/tsp/aarch64/tsp_entrypoint.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -391,7 +391,7 @@ tsp_sel1_intr_return:
 
 	/* Should never reach here */
 tsp_sel1_int_entry_panic:
-	b	tsp_sel1_int_entry_panic
+	bl	plat_panic_handler
 endfunc tsp_sel1_intr_entry
 
 	/*---------------------------------------------
@@ -407,8 +407,9 @@ endfunc tsp_sel1_intr_entry
 func tsp_cpu_resume_entry
 	bl	tsp_cpu_resume_main
 	restore_args_call_smc
-tsp_cpu_resume_panic:
-	b	tsp_cpu_resume_panic
+
+	/* Should never reach here */
+	bl	plat_panic_handler
 endfunc tsp_cpu_resume_entry
 
 	/*---------------------------------------------
@@ -419,8 +420,9 @@ endfunc tsp_cpu_resume_entry
 func tsp_fast_smc_entry
 	bl	tsp_smc_handler
 	restore_args_call_smc
-tsp_fast_smc_entry_panic:
-	b	tsp_fast_smc_entry_panic
+
+	/* Should never reach here */
+	bl	plat_panic_handler
 endfunc tsp_fast_smc_entry
 
 	/*---------------------------------------------
@@ -435,6 +437,7 @@ func tsp_std_smc_entry
 	bl	tsp_smc_handler
 	msr	daifset, #DAIF_FIQ_BIT | DAIF_IRQ_BIT
 	restore_args_call_smc
-tsp_std_smc_entry_panic:
-	b	tsp_std_smc_entry_panic
+
+	/* Should never reach here */
+	bl	plat_panic_handler
 endfunc tsp_std_smc_entry
diff --git a/bl32/tsp/aarch64/tsp_exceptions.S b/bl32/tsp/aarch64/tsp_exceptions.S
index d5e089f6..edcfb718 100644
--- a/bl32/tsp/aarch64/tsp_exceptions.S
+++ b/bl32/tsp/aarch64/tsp_exceptions.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -108,24 +108,23 @@ tsp_exceptions:
 	 * -----------------------------------------------------
 	 */
 sync_exception_sp_el0:
-	wfi
-	b	sync_exception_sp_el0
+	bl	plat_panic_handler
 	check_vector_size sync_exception_sp_el0
 
 	.align	7
 
 irq_sp_el0:
-	b	irq_sp_el0
+	bl	plat_panic_handler
 	check_vector_size irq_sp_el0
 
 	.align	7
 fiq_sp_el0:
-	b	fiq_sp_el0
+	bl	plat_panic_handler
 	check_vector_size fiq_sp_el0
 
 	.align	7
 serror_sp_el0:
-	b	serror_sp_el0
+	bl	plat_panic_handler
 	check_vector_size serror_sp_el0
 
 
@@ -136,8 +135,7 @@ serror_sp_el0:
 	 */
 	.align	7
 sync_exception_sp_elx:
-	wfi
-	b	sync_exception_sp_elx
+	bl	plat_panic_handler
 	check_vector_size sync_exception_sp_elx
 
 	.align	7
@@ -152,7 +150,7 @@ fiq_sp_elx:
 
 	.align	7
 serror_sp_elx:
-	b	serror_sp_elx
+	bl	plat_panic_handler
 	check_vector_size serror_sp_elx
 
 
@@ -163,23 +161,22 @@ serror_sp_elx:
 	 */
 	.align	7
 sync_exception_aarch64:
-	wfi
-	b	sync_exception_aarch64
+	bl	plat_panic_handler
 	check_vector_size sync_exception_aarch64
 
 	.align	7
 irq_aarch64:
-	b	irq_aarch64
+	bl	plat_panic_handler
 	check_vector_size irq_aarch64
 
 	.align	7
 fiq_aarch64:
-	b	fiq_aarch64
+	bl	plat_panic_handler
 	check_vector_size fiq_aarch64
 
 	.align	7
 serror_aarch64:
-	b	serror_aarch64
+	bl	plat_panic_handler
 	check_vector_size serror_aarch64
 
 
@@ -190,22 +187,21 @@ serror_aarch64:
 	 */
 	.align	7
 sync_exception_aarch32:
-	wfi
-	b	sync_exception_aarch32
+	bl	plat_panic_handler
 	check_vector_size sync_exception_aarch32
 
 	.align	7
 irq_aarch32:
-	b	irq_aarch32
+	bl	plat_panic_handler
 	check_vector_size irq_aarch32
 
 	.align	7
 fiq_aarch32:
-	b	fiq_aarch32
+	bl	plat_panic_handler
 	check_vector_size fiq_aarch32
 
 	.align	7
 serror_aarch32:
-	b	serror_aarch32
+	bl	plat_panic_handler
 	check_vector_size serror_aarch32
 	.align	7
diff --git a/common/aarch64/debug.S b/common/aarch64/debug.S
index b3caafb9..d3538792 100644
--- a/common/aarch64/debug.S
+++ b/common/aarch64/debug.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -120,7 +120,7 @@ endfunc asm_print_str
 /*
  * This function prints a hexadecimal number in x4.
  * In: x4 = the hexadecimal to print.
- * Clobber: x30, x0, x5, x1, x2, x3
+ * Clobber: x30, x0 - x3, x5
  */
 func asm_print_hex
 	mov	x3, x30
@@ -178,7 +178,7 @@ el3_panic:
 	mov	x6, x30
 	bl	plat_crash_console_init
 	/* Check if the console is initialized */
-	cbz	x0, _panic_loop
+	cbz	x0, _panic_handler
 	/* The console is initialized */
 	adr	x4, panic_msg
 	bl	asm_print_str
@@ -186,7 +186,10 @@ el3_panic:
 	/* The panic location is lr -4 */
 	sub	x4, x4, #4
 	bl	asm_print_hex
-_panic_loop:
-	b	_panic_loop
-endfunc do_panic
 
+_panic_handler:
+	/* Pass to plat_panic_handler the address from where el3_panic was
+	 * called, not the address of the call from el3_panic. */
+	mov	x30,x6
+	b	plat_panic_handler
+endfunc do_panic
diff --git a/docs/porting-guide.md b/docs/porting-guide.md
index 741ee207..bd1b4489 100644
--- a/docs/porting-guide.md
+++ b/docs/porting-guide.md
@@ -783,6 +783,20 @@ Possible errors reported by the generic code are:
 
 The default implementation simply spins.
 
+### Function : plat_panic_handler()
+
+    Argument : void
+    Return   : void
+
+This API is called when the generic code encounters an unexpected error
+situation from which it cannot recover. This function must not return,
+and must be implemented in assembly because it may be called before the C
+environment is initialized.
+
+Note: The address from where it was called is stored in x30 (Link Register).
+
+The default implementation simply spins.
+
 
 3.  Modifications specific to a Boot Loader stage
 -------------------------------------------------
diff --git a/include/common/el3_common_macros.S b/include/common/el3_common_macros.S
index 32df7d76..0cd85c34 100644
--- a/include/common/el3_common_macros.S
+++ b/include/common/el3_common_macros.S
@@ -196,8 +196,7 @@
 		/* This is a cold boot on a secondary CPU */
 		bl	plat_secondary_cold_boot_setup
 		/* plat_secondary_cold_boot_setup() is not supposed to return */
-	secondary_panic:
-		b	secondary_panic
+		bl	el3_panic
 
 	do_primary_cold_boot:
 	.endif /* _secondary_cold_boot */
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index f37a80f3..5c61f381 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -83,6 +83,7 @@ void plat_report_exception(unsigned long);
 int plat_crash_console_init(void);
 int plat_crash_console_putc(int c);
 void plat_error_handler(int err) __dead2;
+void plat_panic_handler(void) __dead2;
 
 /*******************************************************************************
  * Mandatory BL1 functions
diff --git a/plat/arm/board/fvp/aarch64/fvp_helpers.S b/plat/arm/board/fvp/aarch64/fvp_helpers.S
index fe7358f6..884fee82 100644
--- a/plat/arm/board/fvp/aarch64/fvp_helpers.S
+++ b/plat/arm/board/fvp/aarch64/fvp_helpers.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -111,8 +111,7 @@ secondary_cold_boot_wait:
 	 */
 	dsb	sy
 	wfi
-cb_panic:
-	b	cb_panic
+	bl	plat_panic_handler
 #else
 	mov_imm	x0, PLAT_ARM_TRUSTED_MAILBOX_BASE
 
@@ -174,7 +173,7 @@ warm_reset:
 	 */
 	mov_imm	x0, PLAT_ARM_TRUSTED_MAILBOX_BASE
 	ldr	x0, [x0]
-	cbz	x0, _panic
+	cbz	x0, _panic_handler
 	ret
 
 	/* ---------------------------------------------------------------------
@@ -182,8 +181,8 @@ warm_reset:
 	 * is empty. This should never happen!
 	 * ---------------------------------------------------------------------
 	 */
-_panic:
-	b	_panic
+_panic_handler:
+	bl	plat_panic_handler
 endfunc plat_get_my_entrypoint
 
 	/* -----------------------------------------------------
diff --git a/plat/arm/board/juno/aarch64/juno_helpers.S b/plat/arm/board/juno/aarch64/juno_helpers.S
index 1931535e..377b0cb3 100644
--- a/plat/arm/board/juno/aarch64/juno_helpers.S
+++ b/plat/arm/board/juno/aarch64/juno_helpers.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -201,8 +201,7 @@ func plat_reset_handler
 	JUMP_TO_HANDLER_IF_JUNO_R(2)
 
 	/* Board revision is not supported */
-not_supported:
-	b	not_supported
+	bl	plat_panic_handler
 
 endfunc plat_reset_handler
 
diff --git a/plat/common/aarch64/platform_helpers.S b/plat/common/aarch64/platform_helpers.S
index 29f01ce9..08638303 100644
--- a/plat/common/aarch64/platform_helpers.S
+++ b/plat/common/aarch64/platform_helpers.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -39,6 +39,7 @@
 	.weak	plat_disable_acp
 	.weak	bl1_plat_prepare_exit
 	.weak	plat_error_handler
+	.weak	plat_panic_handler
 
 #if !ENABLE_PLAT_COMPAT
 	.globl	platform_get_core_pos
@@ -131,3 +132,12 @@ endfunc bl1_plat_prepare_exit
 func plat_error_handler
 	b	plat_error_handler
 endfunc plat_error_handler
+
+	/* -----------------------------------------------------
+	 * void plat_panic_handler(void) __dead2;
+	 * Endless loop by default.
+	 * -----------------------------------------------------
+	 */
+func plat_panic_handler
+	b	plat_panic_handler
+endfunc plat_panic_handler