Add sample crash console functions

Platforms that wish to use the sample functions have to add the file to
their Makefile. It is not included by default.

Change-Id: I713617bb58dc218967199248f68da86241d7ec40
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

docs/porting-guide.rst

@@ -2554,8 +2554,13 @@ NOTE: This section assumes that your platform is enabling the MULTI_CONSOLE_API
 flag in its platform.mk. Not using this flag is deprecated for new platforms.
 
 BL31 implements a crash reporting mechanism which prints the various registers
-of the CPU to enable quick crash analysis and debugging. By default, the
-definitions in ``plat/common/aarch64/platform\_helpers.S`` will cause the crash
+of the CPU to enable quick crash analysis and debugging. This mechanism relies
+on the platform implementating ``plat_crash_console_init``,
+``plat_crash_console_putc`` and ``plat_crash_console_flush``.
+
+The file ``plat/common/aarch64/crash_console_helpers.S`` contains sample
+implementation of all of them. Platforms may include this file to their
+makefiles in order to benefit from them. By default, they will cause the crash
 output to be routed over the normal console infrastructure and get printed on
 consoles configured to output in crash state. ``console_set_scope()`` can be
 used to control whether a console is used for crash output.
@@ -2565,8 +2570,12 @@ normal boot console can be set up), platforms may want to control crash output
 more explicitly. For these, the following functions can be overridden by
 platform code. They are executed outside of a C environment and without a stack.
 
-Function : plat\_crash\_console\_init
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+If this behaviour is not desirable, the platform may implement functions that
+redirect the prints to the console driver (``console_xxx_core_init``, etc). Most
+platforms (including Arm platforms) do this and they can be used as an example.
+
+Function : plat\_crash\_console\_init [mandatory]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
 
@@ -2577,9 +2586,10 @@ This API is used by the crash reporting mechanism to initialize the crash
 console. It must only use the general purpose registers x0 through x7 to do the
 initialization and returns 1 on success.
 
-If you are trying to debug crashes before the console driver would normally get
-registered, you can use this to register a driver from assembly with hardcoded
-parameters. For example, you could register the 16550 driver like this:
+When using the sample implementation, if you are trying to debug crashes before
+the console driver would normally get registered, you can use this to register a
+driver from assembly with hardcoded parameters. For example, you could register
+the 16550 driver like this:
 
 ::
 
@@ -2595,11 +2605,11 @@ parameters. For example, you could register the 16550 driver like this:
         b       console_16550_register  /* tail call, returns 1 on success */
     endfunc plat_crash_console_init
 
-If you're trying to debug crashes in BL1, you can call the console_xxx_core_init
-function exported by some console drivers from here.
+If you're trying to debug crashes in BL1, you can call the
+``console_xxx_core_init`` function exported by some console drivers from here.
 
-Function : plat\_crash\_console\_putc
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Function : plat\_crash\_console\_putc [mandatory]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
 
@@ -2612,13 +2622,13 @@ x2 to do its work. The parameter and the return value are in general purpose
 register x0.
 
 If you have registered a normal console driver in ``plat_crash_console_init``,
-you can keep the default implementation here (which calls ``console_putc()``).
+you can keep the sample implementation here (which calls ``console_putc()``).
 
-If you're trying to debug crashes in BL1, you can call the console_xxx_core_putc
-function exported by some console drivers from here.
+If you're trying to debug crashes in BL1, you can call the
+``console_xxx_core_putc`` function exported by some console drivers from here.
 
-Function : plat\_crash\_console\_flush
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Function : plat\_crash\_console\_flush [mandatory]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
 
@@ -2631,7 +2641,7 @@ registers x0 through x5 to do its work. The return value is 0 on successful
 completion; otherwise the return value is -1.
 
 If you have registered a normal console driver in ``plat_crash_console_init``,
-you can keep the default implementation here (which calls ``console_flush()``).
+you can keep the sample implementation here (which calls ``console_flush()``).
 
 If you're trying to debug crashes in BL1, you can call the console_xx_core_flush
 function exported by some console drivers from here.

plat/common/aarch32/crash_console_helpers.S

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/*
+ * If a platform wishes to use the functions in this file it has to be added to
+ * the Makefile of the platform. It is not included in the common Makefile.
+ */
+
+#include <asm_macros.S>
+#include <console.h>
+
+	.globl	plat_crash_console_init
+	.globl	plat_crash_console_putc
+	.globl	plat_crash_console_flush
+
+#if MULTI_CONSOLE_API
+
+	/* -----------------------------------------------------
+	 * int plat_crash_console_init(void)
+	 * Use normal console by default. Switch it to crash
+	 * mode so serial consoles become active again.
+	 * NOTE: This default implementation will only work for
+	 * crashes that occur after a normal console (marked
+	 * valid for the crash state) has been registered with
+	 * the console framework. To debug crashes that occur
+	 * earlier, the platform has to override these functions
+	 * with an implementation that initializes a console
+	 * driver with hardcoded parameters. See
+	 * docs/porting-guide.rst for more information.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_init
+#if defined(IMAGE_BL1)
+	/*
+	 * BL1 code can possibly crash so early that the data segment is not yet
+	 * accessible. Don't risk undefined behavior by trying to run the normal
+	 * console framework. Platforms that want to debug BL1 will need to
+	 * override this with custom functions that can run from registers only.
+	 */
+	mov	r0, #0
+	bx	lr
+#else	/* IMAGE_BL1 */
+	mov	r3, lr
+	mov	r0, #CONSOLE_FLAG_CRASH
+	bl	console_switch_state
+	mov	r0, #1
+	bx	r3
+#endif
+endfunc plat_crash_console_init
+
+	/* -----------------------------------------------------
+	 * void plat_crash_console_putc(int character)
+	 * Output through the normal console by default.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_putc
+	b	console_putc
+endfunc plat_crash_console_putc
+
+	/* -----------------------------------------------------
+	 * void plat_crash_console_flush(void)
+	 * Flush normal console by default.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_flush
+	b	console_flush
+endfunc plat_crash_console_flush
+
+#else	/* MULTI_CONSOLE_API */
+
+	/* -----------------------------------------------------
+	 * In the old API these are all no-op stubs that need to
+	 * be overridden by the platform to be useful.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_init
+	mov	r0, #0
+	bx	lr
+endfunc plat_crash_console_init
+
+func plat_crash_console_putc
+	bx	lr
+endfunc plat_crash_console_putc
+
+func plat_crash_console_flush
+	bx	lr
+endfunc plat_crash_console_flush
+
+#endif

plat/common/aarch64/crash_console_helpers.S

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/*
+ * If a platform wishes to use the functions in this file it has to be added to
+ * the Makefile of the platform. It is not included in the common Makefile.
+ */
+
+#include <asm_macros.S>
+#include <console.h>
+
+	.globl	plat_crash_console_init
+	.globl	plat_crash_console_putc
+	.globl	plat_crash_console_flush
+
+#if MULTI_CONSOLE_API
+
+	/* -----------------------------------------------------
+	 * int plat_crash_console_init(void)
+	 * Use normal console by default. Switch it to crash
+	 * mode so serial consoles become active again.
+	 * NOTE: This default implementation will only work for
+	 * crashes that occur after a normal console (marked
+	 * valid for the crash state) has been registered with
+	 * the console framework. To debug crashes that occur
+	 * earlier, the platform has to override these functions
+	 * with an implementation that initializes a console
+	 * driver with hardcoded parameters. See
+	 * docs/porting-guide.rst for more information.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_init
+#if defined(IMAGE_BL1)
+	/*
+	 * BL1 code can possibly crash so early that the data segment is not yet
+	 * accessible. Don't risk undefined behavior by trying to run the normal
+	 * console framework. Platforms that want to debug BL1 will need to
+	 * override this with custom functions that can run from registers only.
+	 */
+	mov	x0, #0
+	ret
+#else	/* IMAGE_BL1 */
+	mov	x3, x30
+	mov	x0, #CONSOLE_FLAG_CRASH
+	bl	console_switch_state
+	mov	x0, #1
+	ret	x3
+#endif
+endfunc plat_crash_console_init
+
+	/* -----------------------------------------------------
+	 * void plat_crash_console_putc(int character)
+	 * Output through the normal console by default.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_putc
+	b	console_putc
+endfunc plat_crash_console_putc
+
+	/* -----------------------------------------------------
+	 * void plat_crash_console_flush(void)
+	 * Flush normal console by default.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_flush
+	b	console_flush
+endfunc plat_crash_console_flush
+
+#else	/* MULTI_CONSOLE_API */
+
+	/* -----------------------------------------------------
+	 * In the old API these are all no-op stubs that need to
+	 * be overridden by the platform to be useful.
+	 * -----------------------------------------------------
+	 */
+func plat_crash_console_init
+	mov	x0, #0
+	ret
+endfunc plat_crash_console_init
+
+func plat_crash_console_putc
+	ret
+endfunc plat_crash_console_putc
+
+func plat_crash_console_flush
+	ret
+endfunc plat_crash_console_flush
+
+#endif