Convert panic() to C code

Move the implementation of panic into C code. Only a very small part
needs to be in assembler, and the reset is easier to maintain as C.

As part of this, define panic_putc() and panic_puts() which directly
wite to the UART.

To make things more convenience for the future, add a simple printf()
implementation in the panic path. This is not reliant on the uart
buffering system being in a happy state. However, we do call the
emergency flush so that our panic message will appear after previous
output rather that surpressing it (which would be extremely confusing).

Code/data size for panic.o grows by about 200 bytes, but this is mostly
due to the increased flexibility.

   text	   data	    bss	    dec	    hex	filename
    292	    272	      0	    564	    234	old panic.S
    692	      3	     48	    743	    2e7	new panic.c

BUG=chrome-os-partner:10146
TEST=manual:
build and boot on snow:
> rw 0x06000000

=== EXCEPTION: 03 ====== xPSR: 01000000 ===========
r0 :0000000b r1 :00000047 r2 :06000000 r3 :200013dd
r4 :00000000 r5 :080052cc r6 :200013d0 r7 :00000002
r8 :00000000 r9 :200013de r10:00000000 r11:00000000
r12:00000000 sp :200009a0 lr :08002a5d pc :08003962

Rebooting...

Change-Id: If3e3f572e0f32af780b6ebda235b1b3cde4de5e4
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/24503
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 69 insertions, 0 deletions

diff --git a/include/panic.h b/include/panic.h
new file mode 100644
index 0000000000..2cfda9bcee
--- /dev/null
+++ b/include/panic.h
@@ -0,0 +1,69 @@
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Panic handling, including displaying a message on the panic reporting
+ * device, which is currently the UART.
+ */
+
+#ifndef __PANIC_H
+#include <stdarg.h>
+
+/**
+ * Write a character to the panic reporting device
+ *
+ * This function will not return until the character has left the UART
+ * data register. Any previously queued UART traffic is displayed first.
+ *
+ * @param ch	Character to write
+ */
+void panic_putc(int ch);
+
+/**
+ * Write a string to the panic reporting device
+ *
+ * This function will not return until the string has left the UART
+ * data register. Any previously queued UART traffic is displayed first.
+ *
+ * @param ch	Character to write
+ */
+void panic_puts(const char *s);
+
+/**
+ * Very basic vprintf() for use in panic situations
+ *
+ * We only support %s and %nx where n is the number of hex digits to display.
+ * Currently we don't even support %d, and it is aimed at small code size.
+ *
+ * TODO(sjg@chromium.org): Really what we need is a vsnprintf() that is
+ * shared between the console UART and panic (and is also available as an
+ * snprintf()). The only downside is that we would then require a large
+ * printf() implementation to be always present, whereas presumably now we
+ * can turn it off.
+ *
+ * @param format	printf-style format string
+ * @param args		List of arguments to process
+ */
+void panic_vprintf(const char *format, va_list args);
+
+/**
+ * Very basic printf() for use in panic situations
+ *
+ * See panic_vprintf() for full details
+ *
+ * @param format	printf-style format string
+ * @param ...		Arguments to process
+ */
+void panic_printf(const char *format, ...);
+
+/**
+ * Report a panic to the panic reporting device
+ *
+ * This is exported only to permit use from assembler.
+ *
+ * @param msg		Panic message
+ * @param lregs		Registers from the exception: psp, ipsr, lr, r4-r11
+ */
+void report_panic(const char *msg, uint32_t *lregs);
+
+#endif