staging: android: ram_console: split out persistent ram

Split ram_console into two halves.

persistent_ram is a set of apis that handle a block of memory
that does not get erased across a reboot.  It provides functions
to fill it as a single buffer or a ring buffer, and to extract
the old data after a reboot.  It handles ecc on the data to
correct bit errors introduced during reboot.

ram_console is now a small wrapper around persistent_ram that
feeds console data into the ringbuffer, and exports the old
data to /proc/last_kmsg after a reboot.

[jstultz: Moved persistent_ram.h to staging dir]
CC: Greg KH <gregkh@linuxfoundation.org>
CC: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 302 insertions, 0 deletions

diff --git a/drivers/staging/android/persistent_ram.c b/drivers/staging/android/persistent_ram.c
new file mode 100644
index 000000000000..d0f46661de46
--- /dev/null
+++ b/drivers/staging/android/persistent_ram.c
@@ -0,0 +1,302 @@
+/*
+ * Copyright (C) 2012 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include "persistent_ram.h"
+
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+#include <linux/rslib.h>
+#endif
+
+struct persistent_ram_buffer {
+	uint32_t    sig;
+	uint32_t    start;
+	uint32_t    size;
+	uint8_t     data[0];
+};
+
+#define PERSISTENT_RAM_SIG (0x43474244) /* DBGC */
+
+static LIST_HEAD(zone_list);
+
+#define ECC_BLOCK_SIZE CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION_DATA_SIZE
+#define ECC_SIZE CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION_ECC_SIZE
+#define ECC_SYMSIZE CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION_SYMBOL_SIZE
+#define ECC_POLY CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION_POLYNOMIAL
+
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+static void persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
+	uint8_t *data, size_t len, uint8_t *ecc)
+{
+	int i;
+	uint16_t par[ECC_SIZE];
+	/* Initialize the parity buffer */
+	memset(par, 0, sizeof(par));
+	encode_rs8(prz->rs_decoder, data, len, par, 0);
+	for (i = 0; i < ECC_SIZE; i++)
+		ecc[i] = par[i];
+}
+
+static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz,
+	void *data, size_t len, uint8_t *ecc)
+{
+	int i;
+	uint16_t par[ECC_SIZE];
+	for (i = 0; i < ECC_SIZE; i++)
+		par[i] = ecc[i];
+	return decode_rs8(prz->rs_decoder, data, par, len,
+				NULL, 0, NULL, 0, NULL);
+}
+#endif
+
+static void persistent_ram_update(struct persistent_ram_zone *prz,
+	const void *s, unsigned int count)
+{
+	struct persistent_ram_buffer *buffer = prz->buffer;
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+	uint8_t *buffer_end = buffer->data + prz->buffer_size;
+	uint8_t *block;
+	uint8_t *par;
+	int size = ECC_BLOCK_SIZE;
+#endif
+	memcpy(buffer->data + buffer->start, s, count);
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+	block = buffer->data + (buffer->start & ~(ECC_BLOCK_SIZE - 1));
+	par = prz->par_buffer +
+	      (buffer->start / ECC_BLOCK_SIZE) * ECC_SIZE;
+	do {
+		if (block + ECC_BLOCK_SIZE > buffer_end)
+			size = buffer_end - block;
+		persistent_ram_encode_rs8(prz, block, size, par);
+		block += ECC_BLOCK_SIZE;
+		par += ECC_SIZE;
+	} while (block < buffer->data + buffer->start + count);
+#endif
+}
+
+static void persistent_ram_update_header(struct persistent_ram_zone *prz)
+{
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+	struct persistent_ram_buffer *buffer = prz->buffer;
+
+	persistent_ram_encode_rs8(prz, (uint8_t *)buffer, sizeof(*buffer),
+				  prz->par_header);
+#endif
+}
+
+static void __init
+persistent_ram_save_old(struct persistent_ram_zone *prz)
+{
+	struct persistent_ram_buffer *buffer = prz->buffer;
+	size_t old_log_size = buffer->size;
+	char *dest;
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+	uint8_t *block;
+	uint8_t *par;
+
+	block = buffer->data;
+	par = prz->par_buffer;
+	while (block < buffer->data + buffer->size) {
+		int numerr;
+		int size = ECC_BLOCK_SIZE;
+		if (block + size > buffer->data + prz->buffer_size)
+			size = buffer->data + prz->buffer_size - block;
+		numerr = persistent_ram_decode_rs8(prz, block, size, par);
+		if (numerr > 0) {
+#if 0
+			pr_info("persistent_ram: error in block %p, %d\n",
+			       block, numerr);
+#endif
+			prz->corrected_bytes += numerr;
+		} else if (numerr < 0) {
+#if 0
+			pr_info("persistent_ram: uncorrectable error in block %p\n",
+				block);
+#endif
+			prz->bad_blocks++;
+		}
+		block += ECC_BLOCK_SIZE;
+		par += ECC_SIZE;
+	}
+#endif
+
+	dest = kmalloc(old_log_size, GFP_KERNEL);
+	if (dest == NULL) {
+		pr_err("persistent_ram: failed to allocate buffer\n");
+		return;
+	}
+
+	prz->old_log = dest;
+	prz->old_log_size = old_log_size;
+	memcpy(prz->old_log,
+	       &buffer->data[buffer->start], buffer->size - buffer->start);
+	memcpy(prz->old_log + buffer->size - buffer->start,
+	       &buffer->data[0], buffer->start);
+}
+
+int persistent_ram_write(struct persistent_ram_zone *prz,
+	const void *s, unsigned int count)
+{
+	int rem;
+	int c = count;
+	struct persistent_ram_buffer *buffer = prz->buffer;
+
+	if (c > prz->buffer_size) {
+		s += c - prz->buffer_size;
+		c = prz->buffer_size;
+	}
+	rem = prz->buffer_size - buffer->start;
+	if (rem < c) {
+		persistent_ram_update(prz, s, rem);
+		s += rem;
+		c -= rem;
+		buffer->start = 0;
+		buffer->size = prz->buffer_size;
+	}
+	persistent_ram_update(prz, s, c);
+
+	buffer->start += c;
+	if (buffer->size < prz->buffer_size)
+		buffer->size += c;
+	persistent_ram_update_header(prz);
+
+	return count;
+}
+
+ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz,
+	char *str, size_t len)
+{
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+	ssize_t ret;
+
+	if (prz->corrected_bytes || prz->bad_blocks)
+		ret = snprintf(str, len, ""
+			"\n%d Corrected bytes, %d unrecoverable blocks\n",
+			prz->corrected_bytes, prz->bad_blocks);
+	else
+		ret = snprintf(str, len, "\nNo errors detected\n");
+
+	return ret;
+#else
+	return 0;
+#endif
+}
+
+size_t persistent_ram_old_size(struct persistent_ram_zone *prz)
+{
+	return prz->old_log_size;
+}
+
+void *persistent_ram_old(struct persistent_ram_zone *prz)
+{
+	return prz->old_log;
+}
+
+void persistent_ram_free_old(struct persistent_ram_zone *prz)
+{
+	kfree(prz->old_log);
+	prz->old_log = NULL;
+	prz->old_log_size = 0;
+}
+
+static int __init __persistent_ram_init(struct persistent_ram_zone *prz,
+			       void __iomem *mem, size_t buffer_size)
+{
+	struct persistent_ram_buffer *buffer = mem;
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+	int numerr;
+#endif
+
+	INIT_LIST_HEAD(&prz->node);
+
+	prz->buffer = buffer;
+	prz->buffer_size = buffer_size - sizeof(struct persistent_ram_buffer);
+
+	if (prz->buffer_size > buffer_size) {
+		pr_err("persistent_ram: buffer %p, invalid size %zu, datasize %zu\n",
+		       buffer, buffer_size, prz->buffer_size);
+		return -EINVAL;
+	}
+
+#ifdef CONFIG_ANDROID_RAM_CONSOLE_ERROR_CORRECTION
+	prz->buffer_size -= (DIV_ROUND_UP(prz->buffer_size,
+						ECC_BLOCK_SIZE) + 1) * ECC_SIZE;
+
+	if (prz->buffer_size > buffer_size) {
+		pr_err("persistent_ram: buffer %p, invalid size %zu, non-ecc datasize %zu\n",
+		       buffer, buffer_size, prz->buffer_size);
+		return -EINVAL;
+	}
+
+	prz->par_buffer = buffer->data + prz->buffer_size;
+	prz->par_header = prz->par_buffer +
+		DIV_ROUND_UP(prz->buffer_size, ECC_BLOCK_SIZE) * ECC_SIZE;
+
+
+	/* first consecutive root is 0
+	 * primitive element to generate roots = 1
+	 */
+	prz->rs_decoder = init_rs(ECC_SYMSIZE, ECC_POLY, 0, 1, ECC_SIZE);
+	if (prz->rs_decoder == NULL) {
+		pr_info("persistent_ram: init_rs failed\n");
+		return -EINVAL;
+	}
+
+	prz->corrected_bytes = 0;
+	prz->bad_blocks = 0;
+
+	numerr = persistent_ram_decode_rs8(prz, buffer, sizeof(*buffer),
+					   prz->par_header);
+	if (numerr > 0) {
+		pr_info("persistent_ram: error in header, %d\n", numerr);
+		prz->corrected_bytes += numerr;
+	} else if (numerr < 0) {
+		pr_info("persistent_ram: uncorrectable error in header\n");
+		prz->bad_blocks++;
+	}
+#endif
+
+	if (buffer->sig == PERSISTENT_RAM_SIG) {
+		if (buffer->size > prz->buffer_size
+		    || buffer->start > buffer->size)
+			pr_info("persistent_ram: found existing invalid buffer, size %d, start %d\n",
+			       buffer->size, buffer->start);
+		else {
+			pr_info("persistent_ram: found existing buffer, size %d, start %d\n",
+			       buffer->size, buffer->start);
+			persistent_ram_save_old(prz);
+		}
+	} else {
+		pr_info("persistent_ram: no valid data in buffer (sig = 0x%08x)\n",
+			buffer->sig);
+	}
+
+	buffer->sig = PERSISTENT_RAM_SIG;
+	buffer->start = 0;
+	buffer->size = 0;
+
+	list_add_tail(&prz->node, &zone_list);
+
+	return 0;
+}
+
+int __init persistent_ram_init_ringbuffer(struct persistent_ram_zone *prz,
+			       void __iomem *mem, size_t buffer_size)
+{
+	return __persistent_ram_init(prz, mem, buffer_size);
+}