From 6b1ab74a9917012d0c559edc4ed299d9228ac89f Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Sat, 8 Jul 2017 08:26:47 +0200
Subject: kernel: add the new 'crashlog' feature

this tries to store kernel oops/panic logs in a fixed location in RAM to
recover them available to user space using debugfs

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 include/linux/crashlog.h |  17 ++++
 init/Kconfig             |   4 +
 kernel/Makefile          |   1 +
 kernel/crashlog.c        | 213 +++++++++++++++++++++++++++++++++++++++++++++++
 kernel/module.c          |   3 +
 mm/bootmem.c             |   2 +
 mm/memblock.c            |   5 ++
 7 files changed, 245 insertions(+)
 create mode 100644 include/linux/crashlog.h
 create mode 100644 kernel/crashlog.c

--- /dev/null
+++ b/include/linux/crashlog.h
@@ -0,0 +1,17 @@
+#ifndef __CRASHLOG_H
+#define __CRASHLOG_H
+
+#ifdef CONFIG_CRASHLOG
+void crashlog_init_bootmem(struct bootmem_data *bdata);
+void crashlog_init_memblock(phys_addr_t addr, phys_addr_t size);
+#else
+static inline void crashlog_init_bootmem(struct bootmem_data *bdata)
+{
+}
+
+static inline void crashlog_init_memblock(phys_addr_t addr, phys_addr_t size)
+{
+}
+#endif
+
+#endif
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1298,6 +1298,10 @@ config RELAY
 
 	  If unsure, say N.
 
+config CRASHLOG
+	bool "Crash logging"
+	depends on (!NO_BOOTMEM || HAVE_MEMBLOCK)
+
 config BLK_DEV_INITRD
 	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 	depends on BROKEN || !FRV
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -114,6 +114,7 @@ obj-$(CONFIG_TORTURE_TEST) += torture.o
 obj-$(CONFIG_MEMBARRIER) += membarrier.o
 
 obj-$(CONFIG_HAS_IOMEM) += memremap.o
+obj-$(CONFIG_CRASHLOG) += crashlog.o
 
 $(obj)/configs.o: $(obj)/config_data.h
 
--- /dev/null
+++ b/kernel/crashlog.c
@@ -0,0 +1,213 @@
+/*
+ * Crash information logger
+ * Copyright (C) 2010 Felix Fietkau <nbd@nbd.name>
+ *
+ * Based on ramoops.c
+ *   Copyright (C) 2010 Marco Stornelli <marco.stornelli@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/bootmem.h>
+#include <linux/memblock.h>
+#include <linux/debugfs.h>
+#include <linux/crashlog.h>
+#include <linux/kmsg_dump.h>
+#include <linux/module.h>
+#include <linux/pfn.h>
+#include <linux/vmalloc.h>
+#include <asm/io.h>
+
+#define CRASHLOG_PAGES	4
+#define CRASHLOG_SIZE	(CRASHLOG_PAGES * PAGE_SIZE)
+#define CRASHLOG_MAGIC	0xa1eedead
+
+/*
+ * Start the log at 1M before the end of RAM, as some boot loaders like
+ * to use the end of the RAM for stack usage and other things
+ * If this fails, fall back to using the last part.
+ */
+#define CRASHLOG_OFFSET	(1024 * 1024)
+
+struct crashlog_data {
+	u32 magic;
+	u32 len;
+	u8 data[];
+};
+
+static struct debugfs_blob_wrapper crashlog_blob;
+static unsigned long crashlog_addr = 0;
+static struct crashlog_data *crashlog_buf;
+static struct kmsg_dumper dump;
+static bool first = true;
+
+extern struct list_head *crashlog_modules;
+
+static bool crashlog_set_addr(phys_addr_t addr, phys_addr_t size)
+{
+	/* Limit to lower 64 MB to avoid highmem */
+	phys_addr_t limit = 64 * 1024 * 1024;
+
+	if (crashlog_addr)
+		return false;
+
+	if (addr > limit)
+		return false;
+
+	if (addr + size > limit)
+		size = limit - addr;
+
+	crashlog_addr = addr;
+
+	if (addr + size > CRASHLOG_OFFSET)
+		crashlog_addr += size - CRASHLOG_OFFSET;
+
+	return true;
+}
+
+#ifndef CONFIG_NO_BOOTMEM
+void __init crashlog_init_bootmem(bootmem_data_t *bdata)
+{
+	phys_addr_t start, end;
+
+	start = PFN_PHYS(bdata->node_low_pfn);
+	end = PFN_PHYS(bdata->node_min_pfn);
+	if (!crashlog_set_addr(start, end - start))
+		return;
+
+	if (reserve_bootmem(crashlog_addr, CRASHLOG_SIZE, BOOTMEM_EXCLUSIVE) < 0) {
+		printk("Crashlog failed to allocate RAM at address 0x%lx\n",
+		       crashlog_addr);
+		crashlog_addr = 0;
+	}
+}
+#endif
+
+#ifdef CONFIG_HAVE_MEMBLOCK
+void __init_memblock crashlog_init_memblock(phys_addr_t addr, phys_addr_t size)
+{
+	if (!crashlog_set_addr(addr, size))
+		return;
+
+	if (memblock_reserve(crashlog_addr, CRASHLOG_SIZE)) {
+		printk("Crashlog failed to allocate RAM at address 0x%lx\n",
+		       crashlog_addr);
+		crashlog_addr = 0;
+	}
+}
+#endif
+
+static void __init crashlog_copy(void)
+{
+	if (crashlog_buf->magic != CRASHLOG_MAGIC)
+		return;
+
+	if (!crashlog_buf->len || crashlog_buf->len >
+	    CRASHLOG_SIZE - sizeof(*crashlog_buf))
+		return;
+
+	crashlog_blob.size = crashlog_buf->len;
+	crashlog_blob.data = kmemdup(crashlog_buf->data,
+		crashlog_buf->len, GFP_KERNEL);
+
+	debugfs_create_blob("crashlog", 0700, NULL, &crashlog_blob);
+}
+
+static int get_maxlen(void)
+{
+	return CRASHLOG_SIZE - sizeof(*crashlog_buf) - crashlog_buf->len;
+}
+
+static void crashlog_printf(const char *fmt, ...)
+{
+	va_list args;
+	int len = get_maxlen();
+
+	if (!len)
+		return;
+
+	va_start(args, fmt);
+	crashlog_buf->len += vscnprintf(
+		&crashlog_buf->data[crashlog_buf->len],
+		len, fmt, args);
+	va_end(args);
+}
+
+static void crashlog_do_dump(struct kmsg_dumper *dumper,
+		enum kmsg_dump_reason reason)
+{
+	struct timeval tv;
+	struct module *m;
+	char *buf;
+	size_t len;
+
+	if (!first)
+		crashlog_printf("\n===================================\n");
+
+	do_gettimeofday(&tv);
+	crashlog_printf("Time: %lu.%lu\n",
+		(long)tv.tv_sec, (long)tv.tv_usec);
+
+	if (first) {
+		crashlog_printf("Modules:");
+		list_for_each_entry(m, crashlog_modules, list) {
+			crashlog_printf("\t%s@%p+%x", m->name,
+			m->core_layout.base, m->core_layout.size,
+			m->init_layout.base, m->init_layout.size);
+		}
+		crashlog_printf("\n");
+		first = false;
+	}
+
+	buf = (char *)&crashlog_buf->data[crashlog_buf->len];
+
+	kmsg_dump_get_buffer(dumper, true, buf, get_maxlen(), &len);
+
+	crashlog_buf->len += len;
+}
+
+
+int __init crashlog_init_fs(void)
+{
+	struct page *pages[CRASHLOG_PAGES];
+	pgprot_t prot;
+	int i;
+
+	if (!crashlog_addr) {
+		printk("No memory allocated for crashlog\n");
+		return -ENOMEM;
+	}
+
+	printk("Crashlog allocated RAM at address 0x%lx\n", (unsigned long) crashlog_addr);
+	for (i = 0; i < CRASHLOG_PAGES; i++)
+		pages[i] = pfn_to_page((crashlog_addr >> PAGE_SHIFT) + i);
+
+	prot = pgprot_writecombine(PAGE_KERNEL);
+	crashlog_buf = vmap(pages, CRASHLOG_PAGES, VM_MAP, prot);
+
+	crashlog_copy();
+
+	crashlog_buf->magic = CRASHLOG_MAGIC;
+	crashlog_buf->len = 0;
+
+	dump.max_reason = KMSG_DUMP_OOPS;
+	dump.dump = crashlog_do_dump;
+	kmsg_dump_register(&dump);
+
+	return 0;
+}
+module_init(crashlog_init_fs);
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -253,6 +253,9 @@ static void mod_update_bounds(struct mod
 #ifdef CONFIG_KGDB_KDB
 struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
 #endif /* CONFIG_KGDB_KDB */
+#ifdef CONFIG_CRASHLOG
+struct list_head *crashlog_modules = &modules;
+#endif
 
 static void module_assert_mutex(void)
 {
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -14,6 +14,7 @@
 #include <linux/export.h>
 #include <linux/kmemleak.h>
 #include <linux/range.h>
+#include <linux/crashlog.h>
 #include <linux/bug.h>
 #include <linux/io.h>
 #include <linux/bootmem.h>
@@ -174,6 +175,7 @@ static unsigned long __init free_all_boo
 	if (!bdata->node_bootmem_map)
 		return 0;
 
+	crashlog_init_bootmem(bdata);
 	map = bdata->node_bootmem_map;
 	start = bdata->node_min_pfn;
 	end = bdata->node_low_pfn;
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -19,6 +19,7 @@
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #include <linux/memblock.h>
+#include <linux/crashlog.h>
 
 #include <asm/sections.h>
 #include <linux/io.h>
@@ -495,6 +496,8 @@ static void __init_memblock memblock_ins
 	memblock_set_region_node(rgn, nid);
 	type->cnt++;
 	type->total_size += size;
+	if (type == &memblock.memory)
+		crashlog_init_memblock(base, size);
 }
 
 /**
@@ -534,6 +537,8 @@ int __init_memblock memblock_add_range(s
 		type->regions[0].flags = flags;
 		memblock_set_region_node(&type->regions[0], nid);
 		type->total_size = size;
+		if (type == &memblock.memory)
+			crashlog_init_memblock(base, size);
 		return 0;
 	}
 repeat:
