pstore: Add pmsg - user-space accessible pstore object

A secured user-space accessible pstore object. Writes
to /dev/pmsg0 are appended to the buffer, on reboot
the persistent contents are available in
/sys/fs/pstore/pmsg-ramoops-[ID].

One possible use is syslogd, or other daemon, can
write messages, then on reboot provides a means to
triage user-space activities leading up to a panic
as a companion to the pstore dmesg or console logs.

Signed-off-by: Mark Salyzyn <[e-mail]>
Acked-by: Kees Cook <[e-mail]>
Signed-off-by: Tony Luck <[e-mail]>

fs/pstore/Kconfig

···
 	  When the option is enabled, pstore will log all kernel
 	  messages, even if no oops or panic happened.
 
+config PSTORE_PMSG
+	bool "Log user space messages"
+	depends on PSTORE
+	help
+	  When the option is enabled, pstore will export a character
+	  interface /dev/pmsg0 to log user space messages. On reboot
+	  data can be retrieved from /sys/fs/pstore/pmsg-ramoops-[ID].
+
+	  If unsure, say N.
+
 config PSTORE_FTRACE
 	bool "Persistent function tracer"
 	depends on PSTORE

fs/pstore/Makefile

···
 pstore-objs += inode.o platform.o
 obj-$(CONFIG_PSTORE_FTRACE)	+= ftrace.o
 
+obj-$(CONFIG_PSTORE_PMSG)	+= pmsg.o
+
 ramoops-objs += ram.o ram_core.o
 obj-$(CONFIG_PSTORE_RAM)	+= ramoops.o

fs/pstore/inode.c

···
 		scnprintf(name, sizeof(name), "powerpc-common-%s-%lld",
 			  psname, id);
 		break;
+	case PSTORE_TYPE_PMSG:
+		scnprintf(name, sizeof(name), "pmsg-%s-%lld", psname, id);
+		break;
 	case PSTORE_TYPE_UNKNOWN:
 		scnprintf(name, sizeof(name), "unknown-%s-%lld", psname, id);
 		break;

fs/pstore/internal.h

···
 static inline void pstore_register_ftrace(void) {}
 #endif
 
+#ifdef CONFIG_PSTORE_PMSG
+extern void pstore_register_pmsg(void);
+#else
+static inline void pstore_register_pmsg(void) {}
+#endif
+
 extern struct pstore_info *psinfo;
 
 extern void	pstore_set_kmsg_bytes(int);

fs/pstore/platform.c

···
 	if ((psi->flags & PSTORE_FLAGS_FRAGILE) == 0) {
 		pstore_register_console();
 		pstore_register_ftrace();
+		pstore_register_pmsg();
 	}
 
 	if (pstore_update_ms >= 0) {

fs/pstore/pmsg.c

···
+/*
+ * Copyright 2014  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/cdev.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include "internal.h"
+
+static DEFINE_MUTEX(pmsg_lock);
+#define PMSG_MAX_BOUNCE_BUFFER_SIZE (2*PAGE_SIZE)
+
+static ssize_t write_pmsg(struct file *file, const char __user *buf,
+			  size_t count, loff_t *ppos)
+{
+	size_t i, buffer_size;
+	char *buffer;
+
+	if (!count)
+		return 0;
+
+	if (!access_ok(VERIFY_READ, buf, count))
+		return -EFAULT;
+
+	buffer_size = count;
+	if (buffer_size > PMSG_MAX_BOUNCE_BUFFER_SIZE)
+		buffer_size = PMSG_MAX_BOUNCE_BUFFER_SIZE;
+	buffer = vmalloc(buffer_size);
+
+	mutex_lock(&pmsg_lock);
+	for (i = 0; i < count; ) {
+		size_t c = min(count - i, buffer_size);
+		u64 id;
+		long ret;
+
+		ret = __copy_from_user(buffer, buf + i, c);
+		if (unlikely(ret != 0)) {
+			mutex_unlock(&pmsg_lock);
+			vfree(buffer);
+			return -EFAULT;
+		}
+		psinfo->write_buf(PSTORE_TYPE_PMSG, 0, &id, 0, buffer, 0, c,
+				  psinfo);
+
+		i += c;
+	}
+
+	mutex_unlock(&pmsg_lock);
+	vfree(buffer);
+	return count;
+}
+
+static const struct file_operations pmsg_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= noop_llseek,
+	.write		= write_pmsg,
+};
+
+static struct class *pmsg_class;
+static int pmsg_major;
+#define PMSG_NAME "pmsg"
+#undef pr_fmt
+#define pr_fmt(fmt) PMSG_NAME ": " fmt
+
+static char *pmsg_devnode(struct device *dev, umode_t *mode)
+{
+	if (mode)
+		*mode = 0220;
+	return NULL;
+}
+
+void pstore_register_pmsg(void)
+{
+	struct device *pmsg_device;
+
+	pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
+	if (pmsg_major < 0) {
+		pr_err("register_chrdev failed\n");
+		goto err;
+	}
+
+	pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
+	if (IS_ERR(pmsg_class)) {
+		pr_err("device class file already in use\n");
+		goto err_class;
+	}
+	pmsg_class->devnode = pmsg_devnode;
+
+	pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
+					NULL, "%s%d", PMSG_NAME, 0);
+	if (IS_ERR(pmsg_device)) {
+		pr_err("failed to create device\n");
+		goto err_device;
+	}
+	return;
+
+err_device:
+	class_destroy(pmsg_class);
+err_class:
+	unregister_chrdev(pmsg_major, PMSG_NAME);
+err:
+	return;
+}

fs/pstore/ram.c

···
 module_param_named(ftrace_size, ramoops_ftrace_size, ulong, 0400);
 MODULE_PARM_DESC(ftrace_size, "size of ftrace log");
 
+static ulong ramoops_pmsg_size = MIN_MEM_SIZE;
+module_param_named(pmsg_size, ramoops_pmsg_size, ulong, 0400);
+MODULE_PARM_DESC(pmsg_size, "size of user space message log");
+
 static ulong mem_address;
 module_param(mem_address, ulong, 0400);
 MODULE_PARM_DESC(mem_address,
···
 	struct persistent_ram_zone **przs;
 	struct persistent_ram_zone *cprz;
 	struct persistent_ram_zone *fprz;
+	struct persistent_ram_zone *mprz;
 	phys_addr_t phys_addr;
 	unsigned long size;
 	unsigned int memtype;
 	size_t record_size;
 	size_t console_size;
 	size_t ftrace_size;
+	size_t pmsg_size;
 	int dump_oops;
 	struct persistent_ram_ecc_info ecc_info;
 	unsigned int max_dump_cnt;
···
 	unsigned int dump_read_cnt;
 	unsigned int console_read_cnt;
 	unsigned int ftrace_read_cnt;
+	unsigned int pmsg_read_cnt;
 	struct pstore_info pstore;
 };
 
···
 	cxt->dump_read_cnt = 0;
 	cxt->console_read_cnt = 0;
 	cxt->ftrace_read_cnt = 0;
+	cxt->pmsg_read_cnt = 0;
 	return 0;
 }
 
···
 		prz = ramoops_get_next_prz(&cxt->fprz, &cxt->ftrace_read_cnt,
 					   1, id, type, PSTORE_TYPE_FTRACE, 0);
 	if (!prz_ok(prz))
+		prz = ramoops_get_next_prz(&cxt->mprz, &cxt->pmsg_read_cnt,
+					   1, id, type, PSTORE_TYPE_PMSG, 0);
+	if (!prz_ok(prz))
 		return 0;
 
 	if (!persistent_ram_old(prz))
···
 			return -ENOMEM;
 		persistent_ram_write(cxt->fprz, buf, size);
 		return 0;
+	} else if (type == PSTORE_TYPE_PMSG) {
+		if (!cxt->mprz)
+			return -ENOMEM;
+		persistent_ram_write(cxt->mprz, buf, size);
+		return 0;
 	}
 
 	if (type != PSTORE_TYPE_DMESG)
···
 		break;
 	case PSTORE_TYPE_FTRACE:
 		prz = cxt->fprz;
+		break;
+	case PSTORE_TYPE_PMSG:
+		prz = cxt->mprz;
 		break;
 	default:
 		return -EINVAL;
···
 		goto fail_out;
 
 	if (!pdata->mem_size || (!pdata->record_size && !pdata->console_size &&
-			!pdata->ftrace_size)) {
+			!pdata->ftrace_size && !pdata->pmsg_size)) {
 		pr_err("The memory size and the record/console size must be "
 			"non-zero\n");
 		goto fail_out;
···
 		pdata->console_size = rounddown_pow_of_two(pdata->console_size);
 	if (pdata->ftrace_size && !is_power_of_2(pdata->ftrace_size))
 		pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
+	if (pdata->pmsg_size && !is_power_of_2(pdata->pmsg_size))
+		pdata->pmsg_size = rounddown_pow_of_two(pdata->pmsg_size);
 
 	cxt->size = pdata->mem_size;
 	cxt->phys_addr = pdata->mem_address;
···
 	cxt->record_size = pdata->record_size;
 	cxt->console_size = pdata->console_size;
 	cxt->ftrace_size = pdata->ftrace_size;
+	cxt->pmsg_size = pdata->pmsg_size;
 	cxt->dump_oops = pdata->dump_oops;
 	cxt->ecc_info = pdata->ecc_info;
 
 	paddr = cxt->phys_addr;
 
-	dump_mem_sz = cxt->size - cxt->console_size - cxt->ftrace_size;
+	dump_mem_sz = cxt->size - cxt->console_size - cxt->ftrace_size
+			- cxt->pmsg_size;
 	err = ramoops_init_przs(dev, cxt, &paddr, dump_mem_sz);
 	if (err)
 		goto fail_out;
···
 			       LINUX_VERSION_CODE);
 	if (err)
 		goto fail_init_fprz;
+
+	err = ramoops_init_prz(dev, cxt, &cxt->mprz, &paddr, cxt->pmsg_size, 0);
+	if (err)
+		goto fail_init_mprz;
 
 	cxt->pstore.data = cxt;
 	/*
···
 	kfree(cxt->pstore.buf);
 fail_clear:
 	cxt->pstore.bufsize = 0;
+	kfree(cxt->mprz);
+fail_init_mprz:
 	kfree(cxt->fprz);
 fail_init_fprz:
 	kfree(cxt->cprz);
···
 	dummy_data->record_size = record_size;
 	dummy_data->console_size = ramoops_console_size;
 	dummy_data->ftrace_size = ramoops_ftrace_size;
+	dummy_data->pmsg_size = ramoops_pmsg_size;
 	dummy_data->dump_oops = dump_oops;
 	/*
 	 * For backwards compatibility ramoops.ecc=1 means 16 bytes ECC

include/linux/pstore.h

···
 	PSTORE_TYPE_PPC_RTAS	= 4,
 	PSTORE_TYPE_PPC_OF	= 5,
 	PSTORE_TYPE_PPC_COMMON	= 6,
+	PSTORE_TYPE_PMSG	= 7,
 	PSTORE_TYPE_UNKNOWN	= 255
 };
 

include/linux/pstore_ram.h

···
 	unsigned long	record_size;
 	unsigned long	console_size;
 	unsigned long	ftrace_size;
+	unsigned long	pmsg_size;
 	int		dump_oops;
 	struct persistent_ram_ecc_info ecc_info;
 };