Date:	Thu, 17 Nov 2011 13:35:15 +0800
From:	Chen Gong <gong.chen@...ux.intel.com>
To:	Kees Cook <keescook@...omium.org>
CC:	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Ben Gardner <bgardner@...tec.com>,
	Marco Stornelli <marco.stornelli@...il.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: Re: [PATCH 1/2] ramoops: use pstore interface

于 2011/11/17 5:25, Kees Cook 写道:
> Instead of using /dev/mem directly, use the common pstore infrastructure
> to handle Oops gathering and extraction.
>
> Signed-off-by: Kees Cook<keescook@...omium.org>
> ---
>   drivers/char/Kconfig   |    1 +
>   drivers/char/ramoops.c |  195 +++++++++++++++++++++++++++++++++++++-----------
>   2 files changed, 152 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
> index 4364303..f166499 100644
> --- a/drivers/char/Kconfig
> +++ b/drivers/char/Kconfig
> @@ -603,6 +603,7 @@ source "drivers/s390/char/Kconfig"
>   config RAMOOPS
>   	tristate "Log panic/oops to a RAM buffer"
>   	depends on HAS_IOMEM
> +	depends on PSTORE
>   	default n
>   	help
>   	  This enables panic and oops messages to be logged to a circular
> diff --git a/drivers/char/ramoops.c b/drivers/char/ramoops.c
> index 7c7f42a..129d79a 100644
> --- a/drivers/char/ramoops.c
> +++ b/drivers/char/ramoops.c
> @@ -2,6 +2,7 @@
>    * RAM Oops/Panic logger
>    *
>    * Copyright (C) 2010 Marco Stornelli<marco.stornelli@...il.com>
> + * Copyright (C) 2011 Kees Cook<keescook@...omium.org>
>    *
>    * This program is free software; you can redistribute it and/or
>    * modify it under the terms of the GNU General Public License
> @@ -24,7 +25,7 @@
>   #include<linux/kernel.h>
>   #include<linux/err.h>
>   #include<linux/module.h>
> -#include<linux/kmsg_dump.h>
> +#include<linux/pstore.h>
>   #include<linux/time.h>
>   #include<linux/err.h>
>   #include<linux/io.h>
> @@ -51,67 +52,150 @@ module_param(mem_size, ulong, 0400);
>   MODULE_PARM_DESC(mem_size,
>   		"size of reserved RAM used to store oops/panic logs");
>
> -static int dump_oops = 1;
> -module_param(dump_oops, int, 0600);
> -MODULE_PARM_DESC(dump_oops,
> -		"set to 1 to dump oopses, 0 to only dump panics (default 1)");
> -
> -static struct ramoops_context {
> -	struct kmsg_dumper dump;
> +static int ramoops_pstore_open(struct pstore_info *psi);
> +static int ramoops_pstore_close(struct pstore_info *psi);
> +static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
> +				   struct timespec *time,
> +				   char **buf,
> +				   struct pstore_info *psi);
> +static int ramoops_pstore_write(enum pstore_type_id type,
> +				enum kmsg_dump_reason reason, u64 *id,
> +				unsigned int part,
> +				size_t size, struct pstore_info *psi);
> +static int ramoops_pstore_erase(enum pstore_type_id type, u64 id,
> +				struct pstore_info *psi);
> +
> +struct ramoops_context {
>   	void *virt_addr;
>   	phys_addr_t phys_addr;
>   	unsigned long size;
> -	unsigned long record_size;
> -	int dump_oops;
> -	int count;
> -	int max_count;
> -} oops_cxt;
> +	size_t record_size;
> +	unsigned int count;
> +	unsigned int max_count;
> +	unsigned int read_count;
> +	struct pstore_info pstore;
> +};
>
>   static struct platform_device *dummy;
>   static struct ramoops_platform_data *dummy_data;
>
> -static void ramoops_do_dump(struct kmsg_dumper *dumper,
> -		enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
> -		const char *s2, unsigned long l2)
> +static struct ramoops_context oops_cxt = {
> +	.pstore = {
> +		.owner	= THIS_MODULE,
> +		.name	= "ramoops",
> +		.open	= ramoops_pstore_open,
> +		.close	= ramoops_pstore_close,
> +		.read	= ramoops_pstore_read,
> +		.write	= ramoops_pstore_write,
> +		.erase	= ramoops_pstore_erase,
> +	},
> +};
> +
> +static int ramoops_pstore_open(struct pstore_info *psi)
>   {
> -	struct ramoops_context *cxt = container_of(dumper,
> -			struct ramoops_context, dump);
> -	unsigned long s1_start, s2_start;
> -	unsigned long l1_cpy, l2_cpy;
> -	int res, hdr_size;
> -	char *buf, *buf_orig;
> +	struct ramoops_context *cxt =&oops_cxt;
> +
> +	cxt->read_count = 0;
> +	return 0;
> +}
> +
> +static int ramoops_pstore_close(struct pstore_info *psi)
> +{
> +	return 0;
> +}
> +
> +static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
> +				   struct timespec *time,
> +				   char **buf,
> +				   struct pstore_info *psi)
> +{
> +	ssize_t size;
> +	char *rambuf;
> +	struct ramoops_context *cxt =&oops_cxt;
> +
> +	if (cxt->read_count>= cxt->max_count)
> +		return -EINVAL;
> +	*id = cxt->read_count++;
> +	/* Only supports dmesg output so far. */
> +	*type = PSTORE_TYPE_DMESG;
> +	/* TODO(kees): Bogus time for the moment. */
> +	time->tv_sec = 0;
> +	time->tv_nsec = 0;
> +
> +	rambuf = cxt->virt_addr + (*id * cxt->record_size);
> +	size = strnlen(rambuf, cxt->record_size);
> +	*buf = kmalloc(size, GFP_KERNEL);
> +	if (*buf == NULL)
> +		return -ENOMEM;
> +	memcpy(*buf, rambuf, size);
> +
> +	return size;
> +}
> +
> +static int ramoops_pstore_write(enum pstore_type_id type,
> +				enum kmsg_dump_reason reason,
> +				u64 *id,
> +				unsigned int part,
> +				size_t size, struct pstore_info *psi)
> +{
> +	char *buf;
> +	size_t res;
>   	struct timeval timestamp;
> +	struct ramoops_context *cxt =&oops_cxt;
> +	size_t available = cxt->record_size;
>
> +	/* Only store dmesg dumps. */
> +	if (type != PSTORE_TYPE_DMESG)
> +		return -EINVAL;
> +
> +	/* Only store crash dumps. */
>   	if (reason != KMSG_DUMP_OOPS&&
>   	reason != KMSG_DUMP_PANIC&&
>   	reason != KMSG_DUMP_KEXEC)
> -		return;
> +		return -EINVAL;
>
> -	/* Only dump oopses if dump_oops is set */
> -	if (reason == KMSG_DUMP_OOPS&&  !cxt->dump_oops)
> -		return;
> +	/* Explicitly only take the first part of any new crash.
> +	 * If our buffer is larger than kmsg_bytes, this can never happen,
> +	 * and if our buffer is smaller than kmsg_bytes, we don't want the
> +	 * report split across multiple records. */
> +	if (part != 1)
> +		return -ENOSPC;

why only one part is accepted? You are afraid about your filename style?

>
>   	buf = cxt->virt_addr + (cxt->count * cxt->record_size);
> -	buf_orig = buf;
>
> -	memset(buf, '\0', cxt->record_size);
>   	res = sprintf(buf, "%s", RAMOOPS_KERNMSG_HDR);
>   	buf += res;
> +	available -= res;
> +
>   	do_gettimeofday(&timestamp);
>   	res = sprintf(buf, "%lu.%lu\n", (long)timestamp.tv_sec, (long)timestamp.tv_usec);
>   	buf += res;
> +	available -= res;
>
> -	hdr_size = buf - buf_orig;
> -	l2_cpy = min(l2, cxt->record_size - hdr_size);
> -	l1_cpy = min(l1, cxt->record_size - hdr_size - l2_cpy);
> +	if (size>  available)
> +		size = available;
>
> -	s2_start = l2 - l2_cpy;
> -	s1_start = l1 - l1_cpy;
> -
> -	memcpy(buf, s1 + s1_start, l1_cpy);
> -	memcpy(buf + l1_cpy, s2 + s2_start, l2_cpy);
> +	memcpy(buf, cxt->pstore.buf, size);
> +	memset(buf + size, '\0', available - size);
>
>   	cxt->count = (cxt->count + 1) % cxt->max_count;
> +
> +	return 0;
> +}
> +
> +static int ramoops_pstore_erase(enum pstore_type_id type, u64 id,
> +				struct pstore_info *psi)
> +{
> +	char *buf;
> +	struct ramoops_context *cxt =&oops_cxt;
> +
> +	if (id>= cxt->max_count)
> +		return -EINVAL;
> +
> +	buf = cxt->virt_addr + (id * cxt->record_size);
> +	memset(buf, '\0', cxt->record_size);
> +
> +	return 0;
>   }
>
>   static int __init ramoops_probe(struct platform_device *pdev)
> @@ -120,6 +204,12 @@ static int __init ramoops_probe(struct platform_device *pdev)
>   	struct ramoops_context *cxt =&oops_cxt;
>   	int err = -EINVAL;
>
> +	/* Only a single ramoops area allowed at a time, so fail extra
> +	 * probes.
> +	 */
> +	if (cxt->max_count)
> +		goto fail3;

Should be fail4

> +
>   	if (!pdata->mem_size || !pdata->record_size) {
>   		pr_err("The memory size and the record size must be "
>   			"non-zero\n");
> @@ -147,7 +237,6 @@ static int __init ramoops_probe(struct platform_device *pdev)
>   	cxt->size = pdata->mem_size;
>   	cxt->phys_addr = pdata->mem_address;
>   	cxt->record_size = pdata->record_size;
> -	cxt->dump_oops = pdata->dump_oops;
>   	/*
>   	 * Update the module parameter variables as well so they are visible
>   	 * through /sys/module/ramoops/parameters/
> @@ -155,7 +244,14 @@ static int __init ramoops_probe(struct platform_device *pdev)
>   	mem_size = pdata->mem_size;
>   	mem_address = pdata->mem_address;
>   	record_size = pdata->record_size;
> -	dump_oops = pdata->dump_oops;
> +
> +	cxt->pstore.bufsize = cxt->record_size;
> +	cxt->pstore.buf = kmalloc(cxt->pstore.bufsize, GFP_KERNEL);
> +	spin_lock_init(&cxt->pstore.buf_lock);
> +	if (!cxt->pstore.buf) {
> +		pr_err("cannot allocate pstore buffer\n");
> +		goto fail4;
> +	}
>
>   	if (!request_mem_region(cxt->phys_addr, cxt->size, "ramoops")) {
>   		pr_err("request mem region failed\n");
> @@ -169,10 +265,9 @@ static int __init ramoops_probe(struct platform_device *pdev)
>   		goto fail2;
>   	}
>
> -	cxt->dump.dump = ramoops_do_dump;
> -	err = kmsg_dump_register(&cxt->dump);
> +	err = pstore_register(&cxt->pstore);
>   	if (err) {
> -		pr_err("registering kmsg dumper failed\n");
> +		pr_err("registering with pstore failed\n");
>   		goto fail1;
>   	}
>
> @@ -182,7 +277,11 @@ fail1:
>   	iounmap(cxt->virt_addr);
>   fail2:
>   	release_mem_region(cxt->phys_addr, cxt->size);
> +	cxt->max_count = 0;
>   fail3:
> +	kfree(cxt->pstore.buf);
> +fail4:
> +	cxt->pstore.bufsize = 0;

In some situations fail4 maybe hits max_count != 0, so here max_count should be 
cleared. I think you should rearrange the logic in this function carefully.

>   	return err;
>   }
>
> @@ -190,11 +289,20 @@ static int __exit ramoops_remove(struct platform_device *pdev)
>   {
>   	struct ramoops_context *cxt =&oops_cxt;
>
> -	if (kmsg_dump_unregister(&cxt->dump)<  0)
> -		pr_warn("could not unregister kmsg_dumper\n");
> +	/* TODO(kees): It shouldn't be possible to remove ramoops since
> +	 * pstore doesn't support unregistering yet. When it does, remove
> +	 * this early return and add the unregister where noted below.
> +	 */
> +	return -EBUSY;

This style is not reasonable. Maybe it should have a better wrap.

>
>   	iounmap(cxt->virt_addr);
>   	release_mem_region(cxt->phys_addr, cxt->size);
> +	cxt->max_count = 0;
> +
> +	/* TODO(kees): When pstore supports unregistering, call it here. */
> +	kfree(cxt->pstore.buf);
> +	cxt->pstore.bufsize = 0;
> +
>   	return 0;
>   }
>
> @@ -223,7 +331,6 @@ static int __init ramoops_init(void)
>   		dummy_data->mem_size = mem_size;
>   		dummy_data->mem_address = mem_address;
>   		dummy_data->record_size = record_size;
> -		dummy_data->dump_oops = dump_oops;
>   		dummy = platform_create_bundle(&ramoops_driver, ramoops_probe,
>   			NULL, 0, dummy_data,
>   			sizeof(struct ramoops_platform_data));

BTW, you need to update Documentation/ramoops.txt
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