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Commit 5bf6d1b9 authored by Mark Salyzyn's avatar Mark Salyzyn Committed by Kees Cook
Browse files

pstore/pmsg: drop bounce buffer 



Removing a bounce buffer copy operation in the pmsg driver path is
always better. We also gain in overall performance by not requesting
a vmalloc on every write as this can cause precious RT tasks, such
as user facing media operation, to stall while memory is being
reclaimed. Added a write_buf_user to the pstore functions, a backup
platform write_buf_user that uses the small buffer that is part of
the instance, and implemented a ramoops write_buf_user that only
supports PSTORE_TYPE_PMSG.

Signed-off-by: default avatarMark Salyzyn <salyzyn@android.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 79d955af

fs/pstore/platform.c

+36 −0
Original line number Diff line number Diff line
@@ -623,6 +623,40 @@ static int pstore_write_compat(enum pstore_type_id type, 
			     size, psi);

}



static int pstore_write_buf_user_compat(enum pstore_type_id type,

			       enum kmsg_dump_reason reason,

			       u64 *id, unsigned int part,

			       const char __user *buf,

			       bool compressed, size_t size,

			       struct pstore_info *psi)

{

	unsigned long flags = 0;

	size_t i, bufsize = size;

	long ret = 0;



	if (unlikely(!access_ok(VERIFY_READ, buf, size)))

		return -EFAULT;

	if (bufsize > psinfo->bufsize)

		bufsize = psinfo->bufsize;

	spin_lock_irqsave(&psinfo->buf_lock, flags);

	for (i = 0; i < size; ) {

		size_t c = min(size - i, bufsize);



		ret = __copy_from_user(psinfo->buf, buf + i, c);

		if (unlikely(ret != 0)) {

			ret = -EFAULT;

			break;

		}

		ret = psi->write_buf(type, reason, id, part, psinfo->buf,

				     compressed, c, psi);

		if (unlikely(ret < 0))

			break;

		i += c;

	}

	spin_unlock_irqrestore(&psinfo->buf_lock, flags);

	return unlikely(ret < 0) ? ret : size;

}



/*

 * platform specific persistent storage driver registers with

 * us here. If pstore is already mounted, call the platform
@@ -645,6 +679,8 @@ int pstore_register(struct pstore_info *psi) 


	if (!psi->write)

		psi->write = pstore_write_compat;

	if (!psi->write_buf_user)

		psi->write_buf_user = pstore_write_buf_user_compat;

	psinfo = psi;

	mutex_init(&psinfo->read_mutex);

	spin_unlock(&pstore_lock);

fs/pstore/pmsg.c

+6 −29
Original line number Diff line number Diff line
@@ -19,48 +19,25 @@ 
#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;

	u64 id;

	int ret;



	if (!count)

		return 0;



	/* check outside lock, page in any data. write_buf_user also checks */

	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);

	if (!buffer)

		return -ENOMEM;



	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,

	ret = psinfo->write_buf_user(PSTORE_TYPE_PMSG, 0, &id, 0, buf, 0, count,

				     psinfo);



		i += c;

	}



	mutex_unlock(&pmsg_lock);

	vfree(buffer);

	return count;

	return ret ? ret : count;

}



static const struct file_operations pmsg_fops = {

fs/pstore/ram.c

+19 −0
Original line number Diff line number Diff line
@@ -331,6 +331,24 @@ static int notrace ramoops_pstore_write_buf(enum pstore_type_id type, 
	return 0;

}



static int notrace ramoops_pstore_write_buf_user(enum pstore_type_id type,

						 enum kmsg_dump_reason reason,

						 u64 *id, unsigned int part,

						 const char __user *buf,

						 bool compressed, size_t size,

						 struct pstore_info *psi)

{

	if (type == PSTORE_TYPE_PMSG) {

		struct ramoops_context *cxt = psi->data;



		if (!cxt->mprz)

			return -ENOMEM;

		return persistent_ram_write_user(cxt->mprz, buf, size);

	}



	return -EINVAL;

}



static int ramoops_pstore_erase(enum pstore_type_id type, u64 id, int count,

				struct timespec time, struct pstore_info *psi)

{
@@ -369,6 +387,7 @@ static struct ramoops_context oops_cxt = { 
		.open	= ramoops_pstore_open,

		.read	= ramoops_pstore_read,

		.write_buf	= ramoops_pstore_write_buf,

		.write_buf_user	= ramoops_pstore_write_buf_user,

		.erase	= ramoops_pstore_erase,

	},

};

fs/pstore/ram_core.c

+45 −2
Original line number Diff line number Diff line
@@ -17,15 +17,16 @@ 
#include <linux/device.h>

#include <linux/err.h>

#include <linux/errno.h>

#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/io.h>

#include <linux/kernel.h>

#include <linux/list.h>

#include <linux/memblock.h>

#include <linux/pstore_ram.h>

#include <linux/rslib.h>

#include <linux/slab.h>

#include <linux/uaccess.h>

#include <linux/vmalloc.h>

#include <linux/pstore_ram.h>

#include <asm/page.h>



struct persistent_ram_buffer {
@@ -267,6 +268,16 @@ static void notrace persistent_ram_update(struct persistent_ram_zone *prz, 
	persistent_ram_update_ecc(prz, start, count);

}



static int notrace persistent_ram_update_user(struct persistent_ram_zone *prz,

	const void __user *s, unsigned int start, unsigned int count)

{

	struct persistent_ram_buffer *buffer = prz->buffer;

	int ret = unlikely(__copy_from_user(buffer->data + start, s, count)) ?

		-EFAULT : 0;

	persistent_ram_update_ecc(prz, start, count);

	return ret;

}



void persistent_ram_save_old(struct persistent_ram_zone *prz)

{

	struct persistent_ram_buffer *buffer = prz->buffer;
@@ -320,6 +331,38 @@ int notrace persistent_ram_write(struct persistent_ram_zone *prz, 
	return count;

}



int notrace persistent_ram_write_user(struct persistent_ram_zone *prz,

	const void __user *s, unsigned int count)

{

	int rem, ret = 0, c = count;

	size_t start;



	if (unlikely(!access_ok(VERIFY_READ, s, count)))

		return -EFAULT;

	if (unlikely(c > prz->buffer_size)) {

		s += c - prz->buffer_size;

		c = prz->buffer_size;

	}



	buffer_size_add(prz, c);



	start = buffer_start_add(prz, c);



	rem = prz->buffer_size - start;

	if (unlikely(rem < c)) {

		ret = persistent_ram_update_user(prz, s, start, rem);

		s += rem;

		c -= rem;

		start = 0;

	}

	if (likely(!ret))

		ret = persistent_ram_update_user(prz, s, start, c);



	persistent_ram_update_header_ecc(prz);



	return unlikely(ret) ? ret : count;

}



size_t persistent_ram_old_size(struct persistent_ram_zone *prz)

{

	return prz->old_log_size;

include/linux/pstore.h

+8 −3
Original line number Diff line number Diff line
@@ -22,12 +22,13 @@ 
#ifndef _LINUX_PSTORE_H

#define _LINUX_PSTORE_H



#include <linux/time.h>

#include <linux/compiler.h>

#include <linux/errno.h>

#include <linux/kmsg_dump.h>

#include <linux/mutex.h>

#include <linux/types.h>

#include <linux/spinlock.h>

#include <linux/errno.h>

#include <linux/time.h>

#include <linux/types.h>



/* types */

enum pstore_type_id {
@@ -68,6 +69,10 @@ struct pstore_info { 
			enum kmsg_dump_reason reason, u64 *id,

			unsigned int part, const char *buf, bool compressed,

			size_t size, struct pstore_info *psi);

	int		(*write_buf_user)(enum pstore_type_id type,

			enum kmsg_dump_reason reason, u64 *id,

			unsigned int part, const char __user *buf,

			bool compressed, size_t size, struct pstore_info *psi);

	int		(*erase)(enum pstore_type_id type, u64 id,

			int count, struct timespec time,

			struct pstore_info *psi);