| From ltsi-dev-bounces@lists.linuxfoundation.org Sat May 12 10:18:51 2012 |
| From: Marco Stornelli <marco.stornelli@gmail.com> |
| Date: Sat, 12 May 2012 19:12:16 +0200 |
| Subject: pramfs: memory write protection |
| To: LTSI <ltsi-dev@lists.linuxfoundation.org> |
| Message-ID: <4FAE99F0.6020105@gmail.com> |
| |
| |
| From: Marco Stornelli <marco.stornelli@gmail.com> |
| |
| Memory write protection. |
| |
| Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com> |
| |
| --- |
| fs/pramfs/wprotect.c | 41 +++++++++++++ |
| fs/pramfs/wprotect.h | 153 +++++++++++++++++++++++++++++++++++++++++++++++++++ |
| 2 files changed, 194 insertions(+) |
| |
| --- /dev/null |
| +++ b/fs/pramfs/wprotect.c |
| @@ -0,0 +1,41 @@ |
| +/* |
| + * BRIEF DESCRIPTION |
| + * |
| + * Write protection for the filesystem pages. |
| + * |
| + * Copyright 2009-2011 Marco Stornelli <marco.stornelli@gmail.com> |
| + * Copyright 2003 Sony Corporation |
| + * Copyright 2003 Matsushita Electric Industrial Co., Ltd. |
| + * 2003-2004 (c) MontaVista Software, Inc. , Steve Longerbeam |
| + * This file is licensed under the terms of the GNU General Public |
| + * License version 2. This program is licensed "as is" without any |
| + * warranty of any kind, whether express or implied. |
| + */ |
| + |
| +#include <linux/module.h> |
| +#include <linux/fs.h> |
| +#include <linux/mm.h> |
| +#include <linux/io.h> |
| +#include "pram.h" |
| + |
| +DEFINE_SPINLOCK(writeable_lock); |
| + |
| +void pram_writeable(void *vaddr, unsigned long size, int rw) |
| +{ |
| + int ret = 0; |
| + unsigned long nrpages = size >> PAGE_SHIFT; |
| + unsigned long addr = (unsigned long)vaddr; |
| + |
| + /* Page aligned */ |
| + addr &= PAGE_MASK; |
| + |
| + if (size & (PAGE_SIZE - 1)) |
| + nrpages++; |
| + |
| + if (rw) |
| + ret = set_memory_rw(addr, nrpages); |
| + else |
| + ret = set_memory_ro(addr, nrpages); |
| + |
| + BUG_ON(ret); |
| +} |
| --- /dev/null |
| +++ b/fs/pramfs/wprotect.h |
| @@ -0,0 +1,153 @@ |
| +/* |
| + * BRIEF DESCRIPTION |
| + * |
| + * Memory protection definitions for the PRAMFS filesystem. |
| + * |
| + * Copyright 2010-2011 Marco Stornelli <marco.stornelli@gmail.com> |
| + * This file is licensed under the terms of the GNU General Public |
| + * License version 2. This program is licensed "as is" without any |
| + * warranty of any kind, whether express or implied. |
| + */ |
| + |
| +#ifndef __WPROTECT_H |
| +#define __WPROTECT_H |
| + |
| +#include <linux/pram_fs.h> |
| + |
| +/* pram_memunlock_super() before calling! */ |
| +static inline void pram_sync_super(struct pram_super_block *ps) |
| +{ |
| + u16 crc = 0; |
| + ps->s_wtime = cpu_to_be32(get_seconds()); |
| + ps->s_sum = 0; |
| + crc = crc16(~0, (__u8 *)ps + sizeof(__be16), PRAM_SB_SIZE - |
| + sizeof(__be16)); |
| + ps->s_sum = cpu_to_be16(crc); |
| + /* Keep sync redundant super block */ |
| + memcpy((void *)ps + PRAM_SB_SIZE, (void *)ps, PRAM_SB_SIZE); |
| +} |
| + |
| +/* pram_memunlock_inode() before calling! */ |
| +static inline void pram_sync_inode(struct pram_inode *pi) |
| +{ |
| + u16 crc = 0; |
| + pi->i_sum = 0; |
| + crc = crc16(~0, (__u8 *)pi + sizeof(__be16), PRAM_INODE_SIZE - |
| + sizeof(__be16)); |
| + pi->i_sum = cpu_to_be16(crc); |
| +} |
| + |
| +#ifdef CONFIG_PRAMFS_WRITE_PROTECT |
| +extern void pram_writeable(void *vaddr, unsigned long size, int rw); |
| +extern spinlock_t writeable_lock; |
| +static inline int pram_is_protected(struct super_block *sb) |
| +{ |
| + struct pram_sb_info *sbi = (struct pram_sb_info *)sb->s_fs_info; |
| + return sbi->s_mount_opt & PRAM_MOUNT_PROTECT; |
| +} |
| + |
| +static inline void __pram_memunlock_range(void *p, unsigned long len) |
| +{ |
| + /* |
| + * NOTE: Ideally we should lock all the kernel to be memory safe |
| + * and avoid to write in the protected memory, |
| + * obviously it's not possible, so we only serialize |
| + * the operations at fs level. We can't disable the interrupts |
| + * because we could have a deadlock in this path. |
| + */ |
| + spin_lock(&writeable_lock); |
| + pram_writeable(p, len, 1); |
| +} |
| + |
| +static inline void __pram_memlock_range(void *p, unsigned long len) |
| +{ |
| + pram_writeable(p, len, 0); |
| + spin_unlock(&writeable_lock); |
| +} |
| + |
| +static inline void pram_memunlock_range(struct super_block *sb, void *p, |
| + unsigned long len) |
| +{ |
| + if (pram_is_protected(sb)) |
| + __pram_memunlock_range(p, len); |
| +} |
| + |
| +static inline void pram_memlock_range(struct super_block *sb, void *p, |
| + unsigned long len) |
| +{ |
| + if (pram_is_protected(sb)) |
| + __pram_memlock_range(p, len); |
| +} |
| + |
| +static inline void pram_memunlock_super(struct super_block *sb, |
| + struct pram_super_block *ps) |
| +{ |
| + if (pram_is_protected(sb)) |
| + __pram_memunlock_range(ps, PRAM_SB_SIZE); |
| +} |
| + |
| +static inline void pram_memlock_super(struct super_block *sb, |
| + struct pram_super_block *ps) |
| +{ |
| + pram_sync_super(ps); |
| + if (pram_is_protected(sb)) |
| + __pram_memlock_range(ps, PRAM_SB_SIZE); |
| +} |
| + |
| +static inline void pram_memunlock_inode(struct super_block *sb, |
| + struct pram_inode *pi) |
| +{ |
| + if (pram_is_protected(sb)) |
| + __pram_memunlock_range(pi, PRAM_SB_SIZE); |
| +} |
| + |
| +static inline void pram_memlock_inode(struct super_block *sb, |
| + struct pram_inode *pi) |
| +{ |
| + pram_sync_inode(pi); |
| + if (pram_is_protected(sb)) |
| + __pram_memlock_range(pi, PRAM_SB_SIZE); |
| +} |
| + |
| +static inline void pram_memunlock_block(struct super_block *sb, |
| + void *bp) |
| +{ |
| + if (pram_is_protected(sb)) |
| + __pram_memunlock_range(bp, sb->s_blocksize); |
| +} |
| + |
| +static inline void pram_memlock_block(struct super_block *sb, |
| + void *bp) |
| +{ |
| + if (pram_is_protected(sb)) |
| + __pram_memlock_range(bp, sb->s_blocksize); |
| +} |
| + |
| +#else |
| +#define pram_is_protected(sb) 0 |
| +#define pram_writeable(vaddr, size, rw) do {} while (0) |
| +static inline void pram_memunlock_range(struct super_block *sb, void *p, |
| + unsigned long len) {} |
| +static inline void pram_memlock_range(struct super_block *sb, void *p, |
| + unsigned long len) {} |
| +static inline void pram_memunlock_super(struct super_block *sb, |
| + struct pram_super_block *ps) {} |
| +static inline void pram_memlock_super(struct super_block *sb, |
| + struct pram_super_block *ps) |
| +{ |
| + pram_sync_super(ps); |
| +} |
| +static inline void pram_memunlock_inode(struct super_block *sb, |
| + struct pram_inode *pi) {} |
| +static inline void pram_memlock_inode(struct super_block *sb, |
| + struct pram_inode *pi) |
| +{ |
| + pram_sync_inode(pi); |
| +} |
| +static inline void pram_memunlock_block(struct super_block *sb, |
| + void *bp) {} |
| +static inline void pram_memlock_block(struct super_block *sb, |
| + void *bp) {} |
| + |
| +#endif /* CONFIG PRAMFS_WRITE_PROTECT */ |
| +#endif |