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    <p>You should be aware that that you should avoid file I/O when possible. The main idea is to go "one level deeper" and call <a href="http://en.wikipedia.org/wiki/Virtual_file_system" rel="noreferrer">VFS level functions</a> instead of the syscall handler directly:</p> <p>Includes:</p> <pre><code>#include &lt;linux/fs.h&gt; #include &lt;asm/segment.h&gt; #include &lt;asm/uaccess.h&gt; #include &lt;linux/buffer_head.h&gt; </code></pre> <p>Opening a file (similar to open):</p> <pre><code>struct file *file_open(const char *path, int flags, int rights) { struct file *filp = NULL; mm_segment_t oldfs; int err = 0; oldfs = get_fs(); set_fs(get_ds()); filp = filp_open(path, flags, rights); set_fs(oldfs); if (IS_ERR(filp)) { err = PTR_ERR(filp); return NULL; } return filp; } </code></pre> <p>Close a file (similar to close):</p> <pre><code>void file_close(struct file *file) { filp_close(file, NULL); } </code></pre> <p>Reading data from a file (similar to pread):</p> <pre><code>int file_read(struct file *file, unsigned long long offset, unsigned char *data, unsigned int size) { mm_segment_t oldfs; int ret; oldfs = get_fs(); set_fs(get_ds()); ret = vfs_read(file, data, size, &amp;offset); set_fs(oldfs); return ret; } </code></pre> <p>Writing data to a file (similar to pwrite):</p> <pre><code>int file_write(struct file *file, unsigned long long offset, unsigned char *data, unsigned int size) { mm_segment_t oldfs; int ret; oldfs = get_fs(); set_fs(get_ds()); ret = vfs_write(file, data, size, &amp;offset); set_fs(oldfs); return ret; } </code></pre> <p>Syncing changes a file (similar to fsync):</p> <pre><code>int file_sync(struct file *file) { vfs_fsync(file, 0); return 0; } </code></pre> <p>[Edit] Originally, I proposed using file_fsync, which is gone in newer kernel versions. Thanks to the poor guy suggesting the change, but whose change was rejected. The edit was rejected before I could review it.</p>
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    1. POHow to read/write files within a Linux kernel module?
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    1. POHow to read/write files within a Linux kernel module?
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    1. COThank you. I was thinking to do something similar by replicating sys_read/sys_open functionality. But this is great help. A curiosity, is there any way to use system calls declared using SYSCALL_DEFINE?
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    2. COI tried this code in kernel 2.6.30 (Ubuntu 9.04) and reading the file crashes the system. Anyone experienced the same issue?
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    3. CO@Enrico Detoma? Oh, wow. This there any way that you can give me the module you used? Never seen that before?
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