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#include <linux/slab.h>
#include <linux/kernel.h>
struct asbuf {
unsigned long ino;
char *buf;
size_t alloc;
};
ssize_t asbuf_free_alloc(struct asbuf *buf, size_t size) {
char *mem;
mem = kmalloc(size, GFP_KERNEL);
if (!mem)
return -ENOMEM;
if (buf->alloc)
kfree(buf->buf);
buf->buf = mem;
buf->alloc = size;
return 0;
}
void asbuf_free(struct asbuf *buf) {
kfree(buf->buf);
}
ssize_t asbuf_to_user(struct asbuf *buf,
char __user *user_buf,
size_t len,
loff_t *offset) {
size_t chars_left, request;
ssize_t uncopied, copied;
if (!buf->alloc)
return -EINVAL;
if (*offset > buf->alloc)
return -EINVAL;
chars_left = buf->alloc - *offset;
request = min(len, chars_left);
printk(KERN_INFO "buf: %p\t alloc: %zu\t request: %zu\n", buf, buf->alloc, request);
uncopied = copy_to_user(user_buf, buf->buf + *offset, request);
copied = request - uncopied;
*offset += copied;
return copied;
}
ssize_t asbuf_from_user(struct asbuf *buf,
const char __user *user_buf,
size_t len,
loff_t *offset) {
ssize_t rc = 0;
size_t uncopied, copied;
rc = asbuf_free_alloc(buf, len);
if (rc != 0)
return rc;
uncopied = copy_from_user(buf->buf, user_buf, len);
copied = len - uncopied;
*offset = 0;
return copied;
}
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