On 6/12/07, Stelian Pop <[email protected]> wrote: > Le mardi 12 juin 2007 à 11:24 -0500, Nelson Castillo a écrit : > > On 6/12/07, Stelian Pop <[email protected]> wrote: > > (cut) > > > accessing userspace memory with a spinlock taken (moreover an > > > irqsave() > > > one) is bad bad bad. > > > > Hi Stelian. > > > > I'm sending the new patch without kfifo_put_user and kfifo_get_user. > > Ok, I have a few formatting/documentation comments: Applied, thanks. > Other than that I'm ok with this patch. Submitting. Regards, Nelson.- Signed-off-by: Nelson Castillo <[email protected]> --- diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h index 404f446..5c4c416 100644 --- a/include/linux/kfifo.h +++ b/include/linux/kfifo.h @@ -41,8 +41,13 @@ extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, extern void kfifo_free(struct kfifo *fifo); extern unsigned int __kfifo_put(struct kfifo *fifo, unsigned char *buffer, unsigned int len); +extern int __kfifo_put_user(struct kfifo *fifo, + const unsigned char __user *buffer, + unsigned int len); extern unsigned int __kfifo_get(struct kfifo *fifo, unsigned char *buffer, unsigned int len); +extern int __kfifo_get_user(struct kfifo *fifo, unsigned char __user *buffer, + unsigned int len); /** * __kfifo_reset - removes the entire FIFO contents, no locking version diff --git a/kernel/kfifo.c b/kernel/kfifo.c index cee4191..b11024e 100644 --- a/kernel/kfifo.c +++ b/kernel/kfifo.c @@ -23,6 +23,7 @@ #include <linux/module.h> #include <linux/slab.h> #include <linux/err.h> +#include <asm/uaccess.h> #include <linux/kfifo.h> /** @@ -150,6 +151,61 @@ unsigned int __kfifo_put(struct kfifo *fifo, EXPORT_SYMBOL(__kfifo_put); /** + * __kfifo_put_user - puts some data into the FIFO, from userspace + * We don't have a locking version because copy_from_user + * might sleep and you must not sleep holding a spinlock. + * + * @fifo: the fifo to be used. + * @buffer: the user space data to be added. + * @len: the length of the data to be added. + * + * This function copies at most @len bytes from the @buffer into + * the FIFO depending on the free space, and returns the number of + * bytes copied or -EFAULT if copy_from_user fails. + * + * Note that with only one concurrent reader and one concurrent + * writer, you don't need extra locking to use these functions. + */ +int __kfifo_put_user(struct kfifo *fifo, const unsigned char __user *buffer, + unsigned int len) +{ + unsigned int l; + + len = min(len, fifo->size - fifo->in + fifo->out); + + /* + * Ensure that we sample the fifo->out index -before- we + * start putting bytes into the kfifo. + */ + + smp_mb(); + + /* first put the data starting from fifo->in to buffer end */ + l = min(len, fifo->size - (fifo->in & (fifo->size - 1))); + + if (copy_from_user(fifo->buffer + (fifo->in & (fifo->size - 1)), + buffer, l)) + return -EFAULT; + + + /* then put the rest (if any) at the beginning of the buffer */ + if (copy_from_user(fifo->buffer, buffer + l, len - l)) + return -EFAULT; + + /* + * Ensure that we add the bytes to the kfifo -before- + * we update the fifo->in index. + */ + + smp_wmb(); + + fifo->in += len; + + return (int)len; +} +EXPORT_SYMBOL(__kfifo_put_user); + +/** * __kfifo_get - gets some data from the FIFO, no locking version * @fifo: the fifo to be used. * @buffer: where the data must be copied. @@ -194,3 +250,57 @@ unsigned int __kfifo_get(struct kfifo *fifo, return len; } EXPORT_SYMBOL(__kfifo_get); + +/** + * __kfifo_get_user - gets some data from the FIFO to userspace + * We don't have a locking version because copy_to_user + * might sleep and you must not sleep holding a spinlock. + * @fifo: the fifo to be used. + * @buffer: user space buffer where the data must be copied. + * @len: the size of the destination buffer. + * + * This function copies at most @len bytes from the FIFO into the + * @buffer and returns the number of bytes copied or -EFAULT if + * copy_to_user fails. + * + * Note that with only one concurrent reader and one concurrent + * writer, you don't need extra locking to use these functions. + */ + +int __kfifo_get_user(struct kfifo *fifo, + unsigned char __user *buffer, unsigned int len) +{ + unsigned int l; + + len = min(len, fifo->in - fifo->out); + + /* + * Ensure that we sample the fifo->in index -before- we + * start removing bytes from the kfifo. + */ + + smp_rmb(); + + /* first get the data from fifo->out until the end of the buffer */ + l = min(len, fifo->size - (fifo->out & (fifo->size - 1))); + + if (copy_to_user(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l)) + return -EFAULT; + + /* then get the rest (if any) from the beginning of the buffer */ + if (copy_to_user(buffer + l, fifo->buffer, len - l)) + return -EFAULT; + + /* + * Ensure that we remove the bytes from the kfifo -before- + * we update the fifo->out index. + */ + + smp_mb(); + + fifo->out += len; + + return (int)len; +} +EXPORT_SYMBOL(__kfifo_get_user); + -- http://arhuaco.org http://emQbit.com
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