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ptp: reduce stack usage when reading external time stamps

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This patch removes the large buffer from the stack of the read file
operation and replaces it with a kmalloced buffer.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Richard Cochran 2012-11-26 01:44:34 +00:00 committed by David S. Miller
parent cfd1979e81
commit c7ec0badcc
1 changed files with 17 additions and 5 deletions
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22
drivers/ptp/ptp_chardev.c
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@ -21,6 +21,7 @@
#include <linux/posix-clock.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include "ptp_private.h"
@ -136,20 +137,23 @@ unsigned int ptp_poll(struct posix_clock *pc, struct file *fp, poll_table *wait)
return queue_cnt(&ptp->tsevq) ? POLLIN : 0;
}
#define EXTTS_BUFSIZE (PTP_BUF_TIMESTAMPS * sizeof(struct ptp_extts_event))
ssize_t ptp_read(struct posix_clock *pc,
uint rdflags, char __user *buf, size_t cnt)
{
struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
struct timestamp_event_queue *queue = &ptp->tsevq;
struct ptp_extts_event event[PTP_BUF_TIMESTAMPS];
struct ptp_extts_event *event;
unsigned long flags;
size_t qcnt, i;
int result;
if (cnt % sizeof(struct ptp_extts_event) != 0)
return -EINVAL;
if (cnt > sizeof(event))
cnt = sizeof(event);
if (cnt > EXTTS_BUFSIZE)
cnt = EXTTS_BUFSIZE;
cnt = cnt / sizeof(struct ptp_extts_event);
@ -167,6 +171,12 @@ ssize_t ptp_read(struct posix_clock *pc,
return -ENODEV;
}
event = kmalloc(EXTTS_BUFSIZE, GFP_KERNEL);
if (!event) {
mutex_unlock(&ptp->tsevq_mux);
return -ENOMEM;
}
spin_lock_irqsave(&queue->lock, flags);
qcnt = queue_cnt(queue);
@ -185,8 +195,10 @@ ssize_t ptp_read(struct posix_clock *pc,
mutex_unlock(&ptp->tsevq_mux);
result = cnt;
if (copy_to_user(buf, event, cnt))
return -EFAULT;
result = -EFAULT;
return cnt;
kfree(event);
return result;
}