[PATCH] Reduce stack usage in time.c

From: Yum Rayan (yum.rayan_at_gmail.com)
Date: 03/31/05

  • Next message: Randy.Dunlap: "[RFC/PATCH] network configs: disconnect network options from drivers" 
    Date:	Wed, 30 Mar 2005 23:46:51 -0800
To: linux-kernel@vger.kernel.org

    Attempt to reduce stack usage in time.c (linux-2.6.12-rc1-mm3). Stack
    usage was noted using checkstack.pl. Specifically:

    Before patch
    ------------
    sys_adjtimex - 128

    After patch
    -----------
    sys_adjtimex - none (register usage only)

    Signed-off-by: Yum Rayan <yum.rayan@gmail.com>

    --- a/kernel/time.c 2005-03-25 22:11:06.000000000 -0800
    +++ b/kernel/time.c 2005-03-30 16:59:51.000000000 -0800
    @@ -413,17 +413,27 @@
     
     asmlinkage long sys_adjtimex(struct timex __user *txc_p)
     {
    - struct timex txc; /* Local copy of parameter */
    - int ret;
    + struct timex *txc; /* Local copy of parameter */
    + int retval;
    +
    + txc = kmalloc(sizeof(struct timex), GFP_KERNEL);
    + if (!txc)
    + return -ENOMEM;
     
             /* Copy the user data space into the kernel copy
              * structure. But bear in mind that the structures
              * may change
              */
    - if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
    - return -EFAULT;
    - ret = do_adjtimex(&txc);
    - return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
    + if(copy_from_user(txc, txc_p, sizeof(struct timex))) {
    + retval = -EFAULT;
    + goto free_txc;
    + }
    + retval = do_adjtimex(txc);
    + if (copy_to_user(txc_p, txc, sizeof(struct timex)))
    + retval = -EFAULT;
    +free_txc:
    + kfree(txc);
    + return retval;
     }
     
     inline struct timespec current_kernel_time(void)
    -
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