On Mon, Mar 06, 2006 at 03:52:49PM -0800, Dave Hansen wrote:
>
> Right now, sysctls can only deal with global variables. This
> patch makes them a _little_ more flexible by allowing there to
> be an accessor function to get at the variable being changed,
> instead of it being global.
>
> This allows the sysctls to be backed by variables that are,
> for instance, dynamically allocated and not available at
> compile-time.
>
> This also provides a very simple mechanism to take things that
> are currently global and containerize them.
hmm, why do you call the sysctl_table_data() over and
over again? what's the purpose? what about sideeffects?
> Signed-off-by: Dave Hansen <[email protected]>
> ---
>
> work-dave/include/linux/sysctl.h | 8 ++++
> work-dave/kernel/sysctl.c | 65 ++++++++++++++++++++++++++-------------
> 2 files changed, 52 insertions(+), 21 deletions(-)
>
> diff -puN include/linux/sysctl.h~sysctls-for-containers include/linux/sysctl.h
> --- work/include/linux/sysctl.h~sysctls-for-containers 2006-03-06 15:41:55.000000000 -0800
> +++ work-dave/include/linux/sysctl.h 2006-03-06 15:41:55.000000000 -0800
> @@ -872,6 +872,7 @@ extern void sysctl_init(void);
>
> typedef struct ctl_table ctl_table;
>
> +typedef void *ctl_data_access (void);
> typedef int ctl_handler (ctl_table *table, int __user *name, int nlen,
> void __user *oldval, size_t __user *oldlenp,
> void __user *newval, size_t newlen,
> @@ -957,6 +958,13 @@ struct ctl_table
> int ctl_name; /* Binary ID */
> const char *procname; /* Text ID for /proc/sys, or zero */
> void *data;
> + ctl_data_access *data_access; /* set this to a function if you
> + * don't have a static place to point
> + * ->data at compile-time. This
> + * function will be called to dynamically
> + * figure out a ->data pointer. Do not
> + * set this and ->data at once.
> + */
> int maxlen;
> mode_t mode;
> ctl_table *child;
> diff -puN kernel/sysctl.c~sysctls-for-containers kernel/sysctl.c
> --- work/kernel/sysctl.c~sysctls-for-containers 2006-03-06 15:41:55.000000000 -0800
> +++ work-dave/kernel/sysctl.c 2006-03-06 15:41:55.000000000 -0800
> @@ -1197,6 +1197,24 @@ repeat:
> return -ENOTDIR;
> }
>
I'd expect that to be inline, and to vanish when
containers are disabled ...
> +void *sysctl_table_data(ctl_table *table)
> +{
> + void *data;
> +
> + if (table->data && table->data_access) {
> + printk(KERN_WARNING
> + "sysctl: data and accessor function set for: '%s'\n",
> + table->procname);
> + table->data = NULL;
why is ->data and ->data_access evil?
> + }
> +
> + data = table->data;
> + if (!data && table->data_access)
> + data = table->data_access();
> +
> + return data;
> +}
> +
> /* Perform the actual read/write of a sysctl table entry. */
> int do_sysctl_strategy (ctl_table *table,
> int __user *name, int nlen,
> @@ -1205,6 +1223,7 @@ int do_sysctl_strategy (ctl_table *table
> {
> int op = 0, rc;
> size_t len;
> + void *data;
>
> if (oldval)
> op |= 004;
> @@ -1224,14 +1243,15 @@ int do_sysctl_strategy (ctl_table *table
>
> /* If there is no strategy routine, or if the strategy returns
> * zero, proceed with automatic r/w */
> - if (table->data && table->maxlen) {
> + data = sysctl_table_data(table);
> + if (data && table->maxlen) {
> if (oldval && oldlenp) {
> if (get_user(len, oldlenp))
> return -EFAULT;
> if (len) {
> if (len > table->maxlen)
> len = table->maxlen;
> - if(copy_to_user(oldval, table->data, len))
> + if(copy_to_user(oldval, data, len))
> return -EFAULT;
> if(put_user(len, oldlenp))
> return -EFAULT;
> @@ -1241,7 +1261,7 @@ int do_sysctl_strategy (ctl_table *table
> len = newlen;
> if (len > table->maxlen)
> len = table->maxlen;
> - if(copy_from_user(table->data, newval, len))
> + if(copy_from_user(data, newval, len))
> return -EFAULT;
> }
> }
> @@ -1539,7 +1559,7 @@ int proc_dostring(ctl_table *table, int
> char __user *p;
> char c;
>
> - if (!table->data || !table->maxlen || !*lenp ||
> + if (!sysctl_table_data(table) || !table->maxlen || !*lenp ||
> (*ppos && !write)) {
> *lenp = 0;
> return 0;
> @@ -1557,18 +1577,18 @@ int proc_dostring(ctl_table *table, int
> }
> if (len >= table->maxlen)
> len = table->maxlen-1;
> - if(copy_from_user(table->data, buffer, len))
> + if(copy_from_user(sysctl_table_data(table), buffer, len))
> return -EFAULT;
> - ((char *) table->data)[len] = 0;
> + ((char *) sysctl_table_data(table))[len] = 0;
> *ppos += *lenp;
> } else {
> - len = strlen(table->data);
> + len = strlen(sysctl_table_data(table));
> if (len > table->maxlen)
> len = table->maxlen;
> if (len > *lenp)
> len = *lenp;
> if (len)
> - if(copy_to_user(buffer, table->data, len))
> + if(copy_to_user(buffer, sysctl_table_data(table), len))
> return -EFAULT;
> if (len < *lenp) {
> if(put_user('\n', ((char __user *) buffer) + len))
> @@ -1636,13 +1656,13 @@ static int do_proc_dointvec(ctl_table *t
> char buf[TMPBUFLEN], *p;
> char __user *s = buffer;
>
> - if (!table->data || !table->maxlen || !*lenp ||
> + if (!sysctl_table_data(table) || !table->maxlen || !*lenp ||
> (*ppos && !write)) {
> *lenp = 0;
> return 0;
> }
>
> - i = (int *) table->data;
> + i = (int *) sysctl_table_data(table);
> vleft = table->maxlen / sizeof(*i);
> left = *lenp;
>
> @@ -1878,13 +1898,13 @@ static int do_proc_doulongvec_minmax(ctl
> char buf[TMPBUFLEN], *p;
> char __user *s = buffer;
>
> - if (!table->data || !table->maxlen || !*lenp ||
> + if (!sysctl_table_data(table) || !table->maxlen || !*lenp ||
> (*ppos && !write)) {
> *lenp = 0;
> return 0;
> }
>
> - i = (unsigned long *) table->data;
> + i = (unsigned long *) sysctl_table_data(table);
> min = (unsigned long *) table->extra1;
> max = (unsigned long *) table->extra2;
> vleft = table->maxlen / sizeof(unsigned long);
> @@ -2230,7 +2250,9 @@ int sysctl_string(ctl_table *table, int
> void __user *oldval, size_t __user *oldlenp,
> void __user *newval, size_t newlen, void **context)
> {
> - if (!table->data || !table->maxlen)
> + char *data = sysctl_table_data(table);
> +
> + if (!data || !table->maxlen)
> return -ENOTDIR;
>
> if (oldval && oldlenp) {
> @@ -2238,7 +2260,7 @@ int sysctl_string(ctl_table *table, int
> if (get_user(bufsize, oldlenp))
> return -EFAULT;
> if (bufsize) {
> - size_t len = strlen(table->data), copied;
> + size_t len = strlen(data), copied;
>
> /* This shouldn't trigger for a well-formed sysctl */
> if (len > table->maxlen)
> @@ -2247,7 +2269,7 @@ int sysctl_string(ctl_table *table, int
> /* Copy up to a max of bufsize-1 bytes of the string */
> copied = (len >= bufsize) ? bufsize - 1 : len;
>
> - if (copy_to_user(oldval, table->data, copied) ||
> + if (copy_to_user(oldval, data, copied) ||
> put_user(0, (char __user *)(oldval + copied)))
> return -EFAULT;
> if (put_user(len, oldlenp))
> @@ -2258,11 +2280,11 @@ int sysctl_string(ctl_table *table, int
> size_t len = newlen;
> if (len > table->maxlen)
> len = table->maxlen;
> - if(copy_from_user(table->data, newval, len))
> + if(copy_from_user(data, newval, len))
> return -EFAULT;
> if (len == table->maxlen)
> len--;
> - ((char *) table->data)[len] = 0;
> + data[len] = 0;
> }
> return 1;
> }
> @@ -2320,7 +2342,7 @@ int sysctl_jiffies(ctl_table *table, int
> if (olen!=sizeof(int))
> return -EINVAL;
> }
> - if (put_user(*(int *)(table->data)/HZ, (int __user *)oldval) ||
> + if (put_user(*(int *)(sysctl_table_data(table))/HZ, (int __user *)oldval) ||
> (oldlenp && put_user(sizeof(int),oldlenp)))
> return -EFAULT;
> }
> @@ -2330,7 +2352,7 @@ int sysctl_jiffies(ctl_table *table, int
> return -EINVAL;
> if (get_user(new, (int __user *)newval))
> return -EFAULT;
> - *(int *)(table->data) = new*HZ;
> + *(int *)(sysctl_table_data(table)) = new*HZ;
> }
> return 1;
> }
> @@ -2340,6 +2362,7 @@ int sysctl_ms_jiffies(ctl_table *table,
> void __user *oldval, size_t __user *oldlenp,
> void __user *newval, size_t newlen, void **context)
> {
> + int *jiffies_ptr = sysctl_table_data(table);
> if (oldval) {
> size_t olen;
> if (oldlenp) {
> @@ -2348,7 +2371,7 @@ int sysctl_ms_jiffies(ctl_table *table,
> if (olen!=sizeof(int))
> return -EINVAL;
> }
> - if (put_user(jiffies_to_msecs(*(int *)(table->data)), (int __user *)oldval) ||
> + if (put_user(jiffies_to_msecs(*jiffies_ptr), (int __user *)oldval) ||
> (oldlenp && put_user(sizeof(int),oldlenp)))
> return -EFAULT;
> }
> @@ -2358,7 +2381,7 @@ int sysctl_ms_jiffies(ctl_table *table,
> return -EINVAL;
> if (get_user(new, (int __user *)newval))
> return -EFAULT;
> - *(int *)(table->data) = msecs_to_jiffies(new);
> + *jiffies_ptr = msecs_to_jiffies(new);
> }
> return 1;
> }
> _
wouldn't some get/set helper make more sense?
i.e. some virtualizer and devirtualizer functions?
best,
Herbert
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
