[net-next PATCH v6 2/3] sysctl: add proc_do_large_bitmap

Octavian Purdila
2010-02-27T01:24:49Z

The new function can be used to read/write large bitmaps via /proc. A
comma separated range format is used for compact output and input
(e.g. 1,3-4,10-10).

Writing into the file will first reset the bitmap then update it
based on the given input.

Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Cc: WANG Cong <amwang@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
---
include/linux/sysctl.h | 2 +
kernel/sysctl.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 142 insertions(+), 0 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index f66014c..7bb5cb6 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -980,6 +980,8 @@ extern int proc_doulongvec_minmax(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
void __user *, size_t *, loff_t *);
+extern int proc_do_large_bitmap(struct ctl_table *, int,
+ void __user *, size_t *, loff_t *);

/*
* Register a set of sysctl names by calling register_sysctl_table
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 0873846..5d599cd 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2071,6 +2071,23 @@ static bool isanyof(char c, const char *v, unsigned len)
return true;
}

+static int proc_skip_anyof(char __user **buf, size_t *size,
+ const char *v, unsigned len)
+{
+ char c;
+
+ while (*size) {
+ if (get_user(c, *buf))
+ return -EFAULT;
+ if (!isanyof(c, v, len))
+ break;
+ (*size)--;
+ (*buf)++;
+ }
+
+ return 0;
+}
+
#define TMPBUFLEN 22
/**
* proc_get_ulong - reads an ASCII formated integer from a user buffer
@@ -2662,6 +2679,129 @@ static int proc_do_cad_pid(struct ctl_table *table, int write,
return 0;
}

+/**
+ * proc_do_large_bitmap - read/write from/to a large bitmap
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * The bitmap is stored at table->data and the bitmap length (in bits)
+ * in table->maxlen.
+ *
+ * We use a range comma separated format (e.g. 1,3-4,10-10) so that
+ * large bitmaps may be represented in a compact manner. Writing into
+ * the file will clear the bitmap then update it with the given input.
+ *
+ * Returns 0 on success.
+ */
+int proc_do_large_bitmap(struct ctl_table *table, int write,
+ void __user *_buffer, size_t *lenp, loff_t *ppos)
+{
+ int err = 0;
+ bool first = 1;
+ size_t left = *lenp;
+ unsigned long bitmap_len = table->maxlen;
+ char __user *buffer = (char __user *) _buffer;
+ unsigned long *bitmap = (unsigned long *) table->data;
+ char tr_a[] = { '-', ',', '\n', 0 }, tr_b[] = { ',', '\n', 0 }, c;
+ char tr_end[] = { '\n', 0 };
+
+
+ if (!bitmap_len || !left || (*ppos && !write)) {
+ *lenp = 0;
+ return 0;
+ }
+
+ if (write) {
+ err = proc_skip_anyof(&buffer, &left, tr_end, sizeof(tr_end));
+ while (!err && left) {
+ unsigned long val_a, val_b;
+ bool neg;
+
+ err = proc_get_ulong(&buffer, &left, &val_a, &neg, tr_a,
+ sizeof(tr_a), &c);
+ if (err)
+ break;
+ if (val_a >= bitmap_len || neg) {
+ err = -EINVAL;
+ break;
+ }
+
+ val_b = val_a;
+ if (left) {
+ buffer++;
+ left--;
+ }
+
+ if (c == '-') {
+ err = proc_get_ulong(&buffer, &left, &val_b,
+ &neg, tr_b, sizeof(tr_b),
+ &c);
+ if (err)
+ break;
+ if (val_b >= bitmap_len || neg ||
+ val_a > val_b) {
+ err = -EINVAL;
+ break;
+ }
+ if (left) {
+ buffer++;
+ left--;
+ }
+ }
+
+ if (first)
+ bitmap_clear(bitmap, 0, bitmap_len);
+
+ while (val_a <= val_b)
+ set_bit(val_a++, bitmap);
+
+ first = 0;
+ err = proc_skip_anyof(&buffer, &left, tr_end,
+ sizeof(tr_end));
+ }
+ } else {
+ unsigned long bit_a, bit_b = 0;
+
+ while (left) {
+ bit_a = find_next_bit(bitmap, bitmap_len, bit_b);
+ if (bit_a >= bitmap_len)
+ break;
+ bit_b = find_next_zero_bit(bitmap, bitmap_len,
+ bit_a + 1) - 1;
+
+ err = proc_put_ulong(&buffer, &left, bit_a, 0, first,
+ ',');
+ if (err)
+ break;
+ if (bit_a != bit_b) {
+ err = proc_put_char(&buffer, &left, '-');
+ if (err)
+ break;
+ err = proc_put_ulong(&buffer, &left, bit_b, 0,
+ 1, 0);
+ if (err)
+ break;
+ }
+
+ first = 0; bit_b++;
+ }
+ if (!err)
+ err = proc_put_char(&buffer, &left, '\n');
+ }
+
+ if (first) {
+ if (err)
+ return err;
+ bitmap_clear(bitmap, 0, bitmap_len);
+ }
+ *lenp -= left;
+ *ppos += *lenp;
+ return 0;
+}
+
#else /* CONFIG_PROC_FS */

int proc_dostring(struct ctl_table *table, int write,
--
1.5.6.5