sysctl: add proc_do_large_bitmap

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>
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 163 insertions, 0 deletions

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index f66014c90c9f..7bb5cb64f3b8 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 4a976208de29..bcfb79e94ec7 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2049,6 +2049,16 @@ static size_t proc_skip_spaces(char **buf)
         return ret;
 }
 
+static void proc_skip_char(char **buf, size_t *size, const char v)
+{
+        while (*size) {
+                if (**buf != v)
+                        break;
+                (*size)--;
+                (*buf)++;
+        }
+}
+
 #define TMPBUFLEN 22
 /**
  * proc_get_long - reads an ASCII formated integer from a user buffer
@@ -2675,6 +2685,157 @@ 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;
+        unsigned long *bitmap = (unsigned long *) table->data;
+        unsigned long *tmp_bitmap = NULL;
+        char tr_a[] = { '-', ',', '\n' }, tr_b[] = { ',', '\n', 0 }, c;
+
+        if (!bitmap_len || !left || (*ppos && !write)) {
+                *lenp = 0;
+                return 0;
+        }
+
+        if (write) {
+                unsigned long page = 0;
+                char *kbuf;
+
+                if (left > PAGE_SIZE - 1)
+                        left = PAGE_SIZE - 1;
+
+                page = __get_free_page(GFP_TEMPORARY);
+                kbuf = (char *) page;
+                if (!kbuf)
+                        return -ENOMEM;
+                if (copy_from_user(kbuf, buffer, left)) {
+                        free_page(page);
+                        return -EFAULT;
+                }
+                kbuf[left] = 0;
+
+                tmp_bitmap = kzalloc(BITS_TO_LONGS(bitmap_len) * sizeof(unsigned long),
+                                     GFP_KERNEL);
+                if (!tmp_bitmap) {
+                        free_page(page);
+                        return -ENOMEM;
+                }
+                proc_skip_char(&kbuf, &left, '\n');
+                while (!err && left) {
+                        unsigned long val_a, val_b;
+                        bool neg;
+
+                        err = proc_get_long(&kbuf, &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) {
+                                kbuf++;
+                                left--;
+                        }
+
+                        if (c == '-') {
+                                err = proc_get_long(&kbuf, &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) {
+                                        kbuf++;
+                                        left--;
+                                }
+                        }
+
+                        while (val_a <= val_b)
+                                set_bit(val_a++, tmp_bitmap);
+
+                        first = 0;
+                        proc_skip_char(&kbuf, &left, '\n');
+                }
+                free_page(page);
+        } 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;
+
+                        if (!first) {
+                                err = proc_put_char(&buffer, &left, ',');
+                                if (err)
+                                        break;
+                        }
+                        err = proc_put_long(&buffer, &left, bit_a, false);
+                        if (err)
+                                break;
+                        if (bit_a != bit_b) {
+                                err = proc_put_char(&buffer, &left, '-');
+                                if (err)
+                                        break;
+                                err = proc_put_long(&buffer, &left, bit_b, false);
+                                if (err)
+                                        break;
+                        }
+
+                        first = 0; bit_b++;
+                }
+                if (!err)
+                        err = proc_put_char(&buffer, &left, '\n');
+        }
+
+        if (!err) {
+                if (write) {
+                        if (*ppos)
+                                bitmap_or(bitmap, bitmap, tmp_bitmap, bitmap_len);
+                        else
+                                memcpy(bitmap, tmp_bitmap,
+                                        BITS_TO_LONGS(bitmap_len) * sizeof(unsigned long));
+                }
+                kfree(tmp_bitmap);
+                *lenp -= left;
+                *ppos += *lenp;
+                return 0;
+        } else {
+                kfree(tmp_bitmap);
+                return err;
+        }
+}
+
 #else /* CONFIG_PROC_FS */
 
 int proc_dostring(struct ctl_table *table, int write,