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Subject[net-next PATCH v3 2/3] sysctl: add proc_dobitmap
Date
The new function can be used to update bitmaps via /proc. Bits can be
set by writing positive values in the file and cleared by writing
negative values (e.g. 0 2 will set bits 1 and 3, -0 -2 will clear
them). Reading will show only the set bits.

Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Cc: WANG Cong <amwang@redhat.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
---
include/linux/sysctl.h | 2 +
kernel/sysctl.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 78 insertions(+), 0 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 9f236cd..ba89bf2 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -985,6 +985,8 @@ 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_dobitmap(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 b0f9618..b8959f4 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2596,6 +2596,82 @@ static int proc_do_cad_pid(struct ctl_table *table, int write,
return 0;
}

+/**
+ * proc_dobitmap - read/write from/to a 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
+ * @ppos: the current position in the file
+ *
+ * The bitmap is stored at table->data and the bitmap length (in bits)
+ * in table->maxlen. Reading from the proc file will show the set bits.
+ * Writing positive values sets the bits, negative values clears them
+ * (e.g. 0 2 sets the first and 3rd bit, -0 -2 clears them).
+ *
+ * Returns 0 on success.
+ */
+int proc_dobitmap(struct ctl_table *table, int write,
+ void __user *_buffer, size_t *lenp, loff_t *ppos)
+{
+ bool first = 1;
+ unsigned long *bitmap = (unsigned long *) table->data;
+ unsigned long bitmap_len = table->maxlen;
+ int left = *lenp, err = 0;
+ char __user *buffer = (char __user *) _buffer;
+
+ if (!bitmap_len || !left || (*ppos && !write)) {
+ *lenp = 0;
+ return 0;
+ }
+
+ if (write) {
+ while (left) {
+ unsigned long val;
+ bool neg;
+
+ err = proc_get_next_ulong(&buffer, &left, &val, &neg);
+ if (err)
+ break;
+ if (val >= bitmap_len) {
+ err = -EINVAL;
+ break;
+ }
+ if (neg)
+ clear_bit(val, bitmap);
+ else
+ set_bit(val, bitmap);
+ first = 0;
+ }
+ if (!err)
+ err = proc_skip_wspace(&buffer, &left);
+ } else {
+ unsigned long bit = 0;
+
+ while (left) {
+ bit = find_next_bit(bitmap, bitmap_len, bit);
+ if (bit >= bitmap_len)
+ break;
+ err = proc_put_ulong(&buffer, &left, bit, 0, first);
+ if (err)
+ break;
+ first = 0; bit++;
+ }
+ if (!err)
+ err = proc_put_newline(&buffer, &left);
+ }
+
+ if (first && write && !err)
+ err = -EINVAL;
+ if (err == -EFAULT /* do we really need to check for -EFAULT? */ ||
+ (write && first))
+ return err ? : -EINVAL;
+ *lenp -= left;
+ *ppos += *lenp;
+ return 0;
+}
+
#else /* CONFIG_PROC_FS */

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


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