From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/fs/char_dev.c | 90 +++++++++++++++++++++------------------------
1 files changed, 42 insertions(+), 48 deletions(-)
diff --git a/kernel/fs/char_dev.c b/kernel/fs/char_dev.c
index 5fffd50..3f66729 100644
--- a/kernel/fs/char_dev.c
+++ b/kernel/fs/char_dev.c
@@ -88,21 +88,30 @@
/*
* Register a single major with a specified minor range.
*
- * If major == 0 this functions will dynamically allocate a major and return
- * its number.
+ * If major == 0 this function will dynamically allocate an unused major.
+ * If major > 0 this function will attempt to reserve the range of minors
+ * with given major.
*
- * If major > 0 this function will attempt to reserve the passed range of
- * minors and will return zero on success.
- *
- * Returns a -ve errno on failure.
*/
static struct char_device_struct *
__register_chrdev_region(unsigned int major, unsigned int baseminor,
int minorct, const char *name)
{
- struct char_device_struct *cd, **cp;
- int ret = 0;
+ struct char_device_struct *cd, *curr, *prev = NULL;
+ int ret;
int i;
+
+ if (major >= CHRDEV_MAJOR_MAX) {
+ pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
+ name, major, CHRDEV_MAJOR_MAX-1);
+ return ERR_PTR(-EINVAL);
+ }
+
+ if (minorct > MINORMASK + 1 - baseminor) {
+ pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",
+ name, baseminor, baseminor + minorct - 1, 0, MINORMASK);
+ return ERR_PTR(-EINVAL);
+ }
cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
if (cd == NULL)
@@ -120,10 +129,21 @@
major = ret;
}
- if (major >= CHRDEV_MAJOR_MAX) {
- pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
- name, major, CHRDEV_MAJOR_MAX-1);
- ret = -EINVAL;
+ ret = -EBUSY;
+ i = major_to_index(major);
+ for (curr = chrdevs[i]; curr; prev = curr, curr = curr->next) {
+ if (curr->major < major)
+ continue;
+
+ if (curr->major > major)
+ break;
+
+ if (curr->baseminor + curr->minorct <= baseminor)
+ continue;
+
+ if (curr->baseminor >= baseminor + minorct)
+ break;
+
goto out;
}
@@ -132,43 +152,14 @@
cd->minorct = minorct;
strlcpy(cd->name, name, sizeof(cd->name));
- i = major_to_index(major);
-
- for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
- if ((*cp)->major > major ||
- ((*cp)->major == major &&
- (((*cp)->baseminor >= baseminor) ||
- ((*cp)->baseminor + (*cp)->minorct > baseminor))))
- break;
-
- /* Check for overlapping minor ranges. */
- if (*cp && (*cp)->major == major) {
- int old_min = (*cp)->baseminor;
- int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
- int new_min = baseminor;
- int new_max = baseminor + minorct - 1;
-
- /* New driver overlaps from the left. */
- if (new_max >= old_min && new_max <= old_max) {
- ret = -EBUSY;
- goto out;
- }
-
- /* New driver overlaps from the right. */
- if (new_min <= old_max && new_min >= old_min) {
- ret = -EBUSY;
- goto out;
- }
-
- if (new_min < old_min && new_max > old_max) {
- ret = -EBUSY;
- goto out;
- }
-
+ if (!prev) {
+ cd->next = curr;
+ chrdevs[i] = cd;
+ } else {
+ cd->next = prev->next;
+ prev->next = cd;
}
- cd->next = *cp;
- *cp = cd;
mutex_unlock(&chrdevs_lock);
return cd;
out:
@@ -492,6 +483,9 @@
p->dev = dev;
p->count = count;
+ if (WARN_ON(dev == WHITEOUT_DEV))
+ return -EBUSY;
+
error = kobj_map(cdev_map, dev, count, NULL,
exact_match, exact_lock, p);
if (error)
@@ -553,7 +547,7 @@
}
rc = device_add(dev);
- if (rc)
+ if (rc && dev->devt)
cdev_del(cdev);
return rc;
--
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