DragonOS Kernel Core API
Circular Linked List Management Functions
Circular linked list is one of the important data structures in the kernel. It is included in kernel/common/list.h.
void list_init(struct List *list)
Description
Initialize a List structure so that its prev and next pointers point to itself.
Parameters
list
The List structure to be initialized.
void list_add(struct List *entry, struct List *node)
Description
Insert the node after the entry.
Parameters
entry
An existing node in the circular linked list.
node
The node to be inserted.
void list_append(struct List *entry, struct List *node)
Description
Insert the node before the entry.
Parameters
entry
An existing node in the circular linked list.
node
The node to be inserted.
void list_del(struct List *entry)
Description
Remove the node from the list.
Parameters
entry
The node to be removed.
list_del_init(struct List *entry)
Description
Remove the node from the list and re-initialize the entry using list_init().
Parameters
entry
The node to be removed.
bool list_empty(struct List *entry)
Description
Check if the list is empty.
Parameters
entry
A node in the list.
struct List *list_prev(struct List *entry)
Description
Get the previous node of the entry.
Parameters
entry
A node in the list.
struct List *list_next(struct List *entry)
Description
Get the next node of the entry.
Parameters
entry
A node in the list.
void list_replace(struct List *old, struct List *new)
Description
Replace the old node in the list with the new node.
Parameters
old
The node to be removed.
new
The new node to be inserted into the list.
list_entry(ptr, type, member)
Description
This macro can get the address of the structure that contains the List pointed to by ptr.
Parameters
ptr
Pointer to the List structure.
type
The type of the structure that contains the List.
member
The name of the List structure member in the structure that contains the List.
list_first_entry(ptr, type, member)
Description
Get the first element in the list. Please note that this macro requires the list to be non-empty, otherwise it will cause an error.
Parameters
Same as list_entry()
list_first_entry_or_null(ptr, type, member)
Description
Get the first element in the list. If the list is empty, return NULL.
Parameters
Same as list_entry()
list_last_entry(ptr, type, member)
Description
Get the last element in the list. Please note that this macro requires the list to be non-empty, otherwise it will cause an error.
Parameters
Same as list_entry()
list_last_entry_or_full(ptr, type, member)
Description
Get the last element in the list. If the list is empty, return NULL.
Parameters
Same as list_entry()
list_next_entry(pos, member)
Description
Get the next element in the list.
Parameters
pos
Pointer to the outer structure.
member
The name of the List structure member in the outer structure.
list_prev_entry(pos, member)
Description
Get the previous element in the list.
Parameters
Same as list_next_entry()
list_for_each(ptr, head)
Description
Traverse the entire list (from front to back).
Parameters
ptr
Pointer to the List structure.
head
Pointer to the head node of the list (struct List*).
list_for_each_prev(ptr, head)
Description
Traverse the entire list (from back to front).
Parameters
Same as list_for_each()
list_for_each_safe(ptr, n, head)
Description
Traverse the entire list from front to back (supports deletion of the current list node).
This macro uses a temporary variable to prevent errors that may occur during iteration if the current ptr node is deleted.
Parameters
ptr
Pointer to the List structure.
n
Pointer to store the temporary value (List type).
head
Pointer to the head node of the list (struct List*).
list_for_each_prev_safe(ptr, n, head)
Description
Traverse the entire list from back to front (supports deletion of the current list node).
This macro uses a temporary variable to prevent errors that may occur during iteration if the current ptr node is deleted.
Parameters
Same as list_for_each_safe()
list_for_each_entry(pos, head, member)
Description
Iterate through the list of a given type from the beginning.
Parameters
pos
Pointer to a structure of the specific type.
head
Pointer to the head node of the list (struct List*).
member
The name of the List member in the structure pointed to by pos.
list_for_each_entry_reverse(pos, head, member)
Description
Iterate through the list of a given type in reverse order.
Parameters
Same as list_for_each_entry()
list_for_each_entry_safe(pos, n, head, member)
Description
Iterate through the list of a given type from the beginning (supports deletion of the current list node).
Parameters
pos
Pointer to a structure of the specific type.
n
Pointer to store the temporary value (same type as pos).
head
Pointer to the head node of the list (struct List*).
member
The name of the List member in the structure pointed to by pos.
list_prepare_entry(pos, head, member)
Description
Prepare a 'pos' structure for list_for_each_entry_continue() .
Parameters
pos
Pointer to a structure of the specific type, used as the starting point for iteration.
head
Pointer to the struct List structure to start iteration from.
member
The name of the List member in the structure pointed to by pos.
list_for_each_entry_continue(pos, head, member)
Description
Continue iterating through the list from the next element of the specified position.
Parameters
pos
Pointer to a structure of the specific type. This pointer is used as the iteration pointer.
head
Pointer to the struct List structure to start iteration from.
member
The name of the List member in the structure pointed to by pos.
list_for_each_entry_continue_reverse(pos, head, member)
Description
Iterate through the list in reverse order, starting from the previous element of the specified position.
Parameters
Same as list_for_each_entry_continue()
list_for_each_entry_from(pos, head, member)
Description
Continue iterating through the list from the specified position.
Parameters
Same as list_for_each_entry_continue()
list_for_each_entry_safe_continue(pos, n, head, member)
Description
Continue iterating through the list from the next element of the specified position (supports deletion of the current list node).
Parameters
pos
Pointer to a structure of the specific type. This pointer is used as the iteration pointer.
n
Pointer to store the temporary value (same type as pos).
head
Pointer to the struct List structure to start iteration from.
member
The name of the List member in the structure pointed to by pos.
list_for_each_entry_safe_continue_reverse(pos, n, head, member)
Description
Iterate through the list in reverse order, starting from the previous element of the specified position (supports deletion of the current list node).
Parameters
Same as list_for_each_entry_safe_continue()
list_for_each_entry_safe_from(pos, n, head, member)
Description
Continue iterating through the list from the specified position (supports deletion of the current list node).
Parameters
Same as list_for_each_entry_safe_continue()
Basic C Function Library
Kernel programming differs from application layer programming; you will not be able to use functions from LibC. To address this, the kernel implements some commonly used C language functions, trying to make their behavior as close as possible to standard C library functions. It is important to note that the behavior of these functions may differ from standard C library functions, so it is recommended to carefully read the following documentation, which will be helpful to you.
String Operations
int strlen(const char *s)
Description
Measure and return the length of the string.
Parameters
src
Source string.
long strnlen(const char *src, unsigned long maxlen)
Description
Measure and return the length of the string. If the string length is greater than maxlen, return maxlen.
Parameters
src
Source string.
maxlen
Maximum length.
long strnlen_user(const char *src, unsigned long maxlen)
Description
Measure and return the length of the string. If the string length is greater than maxlen, return maxlen.
This function performs address space validation, requiring the src string to be from user space. If the source string is from kernel space, it will return 0.
Parameters
src
Source string, located in user space.
maxlen
Maximum length.
char *strncpy(char *dst, const char *src, long count)
Description
Copy a string of count bytes and return the dst string.
Parameters
src
Source string.
dst
Destination string.
count
Length of the source string to copy.
char *strcpy(char *dst, const char *src)
Description
Copy the source string and return the dst string.
Parameters
src
Source string.
dst
Destination string.
long strncpy_from_user(char *dst, const char *src, unsigned long size)
Description
Copy a string of count bytes from user space to kernel space, and return the size of the copied string.
This function performs address space validation to prevent address space overflow issues.
Parameters
src
Source string.
dst
Destination string.
size
Length of the source string to copy.
int strcmp(char *FirstPart, char *SecondPart)
Description
Compare the sizes of two strings.
Return Value
| Situation | Return Value |
|---|---|
| FirstPart == SecondPart | 0 |
| FirstPart > SecondPart | 1 |
| FirstPart < SecondPart | -1 |
Parameters
FirstPart
First string.
SecondPart
Second string.
Memory Operations
void *memcpy(void *dst, const void *src, uint64_t size)
Description
Copy memory from src to dst.
Parameters
dst
Pointer to the destination address.
src
Pointer to the source address.
size
Size of data to be copied.
void *memmove(void *dst, const void *src, uint64_t size)
Description
Similar to memcpy(), but this function prevents data from being incorrectly overwritten when the source and destination memory regions overlap.
Parameters
dst
Pointer to the destination address.
src
Pointer to the source address.
size
Size of data to be copied.