I've been trying to understand these changes and I thought it might be nice
to share my notes with others. This could be a good example for how to do
certain things in the kernel. For example, from these changes, I figured
out that to create a new system call, you have to:
1) Add entry points into arch/i386/kernel/entry.S
2) Define the new system calls, starting with sys_ and using asmlinkage in
the function definition.
3) Add #defines for each into include/asm-i386/unistd.h
4) Increase NR_syscalls in include/linux/sys.h
I have included some other high-level notes, including a kind of ad-hoc
cross reference for eventpoll.c. I would appreciate any comments if anyone
thinks this kind of documentation would be useful.
diff -Nru linux-2.5.44.vanilla/arch/i386/kernel/entry.S
linux-2.5.44.epoll/arch/i386/kernel/entry.S
// Add entry points for the three new system calls
diff -Nru linux-2.5.44.vanilla/drivers/char/Makefile
linux-2.5.44.epoll/drivers/char/Makefile
// Add eventpoll
diff -Nru linux-2.5.44.vanilla/drivers/char/eventpoll.c
linux-2.5.44.epoll/drivers/char/eventpoll.c
// New module
// In cases where one entity is used by only one other entity, I indent
that entity under its user.
// Define struct eventpoll (created by open_eventpoll and stored in
file->private_data field)
// Define struct epitem, which is contained in a list by eventpoll.
// You can identify the system calls because they all use asmlinkage:
// sys_epoll_create
// Uses ep_getfd();
// Uses get_eventpoll_inode();
// sys_epoll_ctl
// sys_epoll_wait
// Additionally, you have these function pointer tables:
// eventpoll_fops
// Contains write_eventpoll
// Contains ioctl_eventpoll
// Contains mmap_eventpoll
// Contains open_eventpoll
// Contains close_eventpoll
// Uses ep_free();
// Contains poll_eventpoll
// Used by eventpoll_miscdev
// Used by eventpoll_init
// Used by eventpoll_exit
// Used by ep_getfd
// Used by get_eventpoll_inode
// eventpoll_mmap_ops
// Contains eventpoll_mm_open,
// Contains eventpoll_mm_close,
// Used by mmap_eventpoll (part of eventpoll_fops)
// eventpollfs_dentry_operations
// Contains eventpollfs_delete_dentry();
// Used by ep_getfd
// eventpoll_fs_type
// Uses eventpollfs_get_sb()
// Used by eventpoll_init
// Used by eventpoll_exit
// And then you have the functions:
// ep_free_pages();
// Used by ep_free
// Used by ep_do_alloc_pages
// Used by ioctl_eventpoll
// ep_find_nl();
// Used by ep_find
// Used by ep_remove
// Used by ioctl_eventpoll
// ep_find();
// Used by sys_epoll_ctl
// Used by write_eventpoll
// ep_insert();
// Used by sys_epoll_ctl
// Used by write_eventpoll
// Uses ep_hashresize();
// ep_remove();
// Used by sys_epoll_ctl
// Used by write_eventpoll
// notify_proc()
// Used by ep_free (as parm to file_notify_...)
// Used by ep_insert (as parm to file_notify_...)
// Used by ep_remove (as parm to file_notify_...)
// open_eventpoll();
// Used by eventpoll_fops
// Used by sys_epoll_create
// Uses ep_init();
// ep_poll();
// Used by sys_epoll_wait
// Used by ioctl_eventpoll
// ep_do_alloc_pages();
// Used by sys_epoll_create
// Used by ioctl_eventpoll
// Uses ep_alloc_pages();
diff -Nru linux-2.5.44.vanilla/fs/Makefile linux-2.5.44.epoll/fs/Makefile
// Add fcblist
diff -Nru linux-2.5.44.vanilla/fs/fcblist.c linux-2.5.44.epoll/fs/fcblist.c
// New module
diff -Nru linux-2.5.44.vanilla/fs/file_table.c
linux-2.5.44.epoll/fs/file_table.c
// Add calls to file_notify_init and file_notify_cleanup (defined in
fcblist)
diff -Nru linux-2.5.44.vanilla/fs/pipe.c linux-2.5.44.epoll/fs/pipe.c
// Add call to file_send_notify when pipe ceases to be full/empty.
// Add support for POLL_HUP to pipe_release
// Add code to set up/initialize PIPE_READFILE/WRITEFILE
diff -Nru linux-2.5.44.vanilla/include/asm-i386/poll.h
linux-2.5.44.epoll/include/asm-i386/poll.h
// Add POLLREMOVE (reference only by write_eventpoll, perhaps used by
user-code?)
diff -Nru linux-2.5.44.vanilla/include/asm-i386/unistd.h
linux-2.5.44.epoll/include/asm-i386/unistd.h
// Create #defines for the three news system calls.
diff -Nru linux-2.5.44.vanilla/include/linux/eventpoll.h
linux-2.5.44.epoll/include/linux/eventpoll.h
// New module
diff -Nru linux-2.5.44.vanilla/include/linux/fcblist.h
linux-2.5.44.epoll/include/linux/fcblist.h
// New module
diff -Nru linux-2.5.44.vanilla/include/linux/fs.h
linux-2.5.44.epoll/include/linux/fs.h
// Add file callback list and rw lock to ???.
diff -Nru linux-2.5.44.vanilla/include/linux/list.h
linux-2.5.44.epoll/include/linux/list.h
// Added #defines for various generic list-access operations.
// Only one used is list_first, by these functions: ep_free,
ep_hashresize, file_notify_cleanup
diff -Nru linux-2.5.44.vanilla/include/linux/pipe_fs_i.h
linux-2.5.44.epoll/include/linux/pipe_fs_i.h
// Add new fields for rdfile and wrfile
// Add macros PIPE_READFILE and PIPE_WRITEFILE to access new fields.
diff -Nru linux-2.5.44.vanilla/include/linux/sys.h
linux-2.5.44.epoll/include/linux/sys.h
// Increased NR_syscalls (by 4 instead of 3...why???)
diff -Nru linux-2.5.44.vanilla/include/net/sock.h
linux-2.5.44.epoll/include/net/sock.h
// Added code to sk_wake_async to call file_send_notify. This call given
priority over the older method.
// My only question here is what was sk->socket->file being used for
before? It's not a new field, and I see no other code
// that references it.
diff -Nru linux-2.5.44.vanilla/net/ipv4/tcp.c
linux-2.5.44.epoll/net/ipv4/tcp.c
// Changes old call to sock_wake_async to now call sk_wake_async. It
appears that sk_wake_async winds up calling
// sock_wake_async for the old case anyway.
-
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This archive was generated by hypermail 2b29 : Thu Oct 31 2002 - 22:00:48 EST