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Changes in the README, changes to fork template.

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This commit is contained in:
Bahadir Balban
2008-08-16 13:01:18 +03:00
parent d434ad4b40
commit f436b44e81
7 changed files with 138 additions and 42 deletions
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61
README
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@@ -44,10 +44,11 @@ In terms of other features, the microkernel is preemptive, and smp-ready.
Currently only synchronous communication is implemented, but this will change in
the near future.
MM0 is the system task that implements memory management. It contains memory and
page allocators. It implements demand paging by managing page faults, physical
pages and their file/task associations. It provides the default paging mechanism
on Codezero.
There are two system tasks built upon the base microkernel that manage memory
and file-based I/O, called MM0 and FS0. MM0 is the system task that implements
memory management. It contains memory and page allocators. It implements demand
paging by managing page faults, physical pages and their file/task associations.
It provides the default paging mechanism on Codezero.
FS0 is the system task that implements a simple, modern virtual filesystem layer.
It is designed to serve file requests from MM0. Since it abstracts the low-level
@@ -118,19 +119,30 @@ more closely. Many embedded software projects still use older or closed
development methods and the right open source methodology would prove favorable
in the fast-paced nature of embedded software development.
Finally, POSIX compliance is only a step, or a temporary aim for the Codezero
Finally, POSIX compliance is only a step, or a partial aim for the Codezero
microkernel. It is not limited to the goal of just complying with POSIX, which
has been done many times by other operating systems. There are new ideas in
literature that would improve systems software but aren't implemented either
because they have no existing users or may break compatibility (e.g. some are
presented in Plan 9). For example file abstractions could be used more
liberally to cover data exchange and control of devices, services and network
communication. Existing kernels already have established methods of doing such
operations and they would oppose major design overhauls, which limits their
innovation capability for this kind of experimentation. As well as practising
realistic development strategies such as POSIX compliance, Codezero project aims
to keep up with the latest OS literature and provide the opportunity to
incorporate the latest ideas in OS technology.
has been done many times by other operating systems. The idea is to implement
a generic software environment where multiple system services can reside in
the same run-time, but on the other hand, provide natively implemented resource
management services to be used as the default solution. In other words, the
project will provide the mechanism to accomodate multiple operating systems,
and it will also supply its own set of system services with a POSIX-like API.
By providing a variety of system-level software options, the applications
will be able to choose among different speed, safety, determinism policies at
the same run-time. This is expected to prove useful in embedded software
problems.
Furthermore there are new ideas in literature that would improve systems
software but aren't implemented either because they have no existing users or
may break compatibility (e.g. some are presented in Plan 9). For example file
abstractions could be used more liberally to cover data exchange and control of
devices, services and network communication. Existing kernels already have
established methods of doing such operations and they would oppose major design
overhauls, which limits their innovation capability for this kind of
experimentation. As well as practising realistic development strategies such as
native POSIX support, Codezero project aims to keep up with the latest OS
literature and provide the opportunity to incorporate the latest ideas in OS
technology.
Can you summarise all this? Why should I use Codezero, again?
@@ -138,13 +150,14 @@ Can you summarise all this? Why should I use Codezero, again?
Codezero is an operating system that targets embedded systems. It supports the
most fundamental posix calls and it implements modern features such as
demand-paging and virtual filesystem layer. Different from most other posix-like
systems, it is based on a microkernel design. It has a cleanly separated set of
services, it is small and well-focused. Its design is carefully thought out, so
it's not just a mock-up implementation of the existing POSIX API. Its source
code is also freely available (See LICENSE heading). For these reasons it is a
good candidate as systems software to be used on embedded platforms. Currently
it has little or no users, therefore compared to systems with a saturated user
base it is possible to tailor it rapidly towards the needs of any users who want
to be the first to incorporate it for their needs.
systems, it is based on a microkernel design. This makes it possible to use it
also as a base for implementing or running other operating systems. It has a
cleanly separated set of system services, it is small and well-focused. Its
design is carefully thought out, so it's not simply a mock-up implementation of
the existing POSIX API. Its source code is also freely available (See LICENSE
heading). For these reasons it is a good candidate as systems software to be
used on embedded platforms. Currently it has little or no users, therefore
compared to systems with a saturated user base project developers are available
to tailor it rapidly towards the needs of any interested users.

8
src/api/thread.c
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@@ -62,6 +62,14 @@ int thread_start(struct task_ids *ids)
/*
* Creates a thread, with a new thread id, and depending on whether the space
* id exists, either adds it to an existing space or creates a new space.
*
* NOTE: Add: Depending on whether the thread id exists, it creates a new space
* copying the space of that thread id.
*
* For example:
* thread id = inval, space id = inval, -> new thread, new space.
* thread id = x, space id = inval, -> new thread, new space, copying space of x
* thread id = inval, space id = x, -> new thread, use space x.
*/
int thread_create(struct task_ids *ids)
{

46
tasks/libposix/fork.c Normal file
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@@ -0,0 +1,46 @@
/*
* l4/posix glue for fork()
*
* Copyright (C) 2008 Bahadir Balban
*/
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <l4lib/arch/syscalls.h>
#include <l4lib/arch/syslib.h>
#include <l4lib/ipcdefs.h>
#include <l4lib/utcb.h>
#include <l4/macros.h>
#include INC_GLUE(memory.h)
static inline int l4_fork(void)
{
int err;
/* Call pager with open() request. Check ipc error. */
if ((err = l4_sendrecv(PAGER_TID, PAGER_TID, L4_IPC_TAG_FORK)) < 0) {
printf("%s: L4 IPC Error: %d.\n", __FUNCTION__, err);
return err;
}
/* Check if syscall itself was successful */
if ((err = l4_get_retval()) < 0) {
printf("%s: OPEN Error: %d.\n", __FUNCTION__, err);
return err;
}
return err;
}
int fork(void)
{
int ret = l4_fork();
/* If error, return positive error code */
if (ret < 0) {
errno = -ret;
return -1;
}
/* else return value */
return ret;
}

2
tasks/mm0/include/syscalls.h
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@@ -43,5 +43,7 @@ struct sys_shmget_args {
int sys_shmget(key_t key, int size, int shmflg);
int sys_fork(void);
#endif /* __MM0_SYSARGS_H__ */

6
tasks/mm0/main.c
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@@ -100,7 +100,7 @@ void handle_requests(void)
case L4_IPC_TAG_CLOSE:
sys_close(sender, (int)mr[0]);
break;
case L4_IPC_TAG_FSYNC:
sys_fsync(sender, (int)mr[0]);
break;
@@ -120,6 +120,10 @@ void handle_requests(void)
args->flags, args->fd, __pfn(args->offset));
break;
}
case L4_IPC_TAG_MMAP: {
sys_fork(sender);
break;
}
case L4_IPC_TAG_BRK: {
// sys_brk(sender, (void *)mr[0]);
// break;

25
tasks/mm0/src/clone.c
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@@ -3,7 +3,7 @@
*
* Copyright (C) 2008 Bahadir Balban
*/
#include <syscalls.h>
int copy_tcb(struct tcb *p, struct tcb *c)
{
@@ -28,20 +28,33 @@ int do_fork(struct tcb *parent)
{
struct tcb *child;
/* Make all parent shadows read only */
vm_freeze_shadows(parent);
/* Create a new L4 thread with new space */
l4_thread_create(parent);
/* Create a new local tcb */
child = tcb_alloc_init();
/* Make all parent shadows read only */
vm_freeze_shadows(parent);
/* Copy parent tcb to child */
copy_tcb(struct tcb *parent, struct tcb *child);
/* FIXME: Copy parent page tables to child ??? */
/* FIXME: Copy parent register values to child ??? */
/*
* Allocate and copy parent pgd + all pmds to child.
*
* When a write fault occurs on any of the frozen shadows,
* fault handler creates a new shadow on top, if it hasn't,
* and then starts adding writeable pages to the new shadow.
* Every forked task will fault on every page of the frozen shadow,
* until all pages have been made copy-on-write'ed, in which case
* the underlying frozen shadow is collapsed.
*
* Every forked task must have its own copy of pgd + pmds because
* every one of them will have to fault on frozen shadows individually.
*/
/* FIXME: Need to copy parent register values to child ??? */
/* Notify fs0 about forked process */
vfs_send_fork(parent, child);

32
tasks/test0/main.c
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@@ -10,7 +10,8 @@
#include <l4lib/utcb.h>
#include <l4lib/ipcdefs.h>
#include <tests.h>
#include <unistd.h>
#include <sys/types.h>
void wait_pager(l4id_t partner)
{
@@ -23,23 +24,32 @@ void wait_pager(l4id_t partner)
void main(void)
{
pid_t pid;
printf("\n%s: Started with tid %d.\n", __TASKNAME__, self_tid());
/* Sync with pager */
wait_pager(0);
dirtest();
printf("File IO test 1:\n");
if (fileio() == 0)
printf("-- PASSED --\n");
else
printf("-- FAILED --\n");
printf("File IO test 2:\n");
if (fileio2() == 0)
printf("-- PASSED --\n");
else
printf("-- FAILED --\n");
printf("Forking...\n");
if ((pid = fork()) < 0)
printf("Error forking...\n");
if (pid == 0) {
printf("File IO test 1, done by child:\n");
if (fileio() == 0)
printf("-- PASSED --\n");
else
printf("-- FAILED --\n");
} else {
printf("File IO test 2, done by parent, with child pid %d:\n", pid);
if (fileio2() == 0)
printf("-- PASSED --\n");
else
printf("-- FAILED --\n");
}
while (1)
wait_pager(0);
#if 0