For anonymous shm, mmap now adds a shm_file and devzero behind it
as two vm_objects. Faults are handled by copy_on_write(). Just as
shadows copy r/w pages from original files, it should copy r/w
pages from devzero into the shm_file in front.
shmat/shmget uses mmap to set-up their areas.
Untested yet so bugs expected.
modified: tasks/libl4/src/init.c
modified: tasks/mm0/include/shm.h
modified: tasks/mm0/include/vm_area.h
modified: tasks/mm0/src/fault.c
modified: tasks/mm0/src/mmap.c
modified: tasks/mm0/src/shm.c
Removed setting of tag during ipc_return(). So it does not overwrite
return value anymore.
Next stage is for the tasks to map their utcb via shmget/shmat before
accessing.
Tasks boot fine up to doing ipc using their utcbs.
UTCB PLAN:
- Push ipc registers into private environment instead of a shared utcb,
but map-in a shared utcb to pass on long data to server tasks.
- Shared utcb has unique virtual address for every thread.
- Forked child does inherit parent's utcb, but cannot use it to communicate to
any server. It must explicitly obtain its own utcb for that.
- Clone could have a flag to explicitly not inherit parent utcb, which is the
right thing to do.
- MM0 serves a syscall to obtain self utcb.
- By this method, upon forks tasks don't need to map-in a utcb unless they want
to pass long data.
Next issues: For every read fault, the fault must traverse the
vma's object stack until the page is found. The problem was that
we were only searching the first object, that object was a writable
shadow, and the shadow didn't have the read-only page, and the 0
return value was interpreted with IS_ERR() and failed, so address
0 was mapped into the location, and QEMU blew off.
The svc images must be pushed to boot file list in correct order
otherwise if test0 starts earlier than fs0, it gets fs0's predefined
thread and space id (since that's the first unallocated one) and
fs0 fails to initalise. In the future we can pre-allocate ids from
the kernel but current temporary fix is simple enough to use.
utcb as a shared page instead of the message registers.
Implemented the code that passes task information from mm0 to fs0
using the fs0 utcb. The code seems to work OK but:
There's an issue with anon pages that they end up on the same swapfile
and with same file offsets (e.g. utcb and stack at offset 0). Need to
fix this issue but otherwise this implementation seems to work.
TODO:
- Separate anon regions into separate vmfiles.
- Possibly map the stacks from virtual files so that they can be
read from userspace in the future for debugging.
- Possibly utcb could be created as a shared memory object using shmget/shmat
during startup.
Environment is backed by a special per-task file maintained by mm0 for each task.
This file is filled in by the env pager, by simple copying of env data into the
faulty page upon a fault. UTCB and all anon regions (stack) could use the same
scheme.
Fixed IS_ERR(x) to accept negative values that are above -1000 for errors. This
protects against false positives for pointers such as 0xE0000000.
modified: include/l4/generic/scheduler.h
modified: include/l4/macros.h
modified: src/arch/arm/exception.c
modified: tasks/fs0/include/linker.lds
modified: tasks/libl4/src/init.c
modified: tasks/libposix/shm.c
new file: tasks/mm0/include/env.h
modified: tasks/mm0/include/file.h
new file: tasks/mm0/include/lib/addr.h
deleted: tasks/mm0/include/lib/vaddr.h
modified: tasks/mm0/include/task.h
new file: tasks/mm0/include/utcb.h
new file: tasks/mm0/src/env.c
modified: tasks/mm0/src/fault.c
modified: tasks/mm0/src/file.c
modified: tasks/mm0/src/init.c
new file: tasks/mm0/src/lib/addr.c
modified: tasks/mm0/src/lib/idpool.c
deleted: tasks/mm0/src/lib/vaddr.c
modified: tasks/mm0/src/mmap.c
modified: tasks/mm0/src/shm.c
modified: tasks/mm0/src/task.c
new file: tasks/mm0/src/utcb.c
modified: tasks/test0/include/linker.lds
This will help when syscalls have long arguments individual
utcbs can be mapped to server tasks and kept mapped in until the
tasks die, as opposed to map requests every time a server task maps
a different utcb at the same virtual address.
The changes have preparation code to also passing the utcb info
through the stack as part of the environment.
To sum up env and arg regions have also been added above the stack and
env region is to be used to pass on the utcb address information at
task startup.
Added reading pages from the page cache into user buffer for sys_read.
Increases stack sizes to 4 pages.
Updated README to include more details about multi-pager environments.
This implements the infrastructure for read/write system calls where
file content is first searched in mm0's page cache and then read-in
or written via the vfs read/write functions.
modified: tasks/fs0/src/syscalls.c
modified: tasks/mm0/include/lib/bit.h
modified: tasks/mm0/include/lib/idpool.h
modified: tasks/mm0/include/task.h
modified: tasks/mm0/include/vm_area.h
modified: tasks/mm0/main.c
modified: tasks/mm0/src/devzero.c
modified: tasks/mm0/src/fault.c
new file: tasks/mm0/src/file.c
modified: tasks/mm0/src/init.c
modified: tasks/mm0/src/lib/bit.c
modified: tasks/mm0/src/lib/idpool.c
modified: tasks/mm0/src/task.c
We now have a single dirbuf of size PAGE_SIZE kept on the vnode. This is
to be used for directory contents only. The reason it's kept on FS0 is
because the contents are modified by calls such as mkdir or create, and otherwise
these would have been handled by mm0 on the page cache buffers, which wouldn't work.
