The old path walking algorithm requires recursion, which is not
supported in async rust. So we boxed them all as a temporary solution in
previous commits. This would introduce mass overhead even for fast path
walks just because we might sleep in `readlink()` and `lookup()` calls.

The new proposed method is to break the walk into several phases similar
to that in Linux: RCU walk and REF walk. The RCU walk will hold the RCU
lock and never blocks so the function itself can be non-async. If we hit
non-present dentries, we will fallback to REF walk. In REF walks, we
clone the Arcs and consult to the VFS layer for an accurate answer.

Note that in both the two methods mentioned above, symlinks are not
handled and will be returned directly with all path components left
untouched. We have a dedicated async function to follow the symlinks by
recursive calling the walk function. This can be slow and won't be
called frequently. So we wrapped the function with `Box::pin()` to break
the recursion chain. After the symlink resolution is done, we return to
the original position and continue the walk.

We found that the association of an inode to a dentry is one way. So the
`data` RCUPointer field is actually unnecessary and we can use the atomic
dentry type to sync readers with the writer. This way we can eliminate
`DentryData` allocations and improve performance.

We also introduced a new RCU read lock syntax. In the RCU walk mentioned
above, we need to store dentry references protected by some RCU read lock.
With the old syntax, we can't express the lifetime associtated by the
common RCU read lock. The new syntax provides a `rcu_read_lock()` method
to acquire the RCU read lock. The lock returned has a associated lifetime
so we can use it in the RCU session.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Signed-off-by: greatbridf <greatbridf@icloud.com>

If we have invalid format, we should print a None instead of panicking.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Introduce the new page locking mechanism to ensure exclusiveness of
pages when we access them. The underlying locks are not implemented yet
for now because we will change the paging structs in the following few
patches.

Introduce a new `PageExcl` struct representing a page that conforms with
Rust's ownership rules. The page owned exclusively can be accessed
without taking page locks.

Remove the `MemoryBlock` structs as they are not easy to use and
represent barely no semantic meanings.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Separate old UserTLS into UserTLS and UserTLSDescriptor.

UserTLS is for threads to hold infomation about its storage. Descriptors
are used in clone syscalls.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Signed-off-by: greatbridf <greatbridf@icloud.com>

Introduce `Zone`s: a Zone is a region of physical memory that all share
the same NUMA node. The Zone will hold all RawPage structs. Buddy
allocator will now store a reference to the zone that hold all its
pages. Thus, we make the buddy allocator independent of underlying
physical page frame management framework.

Remove unnecessary page flags and structs.

Signed-off-by: greatbridf <greatbridf@icloud.com>

- Bump rust compiler version to nightly-2026-01-09.
- Inode rework: add a generic Inode struct.
- Add a macro to help function tweaks.
- PageCache rework: reduce complexity and try to decouple.
- Adapt fat32, tmpfs to the new page cache system.
- Change the way we process mapped pages and load ELF executables.
- Refine handling flags in `MMArea::handle_mmap`.

Signed-off-by: greatbridf <greatbridf@icloud.com>

- Remove struct `Page` and add `Folio`s to represent adjacent pages.
- Introduce `Zone`s similar to that in Linux. Looking forward to
  removing all occurrence of `ArchPhysAccess` and so on.
- Adapt existing code to new `Folio` interface in a dirty and rough way.

Signed-off-by: greatbridf <greatbridf@icloud.com>

- Add script/backtrace to translate backtraces.
- Add a cut sign in the kernel panic routine to indicate the start of
  stack backtrace.

Signed-off-by: greatbridf <greatbridf@icloud.com>

No functional changes

- Add `{extern_,}symbol_addr` macro to retrieve symbol address.
- Remove manual impl Send and Sync for RawPage
- Make elided '_ lifetimes in return types explicit
- Suppress unused warnings by allowing them
- Remove really unused functions
- Refactor `println_trace` macro to suppress unused variable warnings

Signed-off-by: greatbridf <greatbridf@icloud.com>

Make print message prettier. Also panic when we have an error.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Signed-off-by: greatbridf <greatbridf@icloud.com>

- thd.exit() will set thd.dead and send it to the reaper
- delay the release of process mm until we reap it
- extract futex logic out of exit and exec routine

Signed-off-by: greatbridf <greatbridf@icloud.com>

- Use intrusive lists to store and organize the process hierarchy.
- Remove `FileArray::open_console()`. Do it in the init script instead.
- Fix open logic: acquire controlling terminals only if O_NOCTTY is not
  set. Put this into TerminalFile::open().
- Send SIGHUP and then SIGCONT to foreground pgroup procs when the
  controlling terminal is dropped.
- Set the controlling terminal of sessions in Terminal.
- Limit max line width to 80. Format some codes.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Reformat the files with new the format style to make the real changes
clearer.

Signed-off-by: greatbridf <greatbridf@icloud.com>

We already have `FDT.present_ram().free_ram()`. Remove the impl in
`ArchMemory` to avoid confusion.

Signed-off-by: greatbridf <greatbridf@icloud.com>

- Add `extern_symbol_value` to retrieve far relative symbol values.
- Get `BSS_LENGTH` and `__kernel_end` using `extern_symbol_addr`.
- Get `_ap_start` using `extern_symbol_value`.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Signed-off-by: greatbridf <greatbridf@icloud.com>

With current ldscript, linkers will put vdso data after `__kernel_end`,
which is buggy since we use the symbol to indicate the end of our kernel
image and newly allocated pages may overwrite those positions.

Change by place the vdso inside REGION_DATA. Remove old VDSO memory
region. Align .data section end to page size border.

Add a helper macro to retrieve .vdso section symbol addresses.

Signed-off-by: greatbridf <greatbridf@icloud.com>

Strip out the memory used by the kernel and FDT data out of free memory
block returned by FDT.

Closes: #54 ("Random kernel freezing on process creation / exiting")
Fixes: 4351cf5 ("partial work: fix riscv64 bootstrap")
Signed-off-by: greatbridf <greatbridf@icloud.com>

Using *const (), no bytes are written to the position, which might
result in uninitialized memory access.

Fixes: ebd3d12 ("change(x86): optimize bootstrap code, remove kinit.cpp")
Fixes: 191877a ("feat(hal): impl basic single hart bootstrap for riscv64")
Signed-off-by: greatbridf <greatbridf@icloud.com>

Signed-off-by: greatbridf <greatbridf@icloud.com>

This can shorten qemu memory map.

Signed-off-by: greatbridf <greatbridf@icloud.com>