- move from minix/commands to minix/usr.sbin;
- install into /usr/sbin instead of /usr/bin;
- move manual page into source directory;
- resolve compilation warning;
- convert to KNF.
- move from minix/commands to minix/usr.sbin;
- install into /usr/sbin instead of /usr/bin;
- move manual page into source directory;
- resolve compilation warning;
- convert to KNF.
Currently, the userland ABI uses a single field ('user_sp') far
into the very large 'kinfo' structure on the shared kernel
information page. This precludes us from modifying or getting
rid of 'kinfo' in the future without breaking userland. This
patch adds a separate 'kuserinfo' structure to the kernel
information page, with only information that is part of the
userland ABI, in an extensible manner. Userland now uses this
field if it is present, and falls back to the old field if not.
This change serves to reduce the clutter inside the top-level kerninfo
structure, and allows other ARM-specific values to be added on the
kernel page in one place.
Please note that this information is for use by system services only!
The clock facility is not ready to be used directly by userland, and
thus, this kernel page extension is NOT part of the userland ABI.
For service programmers' convenience, change the prototype of the
getticks(3) to return the uptime clock value directly, since the call
can no longer fail.
Correct the sys_times(2) reply message to use the right field type
for the boot time.
Restructure the kernel internals a bit so as to have all the clock
stuff closer together.
Instead of importing an external _minix_kerninfo variable, any code
using the shared kernel page should now call get_minix_kerninfo(3).
Since this is the only logical name for such a function, rename the
previous get_minix_kerninfo call to ipc_minix_kerninfo.
This commits adds a basic infrastructure to support Address Space
Randomization (ASR). In a nutshell, using the already imported ASR
LLVM pass, multiple versions can be generated for the same system
service, each with a randomized, different address space layout.
Combined with the magic instrumentation for state transfer, a system
service can be live updated into another ASR-randomized version at
runtime, thus providing live rerandomization.
Since MINIX3 is not yet capable of running LLVM linker passes, the
ASR-randomized service binaries have to be pregenerated during
crosscompilation. These pregenerated binaries can then be cycled
through at runtime. This patch provides the basic proof-of-concept
infrastructure for both these parts.
In order to support pregeneration, the clientctl host script has
been extended with a "buildasr" command. It is to be used after
building the entire system with bitcode and magic support, and will
produce a given number of ASR-randomized versions of all system
services. These services are placed in /usr/service/asr in the
image that is generated as final step by the "buildasr" command.
In order to support runtime updating, a new update_asr(8) command
has been added to MINIX3. This command attempts to live-update the
running system services into their next ASR-randomized versions.
For now, this command is not run automatically, and thus must be
invoked manually.
Technical notes:
- For various reasons, magic instrumentation is x86-only for now,
and ASR functionality is therefore to be used on x86 only as well.
- The ASR-randomized binaries are placed in numbered subdirectories
so as not to have to change their actual program names, which are
assumed to be static in various places (system.conf, procfs).
- The root partition is typically too small to contain all the
produced binaries, which is why we introduce /usr/service. There
is a symlink from /service/asr to /usr/service/asr for no other
reason than to let userland continue to assume that all services
are reachable through /service.
- The ASR count field (r_asr_count/ASRcount) maintained by RS is not
used within RS in any way; it is only passed through procfs to
userland in order to allow update_asr(8) to keep track of which
version is currently loaded without having to maintain own state.
- Ideally, pre-instrumentation linking of a service would remove all
its randomized versions. Currently, the user is assumed not to
perform ASR instrumentation and then recompile system services
without performing ASR instrumentation again, as the randomized
binaries included in the image would then be stale. This aspect
has to be improved later.
- Various other issues are flagged in the comments of the various
parts of this patch.
The code could not decide whether to apply the padding to the start
or the end of the region, resulting in strange behavior because part
of the returned range might not have the right properties. With this
patch, padding is now consistently applied at the end of the region,
since virtual mmap addresses are allocated from high to low.
Also fix a few small related bugs in error handling code.
Lack of alignment causes minix_stack_fill to produce an incorrect
frame layout, subsequently resulting in a crash of the started
process. For now, we assume that the other callers of
minix_stack_fill do get an aligned buffer through sbrk(3), but this
may have to be changed later as well.
The libexec ELF parser expects to be given a word-aligned buffer,
but the ASR pass may cause VM and VFS to pass it an arbitrarily
aligned buffer, causing libexec to refuse loading the executable.
This patch aligns the buffers explicitly.
- do not allow live update for request and protocol free states if
there are any worker threads that have pending or active work;
- destroy all worker threads before such live updates and recreate
them afterwards, because transferring (the contents of) the
thread stacks is not an option at this time;
- recreate worker threads in the new instance only if they were
shut down before the state transfer, by letting RS provide the
original preparation state as initialization information.
The bitcode file given to the instrumentation pass does not include
certain weak symbols, in particular regcomp and regfree, which are
required to be visible to the magic pass for state transfer to work
correctly. This patch forces DS to make the calls using their actual
symbol names (with leading underscore), thus resolving the issue, but
this issue should really be solved in a cleaner and more generic way.
This patch is a first step towards working around the larger problem of
LLVM 3.x's use of bitcasting between structures and their elements to
deal with opaque types, replacing LLVM 2.x's actual unification. The
patch allows the pass to register a larger number of compatible types,
in particular for structure pointers passed through function calls.
A skeleton is provided for dealing with structure elements as well, but
that part requires much more work. It remains to be seen whether a
more structural approach to dealing with this problem may be warranted.
For now, this change is necessary to allow instrumented state transfer
of various "minix_timer" structures and pointers in PM and VFS.
Due to the current linker command line ordering, parts of lib(min)c
that are used exclusively by libmagic end up not being instrumented,
which then causes problems transferring pointers such as _ctype_tab_
and _tolower_tab_. As a temporary workaround, we redefine the macros
that use those pointers. A better long-term solution should
eventually render this patch obsolete.
- test multicomponent live update with and without rs and/or vm;
- retry the update a few times if the failure code suggests it might
be a transient failure.
When the malloc code is instrumented, the global _brksize variable
should not be transferred. However, when the malloc code is not
instrumented, failing to transfer _brksize would reset the heap
upon state transfer. In this patch, the magic pass stores the flag
indicating whether memory function instrumentation is disabled, in
the target process. This allows libmagic to check this flag during
state transfer, to see whether it should transfer _brksize or not.
This patch changes the VM makefile to specify that the magic pass is
to skip memory function instrumentation, and to transfer the data
variables of the malloc code (thus overriding the exception we made
for all other system services). We add two magic pass flags to
achieve this. Since the magic pass is a big bowl of spaghetti code,
ignoring whitespace changes while viewing this patch is recommended.
The NetBSD libc malloc implementation uses a memory-mapped area for
its page directory. Since the process heap is reconstructed upon
state transfer for live update, this memory-mapped area must not be
transferred to the new process. However, as the new instance of the
process being updated inherits all memory-mapped areas of the old
instance, it also automatically inherits the malloc implementation's
page directory. Thus, we must explicitly free this area in order to
avoid a memory leak.
The magic pass already detects (de)allocation functions called from
within other (de)allocation functions, which is why the mmap(2) and
munmap(2) calls of the malloc code are not instrumented as it is.
This patch changes that particular case to allow a different hook
function to be called for such "nested" allocation calls, for a
particular set of nested calls. In particular, the malloc(3) code's
mmap(2) and munmap(2) calls are replaced with magic_nested_mmap and
magic_nested_munmap calls, respectively. The magic library then
tracks memory mapping allocations of the malloc code by providing an
implementation for these two wrappers, and frees the allocations upon
state transfer.
This approach was chosen over various alternatives:
- While it appears that nesting could be established by setting a
flag while the malloc(3) wrapper is active, and testing the flag in
the mmap(2)/munmap(2) wrappers, this approach would fail to detect
memory-mapped allocations made from uninstrumented malloc(3) calls,
and therefore not a viable option.
- It would be possible to obtain the value of the variables that
store the information about the memory-mapped area in the malloc
code. However, this is rather difficult in practice due to the way
the libc malloc implementation stores the size of the are, and it
would make the solution more dependent on the specific libc malloc
implementation.
- It would be possible to use the special "nested" instrumentation
for allocations made from certain marked sections. Since we mark
the data section of the malloc code already, this would not be hard
to do. Switching to this alternative would change very little, and
if for any reason this approach yields more advantages in the
future, we can still choose to do so.
Since the heap is reconstructed upon state transfer, the old malloc
state is discarded. In order to avoid state transfer errors, we can
and in fact must discard the internal state of the malloc
implementation. This patch achieves this by using the sectionify
pass to mark the variables in the libminc malloc object as state that
must be skipped during state transfer.
RS/VM: proper preparation for multi-VM live update
Due to changed VM internals, more elaborate preparation is required
before a live update with multiple components including VM can take
place. This patch adds the essential preparation infrastructure to
VM and adapts RS to make use of it. As a side effect, it is no
longer necessary to supply RS as the last component (if at all)
during the set-up of a multicomponent live update operation.
During live update, the new instance of VM may make changes that,
after a rollback, have to be undone by the old instance of VM, in
particular because both instances share (read-write) all dynamically
allocated pages.
Make the passes we have so far, hello and WeakAliasModuleOverride,
use settings from a Makefile include file in the parent directory.
This change is in preparation of adding other passes.
Lionel Sambuc [Fri, 23 Jan 2015 17:30:39 +0000 (18:30 +0100)]
QEMU default command lines updates
- Fix a bug in clientctl which tried to test for kvm. This simply
remove this faulty test as the kvm command has been deprecated by the
QEMU project for a couple of years now.
- Specify by default 256M of RAM as this is the minimal amount required
for the whole-OS live update test to succeed.
- Update the default command printed out at the end of the x86_hdimage
script to be more generic, less focused on one use-case.
The filtering also exposed the risk that a process be killed or
swapped while on the list of VM memory requests. These cases are
now handled properly as well.
Lionel Sambuc [Mon, 26 Jan 2015 14:09:05 +0000 (15:09 +0100)]
VM: set recovery policy to restart
- Update proc to select restart policy for VM
- Update testrelpol to test the supported modes of recovery for VM
- Small code cleanups in testrelpol as well.
A missing check to see whether the range being transferred is sane
(with a starting address lower than an ending address) caused extra
memory to be marked erroneously as copy-on-write for some processes,
ultimately resulting in pagefaults on the stack during live update
rollback.
Dirk Vogt [Mon, 19 Jan 2015 14:20:30 +0000 (15:20 +0100)]
VM: live update - check for regions above stack
If the stack is not mapped at the VM_DATATOP (e.g. booted with
ac_layout = 1), there might be some more regions hiding above
the stack. We also have to transfer those.
The 'memory' service has holes in its data section, which causes
problems during state transfer. Since VM cannot handle page faults
during a multicomponent-with-VM live update, the state transfer must
ensure that no page faults occur during copying. Therefore, we now
query VM about the regions to copy, thus skipping holes. While the
solution is not ideal, it is sufficiently generic that it can be used
for the data section state transfer of all processes, and possibly
for state transfer of other regions in the future as well.
Ben Gras [Thu, 15 Jan 2015 15:47:46 +0000 (16:47 +0100)]
vm: restartability improvements (#1)
Two bugs fixed wrt vm restartability.
. make sure pagetable data is only allocated
using dynamic data instead of static spare pages
(bootstrap pages). They are needed for bootstrap
but now repeat some of the initialization so only
dynamic data remains. This solves the problem of
physical addresses changing (as static pages are
re-allocated for the new instance) after update.
. pt_ptalloc has to be specified in bytes instead of
pde slot numbers. leaving pt_pt NULL causes mapping
transfers to fail because NULL happens to be mapped in
then and updates then happen there.
. added some sanity checks against the above happening.
The new state is that VM can update many times, but the system
isn't fully reliable afterwards yet.
Ben Gras [Sun, 28 Jun 2015 22:07:29 +0000 (00:07 +0200)]
Kernel: delivermsg improvements
. make arch-independent, and local to proc.c, reduce code duplication
. make vm_suspend public but unduplicated in proc.c
. ask VM for handling once, 2nd time SIGSEGV process
. remove debug printfs
. test case for bogus sendrec() address argument
Allow extra space for in-band metadata when allocating cache blocks.
Edited by David van Moolenbroek: since this effectively halves the
potential size of the typical file system cache, do this only when
compiling with instrumentation.
Edited by David van Moolenbroek to deallocate the guard page as well.
Note that while the new approach is better in theory (previously, the
hole could end up being filled by another allocated page), guard page
protection is now broken in practice, because VM does not support
setting specific page permissions (in this case, PROT_NONE).
VM used to call sendrec to send a boot-time RS_INIT reply to RS, but
RS could run into a pagefault at the same time, thus spawning a
message to VM, resulting in a deadlock. We resolve this situation by
making VM acknowledge RS_INIT asynchronously at boot time, while
retaining the synchronous sendrec for subsequent RS_INIT responses.
The following services have been updated to support stateful restarts:
- Drivers: tty
- Filesystems: isofs, mfs, pfs, libvtreefs-based file servers
- System servers: tty, ds, pm, vfs, vm
Previously, RS would clean up dead services only when it is idle.
During shutdown, all services are marked with the 'exiting' flag,
and these flags lead RS to conclude it is not idle. Therefore, at
shutdown time, no services were cleaned up anymore, leading to
deadlock situations. For example, VFS could end up waiting for a
service that was already dead, or one driver could end up waiting
for an interrupt on a line shared with another dead driver.
While it may be possible to ignore RS_EXITING when checking idle
status, other flags may have the same ultimate effect. Therefore,
this patch skips the idle check altogether when in shutdown mode.
While in a multicomponent live update that includes RS, the new RS
instance may receive heartbeat replies which, after a rollback, the
old RS instance will then never see. As a result, the rolled-back
RS instance may end up killing well-behaving services.