This patch also takes the first step to remove backward compatibility
code from the passes. We only support the in-tree LLVM version.
Change-Id: I7836e524404afba151d1a8bfa539b505e1dbdb8e
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.
Change-Id: Ib717d86ccfced53387e72a92750d22ae980c3466
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.
Change-Id: Ia004651e21e08b0ed3f5305865c53c6659e18f38
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.
Change-Id: I5ab83b23d8437b37c44dea99537bc202469c9df6
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.
Change-Id: Id977405da86a72458dd10f18e076d8460fd2fb75
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.
Change-Id: Ie330f582c8bd45f37a878ea41fa0f9d4a18045e1
