Provides a new mechanism for dumpstate (while running as root)
to request that debuggerd dump the stacks of native processes that
we care about in bug reports. In this mode, the backtrace
is formatted to look similar to a Dalvik backtrace.
Moved the tombstone generating code into a separate file to
make it easier to maintain.
Fixed a bug where sometimes the stack traces would be incomplete
because we were not waiting for each thread to stop after issuing
PTRACE_ATTACH, only the main thread. So sometimes we were missing
traces for some threads.
Refactored the logging code to prevent accidentally writing data
to logcat when explicitly dumping a tombstone or backtrace from the
console.
Only root or system server can request to dump backtraces but
only root can dump tombstones.
Bug: 6615693
Change-Id: Ib3edcc16f9f3a687e414e3f2d250d9500566123b
Keep track of whether memory maps are readable. Use the information
in try_get_word to try to avoid accidentally dereferencing an invalid
pointer within the current process. (Note that I haven't ever
seen that happen during normal unwinding, but it pays to be
a little more careful.)
Refactored try_get_word a little to make it easier to pass it the
needed state for validation checks by way of a little memory_t struct.
Improved how the memory map for the current process is cached. This is
important because we need up to date information about readable maps.
Use a 5 second cache expiration.
Improved the PC -> LR fallback logic in the unwinder so we can
eke out an extra frame sometimes.
Fixed a bug reading ELF program headers. The phnum & phentsize
fields are half-words. We were incorrectly interpreting
phnum as a whole word.
Used android_atomic_* operations carefully in the unwinder
to prevent possible memory races between the dumper and the dumpee.
This was highly unlikely (or even impossible due to the presence
of other barriers along the way) but the code is clearer now about
its invariants.
Fixed a bug in debuggerd where the pid was being passed to have
its stack dump taken instead of the tid, resulting in short
stacks because ptrace couldn't read the data if pid != tid.
Did a full sweep to ensure that we use pid / tid correctly everywhere.
Ported old code from debuggerd to rewind the program counter back
one instruction so that it points to the branch instruction itself
instead of the return address.
Change-Id: Icc4eb08320052975a4ae7f0f5f0ac9308a2d33d7
