Adds new function to perform a pure stack walk without unwinding,
functionally similar to backtrace() but accelerated by an address
attribute cache the caller maintains across calls.
bad/missing unwind information, which could result in libunwind
dereferencing bad pointers. This mechanism is based on msync(2) system
call and significantly reduces the chances of a bad pointer
dereference in libunwind.
The original idea was to turn this mechanism on only when necessary
i.e. libunwind didn't find proper unwind information for a IP.
There are a couple of problems in the current implementation.
* The flag is global and is modified without locking
* The flag isn't reset when starting a new unwind
The attached patch makes ->validate a per-thread setting by moving it
into struct cursor from unw_local_addr_space and resets it to false
when starting a new unwind. As a result, cursor->as_arg points to the
cursor itself instead of the ucontext (for the local case).
This was found to reduce the number of msync() system calls from an
application using libunwind significantly.
Signed-off-by: Paul Pluzhnikov <ppluzhnikov@google.com>
Signed-off-by: Arun Sharma <arun.sharma@google.com>
include/dwarf.h: Declare dwarf_reg_state_pool and dwarf_cie_info_pool.
include/dwarf_i.h: Include libunwind_i.h instead of tdep.h.
Make dwarf_to_unw_regnum() a macro so it doesn't get compiled
into an object file merely because it include dwarf_i.h (important
when optimization is turned off).
(dwarf_read_encoded_pointer_inlined): New function.
include/tdep-x86/libunwind_i.h: Add include of "mempool.h".
include/tdep-x86_64/libunwind_i.h: Add include of "mempool.h".
