Explicitly set entry point arch when it's thumb [Second Try]
I found a case where the main android binary (app_process32) had thumb code at its entry point but no entry in the symbol table indicating this. This made lldb set a 4 byte breakpoint at that address (we default to arm code) instead of a 2 byte one (like we should for thumb).
The big deal with this is that the expression evaluator uses the entry point as a way to know when a JITed expression has finished executing by putting a breakpoint there. Because of this, evaluating expressions on certain android devices (Google Pixel something) made the process crash.
This was fixed by checking this specific situation when we parse the symbol table and add an artificial symbol for this 2 byte range and indicating that it's arm thumb.
I created 2 unit tests for this, one to check that now we know that the entry point is arm thumb, and the other to make sure we didn't change the behaviour for arm code.
I also run the following on the command line with the app_process32 where I found the issue:
(lldb) dis -s 0x1640 -e 0x1644 app_process32[0x1640]: .long 0xf0004668 ; unknown opcode
(lldb) dis -s 0x1640 -e 0x1644 app_process32`: app_process32[0x1640] <+0>: mov r0, sp app_process32[0x1642]: andeq r0, r0, r0
Reviewers: clayborg, labath, wallace, espindola
Reviewed By: labath
Subscribers: labath, lldb-commits, MaskRay, kristof.beyls, arichardson, emaste, srhines
Differential Revision: https://reviews.llvm.org/D68533