> On Dec 12, 2014, at 12:17 PM, Philippe Lavoie <philippe.lav...@octasic.com> > wrote: > > Hi, > > I have an issue with frame unwinding using .eh_frame > > The PC for our architecture is a dword pointer. To enable the LLDB frame > unwinder to see it as a byte pointer when using CFI, I encoded the return > address value in a DWARF expression. > > When RA (r3) is in a register the expression is: > DW_CFA_val_expression: r3 (DW_OP_reg3 (r3); DW_OP_lit2; DW_OP_shl) > > When RA has been pushed on the stack (r2), the expression is: > DW_CFA_val_expression: r3 (DW_OP_breg2 (r2): -8; DW_OP_deref; DW_OP_lit2; > DW_OP_shl) > > Up until r217185 the stack unwinding was working fine. But since we resynced > our code with the more recent r221593, the return address is not evaluated > according to the DWARF expression. The unwinder just uses R3. > > (lldb) bt > th1/fr0 requested caller's saved PC but this UnwindPlan uses a RA reg; > getting r3 (3) instead > th1/fr0 supplying caller's register r3 (3) from the live RegisterContext at > frame 0, saved in 3 <<<<<<<<<<<< > th1/fr1 pc = 0x100014 > th1/fr0 supplying caller's saved r2 (2)'s location using eh_frame CFI > UnwindPlan > th1/fr0 supplying caller's register r2 (2) from the stack, saved at CFA plus > offset -4 > th1/fr1 fp = 0x7fff7f8 > th1/fr0 supplying caller's stack pointer r1 (1) value, computed from CFA > th1/fr1 sp = 0x7fff7d8 > > Was a bug introduced in LLDB? Or is our use of DWARF expressions to retrieve > the return address not "standards compliant"?
I am not sure, you can put a breakpoint in: DWARFExpression::Evaluate() at DWARFExpression.cpp:1348 And you can step through it to verify. It will get run in the "if" statement at RegisterContextLLDB.cpp:1445. Let us know what you find. Greg _______________________________________________ lldb-dev mailing list lldb-dev@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
