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Fix an x86 assembler stack unwind calculation for non-volatile registers. 

This change has the practical effect of fixing some backtrace
scenarios that would fail with inferiors running on the Android Art
host-side JVM under Linux x86_64 on Ubuntu 14.04.

See this lldb-commits thread for more details:
http://lists.cs.uiuc.edu/pipermail/lldb-commits/Week-of-Mon-20140721/011988.html

Change by Tong Shen.
Reviewed by Jason Molenda.

Tested:
Ubuntu 14.04 x86_64, clang-3.5-built lldb.
MacOSX 10.10 Preview 4, Xcode 6 Beta 4-built lldb.

llvm-svn: 213914
This commit is contained in:
Todd Fiala 2014-07-25 01:15:34 +00:00
parent c6abd96bff
commit d947406427
1 changed files with 13 additions and 1 deletions
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14
lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
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@ -373,6 +373,12 @@ bool AssemblyParse_x86::push_reg_p (int& regno) {
// movq %rax, -0x10(%rbp) [0x48 0x89 0x45 0xf0]
// movl %eax, -0xc(%ebp) [0x89 0x45 0xf4]
// The offset value returned in rbp_offset will be positive --
// but it must be subtraced from the frame base register to get
// the actual location. The positive value returned for the offset
// is a convention used elsewhere for CFA offsets et al.
bool AssemblyParse_x86::mov_reg_to_local_stack_frame_p (int& regno, int& rbp_offset) {
uint8_t *p = m_cur_insn_bytes;
int src_reg_prefix_bit = 0;
@ -633,7 +639,13 @@ AssemblyParse_x86::get_non_call_site_unwind_plan (UnwindPlan &unwind_plan)
{
row->SetOffset (current_func_text_offset + insn_len);
UnwindPlan::Row::RegisterLocation regloc;
regloc.SetAtCFAPlusOffset (-row->GetCFAOffset());
// stack_offset for 'movq %r15, -80(%rbp)' will be 80.
// In the Row, we want to express this as the offset from the CFA. If the frame base
// is rbp (like the above instruction), the CFA offset for rbp is probably 16. So we
// want to say that the value is stored at the CFA address - 96.
regloc.SetAtCFAPlusOffset (-(stack_offset + row->GetCFAOffset()));
row->SetRegisterInfo (lldb_regno, regloc);
unwind_plan.AppendRow (row);
// Allocate a new Row, populate it with the existing Row contents.