[lldb-dev] lldb test failures on 32bit
andrew.kaylor at intel.com
Fri Aug 16 16:07:17 PDT 2013
A variation of reloc-fix-32.patch was committed today by Richard Mitton.
I need to do something with stack-fix-32.patch. If I'm reading the documentation correctly, it appears that stack frames really do need to be 8-byte aligned in Darwin even for 32-bit code.
Unfortunately, we're using the same ABI plugin for 32-bit x86 code on Darwin and Linux and at the level where this check is performed we don't know which we're looking at. As far as I know, there really isn't a significant difference between the two scenarios, so I don't think we'd want a totally separate ABI plug-in. I just need to see if there's an easy way to give it a little target information when it's created so it can handle the special cases.
As for your patch, am I correct in thinking that I should ignore the history in that review? Can you explain the change to me? What values were you seeing for sh_entsize and sh_addralign?
From: Michael Sartain [mailto:mikesart at gmail.com]
Sent: Thursday, August 15, 2013 1:07 PM
To: Greg Clayton; Kaylor, Andrew
Cc: lldb-dev at cs.uiuc.edu
Subject: Re: [lldb-dev] lldb test failures on 32bit
I realized Andrew's reloc-fix-32.patch & stack-fix-32.patch weren't checked in and I didn't have them. Applying both of those with my patch below allows me to step over the 32-bit printf() calls now.
Are those patches what you hope to check in at some point Andrew?
And please let me know if it's ok to check this in:
On Thu, Aug 15, 2013 at 10:39 AM, Michael Sartain <mikesart at gmail.com<mailto:mikesart at gmail.com>> wrote:
On Tue, Aug 13, 2013 at 6:22 PM, Michael Sartain <mikesart at gmail.com<mailto:mikesart at gmail.com>> wrote:
Unwind info does exist for addresses in main(), and all of this works as expected in x64.
I'll start debugging where this is failing...
For x86 elf files, the plt_entsize wasn't being rounded to the proper alignment - this was causing the .plt symbols to be incorrect, along with unwind info, etc. This patch fixes that:
The next problem is we're using the x64 register set, but then calling into the i386 ABI. Ie, this call:
246| addr_t pc;
247+> if (!ReadGPRValue (eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC, pc))
Winds up here:
1092| ExecutionContext exe_ctx(m_thread.shared_from_this());
1093| Process *process = exe_ctx.GetProcessPtr();
1094| if (have_unwindplan_regloc == false)
1096| // If a volatile register is being requested, we don't want to forward the next frame's register contents
1097| // up the stack -- the register is not retrievable at this frame.
1098| ABI *abi = process ? process->GetABI().get() : NULL;
1099| if (abi)
1101+> const RegisterInfo *reg_info = GetRegisterInfoAtIndex(lldb_regnum);
1102| if (reg_info && abi->RegisterIsVolatile (reg_info))
1104| UnwindLogMsg ("did not supply reg location for %d (%s) because it is volatile",
1105| lldb_regnum, reg_info->name ? reg_info->name : "??");
1106| return UnwindLLDB::RegisterSearchResult::eRegisterIsVolatile;
Which calls into this function:
903| ABIMacOSX_i386::RegisterIsCalleeSaved (const RegisterInfo *reg_info)
905| if (reg_info)
907| // Saved registers are ebx, ebp, esi, edi, esp, eip
908| const char *name = reg_info->name;
909| if (name == 'e')
reg_info->name is "rip", and so ABIMacOSX_i386::RegisterIsCalleeSaved() is returning false.
ABIMacOSX_i386.cpp looks like it does several things using register names.
> Actually, RegisterContext_i386 doesn't get used in the case of a 32-bit inferior on a 64-bit host. In that scenario we use RegisterContext_x86_64 and do some mapping under the covers for 32-bit targets.
Does this mean this is an issue with RegisterContext_x86_64 returning "rip" and not "eip"?
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