[lldb-dev] lldb test failures on 32bit
Kaylor, Andrew
andrew.kaylor at intel.com
Mon Jul 22 14:20:10 PDT 2013
I think the issue is the behavior of ptrace. The data structures we need with ptrace are determined by the host regardless of the target. This is, of course, assuming a local target. I believe we can be sure we have that by the time the RegisterContext is created.
-Andy
-----Original Message-----
From: Greg Clayton [mailto:gclayton at apple.com]
Sent: Monday, July 22, 2013 11:38 AM
To: Kaylor, Andrew
Cc: Michael Sartain; lldb-dev at cs.uiuc.edu
Subject: Re: [lldb-dev] lldb test failures on 32bit
So we have two code paths for i386? One for native 32 on 32 and one for cross 32 on 64? Can/should this be fixed?
Greg
On Jul 22, 2013, at 10:56 AM, "Kaylor, Andrew" <andrew.kaylor at intel.com> wrote:
> 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.
>
> -Andy
>
> -----Original Message-----
> From: Greg Clayton [mailto:gclayton at apple.com]
> Sent: Monday, July 22, 2013 10:19 AM
> To: Kaylor, Andrew
> Cc: Michael Sartain; lldb-dev at cs.uiuc.edu
> Subject: Re: [lldb-dev] lldb test failures on 32bit
>
> I think the i386 problems are due to RegisterContext_i386 not doing its job:
>
> bool
> RegisterContext_i386::ReadAllRegisterValues(DataBufferSP &data_sp) {
> return false;
> }
>
>
> bool
> RegisterContext_i386::WriteAllRegisterValues(const DataBufferSP &data) {
> return false;
> }
>
>
> It also seems that WriteGPR() and WriteFPR() are not implemented???
>
>
> The ReadAllRegisterValues() call is used to backup the entire register state prior to running expressions and WriteAllRegisterValues() is used to restore them after running expressions.
>
> On Jul 19, 2013, at 5:25 PM, "Kaylor, Andrew" <andrew.kaylor at intel.com> wrote:
>
>> Hmmm...
>>
>> The program I was testing with passed a format argument to printf, and that works. If I just pass a string, I do see the failure you describe below.
>>
>> The logging output says it ran into an invalid RegisterContext while unwinding. I'll take a closer look on Monday.
>>
>> -Andy
>>
>> From: Michael Sartain [mailto:mikesart at gmail.com]
>> Sent: Friday, July 19, 2013 4:24 PM
>> To: Kaylor, Andrew
>> Cc: lldb-dev at cs.uiuc.edu; Malea, Daniel; Kopec, Matt; Thirumurthi,
>> Ashok
>> Subject: Re: lldb test failures on 32bit
>>
>> I applied both patches, and the 'expr (int)printf("blah\n")' statement now works, but "n" over the printf() statement in the code still throws me somewhere else entirely. I'm on the call printf() asm instruction down below, I type "ni", and I wind up at address 0x80486f0.
>>
>> Is this working for you?
>>
>> And thanks for looking at this Andrew. Very cool we can call functions now in 32-bit targets...
>> -Mike
>>
>> (lldb) ni
>> Process 18815 stopped
>> * thread #1: tid = 0x497f, 0x08048855 blah`main(argc=1, argv=0xff985674) + 37 at blah.cpp:29, name = 'blah, stop reason = instruction step over
>> frame #0: 0x08048855 blah`main(argc=1, argv=0xff985674) + 37 at blah.cpp:29
>> 26
>> 27 int main( int argc, char *argv[] )
>> 28 {
>> -> 29 printf("hello world.\n");
>> 30
>> 31 Set *foo = new Set();
>> 32
>> (lldb) disassemble
>> blah`main at blah.cpp:28:
>> 0x8048830: push EBP
>> 0x8048831: mov EBP, ESP
>> 0x8048833: push ESI
>> 0x8048834: sub ESP, 32820
>> 0x804883a: mov EAX, DWORD PTR [EBP + 12]
>> 0x804883d: mov ECX, DWORD PTR [EBP + 8]
>> 0x8048840: mov DWORD PTR [EBP - 8], 0
>> 0x8048847: mov DWORD PTR [EBP - 12], ECX
>> 0x804884a: mov DWORD PTR [EBP - 16], EAX
>> 0x804884d: mov EAX, ESP
>> 0x804884f: mov DWORD PTR [EAX], 134515168
>> -> 0x8048855: call 0x80486f0
>> 0x804885a: mov ECX, ESP
>> 0x804885c: mov DWORD PTR [ECX], 1
>> 0x8048862: mov DWORD PTR [EBP - 32804], EAX
>> 0x8048868: call 0x8048700
>> 0x804886d: mov ECX, EAX
>> 0x804886f: mov EDX, EAX
>> 0x8048871: mov ESI, ESP
>> 0x8048873: mov DWORD PTR [ESI], EAX
>> 0x8048875: mov DWORD PTR [EBP - 32808], EDX
>> 0x804887b: mov DWORD PTR [EBP - 32812], ECX
>> 0x8048881: call 0x8048800 ; Set at blah.cpp:23
>> 0x8048886: jmp 0x804888b ; main + 91 at blah.cpp:31
>> 0x804888b: mov EAX, DWORD PTR [EBP - 32812]
>> 0x8048891: mov DWORD PTR [EBP - 20], EAX
>> 0x8048894: mov DWORD PTR [EBP - 32800], 0
>> 0x804889e: cmp DWORD PTR [EBP - 32800], 8192
>> 0x80488a8: jae 0x80488ef ; main + 191 at blah.cpp:38
>> 0x80488ae: call 0x8048710
>> 0x80488b3: mov ECX, DWORD PTR [EBP - 32800]
>> 0x80488b9: mov DWORD PTR [EBP + 4*ECX - 32796], EAX
>> 0x80488c0: mov EAX, DWORD PTR [EBP - 32800]
>> 0x80488c6: add EAX, 1
>> 0x80488cb: mov DWORD PTR [EBP - 32800], EAX
>> 0x80488d1: jmp 0x804889e ; main + 110 at blah.cpp:34
>> 0x80488d6: mov DWORD PTR [EBP - 24], EAX
>> 0x80488d9: mov DWORD PTR [EBP - 28], EDX
>> 0x80488dc: mov EAX, DWORD PTR [EBP - 32808]
>> 0x80488e2: mov DWORD PTR [ESP], EAX
>> 0x80488e5: call 0x80486d0 ; symbol stub for: _Unwind_Resume
>> 0x80488ea: jmp 0x80488fb ; main + 203 at blah.cpp:31
>> 0x80488ef: mov EAX, DWORD PTR [EBP - 8]
>> 0x80488f2: add ESP, 32820
>> 0x80488f8: pop ESI
>> 0x80488f9: pop EBP
>> 0x80488fa: ret
>> 0x80488fb: mov EAX, DWORD PTR [EBP - 24]
>> 0x80488fe: mov DWORD PTR [ESP], EAX
>> 0x8048901: call 0x8048730
>> (lldb) ni
>> Process 18815 stopped
>> * thread #1: tid = 0x497f, 0x080486f0 blah, name = 'blah, stop reason = instruction step over
>> frame #0: 0x080486f0 blah
>> -> 0x80486f0: jmp DWORD PTR [134520844]
>> 0x80486f6: push 24
>> 0x80486fb: jmp 0x80486b0 ; blah..plt + 0
>> 0x8048700: jmp DWORD PTR [134520848]
>>
>> On Fri, Jul 19, 2013 at 3:34 PM, Kaylor, Andrew <andrew.kaylor at intel.com> wrote:
>> Hi Mike,
>>
>> I think I've tracked down the sources of both of these problems.
>>
>> The problem with not being able to call functions in the target seems to be a failure in the MCJIT relocation mechanism. Because LLDB is generating IR with absolute addresses for function calls, the JITed code contains relocations with absolute values rather than symbols. This is a problem I fixed a short time ago, but it seems to have come undone again (at least in this particular case). The attached 'reloc-fix-32.patch' (to be applied to the LLVM repository) should fix that.
>>
>> I need to do a bit of investigation to settle some questions about why this condition came back or was specific to the 32-bit case before I commit this, but I think this is correct.
>>
>> The problem where you lose source after stepping seems to be a matter of incorrect stack unwinding. There were two problems lurking here.
>>
>> First, the RegisterContext::ConvertBetweenRegisterKinds() function wasn't making any provision for a 32-bit inferior running on a 64-bit target. The way the x86-64 register context class is implemented it defines 64-bit registers and 32-bit registers in the same RegisterInfo structure, and there is some overlap in how these get mapped to DWARF/GDB/GCC register numbers. RegisterContext::ConvertBetweenRegisterKinds() was just iterating through the list and returning the first match it found, which was the 64-bit register.
>>
>> I added a special case to call RegisterContext::ConvertRegisterKindToRegisterNumber() when the target kind is eRegisterKindLLDB. This invokes the RegisterContext_x86_64 overload of that method which knows how to distinguish the 32-bit and 64-bit registers. I'm not convinced that this is the best way to solve this problem, but it works.
>>
>> The second issue was that the ABIMacOSX_i386 plug-in (which also gets used for 32-bit inferiors on Linux) was rejecting call frame addresses that weren't 8-byte aligned whereas, at least on Linux, 4-byte alignment is allowed. If 32-bit processes on MacOSX require 8-byte alignment then we'll need to do some additional checking, but for now I just modified it to only check for 4-byte alignment.
>>
>> Both of the stack unwinding issues should be fixed by the attached 'stack-fix-32.patch' file.
>>
>> Can you try out these patches and verify that they work for you?
>>
>> Thanks,
>> Andy
>>
>> From: Michael Sartain [mailto:mikesart at gmail.com]
>> Sent: Tuesday, July 16, 2013 6:14 PM
>> To: Malea, Daniel; Kaylor, Andrew; Kopec, Matt; Thirumurthi, Ashok
>> Cc: Matthew Sorrels
>> Subject: Fwd: lldb test failures on 32bit
>>
>> I think the below are the largest 32-bit blocking issues right now.
>>
>> Is this something any of you have any familiarity with and have time to look at?
>>
>> If not, let me know and I'll start investigating...
>>
>> Thanks much!
>> -Mike
>>
>> #################################
>> ## Can't call functions in target
>> #################################
>> mikesart at mikesart-rad:~/data/src/blah2/build$ lldb -x -- blah Current
>> executable set to 'blah' (i386).
>> (lldb) b main
>> Breakpoint 1: where = blah`main + 29 at blah.cpp:29, address =
>> 0x0804884d
>> (lldb) r
>> Process 6745 launched: '/home/mikesart/data/src/blah2/build/blah'
>> (i386) Process 6745 stopped
>> * thread #1: tid = 0x1a59, 0x0804884d blah`main(argc=1, argv=0xfffc8c54) + 29 at blah.cpp:29, name = 'blah, stop reason = breakpoint 1.1
>> frame #0: 0x0804884d blah`main(argc=1, argv=0xfffc8c54) + 29 at blah.cpp:29
>> 26
>> 27 int main( int argc, char *argv[] )
>> 28 {
>> -> 29 printf("hello world.\n");
>> 30
>> 31 Set *foo = new Set();
>> 32
>> (lldb) expr (int)printf("hi there!\n");
>> error: Execution was interrupted, reason: invalid address (fault address: 0xeef60020).
>> The process has been returned to the state before expression evaluation.
>> (lldb) n
>> Process 6745 exited with status = -1 (0xffffffff)
>>
>> #################################
>> ## Lose source with first next command
>> #################################
>> mikesart at mikesart-rad:~/data/src/blah2/build$ lldb -x -- blah Current
>> executable set to 'blah' (i386).
>> (lldb) b main
>> Breakpoint 1: where = blah`main + 29 at blah.cpp:29, address =
>> 0x0804884d
>> (lldb) r
>> Process 7471 launched: '/home/mikesart/data/src/blah2/build/blah'
>> (i386) Process 7471 stopped
>> * thread #1: tid = 0x1d2f, 0x0804884d blah`main(argc=1, argv=0xffb36464) + 29 at blah.cpp:29, name = 'blah, stop reason = breakpoint 1.1
>> frame #0: 0x0804884d blah`main(argc=1, argv=0xffb36464) + 29 at blah.cpp:29
>> 26
>> 27 int main( int argc, char *argv[] )
>> 28 {
>> -> 29 printf("hello world.\n");
>> 30
>> 31 Set *foo = new Set();
>> 32
>> (lldb) n
>> Process 7471 stopped
>> * thread #1: tid = 0x1d2f, 0x080486f0 blah, name = 'blah, stop reason = step over
>> frame #0: 0x080486f0 blah
>> -> 0x80486f0: jmpl *134520844
>> 0x80486f6: pushl $24
>> 0x80486fb: jmp 0x80486b0 ; blah..plt + 0
>> 0x8048700: jmpl *134520848
>> (lldb)
>>
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