[Lldb-commits] [PATCH] 32-bit linux Remove WriteRegOperation's explicit GetAsUInt32() call

[Todd Fiala]

This also is now in as part of r202887.


On Tue, Mar 4, 2014 at 1:34 AM, Matthew Gardiner <mg11 at csr.com> wrote:

> Hi folks
>
> Even with the register map fixed (see UserArea in
> RegisterContextLinux_i386.cpp)
> an assertion failure occurs:
>
> $ lldb hello
> Current executable set to 'hello' (i386).
> (lldb) log enable linux ptrace
> (lldb) run
> operation ptrace(PTRACE_SETOPTIONS, 2667, (nil), 0x58, 0)=0 called from
> file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 1456
> Process 2667 launching
> operation ptrace(PTRACE_TRACEME, 0, (nil), (nil), 0)=0 called from file
> /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 1196
> operation ptrace(PTRACE_PEEKDATA, 2667, 0x8048340, (nil), 0)=895EED31
> called from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 245
> operation ptrace(PTRACE_PEEKDATA, 2667, 0x8048340, (nil), 0)=895EED31
> called from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 245
> operation ptrace(PTRACE_POKEDATA, 2667, 0x8048340, 0x895eedcc, 0)=0 called
> from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 319
> operation ptrace(PTRACE_PEEKDATA, 2667, 0x8048340, (nil), 0)=895EEDCC
> called from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 245
> operation ptrace(PTRACE_POKEUSER, 2667, 0x114, 0xffffffff, 0)=0 called
> from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 543
> operation ptrace(PTRACE_POKEUSER, 2667, 0x118, 0xffffffff, 0)=0 called
> from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 543
> operation ptrace(PTRACE_PEEKUSER, 2667, 0x114, (nil), 0)=FFFFFFFF called
> from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 494
> operation ptrace(PTRACE_PEEKUSER, 2667, 0x114, (nil), 0)=FFFFFFFF called
> from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 494
> operation ptrace(PTRACE_POKEUSER, 2667, 0x114, 0xffffffff, 0)=0 called
> from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 543
> operation ptrace(PTRACE_PEEKUSER, 2667, 0x118, (nil), 0)=FFFFFFFF called
> from file /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 494
> operation ptrace(PTRACE_PEEKUSER, 2667, 0xfc, (nil), 0)=0 called from file
> /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/Linux/ProcessMonitor.cpp line 494
> lldb: /home/mg11/src/heracles/llvm/tools/lldb/source/Plugins/
> Process/POSIX/POSIXThread.cpp:530: void POSIXThread::WatchNotify(const
> ProcessMessage&): Assertion `wp_sp.get() && "No watchpoint found"' failed.
> Aborted (core dumped)
>
> The root cause of this is that 0xffffffff is written to dr6/7 originally
> from
> RegisterContextPOSIXProcessMonitor_x86.cpp, whereas the programmer
> intended
> 0 to be written:
>
> RegisterContextPOSIXProcessMonitor_x86_64::IsWatchpointHit(uint32_t
> hw_index)
> {
> <snip>
>         RegisterValue zero_bits = RegisterValue(uint64_t(0));
>         if (!WriteRegister(m_reg_info.first_dr + 6, zero_bits) ||
> !WriteRegister(m_reg_info.first_dr + 7, zero_bits))
>
> Construction of the RegisterValue as uint64_t and the subsequent
> conditional
> compilation of 32-bit code within ProcessMonitor.cpp
>
> void
> WriteRegOperation::Execute(ProcessMonitor *monitor)
> {
> <snip>
> #if __WORDSIZE == 32
>     buf = (void*) m_value.GetAsUInt32();
> #else
>
> combined with RegisterValue's implementation returning "fail_value" for
> wrapped 64-bit data accessed as 32-bits.
>
> Removal of the preprocessing step, relies on the compiler forcing
> truncation
> to 32-bit, when compiled on 32-bit platform, more faithfully than the
> explicit GetAsUInt32().
>
> Please could someone apply the attached patch which fixes the fail_value
> return. I tested this on 32-bit by launching a program, stopping, setting
> a break, then resuming it. It was fine. I can't test 64-bit yet, but
> clearly
> my proposed patch results in the 64-bit code being unchanged.
>
> Index: source/Plugins/Process/Linux/ProcessMonitor.cpp
> ===================================================================
> --- source/Plugins/Process/Linux/ProcessMonitor.cpp     (revision 202675)
> +++ source/Plugins/Process/Linux/ProcessMonitor.cpp     (working copy)
> @@ -532,11 +532,7 @@
>      void* buf;
>      Log *log (ProcessPOSIXLog::GetLogIfAllCategoriesSet
> (POSIX_LOG_REGISTERS));
>
> -#if __WORDSIZE == 32
> -    buf = (void*) m_value.GetAsUInt32();
> -#else
>      buf = (void*) m_value.GetAsUInt64();
> -#endif
>
>      if (log)
>          log->Printf ("ProcessMonitor::%s() reg %s: %p", __FUNCTION__,
> m_reg_name, buf);
>
> thanks
> Matt
>
> PS
>
> (If this patch is applied *and* the debug register offset problem fixed -
> I'm uploading separate patch - then 32-bit linux debug experience is
> sane).
>
>
>
>
>
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-- 
Todd Fiala | Software Engineer | tfiala at google.com | 650-943-3180
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