<div dir="rtl"><div dir="ltr">I see. It is different than the gcc runtime libgcc. </div><div dir="ltr"><br></div><div dir="ltr">libgcc always uses the set of FDE which was registered by __register_frame. This data is private to every process since unwind runs in user space as part of the process.</div>
<div dir="ltr"><br></div><div dir="ltr">Here, the OS first locates which set of FDE is relevant. </div><div dir="ltr">Does this mean that in OS-X unwind runs in system space and holds FDE data for all processes?</div><div dir="ltr">
<br></div><div dir="ltr">Yaron</div><div dir="ltr"><br></div><div dir="ltr"><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote"><div dir="ltr">2013/10/31 Nick Kledzik <span dir="ltr"><<a href="mailto:kledzik@apple.com" target="_blank">kledzik@apple.com</a>></span></div>
<blockquote class="gmail_quote" style="margin:0 .8ex;border-left:1px #ccc solid;border-right:1px #ccc solid;padding-left:1ex;padding-right:1ex"><div style="word-wrap:break-word"><br><div><div class="im"><div>On Oct 30, 2013, at 3:22 PM, Yaron Keren <<a href="mailto:yaron.keren@gmail.com" target="_blank">yaron.keren@gmail.com</a>> wrote:</div>
<br><blockquote type="cite"><div dir="rtl"><div dir="ltr">Hi,</div><div dir="ltr"><br></div><div dir="ltr">You are exactly correct, LocalAddressSpace::findUnwindSections does nothing #if !APPLE so the output value is random.</div>
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<div dir="ltr">LocalAddressSpace::findOtherFDE and LocalAddressSpace::findFunctionName also currently do nothing. Are these also required for regular exceptions?</div></div></blockquote></div><div>No. </div><div><br></div>
<div>findOtherFDE() is only need if the OS has an alternate way to locate FDEs such as those for JITed code.</div><div><br></div><div>findFunctionNam() is used in debug builds to print out the name of functions as the unwinding happens.</div>
<span class="HOEnZb"><font color="#888888"><div><br></div><div>-Nick</div></font></span><div><div class="h5"><div><br></div><br><blockquote type="cite"><div dir="rtl"><div dir="ltr"><br></div></div><div class="gmail_extra">
<div class="gmail_quote"><div dir="ltr">2013/10/31 Nick Kledzik <span dir="ltr"><<a href="mailto:kledzik@apple.com" target="_blank">kledzik@apple.com</a>></span></div>
<blockquote class="gmail_quote" style="margin:0 .8ex;border-left:1px #ccc solid;border-right:1px #ccc solid;padding-left:1ex;padding-right:1ex"><div style="word-wrap:break-word"><div>Yaron,</div><div><br></div><div>Each separately linked image (program, DLLs, etc) has its own set of FDEs (in its .eh_frame) section. The method LocalAddressSpace::findUnwindSections() needs to be updated in an OS specific way to: 1) find the image for a given pc value, and 2) find the .eh_frame section bounds for that image.</div>
<span><font color="#888888"><div><br></div><div>-Nick</div></font></span><div><div><div><br></div><br><div><div>On Oct 30, 2013, at 3:03 PM, Yaron Keren <<a href="mailto:yaron.keren@gmail.com" target="_blank">yaron.keren@gmail.com</a>> wrote:</div>
<blockquote type="cite"><div dir="rtl"><div dir="ltr">Hi Nick,</div><div dir="ltr"><br></div><div dir="ltr">I looked at the disassembly, unw_getcontext() gets the correct IP into the context and later setInfoBasedOnIPRegister gets it right into "pc". This is OK.</div>
<div dir="ltr"> </div><div dir="ltr">The trouble is, the whole address space is nowhere near the fde values. For example, </div><div dir="ltr"><br></div><div dir="ltr"><font face="courier new, monospace">p = 0x66179070 <libunwind::DwarfFDECache<libunwind::LocalAddressSpace>::_initialBuffer></font></div>
<div dir="ltr"><font face="courier new, monospace">pc = 0x6604e7d9</font></div><div dir="ltr"><font face="courier new, monospace">fde = 0x40801c0</font></div><div dir="ltr"><font face="courier new, monospace">p->ip_start = 0x4080010</font></div>
<div dir="ltr"><font face="courier new, monospace">p->ip_end = 0x408010c</font></div><div dir="ltr"><br></div><div dir="ltr">p is consistent with pc and local vars and addresses in unwind.dll (0x66YYYYYY)</div><div dir="ltr">
fde is consistent with the ip ranges and with the caller of unwind.dll (the throwing function) address space (0x40800YY)</div><div dir="ltr"><br></div><div dir="ltr">they live in different memory ranges, the fde addresses are in caller range whereas the unwind addresses are in the DLL range so when it tries to find its IP in the fde tables it can't find.</div>
<div dir="ltr"><br></div><div dir="ltr">It's as if the DLL is supposed to load in other memory range, some linker option required?</div><div dir="ltr"><br></div><div dir="ltr">Yaron</div><div dir="ltr"><br></div></div>
<div class="gmail_extra"><br><br><div class="gmail_quote"><div dir="ltr">2013/10/29 Nick Kledzik <span dir="ltr"><<a href="mailto:kledzik@apple.com" target="_blank">kledzik@apple.com</a>></span></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><br>
On Oct 29, 2013, at 12:11 AM, Yaron Keren <<a href="mailto:yaron.keren@gmail.com" target="_blank">yaron.keren@gmail.com</a>> wrote:<br>
<br>
> Hello,<br>
><br>
> I'm trying to make libcxxabi / Unwind work on Windows / MingW 32 bit. Attached is a patch to make it compile without warnings and run without crashing.<br>
><br>
> However the functionality isn't working yet: upon exception, the IP seems to be completely out of range the FDE tables. This may be related to the memory model / compilation options???<br>
</div>Take a look at UnwindRegisterRestore.s. When an exception is thrown, unw_getcontext() is called which saves all registers and the return address into a register struct. Then the FDE info is used to step through each frame and modify the register set. At which step is the IP register out of bounds?<br>
<br>
It might be that the C files need to be compiled with -fexceptions so that they have unwind tables.<br>
<span><font color="#888888"><br>
-Nick<br>
<br>
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