<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: arial,helvetica,sans-serif; font-size: 10pt; color: #000000'><br><hr id="zwchr"><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; color: rgb(0, 0, 0); font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><b>From: </b>"Eric Christopher" <echristo@gmail.com><br><b>To: </b>"Tim Shen" <timshen@google.com>, llvm-dev@lists.llvm.org, "Hal Finkel" <hfinkel@anl.gov>, "Kit Barton" <kbarton@ca.ibm.com><br><b>Sent: </b>Wednesday, February 10, 2016 6:59:50 PM<br><b>Subject: </b>Re: [llvm-dev] [PPC] Linker fails on -fstack-protector<br><br><div dir="ltr"><br><br><div id="DWT10746" class="gmail_quote"><div dir="ltr">On Mon, Jan 25, 2016 at 11:58 AM Tim Shen via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div dir="ltr"><div>When -fstack-protector is turned on, linker fails to find the symbol "<span style="color: rgb(0, 0, 0); line-height: normal; white-space: pre-wrap;">__stack_chk_guard" because at least for powerpc64le, glibc doesn't provide this symbol. Instead, they put the stack guard into TCB.</span></div><div><span style="color: rgb(0, 0, 0); line-height: normal; white-space: pre-wrap;"><br></span></div><div><span id="DWT10745" style="color: rgb(0, 0, 0); line-height: normal; white-space: pre-wrap;">x86 fixed this issue by injecting a special address space (which is later translated to TCB register access) and hard code the offset of stack_guard, but I don't see a easy way to handle address spaces in ppc.</span></div></div></blockquote><br></div></div></blockquote><br>Why is handling address spaces in ppc any more difficult than doing so for x86?<br><br> -Hal<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; color: rgb(0, 0, 0); font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><div dir="ltr"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div dir="ltr"><div><span style="color: rgb(0, 0, 0); line-height: normal; white-space: pre-wrap;"></span></div><div><span style="color: rgb(0, 0, 0); line-height: normal; white-space: pre-wrap;"><br></span></div><div><span style="color: rgb(0, 0, 0); line-height: normal; white-space: pre-wrap;">A cleaner solution could be adding an IR intrinsic llvm.get_tcb_address() and hard code the offset of stack_guard member, since they aren't supposed to change.</span></div><div><br></div>Details are in the bug: <a href="https://llvm.org/bugs/show_bug.cgi?id=26226" target="_blank">https://llvm.org/bugs/show_bug.cgi?id=26226</a><br><div><br></div><div>Any ideas?</div><div><br></div></div></blockquote><div><br></div><div>Not a huge fan of a ppc specific intrinsic (which it should be, so llvm.ppc... if we go that route) to do this. I actually rather liked the cleanliness of the address space solution for x86. How much work would it be to do that? Alternately: Hal, Kit, what do you two think as far as the ppc backend?</div><div><br></div><div>The other solution you mentioned - combining the slot load into the existing intrinsic might work, we'd just need to figure out how to autoupgrade everything into it which might be a bit more difficult than fixing the backends and dealing. Have you looked into how the autoupgrade would work?</div><div><br></div><div>Thanks!</div><div><br></div><div>-eric</div><div> </div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div dir="ltr"><div></div><div>Thanks!</div></div>
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</blockquote><br><br><br>-- <br><div><span name="x"></span>Hal Finkel<br>Assistant Computational Scientist<br>Leadership Computing Facility<br>Argonne National Laboratory<span name="x"></span><br></div></div></body></html>