Date: Sun, 06 Mar 2016 11:43:29 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 207736] clang 3.8.0/powerpc's _Unwind_RaiseException code generation has messed up r31 (frame pointer) save/restore code (SEGV's can result) Message-ID: <bug-207736-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D207736 Bug ID: 207736 Summary: clang 3.8.0/powerpc's _Unwind_RaiseException code generation has messed up r31 (frame pointer) save/restore code (SEGV's can result) Product: Base System Version: 11.0-CURRENT Hardware: ppc OS: Any Status: New Severity: Affects Only Me Priority: --- Component: bin Assignee: freebsd-bugs@FreeBSD.org Reporter: markmi@dsl-only.net [This has been reported on llvm bugzilla: 26856.] The below causes gdb difficulties for its stack handling: more than just exception handling is at issue. I just happened to notice it via exception handling. Function _Unwind_RaiseException below is from a FreeBSD "buildworld" using clang 3.8.0. Dump of assembler code for function _Unwind_RaiseException: 0x41b2ab80 <+0>: mflr r0 0x41b2ab84 <+4>: stw r31,-148(r1) 0x41b2ab88 <+8>: stw r30,-152(r1) 0x41b2ab8c <+12>: stw r0,4(r1) 0x41b2ab90 <+16>: stwu r1,-2992(r1) 0x41b2ab94 <+20>: mr r31,r1 . . . 0x41b2abe0 <+96>: stw r31,2844(r31) (which replaces the earlier save of the old Frame pointer R31 value with a copy of r1's current value. Note the offset relationships with the r1 adjustment: -2992+2844=3D-148) . . . 0x41b2add0 <+592>: lwz r31,2844(r31) (This restores the r1 value that resulted from the "stwu r1,-2992(r1)" into R31.) . . . 0x41b2ae30 <+688>: lwz r31,-148(r1) (This restores the r1 value that resulted from the "stwu r1,-2992(r1)" into R31.) . . . The wrong r31 value is present when _Unwind_RaiseException returns. But before that while _Unwind_RaiseException is active the C++ exception handling infrastructure has been given bad r31 information for around _Unwind_RaiseException's frame. --=20 You are receiving this mail because: You are the assignee for the bug.=
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