Crashes in world built w/ clang: FP registers?

[Kostik Belousov]

On Fri, Sep 16, 2011 at 10:34:40PM -0500, Jason Harmening wrote:
> Hi everyone,
> 
> Using clang as the default compiler, the kernel and drivers will work
> fine, but a lot of programs in the base system and ports will crash w/
> SIGBUS.  In fact, so much of the stuff in the chroot'ed world will
> crash (everything from csh to gcc) that it's basically unusable.  I
> finally got around to building w/ debug symbols, and ran gdb on a
> coredump generated while I was trying to use tab completion in csh:
> 
> (gdb) bt
> #0  tw_collect (command=dwarf2_read_address: Corrupted DWARF expression.)
>     at /usr/src/bin/csh/../../contrib/tcsh/tw.parse.c:1308
> #1  0x000000000042777b in t_search (word=Unhandled dwarf expression opcode 0x0)
>     at /usr/src/bin/csh/../../contrib/tcsh/tw.parse.c:1725
> #2  0x0000000000426829 in tenematch (inputline=Variable "inputline" is
> not avail               able.)
>     at /usr/src/bin/csh/../../contrib/tcsh/tw.parse.c:301
> #3  0x000000000043545d in Inputl ()
>     at /usr/src/bin/csh/../../contrib/tcsh/ed.inputl.c:415
> #4  0x0000000000417a90 in readc (wanteof=Variable "wanteof" is not available.)
>     at /usr/src/bin/csh/../../contrib/tcsh/sh.lex.c:1653
> #5  0x0000000000416f37 in lex (hp=Variable "hp" is not available.)
>     at /usr/src/bin/csh/../../contrib/tcsh/sh.lex.c:162
> #6  0x0000000000405afb in process (catch=Unhandled dwarf expression opcode 0x0)
>     at /usr/src/bin/csh/../../contrib/tcsh/sh.c:1922
> #7  0x0000000000404b51 in main (argc=Variable "argc" is not available.)
>     at /usr/src/bin/csh/../../contrib/tcsh/sh.c:1289
> 
> gdb) disas
> Dump of assembler code for function tw_collect:
> 0x00000000004288b0 <tw_collect+0>:      push   %rbp
> 0x00000000004288b1 <tw_collect+1>:      mov    %rsp,%rbp
> 0x00000000004288b4 <tw_collect+4>:      push   %r15
> 0x00000000004288b6 <tw_collect+6>:      push   %r14
> 0x00000000004288b8 <tw_collect+8>:      push   %r13
> 0x00000000004288ba <tw_collect+10>:     push   %r12
> 0x00000000004288bc <tw_collect+12>:     push   %rbx
> 0x00000000004288bd <tw_collect+13>:     sub    $0x2e8,%rsp
> 0x00000000004288c4 <tw_collect+20>:     mov    %r9,-0x308(%rbp)
> 0x00000000004288cb <tw_collect+27>:     mov    %r8,-0x300(%rbp)
> 0x00000000004288d2 <tw_collect+34>:     mov    %rcx,-0x2f8(%rbp)
> 0x00000000004288d9 <tw_collect+41>:     mov    %rdx,-0x2f0(%rbp)
> 0x00000000004288e0 <tw_collect+48>:     mov    %esi,-0x2e8(%rbp)
> 0x00000000004288e6 <tw_collect+54>:     mov    %edi,-0x2e4(%rbp)
> 0x00000000004288ec <tw_collect+60>:     movl   $0x0,-0x1d4(%rbp)
> 0x00000000004288f6 <tw_collect+70>:     movaps 0x23115b(%rip),%xmm0
>     # 0x6                                                   59a58
> <reslab+48>
This is actually 0x659a58 <reslab+48>
movaps tried to load %xmm0 from the unaligned address, which is forbidden
and causes #GP.

I have no idea why clang generates unaligned loads.
> 0x00000000004288fd <tw_collect+77>:     lea    -0x2(%rdi),%eax
> 0x0000000000428900 <tw_collect+80>:     mov    %eax,-0x2e0(%rbp)
> 0x0000000000428906 <tw_collect+86>:     test   %edi,%edi
> 0x0000000000428908 <tw_collect+88>:     movaps %xmm0,-0x210(%rbp)
> 0x000000000042890f <tw_collect+95>:     sete   %al
> ---Type <return> to continue, or q <return> to quit---q
> Quit
> (gdb) info line tw.parse.c:1308
> Line 1308 of "/usr/src/bin/csh/../../contrib/tcsh/tw.parse.c"
>    starts at address 0x4288f6 <tw_collect+70>
>    and ends at 0x4288fd <tw_collect+77>.
> 
> 
> Looks like it's crashing as soon as it tries to use the XMM registers.
>  I'm not sure if all of the crashes I'm getting are like this one, but
> I was surprised to see FP registers in code like this.
> 
> I'm using march=corei7 and -O2 for both world and kernel, but using
> march=nocona or just leaving out CPUTYPE has no effect (actual CPU is
> Nehalem Xeon 5520)
> Here's the relevant part of make.conf for completeness:
> 
> .if !defined(CC) || ${CC} == "cc"
> CC=clang
> .endif
> .if !defined(CXX) || ${CXX} == "c++"
> CXX=clang++
> .endif
> .if !defined(CPP) || ${CPP} == "cpp"
> CPP=clang -E
> .endif
> NO_WERROR=
> WERROR=
> NO_FSCHG=
> CPUTYPE?=corei7
> CFLAGS= -O2 -pipe
> COPTFLAGS= -O2 -pipe
> 
> Any thoughts? Is there some simple fix for this I'm missing?
> 
> Thanks,
> Jason
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