SIGILL crashes JVM on PPC64 LE

[Andrew Hughes]

----- Original Message -----
> Hi Volker
> 
> The following test case has been isolated by Hiroshi Horii and generates
> the illegal instruction, crashing the JVM on PPC64 LE:
> 
> UnalignedUnsafeAccess.java:
> http://hastebin.com/raw/uqegukific
> 
> $ javac UnalignedUnsafeAccess.java
> $ java -Xcomp -Xbatch UnalignedUnsafeAccess
> 
> The issue can be reproduced on OpenJDK 8 downstream, OpenJDK 8, and
> OpenJDK 9 - hs_err logs:
> 
> OpenJDK 9, tag 0be6f4f5d186 jdk-9+120:
> http://hastebin.com/raw/ecuhukutur
> 
> OpenJDK 8, tag 5aaa43d91c73 tip:
> http://hastebin.com/raw/ipohoyafos
> 
> OpenJDK 8 downstream:
> 
> Ubuntu 16.04 LTS
> build 1.8.0_91-8u91-b14-0ubuntu4~16.04.1-b14
> http://hastebin.com/raw/yetizebofo
> 
> RHEL 7.2:
> build 1.8.0_91-b14
> http://hastebin.com/raw/irequfawaw
> 
> The crash happens when an illegal instruction - 0xea2f0013 - is executed.
> 
> The backtrace shows:
> 
> Stack: [0x00003fff56030000,0x00003fff56430000],  sp=0x00003fff5642b8d0,  free
> space=4078k
> Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native
> code)
> V  [libjvm.so+0x162104]  loadI2LNode::emit(CodeBuffer&, PhaseRegAlloc*)
> const+0x194
> V  [libjvm.so+0x8ece28]  Compile::fill_buffer(CodeBuffer*, unsigned
> int*)+0x4e8
> V  [libjvm.so+0x368e08]  Compile::Code_Gen()+0x3c8
> V  [libjvm.so+0x369e04]  Compile::Compile(ciEnv*, C2Compiler*, ciMethod*,
> int, bool, bool, bool)+0xf64
> V  [libjvm.so+0x271380]  C2Compiler::compile_method(ciEnv*, ciMethod*,
> int)+0x1f0
> V  [libjvm.so+0x3785a4]
> CompileBroker::invoke_compiler_on_method(CompileTask*)+0xd54
> V  [libjvm.so+0x379dc8]  CompileBroker::compiler_thread_loop()+0x488
> V  [libjvm.so+0xa5de90]  compiler_thread_entry(JavaThread*, Thread*)+0x20
> V  [libjvm.so+0xa690c8]  JavaThread::thread_main_inner()+0x178
> V  [libjvm.so+0x8c8c10]  java_start(Thread*)+0x170
> C  [libpthread.so.0+0x833c]  start_thread+0xfc
> C  [libc.so.6+0x12b014]  clone+0xe4
> 
> loadI2LNode class is generated according to the following ADL code in
> ppc.ad file:
> 
> instruct loadI2L(iRegLdst dst, memory mem) %{
>   match(Set dst (ConvI2L (LoadI mem)));
>   predicate(_kids[0]->_leaf->as_Load()->is_unordered());
>   ins_cost(MEMORY_REF_COST);
> 
>   format %{ "LWA     $dst, $mem \t// loadI2L" %}
>   size(4);
>   ins_encode %{
>     // TODO: PPC port $archOpcode(ppc64Opcode_lwa);
>     int Idisp = $mem$$disp + frame_slots_bias($mem$$base, ra_);
>     __ lwa($dst$$Register, Idisp, $mem$$base$$Register);
>   %}
>   ins_pipe(pipe_class_memory);
> %}
> 
> So the generated illegal instruction comes from:
> lwa 17,17,15  (DS-form: lwa RT, DS, RA)
> 
> As DS field must always be 4-byte aligned (i.e. DS field is always
> concatenated with 0b00), 17 as DS (middle 17 value) is illegal,
> generating the illegal instruction in question:
> 
> 11101010000000000000000000000010: LWA
> 00000010001000000000000000000000: 17
> 00000000000000000000000000010001: 17
> 00000000000011110000000000000000: 15
> --------------------------------
> 11101010001011110000000000010011: 0xEA2F0013 => Illegal instruction
> 
> The following change is proposed to fix the issue and deals with the
> unaligned displacements:
> 
> OpenJDK 9 webrev:
> 81.de.7a9f.ip4.static.sl-reverse.com./illegal/9
> 
> OpenJDK 8 webrev:
> 81.de.7a9f.ip4.static.sl-reverse.com./illegal/8
> 
> Could we open a JIRA ticket regarding this issue in order to include it
> in the webrev?
> 

Done:

https://bugs.openjdk.java.net/browse/JDK-8158318

Reproduced on IcedTea 2.6.6 & OpenJDK 8u92:

# JRE version: OpenJDK Runtime Environment (7.0_101) (build 1.7.0_101-mockbuild_2016_04_19_09_08-b00)
# Java VM: OpenJDK 64-Bit Server VM (24.95-b01 compiled mode linux-ppc64 compressed oops)
# Derivative: IcedTea 2.6.6pre01
# Distribution: Red Hat Enterprise Linux Server release 7.2 (Maipo), package rhel-2.6.6.2.el7-ppc64le u101-b00
# Problematic frame:
# J 602 C2 UnalignedUnsafeAccess$NativeCell.path()Ljava/lang/String; (106 bytes) @ 0x00003fff88184430 [0x00003fff88184400+0x30]

# JRE version: OpenJDK Runtime Environment (8.0_92-b14) (build 1.8.0_92-b14)
# Java VM: OpenJDK 64-Bit Server VM (25.92-b14 compiled mode linux-ppc64 compressed oops)
# Problematic frame:
# J 485 C2 UnalignedUnsafeAccess$NativeCell.path()Ljava/lang/String; (106 bytes) @ 0x00003fff8015f030 [0x00003fff8015f000+0x30]
-- 
Andrew :)

Senior Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

PGP Key: ed25519/35964222 (hkp://keys.gnupg.net)
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