AIX : -bnorwexec linker flag

Erik Joelsson erik.joelsson at oracle.com
Fri Apr 12 13:29:30 UTC 2019


 From a build point of view, the patch looks good. I cannot comment on 
the validity of adding the flag though.

/Erik

On 2019-04-12 02:15, Baesken, Matthias wrote:
> Hello,  I have a question regarding the  AIX  -bnorwexec linker flag .
> I think it is related to an AIX  security feature  SED , see also  :
>
> https://www.ibm.com/support/knowledgecenter/en/ssw_aix_71/com.ibm.aix.security/stack_exec_disable_flags.htm
>
> When building with the additional  -bnorwexec linker flag    we signal  the OS  that we "request"  the SED  feature .
> Please compare  a patched  and an unpatched  java   ( patched is flagged "request"  while   unpatched uses the  "system" setting ).
>
> bash-4.3$ sedmgr -d /patched_jdk/images/jdk/bin/java
> /patched_jdk/images/images/jdk/bin/java : request
>
>
> bash-4.3$ sedmgr -d /normal_jdk/images/jdk/bin/java
> /normal_jdk/images/jdk/bin/java : system
>
>
> System config on the example machine is "normal" (default) select :
> bash-4.3$ sedmgr
> Stack Execution Disable (SED) mode: select
> SED configured in kernel: select
>
>
> In our  internal tests  I noticed so far no issues when setting the  -bnorwexec linker flag  in OpenJDK  on AIX  .
> Do you have any experience  with it, do you see issues when setting the flag ?
>
>
> The documentation of the  flag is a bit short .
>
>
> https://www.ibm.com/support/knowledgecenter/en/ssw_aix_72/com.ibm.aix.cmds3/ld.htm
>
>
> norwexec
>
> Specifies that if the system's sed_config setting is not off, the process' private data areas will have non-execute permission.
>
>
>
>
> Patch would be :
>
> diff -r 0d7fb7f07134 make/autoconf/flags-ldflags.m4
> --- a/make/autoconf/flags-ldflags.m4    Mon Apr 08 06:56:37 2019 +0100
> +++ b/make/autoconf/flags-ldflags.m4 Mon Apr 08 10:50:07 2019 +0200
> @@ -1,5 +1,5 @@
> #
> -# Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
> +# Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
> # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
> #
> # This code is free software; you can redistribute it and/or modify it
> @@ -88,7 +88,7 @@
>       BASIC_LDFLAGS_JVM_ONLY="-library=%none -mt -z noversion"
>     elif test "x$TOOLCHAIN_TYPE" = xxlc; then
> -    BASIC_LDFLAGS="-b64 -brtl -bnolibpath -bexpall -bernotok -btextpsize:64K \
> +    BASIC_LDFLAGS="-b64 -brtl -bnorwexec -bnolibpath -bexpall -bernotok -btextpsize:64K \
>           -bdatapsize:64K -bstackpsize:64K"
>       # libjvm.so has gotten too large for normal TOC size; compile with qpic=large and link with bigtoc
>       BASIC_LDFLAGS_JVM_ONLY="-Wl,-lC_r -bbigtoc"
>
>
> Best regards, Matthias
>


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