Re: [patch] Fix oddity in personality routine

[Jack Howarth <howarth@bromo.med.uc.edu>]

On Thu, Dec 03, 2009 at 10:25:30AM +0000, Andrew Haley wrote:
> Jack Howarth wrote:
> > On Wed, Dec 02, 2009 at 09:34:33AM +0000, Andrew Haley wrote:
> >> Jack Howarth wrote:
> >>> On Tue, Dec 01, 2009 at 05:24:29PM +0000, Andrew Haley wrote:
> >>>> Jack Howarth wrote:
> >>>>> On Tue, Dec 01, 2009 at 09:29:36AM +0000, Andrew Haley wrote:
> >>>>>> Jack Howarth wrote:
> >>>>>>
> >>>>>>> (gdb) 
> >>>>>>> 54	  (*real_main) (args);
> >>>>>>> (gdb) 
> >>>>>>>
> >>>>>>> Program received signal EXC_BAD_ACCESS, Could not access memory.
> >>>>>>> Reason: KERN_PROTECTION_FAILURE at address: 0x0000000103f05db0
> >>>>>>> 0x0000000103f05db0 in ?? () at RowSetEvent.java:51
> >>>>>>> 51	RowSetEvent.java: No such file or directory.
> >>>>>>> 	in RowSetEvent.java
> >>>>>>> (gdb) 
> >>>>>>>
> >>>>>>> A backtrace only shows...
> >>>>>>>
> >>>>>>> (gdb) bt
> >>>>>>> #0  0x0000000103f05db0 in ?? () at RowSetEvent.java:51
> >>>>>>> #1  0x00000001000485be in gnu::java::lang::MainThread::call_main (this=0x104875dc0) at ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc:54
> >>>>>>> Previous frame inner to this frame (gdb could not unwind past this frame)
> >>>>>>>
> >>>>>>> Let me know if you have any suggestions for debugging this further.
> >>>>>> Disassemble the first 10 or so instructions at the instruction where the
> >>>>>> EXC_BAD_ACCESS occurs.  I think this is a libffi bug.
> >>>>>>
> >>>>>> Andrew.
> >>>>> Andrew,
> >>>>>    So just to clarify, for the instance of...
> >>>>>
> >>>>> -------------------
> >>>>>
> >>>>> (gdb) 
> >>>>> 0x00000001004168df in _ZN4java4lang7reflect8Modifier8isPublicEJbi (mod=9) at Modifier.java:258
> >>>>> 258	    return (mod & PUBLIC) != 0;
> >>>>> (gdb) 
> >>>>> gnu::java::lang::MainThread::call_main (this=0x104875dc0) at ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc:46
> >>>>> 46	    msg =  "`main' must be public";
> >>>>> (gdb) 
> >>>>> 45	  else if (! ::java::lang::reflect::Modifier::isPublic(meth->accflags))
> >>>>> (gdb) 
> >>>>> 54	  (*real_main) (args);
> >>>>> (gdb) 
> >>>>>
> >>>>> Program received signal EXC_BAD_ACCESS, Could not access memory.
> >>>>> Reason: KERN_PROTECTION_FAILURE at address: 0x0000000103f05db0
> >>>>> 0x0000000103f05db0 in ?? () at RowSetEvent.java:51
> >>>>> 51	RowSetEvent.java: No such file or directory.
> >>>>> 	in RowSetEvent.java
> >>>>> (gdb) 
> >>>>>
> >>>>> A backtrace only shows...
> >>>>>
> >>>>> (gdb) bt
> >>>>> #0  0x0000000103f05db0 in ?? () at RowSetEvent.java:51
> >>>>> #1  0x00000001000485be in gnu::java::lang::MainThread::call_main (this=0x104875dc0) at ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc:54
> >>>>> Previous frame inner to this frame (gdb could not unwind past this frame)
> >>>>>
> >>>>> -----------------
> >>>>>
> >>>>> I want to disassemble from 0x00000001000485be, right?
> >>>> 0x0000000103f05db0, where the fault happens.  I think it's a libffi stub,
> >>>> and I think its page permissions are not correctly set.
> >>>>
> >>>> But let's see.
> >>>>
> >>>> What I would do is, at
> >>>>
> >>>>> 54	  (*real_main) (args);
> >>>> disassemble the call instruction, it's probably  call ($rax)  or somesuch.
> >>>> look in $rax with
> >>>>
> >>>> p $rax
> >>>>
> >>>> and disassemble from the address that's in there.
> >>>>
> >>>> Andrew.
> >>> Andrew,
> >>>    I can't disassemble 0x0000000103f05db0...
> >>>
> >>> (gdb) disassemble 0x0000000103f05db0
> >>> No function contains specified address.
> >> x/10i 0x0000000103f05db0
> >>
> >> Andrew.
> > 
> > Andrew,
> >    Okay, I see...
> > 
> > gdb /sw/lib/gcc4.5/libexec/gcc/x86_64-apple-darwin9.8.0/4.5.0/ecj1
> > ...
> > gdb) break ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc:46
> > Breakpoint 1 at 0x20c49ba4b0a5ab: file ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc, line 46.
> > (gdb) r testme.java -fbootclasspath=/sw/share/java/ecj/ecj.jar:./:/sw/lib/gcc4.5/share/java/libgcj-4.5.0.jar -fsource=1.5 -ftarget=1.5 -fzip-dependency /var/folders/1C/1CdoNxmNFHyOIjNBLNuJh++++TM/-Tmp-//ccQOWl1c.zip -fzip-target /var/folders/1C/1CdoNxmNFHyOIjNBLNuJh++++TM/-Tmp-//cc4p4DHj.jar
> > Starting program: /sw/lib/gcc4.5/libexec/gcc/x86_64-apple-darwin9.8.0/4.5.0/ecj1 testme.java -fbootclasspath=/sw/share/java/ecj/ecj.jar:./:/sw/lib/gcc4.5/share/java/libgcj-4.5.0.jar -fsource=1.5 -ftarget=1.5 -fzip-dependency /var/folders/1C/1CdoNxmNFHyOIjNBLNuJh++++TM/-Tmp-//ccQOWl1c.zip -fzip-target /var/folders/1C/1CdoNxmNFHyOIjNBLNuJh++++TM/-Tmp-//cc4p4DHj.jar
> > warning: posix_spawn failed, trying execvp, error: 86
> > Reading symbols for shared libraries +++++.. done
> > Breakpoint 1 at 0x1000485ab: file ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc, line 46.
> > 
> > Breakpoint 1, gnu::java::lang::MainThread::call_main (this=0x104875dc0) at ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc:46
> > 46	    msg =  "`main' must be public";
> > (gdb) s
> > Current language:  auto; currently c++
> > 45	  else if (! ::java::lang::reflect::Modifier::isPublic(meth->accflags))
> > (gdb) s
> > 54	  (*real_main) (args);
> > (gdb) x/10i 0x0000000103f05db0
> > 0x103f05db0:	mov    $0x1009814e8,%r11
> > 0x103f05dba:	mov    $0x103f05db0,%r10
> > 0x103f05dc4:	clc    
> > 0x103f05dc5:	rex.WB jmpq   *%r11
> > 0x103f05dc8:	add    %bl,-0x10(%rsi)
> > 0x103f05dcb:	add    (%rcx),%eax
> > 0x103f05dcd:	add    %al,(%rax)
> > 0x103f05dcf:	add    %ah,%al
> > 0x103f05dd1:	(bad)  
> > 0x103f05dd2:	cwtl   
> > (gdb) bt
> > #0  gnu::java::lang::MainThread::call_main (this=0x104875dc0) at ../../../gcc-4.5-20091128/libjava/gnu/java/lang/natMainThread.cc:54
> > #1  0x0000000104875dc0 in ?? () at ClassHelper.java:106
> > #2  0x0000000104875f00 in ?? () at ClassHelper.java:106
> > #3  0x000000010493e980 in ?? () at ClassHelper.java:106
> > #4  0x00000001000b1b74 in _ZN3gnu4java4lang10MainThread3runEJvv (this=0x104875dc0) at MainThread.java:106
> > Previous frame inner to this frame (gdb could not unwind past this frame)
> > (gdb) p $rax
> > $1 = 1
> > 
> > (gdb) s
> > 
> > Program received signal EXC_BAD_ACCESS, Could not access memory.
> > Reason: KERN_PROTECTION_FAILURE at address: 0x0000000103f05db0
> > 0x0000000103f05db0 in ?? () at ClassHelper.java:106
> > 106	ClassHelper.java: No such file or directory.
> > 	in ClassHelper.java
> > 
> > What do you make of the bad assembly at 0x103f05dd1?
> 
> There is no bad assembly: there's a jump at 0x103f05dc5.
> 
> I know what's going on.
> 
> The OS forbids execution of memory in the heap.  But, there is an extra
> flag, -Wl,-allow_stack_execute, that allows this permission.  This is
> a misnamed flag, since we never execute code on the stack.  I think it's
> really controlling heap execution, not stack execution.
> 
> We need to pass this flag everywhere, whenever a program is compiled by
> gcj.
> 
> Andrew.

Andrew,
   This sounds like the patch that Andreas proposed in...

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41991#c3

which didn't solve the problem on my MacPro or MacBook Pro
under darwin9 or darwin10. He also ran into the issue again
later...

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41991#c17

Do you think that  -Wl,-allow_stack_execute needs to be passed
even more widely than on just ecjx_LDFLAGS? Any suggestions as
to where I should be passing it? Perhaps on something like
LIBJAVA_LDFLAGS_NOUNDEF at the toplevel of libjava? Or should
we even be building libffi and boehm-gc with that as well?
                     Jack