http://d.puremagic.com/issues/show_bug.cgi?id=5484

           Summary: GC segfaults on FreeBSD 64 / scanning issues for .data
                    and .bss sections
           Product: D
           Version: D2
          Platform: All
        OS/Version: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: druntime
        AssignedTo: nobody@puremagic.com
        ReportedBy: dawg@dawgfoto.de


--- Comment #0 from dawg@dawgfoto.de 2011-01-25 11:34:53 PST ---
Created an attachment (id=877)
elf64-x86-64-freebsd

IMHO FreeBSD is missing _data__start/_data__end/_bss_start__/_bss_end__
symbols.
The current strategy is to use etext and _end as scanning range.

From compiling "void main() {}"
-m32:
nm out | grep etext -> 08055b38 A etext
nm out | grep _end  -> 0805ba04 A _end

-m64:
nm out | grep etext -> 0000000000411012 A etext
nm out | grep _end  -> 0000000000619988 A _end


This is not optimal as it spans over some read only sections but it's a minor
issue for 32.
With elf64-x86-64-freebsd there is a big non-readable area between .eh_frame
and .tdata. This leads to segfaulting when running the garbage collector.
I don't know any portable/official solution to this but observed that _progname
is always the first symbol in .data for 32/64 bit.

The boehm collector is installing a signal handler and tries to read from _end upwards until it fails.

I've appended objdump section headers.

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--- Comment #1 from dawg@dawgfoto.de 2011-01-25 11:35:56 PST ---
Created an attachment (id=878)
elf32-i386-freebsd

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Brad Roberts <braddr@puremagic.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |braddr@puremagic.com
           Platform|All                         |x86_64
           Severity|normal                      |critical


--- Comment #2 from Brad Roberts <braddr@puremagic.com> 2011-05-22 22:19:02 PDT ---
Here's the change I'm proposing for druntime, based on your previous data and from inspection of current binaries.  So far, testing looks promising:

diff --git a/src/rt/memory.d b/src/rt/memory.d
index ccf3c57..b32dfab 100644
--- a/src/rt/memory.d
+++ b/src/rt/memory.d
@@ -202,8 +202,19 @@ private
         {
             extern __gshared
             {
-                int etext;
-                int _end;
+                size_t etext;
+                size_t _end;
+            }
+        }
+        version (X86_64)
+        {
+            extern (C)
+            {
+                extern __gshared
+                {
+                    size_t _deh_end;
+                    size_t __progname;
+                }
             }
         }
     }
@@ -237,7 +248,8 @@ void initStaticDataGC()
     }
     else version( FreeBSD )
     {
-        gc_addRange( &etext, cast(size_t) &_end - cast(size_t) &etext );
+        gc_addRange( &etext, cast(size_t) &_deh_end - cast(size_t) &etext );
+        gc_addRange( &__progname, cast(size_t) &_end - cast(size_t)
&__progname );
     }
     else version( Solaris )
     {

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--- Comment #3 from Brad Roberts <braddr@puremagic.com> 2011-05-22 22:19:37 PDT ---
*** Issue 6008 has been marked as a duplicate of this issue. ***

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dawg@dawgfoto.de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
    Attachment #878|application/octet-stream    |text/plain
          mime type|                            |


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dawg@dawgfoto.de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
    Attachment #877|application/octet-stream    |text/plain
          mime type|                            |


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--- Comment #4 from dawg@dawgfoto.de 2011-06-02 21:34:19 PDT ---
Why is it that etext -> _deh_end is scanned? Can readonly sections be the only root of dynamic memory pointers? I'm also unsure about the TLS sections, will investigate this.

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--- Comment #5 from Brad Roberts <braddr@puremagic.com> 2011-06-02 21:46:14 PDT ---
(In reply to comment #4)
> Why is it that etext -> _deh_end is scanned? Can readonly sections be the only root of dynamic memory pointers? I'm also unsure about the TLS sections, will investigate this.

I tried to be as conservative as I could with removing ranges from what's being scanned on every other platform.

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Brad Roberts <braddr@puremagic.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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