N2X, GR740 and coverage: The impact of a linkcmds patch from 2014 to gcov_init calls
Sebastian Huber
sebastian.huber at embedded-brains.de
Wed Feb 28 12:08:07 UTC 2018
It was a bug in the linker command file. See attached patches.
----- Am 28. Feb 2018 um 12:50 schrieb Thanassis Tsiodras Thanassis.Tsiodras at esa.int:
>> However, I am not able to reproduce this problem.
>
> Hi Sebastian.
>
> Look at the reply I sent this morning to the mailing list - I uploaded the
> code in a GitHub repository and provided instructions in the mailing list
> with the exact invocations that reproduce the issue.
>
> Hope this helps!
> Thanassis.
>
> Thanassis Tsiodras
> Real-time Embedded Software Engineer
> System, Software and Technology Department
>
> ESTEC
> Keplerlaan 1, PO Box 299
> NL-2200 AG Noordwijk, The Netherlands
> Thanassis.Tsiodras at esa.int | www.esa.int
> T +31 71 565 5332
>
>
>
> From: Sebastian Huber <sebastian.huber at embedded-brains.de>
> To: Thanassis Tsiodras <Thanassis.Tsiodras at esa.int>
> Cc: devel <devel at rtems.org>
> Date: 28/02/2018 12:11
> Subject: Re: N2X, GR740 and coverage: The impact of a linkcmds
> patch from 2014 to gcov_init calls
>
>
>
> ----- Am 27. Feb 2018 um 17:30 schrieb Thanassis Tsiodras
> Thanassis.Tsiodras at esa.int:
>
> [...]
>> After quite a lot of hunting, we traced this failure to a patch in the
>> "linkcmds.base" - done back in 2014 ( commit 95cb09ed746 ) :
>>
>> This commit changed
> "c/src/lib/libbsp/sparc/shared/startup/linkcmds.base"
>> from this:
>>
>> KEEP (*(SORT(.ctors.*)))
>> KEEP (*(.ctors))
>> KEEP (*crtbegin.o(.dtors))
>> KEEP (*crtbegin?.o(.dtors))
>> KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
>> KEEP (*(SORT(.dtors.*)))
>> KEEP (*(.dtors))
>>
>> ...to this:
>>
>> KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
>> KEEP (*(SORT(.ctors*)))
>> KEEP (*crtbegin.o(.dtors))
>> KEEP (*crtbegin?.o(.dtors))
>> KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
>> KEEP (*(SORT(.dtors*)))
>>
>> Reverting this change, the gcov stubs revert back to their proper place,
>> and __gcov_inits are called properly.
>>
>> The reason I tried this patch, was because I noticed that the coverage
>> stubs are no longer placed in ".ctor" sections - they are instead placed
>> by the newer compilers at ".ctor.NUMBER" sections (with NUMBER set to
>> 65435 in my case - but I am guessing this will change from invocation to
>> invocation).
>>
>> The comment provided by Joel back in 2014, only indicated that this
> patch
>> was done to address C++ concerns:
>>
>> commit 95cb09ed746e7daeca2158c7ecdf0249cfcbc5c8
>> Author: Joel Sherrill <joel.sherrill at oarcorp.com>
>> Date: Wed Apr 2 11:39:20 2014 -0500
>>
>> sparc/shared/.../linkcmds.base: Correct C++ support
>> Add KEEP() for .eh_frame*, .ctor*, and .dtor*.
>
> It could be a bug in the linker. The standard sections should be exactly
> like the Binutils default:
>
> sparc-rtems5-ld --verbose | grep ctor -C 3
> *(.rela.data .rela.data.* .rela.gnu.linkonce.d.*)
> *(.rela.tdata .rela.tdata.* .rela.gnu.linkonce.td.*)
> *(.rela.tbss .rela.tbss.* .rela.gnu.linkonce.tb.*)
> *(.rela.ctors)
> *(.rela.dtors)
> *(.rela.got)
> *(.rela.bss .rela.bss.* .rela.gnu.linkonce.b.*)
> --
> .init_array :
> {
> PROVIDE_HIDDEN (__init_array_start = .);
> KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*)
> SORT_BY_INIT_PRIORITY(.ctors.*)))
> KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o
> *crtend?.o ) .ctors))
> PROVIDE_HIDDEN (__init_array_end = .);
> }
> .fini_array :
> --
> KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o
> *crtend?.o ) .dtors))
> PROVIDE_HIDDEN (__fini_array_end = .);
> }
> .ctors :
> {
> /* gcc uses crtbegin.o to find the start of
> the constructors, so we make sure it is
> first. Because this is a wildcard, it
> doesn't matter if the user does not
> actually link against crtbegin.o; the
> linker won't look for a file to match a
> wildcard. The wildcard also means that it
> doesn't matter which directory crtbegin.o
> is in. */
> KEEP (*crtbegin.o(.ctors))
> KEEP (*crtbegin?.o(.ctors))
> /* We don't want to include the .ctor section from
> the crtend.o file until after the sorted ctors.
> The .ctor section from the crtend file contains the
> end of ctors marker and it must be last */
> KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
> KEEP (*(SORT(.ctors.*)))
> KEEP (*(.ctors))
> }
> .dtors :
> {
>
> However, I am not able to reproduce this problem. For example in the
> sptls04 linker map file (-Wl,-Map,map.txt) we have this:
>
> *crtbegin.o(.ctors)
> .ctors 0x0000000002011330 0x4
> /opt/rtems/5/lib/gcc/sparc-rtems5/7.3.0/crtbegin.o
> *crtbegin?.o(.ctors)
> *(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
> .ctors 0x0000000002011334 0x4 init.o
> *(SORT_BY_NAME(.ctors*))
> .ctors 0x0000000002011338 0x4
> /opt/rtems/5/lib/gcc/sparc-rtems5/7.3.0/crtend.o
>
> Who do the linker map files look in your test case?
>
>
>
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