Re: [Xen-devel] [PATCH v10 1/5] gcov: Call constructors during initialization

[Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>]

On Fri, 2013-02-22 at 08:50 +0000, Ian Campbell wrote:
> On Thu, 2013-02-21 at 16:13 +0000, Frediano Ziglio wrote:
> > diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> > index 410d7db..50e0c4b 100644
> > --- a/xen/arch/arm/xen.lds.S
> > +++ b/xen/arch/arm/xen.lds.S
> > @@ -84,6 +84,13 @@ SECTIONS
> >         *(.init.data)
> >         *(.init.data.rel)
> >         *(.init.data.rel.*)
> > +
> > +       . = ALIGN(4);
> > +       __CTOR_LIST__ = .;
> > +       LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
> > +       *(.ctors)
> > +       LONG(0)
> > +       __CTOR_END__ = .;
> >    } :text
> >    . = ALIGN(32);
> >    .init.setup : { 
> 
> 
> This broke my 64-bit branch (not your fault, it's not merged yet, but I
> was planning to commit it shortly):
>         prelink.o: In function `init_constructors':
>         
> /local/scratch/ianc/devel/arm/xen.git/xen/common/lib.c:491:(.init.text+0xc44):
>  relocation truncated to fit: R_AARCH64_LDST64_ABS_LO12_NC against symbol 
> `__CTOR_LIST__' defined in .init.data section in 
> /local/scratch/ianc/devel/arm/xen.git/xen/.xen-arm64-syms.0
>         
> To fixup I intend to add the following to my "xen: arm64: initial build
> + config changes, start of day code".
> 
> Xen doesn't have a xen/xen.lds.h header, but perhaps adding that and
> using it to define common things like this as macros might be an
> interesting future cleanup.
> 
> 8<--------------------------------------
> 
> diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> index 9043994..5136b79 100644
> --- a/xen/arch/arm/xen.lds.S
> +++ b/xen/arch/arm/xen.lds.S
> @@ -91,9 +91,9 @@ SECTIONS
>         *(.init.data.rel)
>         *(.init.data.rel.*)
>  
> -       . = ALIGN(4);
> +       . = ALIGN(BYTES_PER_LONG);
>         __CTOR_LIST__ = .;
> -       LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
> +       LONG((__CTOR_END__ - __CTOR_LIST__) / BYTES_PER_LONG - 2)
>         *(.ctors)
>         LONG(0)
>         __CTOR_END__ = .;
> 
> 
> 
> 

Hi,
  this does not work, LONG is always 32 bit but if you use pointers
should be QUAD. Or I can change structure to be just a range of pointers
addressed by start and end, so in ld script

       . = ALIGN(8);
       __CTOR_LIST__ = .;
       *(.ctors)
       __CTOR_END__ = .;

In code:

typedef void (*ctor_func_t)(void);
extern const ctor_func_t __CTOR_LIST__[1], __CTOR_END__[1];

void __init init_constructors(void)
{
    const ctor_func_t pf = __CTOR_LIST__;
    for ( ; pf < __CTOR_END__; ++pf )
        pf();
}

This will work for both 32 and 64 bit. At this point I would rename 
__CTOR_LIST__ with a more "Xen" name.

Frediano

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel