Re: [Xen-devel] [RFC 6/7] arm: Introduce dummy empty functions for data only C files

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 6 Nov 2019, Andrii Anisov wrote:
> From: Andrii Anisov <andrii_anisov@xxxxxxxx>
> 
> ARM Compiler 6 has a proven bug: it compiles data only C files with
> SoftVFP attributes. This leads to a failed linkage afterwards with
> an error:
> 
> Error: L6242E: Cannot link object built_in.o as its attributes are 
> incompatible with the image attributes.
> ... A64 clashes with SoftVFP.
> 
> The known workaround is introducing some code into the affected file,
> e.g. an empty (non-static) function is enough.

Oh man, this is truly horrible.

If we really have to do this please:

- use the same dummy function name in all files
- the function should be static
- hiding the function within a #ifdef ARMCC block
- potentially hide the whole horrible hack behind a #define so that it
  would become at the call site:

 +ARMCC_DUMMY_FUNC_HACK()



> Signed-off-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
>
> ---
>  xen/arch/arm/platforms/brcm-raspberry-pi.c | 2 ++
>  xen/arch/arm/platforms/thunderx.c          | 2 ++
>  xen/xsm/flask/gen-policy.py                | 4 ++++
>  3 files changed, 8 insertions(+)
> 
> diff --git a/xen/arch/arm/platforms/brcm-raspberry-pi.c 
> b/xen/arch/arm/platforms/brcm-raspberry-pi.c
> index b697fa2..7ab1810 100644
> --- a/xen/arch/arm/platforms/brcm-raspberry-pi.c
> +++ b/xen/arch/arm/platforms/brcm-raspberry-pi.c
> @@ -40,6 +40,8 @@ static const struct dt_device_match rpi4_blacklist_dev[] 
> __initconst =
>      { /* sentinel */ },
>  };
>  
> +void brcm_raspberry_pi_dummy_func(void) {}
> +
>  PLATFORM_START(rpi4, "Raspberry Pi 4")
>      .compatible     = rpi4_dt_compat,
>      .blacklist_dev  = rpi4_blacklist_dev,
> diff --git a/xen/arch/arm/platforms/thunderx.c 
> b/xen/arch/arm/platforms/thunderx.c
> index 9b32a29..8015323 100644
> --- a/xen/arch/arm/platforms/thunderx.c
> +++ b/xen/arch/arm/platforms/thunderx.c
> @@ -33,6 +33,8 @@ static const struct dt_device_match 
> thunderx_blacklist_dev[] __initconst =
>      { /* sentinel */ },
>  };
>  
> +void thunderx_dummy_func(void) {}
> +
>  PLATFORM_START(thunderx, "THUNDERX")
>      .compatible = thunderx_dt_compat,
>      .blacklist_dev = thunderx_blacklist_dev,
> diff --git a/xen/xsm/flask/gen-policy.py b/xen/xsm/flask/gen-policy.py
> index c7501e4..73bf7d2 100644
> --- a/xen/xsm/flask/gen-policy.py
> +++ b/xen/xsm/flask/gen-policy.py
> @@ -21,3 +21,7 @@ sys.stdout.write("""
>  };
>  const unsigned int __initconst xsm_flask_init_policy_size = %d;
>  """ % policy_size)
> +
> +sys.stdout.write("""
> +void policy_dummy_func(void) {}
> +""")
> -- 
> 2.7.4
> 

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