[boot-wrapper PATCH v2 1/9] Makefile: Avoid .got section creation

[Mark Rutland]

On Wed, Dec 22, 2021 at 06:15:59PM +0000, Andre Przywara wrote:
> At the moment we build the boot-wrapper with the default toolchain
> settings, which has issues if that is a toolchain targeted to Linux
> userland, for instance. Since boot-wrapper is rather simple, we get away
> with this, *mostly*, but there is at least one case where this breaks:
> Many distributions enable PIE builds by default when building GCC, so by
> just calling "gcc" we build the .o files for PIE (although we don't link
> them accordingly, since we use "ld" directly).
> When we moved the PSCI code from assembly to C, we also introduced
> global variables, which a PIE enabled GCC will put into a .got section
> (global offset table), to be able to easily relocate them at runtime
> (if needed). This section happens to be outside of the memory region
> we reserve, so can (and will be) overwritten by Linux at some point.
> Doing PSCI calls afterwards does not end well then. "memtest=1" is one
> way to trigger this.
> 
> To avoid the (in our case pointless) creation of the GOT, we specify
> -fno-pic and -fno-pie, to override any potential toolchain default.
> 
> This fixes boot-wrapper builds on many distro compilers, for instance
> as provided by Ubuntu and Arch Linux.
> 
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>

Thanks; applied.

Mark.

> ---
>  Makefile.am | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Makefile.am b/Makefile.am
> index d0a68df..3e970a3 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -126,6 +126,7 @@ CPPFLAGS	+= $(INITRD_FLAGS)
>  CFLAGS		+= -I$(top_srcdir)/include/ -I$(top_srcdir)/$(ARCH_SRC)/include/
>  CFLAGS		+= -Wall -fomit-frame-pointer
>  CFLAGS		+= -ffunction-sections -fdata-sections
> +CFLAGS		+= -fno-pic -fno-pie
>  LDFLAGS		+= --gc-sections
>  
>  OBJ		:= $(addprefix $(ARCH_SRC),$(ARCH_OBJ)) $(addprefix $(COMMON_SRC),$(COMMON_OBJ))
> -- 
> 2.25.1
>