On Fri, Apr 10, 2020 at 10:20:42AM +0200, Ard Biesheuvel wrote: > On Thu, 9 Apr 2020 at 23:08, Arvind Sankar <nivedita@xxxxxxxxxxxx> wrote: > > > > On Thu, Apr 09, 2020 at 04:53:07PM -0400, Brian Gerst wrote: > > > > Can we use the -fno-zero-initialized-in-bss compiler flag instead of > > > > explicitly marking global variables? > > > > > > Scratch that. Apparently it only works when a variable is explicitly > > > initialized to zero. > > > > > > -- > > > Brian Gerst > > > > Right, there doesn't seem to be a compiler option to turn off the use of > > .bss altogether. > > Yeah. I'll try to come up with a way to consolidate this a bit across > architectures (which is a bit easier now that all of the EFI stub C > code lives in the same place). It is probably easiest to use a section > renaming trick similar to the one I added for ARM (as Arvind suggested > as well, IIRC), and get rid of the per-symbol annotations altogether. Does that work for 32-bit ARM, or does it need to be .data to tell the compiler to avoid generating GOT references? If that's fine, we don't actually need to rename sections -- linker script magic is enough. For eg, the below pulls the EFI stub bss into .data for x86 without the need for the annotations. diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S index 508cfa6828c5..e324819c95bc 100644 --- a/arch/x86/boot/compressed/vmlinux.lds.S +++ b/arch/x86/boot/compressed/vmlinux.lds.S @@ -52,6 +52,7 @@ SECTIONS _data = . ; *(.data) *(.data.*) + drivers/firmware/efi/libstub/lib.a:(.bss .bss.*) _edata = . ; } . = ALIGN(L1_CACHE_BYTES);
