On Wed, Apr 04, 2018 at 11:46:45AM +0200, Alexander Graf wrote: > On 03.04.18 21:59, Heinrich Schuchardt wrote: > > The UEFI spec mandates that unaligned memory access should be enabled if > > supported by the CPU architecture. > > > > This patch implements the function unaligned_access() to reset the aligned > > access flag in the system control register (SCTLR). It is called when the > > bootefi command is invoked. > > > > Signed-off-by: Heinrich Schuchardt <xypron.g...@gmx.de> > > This will not work unfortunately. Unaligned accesses are only handled by > hardware on armv7 (and armv8) when the underlying memory is mapped as > cached. Given the extremely wild situation on armv7 for page table > setups, I'm not terribly confident to give anyone even the slightest > hint that unaligned accesses would work on armv7.
Then having RAM mapped as Normal (not necessarily cacheable) should be an automatic prerequisite for CONFIG_EFI, and if possible we should write scary error messages to the console if this is not the case. > IMHO we should really update the UEFI spec and mandate that all memory > accesses have to be aligned on armv7. Changing ABIs in backwards-incompatible ways is the opposite of what UEFI is for. > It's what grub is doing today already: > > http://git.savannah.gnu.org/cgit/grub.git/tree/configure.ac#n1279 Don't read too much into that. That comes for three reasons: 1) The U-boot API port. 2) Support for pre-v7 devices (like raspberry pi 1). 3) The wild changes in toolchain behaviour seen between various releases between gcc ~4.5 and gcc5. There is no reason for that to be used for the arm-efi target, it's just pure laziness on my behalf not to have changed it when the arm-efi port was added. > My recommendation would be to just pass the same compiler flags to iPXE > on armv7. Please don't. / Leif > > Alex > > > --- > > arch/arm/cpu/armv7/Makefile | 4 ++++ > > arch/arm/cpu/armv7/sctlr.S | 23 +++++++++++++++++++++++ > > 2 files changed, 27 insertions(+) > > create mode 100644 arch/arm/cpu/armv7/sctlr.S > > > > diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile > > index b14ee54519..cdb56e490b 100644 > > --- a/arch/arm/cpu/armv7/Makefile > > +++ b/arch/arm/cpu/armv7/Makefile > > @@ -12,6 +12,10 @@ obj-y += cache_v7.o cache_v7_asm.o > > obj-y += cpu.o cp15.o > > obj-y += syslib.o > > > > +ifneq ($(CONFIG_SPL_BUILD),y) > > +obj-$(CONFIG_EFI_LOADER) += sctlr.o > > +endif > > + > > ifneq ($(CONFIG_SKIP_LOWLEVEL_INIT),y) > > obj-y += lowlevel_init.o > > endif > > diff --git a/arch/arm/cpu/armv7/sctlr.S b/arch/arm/cpu/armv7/sctlr.S > > new file mode 100644 > > index 0000000000..cfdb7d2a52 > > --- /dev/null > > +++ b/arch/arm/cpu/armv7/sctlr.S > > @@ -0,0 +1,23 @@ > > +/* > > + * Routines to access the system control register > > + * > > + * Copyright (c) 2018 Heinrich Schuchardt > > + * > > + * SPDX-License-Identifier: GPL-2.0+ > > + */ > > + > > +#include <linux/linkage.h> > > + > > +/* > > + * void allow_unaligned(void) - allow unaligned access > > + * > > + * This routine clears the aligned flag in the system control register. > > + * After calling this routine unaligned access does no longer lead to a > > + * data abort but is handled by the CPU. > > + */ > > +ENTRY(allow_unaligned) > > + mrc p15, 0, r0, c1, c0, 0 @ load system control register > > + bic r0, r0, #2 @ clear aligned flag > > + mcr p15, 0, r0, c1, c0, 0 @ write system control register > > + bx lr @ return > > +ENDPROC(allow_unaligned) > > _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
