On Fri, Apr 12, 2019 at 01:38:12PM -0700, Ard Biesheuvel wrote: > On Tue, 9 Apr 2019 at 09:42, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > > > > The EFI stub is entered with the caches and MMU enabled by the > > firmware, and once the stub is ready to hand over to the decompressor, > > we clean and disable the caches. > > > > The cache clean routines use CP15 barrier instructions, which can be > > disabled via SCTLR. Normally, when using the provided cache handling > > routines to enable the caches and MMU, this bit is enabled as well. > > However, but since we entered the stub with the caches already enabled, > > this routine is not executed before we call the cache clean routines, > > resulting in undefined instruction exceptions if the firmware never > > enabled this bit. > > > > So set the bit explicitly in the EFI entry code, but do so in a way that > > guarantees that the resulting code can still run on v6 cores as well > > (which are guaranteed to have CP15 barriers enabled) > > > > Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > > --- > > arch/arm/boot/compressed/head.S | 16 +++++++++++++++- > > 1 file changed, 15 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S > > index 6c7ccb428c07..c174098acdf1 100644 > > --- a/arch/arm/boot/compressed/head.S > > +++ b/arch/arm/boot/compressed/head.S > > @@ -1438,7 +1438,21 @@ ENTRY(efi_stub_entry) > > > > @ Preserve return value of efi_entry() in r4 > > mov r4, r0 > > - bl cache_clean_flush > > + > > + @ our cache maintenance code relies on CP15 barrier instructions > > + @ but since we arrived here with the MMU and caches configured > > + @ by UEFI, we must check that the CP15BEN bit is set in SCTLR. > > + @ Note that this bit is RAO/WI on v6 and earlier, so the ISB in > > + @ the enable path will be executed on v7+ only. > > + mrc p15, 0, r1, c1, c0, 0 @ read SCTLR > > + tst r1, #(1 << 5) @ CP15BEN bit set? > > + bne 0f > > + orr r1, r1, #(1 << 5) @ CP15 barrier instructions > > + mcr p15, 0, r1, c1, c0, 0 @ write SCTLR > > + ARM( .inst 0xf57ff06f @ isb ) > > + THUMB( isb ) > > + > > +0: bl cache_clean_flush > > bl cache_off > > > > @ Set parameters for booting zImage according to boot protocol > > -- > > 2.17.1 > > > > Russell, do you mind if I take this through the EFI tree? Yes I do mind. > I had trouble logging into your patch system (it no longer recognizes my > email address I can't debug it based on that - what does it say? > but when I try to re-create the account, my name is already taken) Yes, duplicate accounts can't be created, but there is also a forgotten password feature. I've just checked and I can log in fine. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
