On Tue, Mar 27, 2018 at 11:01:44PM +1100, Michael Ellerman wrote:
> This commit adds security feature flags to reflect the settings we
> receive from firmware regarding Spectre/Meltdown mitigations.
>
> The feature names reflect the names we are given by firmware on bare
> metal machines. See the hostboot source for details.
>
> Arguably these could be firmware features, but that then requires them
> to be read early in boot so they're available prior to asm feature
> patching, but we don't actually want to use them for patching. We may
> also want to dynamically update them in future, which would be
> incompatible with the way firmware features work (at the moment at
> least). So for now just make them separate flags.
>
> Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
> ---
> arch/powerpc/include/asm/security_features.h | 65
> ++++++++++++++++++++++++++++
> arch/powerpc/kernel/Makefile | 2 +-
> arch/powerpc/kernel/security.c | 15 +++++++
> 3 files changed, 81 insertions(+), 1 deletion(-)
> create mode 100644 arch/powerpc/include/asm/security_features.h
> create mode 100644 arch/powerpc/kernel/security.c
>
>
> v2: Rebased on top of LPM changes.
>
> diff --git a/arch/powerpc/include/asm/security_features.h
> b/arch/powerpc/include/asm/security_features.h
> new file mode 100644
> index 000000000000..db00ad2c72c2
> --- /dev/null
> +++ b/arch/powerpc/include/asm/security_features.h
> @@ -0,0 +1,65 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Security related feature bit definitions.
> + *
> + * Copyright 2018, Michael Ellerman, IBM Corporation.
> + */
> +
> +#ifndef _ASM_POWERPC_SECURITY_FEATURES_H
> +#define _ASM_POWERPC_SECURITY_FEATURES_H
> +
> +
> +extern unsigned long powerpc_security_features;
> +
> +static inline void security_ftr_set(unsigned long feature)
> +{
> + powerpc_security_features |= feature;
> +}
> +
> +static inline void security_ftr_clear(unsigned long feature)
> +{
> + powerpc_security_features &= ~feature;
> +}
> +
> +static inline bool security_ftr_enabled(unsigned long feature)
> +{
> + return !!(powerpc_security_features & feature);
> +}
> +
> +
> +// Features indicating support for Spectre/Meltdown mitigations
> +
> +// The L1-D cache can be flushed with ori r30,r30,0
> +#define SEC_FTR_L1D_FLUSH_ORI30 0x0000000000000001ull
> +
> +// The L1-D cache can be flushed with mtspr 882,r0 (aka SPRN_TRIG2)
> +#define SEC_FTR_L1D_FLUSH_TRIG2 0x0000000000000002ull
> +
> +// ori r31,r31,0 acts as a speculation barrier
> +#define SEC_FTR_SPEC_BAR_ORI31 0x0000000000000004ull
> +
> +// Speculation past bctr is disabled
> +#define SEC_FTR_BCCTRL_SERIALISED 0x0000000000000008ull
Nitpicks:
1) bcctr or bcctrL ?
2) seraliaZe seems to be more popular than serialiSe in the kernel
(1769 hits from "grep -ir serializ", 264 with the "s")
Still needs to grep for both in any case, bummer!
Gabriel
> +
> +// Entries in L1-D are private to a SMT thread
> +#define SEC_FTR_L1D_THREAD_PRIV 0x0000000000000010ull
> +
> +// Indirect branch prediction cache disabled
> +#define SEC_FTR_COUNT_CACHE_DISABLED 0x0000000000000020ull
> +
> +
> +// Features indicating need for Spectre/Meltdown mitigations
> +
> +// The L1-D cache should be flushed on MSR[HV] 1->0 transition (hypervisor
> to guest)
> +#define SEC_FTR_L1D_FLUSH_HV 0x0000000000000040ull
> +
> +// The L1-D cache should be flushed on MSR[PR] 0->1 transition (kernel to
> userspace)
> +#define SEC_FTR_L1D_FLUSH_PR 0x0000000000000080ull
> +
> +// A speculation barrier should be used for bounds checks (Spectre variant 1)
> +#define SEC_FTR_BNDS_CHK_SPEC_BAR 0x0000000000000100ull
> +
> +// Firmware configuration indicates user favours security over performance
> +#define SEC_FTR_FAVOUR_SECURITY 0x0000000000000200ull
> +
> +#endif /* _ASM_POWERPC_SECURITY_FEATURES_H */
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 1b6bc7fba996..d458c45e5004 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -42,7 +42,7 @@ obj-$(CONFIG_VDSO32) += vdso32/
> obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o
> obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
> obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_ppc970.o cpu_setup_pa6t.o
> -obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_power.o
> +obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_power.o security.o
> obj-$(CONFIG_PPC_BOOK3S_64) += mce.o mce_power.o
> obj-$(CONFIG_PPC_BOOK3E_64) += exceptions-64e.o idle_book3e.o
> obj-$(CONFIG_PPC64) += vdso64/
> diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
> new file mode 100644
> index 000000000000..4ccba00d224c
> --- /dev/null
> +++ b/arch/powerpc/kernel/security.c
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +//
> +// Security related flags and so on.
> +//
> +// Copyright 2018, Michael Ellerman, IBM Corporation.
> +
> +#include <linux/kernel.h>
> +#include <asm/security_features.h>
> +
> +
> +unsigned long powerpc_security_features __read_mostly = \
> + SEC_FTR_L1D_FLUSH_HV | \
> + SEC_FTR_L1D_FLUSH_PR | \
> + SEC_FTR_BNDS_CHK_SPEC_BAR | \
> + SEC_FTR_FAVOUR_SECURITY;
> --
> 2.14.1
>
