From: Russell King rmk+kernel@armlinux.org.uk
Commit e388b80288aade31135aca23d32eee93dd106795 upstream.
When the branch predictor hardening is enabled, firmware must have set the IBE bit in the auxiliary control register. If this bit has not been set, the Spectre workarounds will not be functional.
Add validation that this bit is set, and print a warning at alert level if this is not the case.
Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Reviewed-by: Florian Fainelli f.fainelli@gmail.com Boot-tested-by: Tony Lindgren tony@atomide.com Reviewed-by: Tony Lindgren tony@atomide.com Signed-off-by: David A. Long dave.long@linaro.org --- arch/arm/mm/Makefile | 2 +- arch/arm/mm/proc-v7-bugs.c | 36 ++++++++++++++++++++++++++++++++++++ arch/arm/mm/proc-v7.S | 4 ++-- 3 files changed, 39 insertions(+), 3 deletions(-) create mode 100644 arch/arm/mm/proc-v7-bugs.c
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile index f353ee5..93a622a 100644 --- a/arch/arm/mm/Makefile +++ b/arch/arm/mm/Makefile @@ -95,7 +95,7 @@ obj-$(CONFIG_CPU_MOHAWK) += proc-mohawk.o obj-$(CONFIG_CPU_FEROCEON) += proc-feroceon.o obj-$(CONFIG_CPU_V6) += proc-v6.o obj-$(CONFIG_CPU_V6K) += proc-v6.o -obj-$(CONFIG_CPU_V7) += proc-v7.o +obj-$(CONFIG_CPU_V7) += proc-v7.o proc-v7-bugs.o obj-$(CONFIG_CPU_V7M) += proc-v7m.o
AFLAGS_proc-v6.o :=-Wa,-march=armv6 diff --git a/arch/arm/mm/proc-v7-bugs.c b/arch/arm/mm/proc-v7-bugs.c new file mode 100644 index 0000000..e46557d --- /dev/null +++ b/arch/arm/mm/proc-v7-bugs.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/kernel.h> +#include <linux/smp.h> + +static __maybe_unused void cpu_v7_check_auxcr_set(bool *warned, + u32 mask, const char *msg) +{ + u32 aux_cr; + + asm("mrc p15, 0, %0, c1, c0, 1" : "=r" (aux_cr)); + + if ((aux_cr & mask) != mask) { + if (!*warned) + pr_err("CPU%u: %s", smp_processor_id(), msg); + *warned = true; + } +} + +static DEFINE_PER_CPU(bool, spectre_warned); + +static void check_spectre_auxcr(bool *warned, u32 bit) +{ + if (IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR) && + cpu_v7_check_auxcr_set(warned, bit, + "Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable\n"); +} + +void cpu_v7_ca8_ibe(void) +{ + check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(6)); +} + +void cpu_v7_ca15_ibe(void) +{ + check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(0)); +} diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S index 53ba294..14cb0db 100644 --- a/arch/arm/mm/proc-v7.S +++ b/arch/arm/mm/proc-v7.S @@ -569,7 +569,7 @@ __v7_setup_stack: globl_equ cpu_ca8_do_suspend, cpu_v7_do_suspend globl_equ cpu_ca8_do_resume, cpu_v7_do_resume #endif - define_processor_functions ca8, dabort=v7_early_abort, pabort=v7_pabort, suspend=1 + define_processor_functions ca8, dabort=v7_early_abort, pabort=v7_pabort, suspend=1, bugs=cpu_v7_ca8_ibe
@ Cortex-A9 - needs more registers preserved across suspend/resume @ and bpiall switch_mm for hardening @@ -602,7 +602,7 @@ __v7_setup_stack: globl_equ cpu_ca15_suspend_size, cpu_v7_suspend_size globl_equ cpu_ca15_do_suspend, cpu_v7_do_suspend globl_equ cpu_ca15_do_resume, cpu_v7_do_resume - define_processor_functions ca15, dabort=v7_early_abort, pabort=v7_pabort, suspend=1 + define_processor_functions ca15, dabort=v7_early_abort, pabort=v7_pabort, suspend=1, bugs=cpu_v7_ca15_ibe #ifdef CONFIG_CPU_PJ4B define_processor_functions pj4b, dabort=v7_early_abort, pabort=v7_pabort, suspend=1 #endif