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ARM: report Spectre v2 status through sysfs

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commit 9dd78194a3722fa6712192cdd4f7032d45112a9a upstream.

As per other architectures, add support for reporting the Spectre
vulnerability status via sysfs CPU.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
[ preserve res variable - gregkh ]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Russell King (Oracle) 2022-02-11 16:45:54 +00:00 committed by Greg Kroah-Hartman
parent 26171b016b
commit fdfc0baf82
5 changed files with 185 additions and 31 deletions
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28
arch/arm/include/asm/spectre.h Normal file
View File

@ -0,0 +1,28 @@
/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef __ASM_SPECTRE_H
#define __ASM_SPECTRE_H
enum {
SPECTRE_UNAFFECTED,
SPECTRE_MITIGATED,
SPECTRE_VULNERABLE,
};
enum {
__SPECTRE_V2_METHOD_BPIALL,
__SPECTRE_V2_METHOD_ICIALLU,
__SPECTRE_V2_METHOD_SMC,
__SPECTRE_V2_METHOD_HVC,
};
enum {
SPECTRE_V2_METHOD_BPIALL = BIT(__SPECTRE_V2_METHOD_BPIALL),
SPECTRE_V2_METHOD_ICIALLU = BIT(__SPECTRE_V2_METHOD_ICIALLU),
SPECTRE_V2_METHOD_SMC = BIT(__SPECTRE_V2_METHOD_SMC),
SPECTRE_V2_METHOD_HVC = BIT(__SPECTRE_V2_METHOD_HVC),
};
void spectre_v2_update_state(unsigned int state, unsigned int methods);
#endif

2
arch/arm/kernel/Makefile
View File

@ -106,4 +106,6 @@ endif
obj-$(CONFIG_HAVE_ARM_SMCCC) += smccc-call.o
obj-$(CONFIG_GENERIC_CPU_VULNERABILITIES) += spectre.o
extra-y := $(head-y) vmlinux.lds

54
arch/arm/kernel/spectre.c Normal file
View File

@ -0,0 +1,54 @@
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/cpu.h>
#include <linux/device.h>
#include <asm/spectre.h>
ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
char *buf)
{
return sprintf(buf, "Mitigation: __user pointer sanitization\n");
}
static unsigned int spectre_v2_state;
static unsigned int spectre_v2_methods;
void spectre_v2_update_state(unsigned int state, unsigned int method)
{
if (state > spectre_v2_state)
spectre_v2_state = state;
spectre_v2_methods |= method;
}
ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
char *buf)
{
const char *method;
if (spectre_v2_state == SPECTRE_UNAFFECTED)
return sprintf(buf, "%s\n", "Not affected");
if (spectre_v2_state != SPECTRE_MITIGATED)
return sprintf(buf, "%s\n", "Vulnerable");
switch (spectre_v2_methods) {
case SPECTRE_V2_METHOD_BPIALL:
method = "Branch predictor hardening";
break;
case SPECTRE_V2_METHOD_ICIALLU:
method = "I-cache invalidation";
break;
case SPECTRE_V2_METHOD_SMC:
case SPECTRE_V2_METHOD_HVC:
method = "Firmware call";
break;
default:
method = "Multiple mitigations";
break;
}
return sprintf(buf, "Mitigation: %s\n", method);
}

1
arch/arm/mm/Kconfig
View File

@ -833,6 +833,7 @@ config CPU_BPREDICT_DISABLE
config CPU_SPECTRE
bool
select GENERIC_CPU_VULNERABILITIES
config HARDEN_BRANCH_PREDICTOR
bool "Harden the branch predictor against aliasing attacks" if EXPERT

131
arch/arm/mm/proc-v7-bugs.c
View File

@ -7,8 +7,35 @@
#include <asm/cp15.h>
#include <asm/cputype.h>
#include <asm/proc-fns.h>
#include <asm/spectre.h>
#include <asm/system_misc.h>
#ifdef CONFIG_ARM_PSCI
static int __maybe_unused spectre_v2_get_cpu_fw_mitigation_state(void)
{
struct arm_smccc_res res;
arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
ARM_SMCCC_ARCH_WORKAROUND_1, &res);
switch ((int)res.a0) {
case SMCCC_RET_SUCCESS:
return SPECTRE_MITIGATED;
case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
return SPECTRE_UNAFFECTED;
default:
return SPECTRE_VULNERABLE;
}
}
#else
static int __maybe_unused spectre_v2_get_cpu_fw_mitigation_state(void)
{
return SPECTRE_VULNERABLE;
}
#endif
#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
DEFINE_PER_CPU(harden_branch_predictor_fn_t, harden_branch_predictor_fn);
@ -37,13 +64,60 @@ static void __maybe_unused call_hvc_arch_workaround_1(void)
arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
}
static void cpu_v7_spectre_init(void)
static unsigned int spectre_v2_install_workaround(unsigned int method)
{
const char *spectre_v2_method = NULL;
int cpu = smp_processor_id();
if (per_cpu(harden_branch_predictor_fn, cpu))
return;
return SPECTRE_MITIGATED;
switch (method) {
case SPECTRE_V2_METHOD_BPIALL:
per_cpu(harden_branch_predictor_fn, cpu) =
harden_branch_predictor_bpiall;
spectre_v2_method = "BPIALL";
break;
case SPECTRE_V2_METHOD_ICIALLU:
per_cpu(harden_branch_predictor_fn, cpu) =
harden_branch_predictor_iciallu;
spectre_v2_method = "ICIALLU";
break;
case SPECTRE_V2_METHOD_HVC:
per_cpu(harden_branch_predictor_fn, cpu) =
call_hvc_arch_workaround_1;
cpu_do_switch_mm = cpu_v7_hvc_switch_mm;
spectre_v2_method = "hypervisor";
break;
case SPECTRE_V2_METHOD_SMC:
per_cpu(harden_branch_predictor_fn, cpu) =
call_smc_arch_workaround_1;
cpu_do_switch_mm = cpu_v7_smc_switch_mm;
spectre_v2_method = "firmware";
break;
}
if (spectre_v2_method)
pr_info("CPU%u: Spectre v2: using %s workaround\n",
smp_processor_id(), spectre_v2_method);
return SPECTRE_MITIGATED;
}
#else
static unsigned int spectre_v2_install_workaround(unsigned int method)
{
pr_info("CPU%u: Spectre V2: workarounds disabled by configuration\n");
return SPECTRE_VULNERABLE;
}
#endif
static void cpu_v7_spectre_v2_init(void)
{
unsigned int state, method = 0;
switch (read_cpuid_part()) {
case ARM_CPU_PART_CORTEX_A8:
@ -52,32 +126,37 @@ static void cpu_v7_spectre_init(void)
case ARM_CPU_PART_CORTEX_A17:
case ARM_CPU_PART_CORTEX_A73:
case ARM_CPU_PART_CORTEX_A75:
per_cpu(harden_branch_predictor_fn, cpu) =
harden_branch_predictor_bpiall;
spectre_v2_method = "BPIALL";
state = SPECTRE_MITIGATED;
method = SPECTRE_V2_METHOD_BPIALL;
break;
case ARM_CPU_PART_CORTEX_A15:
case ARM_CPU_PART_BRAHMA_B15:
per_cpu(harden_branch_predictor_fn, cpu) =
harden_branch_predictor_iciallu;
spectre_v2_method = "ICIALLU";
state = SPECTRE_MITIGATED;
method = SPECTRE_V2_METHOD_ICIALLU;
break;
#ifdef CONFIG_ARM_PSCI
case ARM_CPU_PART_BRAHMA_B53:
/* Requires no workaround */
state = SPECTRE_UNAFFECTED;
break;
default:
/* Other ARM CPUs require no workaround */
if (read_cpuid_implementor() == ARM_CPU_IMP_ARM)
if (read_cpuid_implementor() == ARM_CPU_IMP_ARM) {
state = SPECTRE_UNAFFECTED;
break;
}
/* fallthrough */
/* Cortex A57/A72 require firmware workaround */
/* Cortex A57/A72 require firmware workaround */
case ARM_CPU_PART_CORTEX_A57:
case ARM_CPU_PART_CORTEX_A72: {
struct arm_smccc_res res;
state = spectre_v2_get_cpu_fw_mitigation_state();
if (state != SPECTRE_MITIGATED)
break;
if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
break;
@ -87,10 +166,7 @@ static void cpu_v7_spectre_init(void)
ARM_SMCCC_ARCH_WORKAROUND_1, &res);
if ((int)res.a0 != 0)
break;
per_cpu(harden_branch_predictor_fn, cpu) =
call_hvc_arch_workaround_1;
cpu_do_switch_mm = cpu_v7_hvc_switch_mm;
spectre_v2_method = "hypervisor";
method = SPECTRE_V2_METHOD_HVC;
break;
case PSCI_CONDUIT_SMC:
@ -98,28 +174,21 @@ static void cpu_v7_spectre_init(void)
ARM_SMCCC_ARCH_WORKAROUND_1, &res);
if ((int)res.a0 != 0)
break;
per_cpu(harden_branch_predictor_fn, cpu) =
call_smc_arch_workaround_1;
cpu_do_switch_mm = cpu_v7_smc_switch_mm;
spectre_v2_method = "firmware";
method = SPECTRE_V2_METHOD_SMC;
break;
default:
state = SPECTRE_VULNERABLE;
break;
}
}
#endif
}
if (spectre_v2_method)
pr_info("CPU%u: Spectre v2: using %s workaround\n",
smp_processor_id(), spectre_v2_method);
if (state == SPECTRE_MITIGATED)
state = spectre_v2_install_workaround(method);
spectre_v2_update_state(state, method);
}
#else
static void cpu_v7_spectre_init(void)
{
}
#endif
static __maybe_unused bool cpu_v7_check_auxcr_set(bool *warned,
u32 mask, const char *msg)
@ -149,16 +218,16 @@ static bool check_spectre_auxcr(bool *warned, u32 bit)
void cpu_v7_ca8_ibe(void)
{
if (check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(6)))
cpu_v7_spectre_init();
cpu_v7_spectre_v2_init();
}
void cpu_v7_ca15_ibe(void)
{
if (check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(0)))
cpu_v7_spectre_init();
cpu_v7_spectre_v2_init();
}
void cpu_v7_bugs_init(void)
{
cpu_v7_spectre_init();
cpu_v7_spectre_v2_init();
}