In order to prevent aliasing attacks on the branch predictor,
invalidate the BTB or instruction cache on CPUs that are known to be
affected when taking an abort on a address that is outside of a user
task limit:
Cortex A8, A9, A12, A17, A73, A75: flush BTB.
Cortex A15, Brahma B15: invalidate icache.
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
---
arch/arm/include/asm/cp15.h | 3 +++
arch/arm/include/asm/system_misc.h | 8 ++++++
arch/arm/mm/fault.c | 3 +++
arch/arm/mm/proc-v7-bugs.c | 51 ++++++++++++++++++++++++++++++++++++++
arch/arm/mm/proc-v7.S | 8 +++---
5 files changed, 70 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/cp15.h b/arch/arm/include/asm/cp15.h
index 4c9fa72b59f5..07e27f212dc7 100644
--- a/arch/arm/include/asm/cp15.h
+++ b/arch/arm/include/asm/cp15.h
@@ -65,6 +65,9 @@
#define __write_sysreg(v, r, w, c, t) asm volatile(w " " c : : "r" ((t)(v)))
#define write_sysreg(v, ...) __write_sysreg(v, __VA_ARGS__)
+#define BPIALL __ACCESS_CP15(c7, 0, c5, 6)
+#define ICIALLU __ACCESS_CP15(c7, 0, c5, 0)
+
extern unsigned long cr_alignment; /* defined in entry-armv.S */
static inline unsigned long get_cr(void)
diff --git a/arch/arm/include/asm/system_misc.h b/arch/arm/include/asm/system_misc.h
index 78f6db114faf..3cfe010c5734 100644
--- a/arch/arm/include/asm/system_misc.h
+++ b/arch/arm/include/asm/system_misc.h
@@ -15,6 +15,14 @@ void soft_restart(unsigned long);
extern void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
extern void (*arm_pm_idle)(void);
+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+extern void (*harden_branch_predictor)(void);
+#define harden_branch_predictor() \
+ do { if (harden_branch_predictor) harden_branch_predictor(); } while (0)
+#else
+#define harden_branch_predictor() do { } while (0)
+#endif
+
#define UDBG_UNDEFINED (1 << 0)
#define UDBG_SYSCALL (1 << 1)
#define UDBG_BADABORT (1 << 2)
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index b75eada23d0a..3b1ba003c4f9 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -163,6 +163,9 @@ __do_user_fault(struct task_struct *tsk, unsigned long addr,
{
struct siginfo si;
+ if (addr > TASK_SIZE)
+ harden_branch_predictor();
+
#ifdef CONFIG_DEBUG_USER
if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
((user_debug & UDBG_BUS) && (sig == SIGBUS))) {
diff --git a/arch/arm/mm/proc-v7-bugs.c b/arch/arm/mm/proc-v7-bugs.c
index a32ce13479d9..65a9b8141f86 100644
--- a/arch/arm/mm/proc-v7-bugs.c
+++ b/arch/arm/mm/proc-v7-bugs.c
@@ -2,6 +2,12 @@
#include <linux/kernel.h>
#include <linux/smp.h>
+#include <asm/cp15.h>
+#include <asm/cputype.h>
+#include <asm/system_misc.h>
+
+void cpu_v7_bugs_init(void);
+
static __maybe_unused void cpu_v7_check_auxcr_set(u32 mask, const char *msg)
{
u32 aux_cr;
@@ -21,9 +27,54 @@ static void check_spectre_auxcr(u32 bit)
void cpu_v7_ca8_ibe(void)
{
check_spectre_auxcr(BIT(6));
+ cpu_v7_bugs_init();
}
void cpu_v7_ca15_ibe(void)
{
check_spectre_auxcr(BIT(0));
+ cpu_v7_bugs_init();
+}
+
+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+void (*harden_branch_predictor)(void);
+
+static void harden_branch_predictor_bpiall(void)
+{
+ write_sysreg(0, BPIALL);
+}
+
+static void harden_branch_predictor_iciallu(void)
+{
+ write_sysreg(0, ICIALLU);
+}
+
+void cpu_v7_bugs_init(void)
+{
+ const char *spectre_v2_method = NULL;
+
+ if (harden_branch_predictor)
+ return;
+
+ switch (read_cpuid_part()) {
+ case ARM_CPU_PART_CORTEX_A8:
+ case ARM_CPU_PART_CORTEX_A9:
+ case ARM_CPU_PART_CORTEX_A12:
+ case ARM_CPU_PART_CORTEX_A17:
+ case ARM_CPU_PART_CORTEX_A73:
+ case ARM_CPU_PART_CORTEX_A75:
+ harden_branch_predictor = harden_branch_predictor_bpiall;
+ spectre_v2_method = "BPIALL";
+ break;
+
+ case ARM_CPU_PART_CORTEX_A15:
+ case ARM_CPU_PART_BRAHMA_B15:
+ harden_branch_predictor = harden_branch_predictor_iciallu;
+ spectre_v2_method = "ICIALLU";
+ break;
+ }
+ if (spectre_v2_method)
+ pr_info("CPU: Spectre v2: using %s workaround\n",
+ spectre_v2_method);
}
+#endif
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index fa9214036fb3..79510011e7eb 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -532,8 +532,10 @@ ENDPROC(__v7_setup)
__INITDATA
+ .weak cpu_v7_bugs_init
+
@ define struct processor (see <asm/proc-fns.h> and proc-macros.S)
- define_processor_functions v7, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
+ define_processor_functions v7, dabort=v7_early_abort, pabort=v7_pabort, suspend=1, bugs=cpu_v7_bugs_init
#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
@ generic v7 bpiall on context switch
@@ -548,7 +550,7 @@ ENDPROC(__v7_setup)
globl_equ cpu_v7_bpiall_do_suspend, cpu_v7_do_suspend
globl_equ cpu_v7_bpiall_do_resume, cpu_v7_do_resume
#endif
- define_processor_functions v7_bpiall, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
+ define_processor_functions v7_bpiall, dabort=v7_early_abort, pabort=v7_pabort, suspend=1, bugs=cpu_v7_bugs_init
#define HARDENED_BPIALL_PROCESSOR_FUNCTIONS v7_bpiall_processor_functions
#else
@@ -584,7 +586,7 @@ ENDPROC(__v7_setup)
globl_equ cpu_ca9mp_switch_mm, cpu_v7_switch_mm
#endif
globl_equ cpu_ca9mp_set_pte_ext, cpu_v7_set_pte_ext
- define_processor_functions ca9mp, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
+ define_processor_functions ca9mp, dabort=v7_early_abort, pabort=v7_pabort, suspend=1, bugs=cpu_v7_bugs_init
#endif
@ Cortex-A15 - needs iciallu switch_mm for hardening
--
2.7.4
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