[PATCH 47/52] arm: Invalidate BTB on prefetch abort outside of user mapping on Cortex A8, A9, A12 and A17

From: Alex Shi
Date: Mon Feb 26 2018 - 03:27:32 EST

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From: Marc Zyngier <marc.zyngier@xxxxxxx>

** Not yet queued for inclusion in mainline **

In order to prevent aliasing attacks on the branch predictor,
invalidate the BTB on CPUs that are known to be affected when taking
a prefetch abort on a address that is outside of a user task limit.

Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxx>
---
arch/arm/include/asm/cp15.h | 2 ++
arch/arm/mm/fault.c | 25 ++++++++++++++++
arch/arm/mm/fsr-2level.c | 4 +--
arch/arm/mm/fsr-3level.c | 69 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 98 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/cp15.h b/arch/arm/include/asm/cp15.h
index dbdbce1..0672ddc 100644
--- a/arch/arm/include/asm/cp15.h
+++ b/arch/arm/include/asm/cp15.h
@@ -64,6 +64,8 @@
#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)
+
extern unsigned long cr_alignment; /* defined in entry-armv.S */

static inline unsigned long get_cr(void)
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index f7861dc..17fd0c7 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -20,6 +20,7 @@
#include <linux/highmem.h>
#include <linux/perf_event.h>

+#include <asm/cp15.h>
#include <asm/exception.h>
#include <asm/pgtable.h>
#include <asm/system_misc.h>
@@ -395,12 +396,36 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
__do_kernel_fault(mm, addr, fsr, regs);
return 0;
}
+
+static int __maybe_unused
+do_pabt_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+{
+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+ if (addr > TASK_SIZE) {
+ 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:
+ write_sysreg(0, BPIALL);
+ break;
+ }
+ }
+#endif
+ return do_page_fault(addr, fsr, regs);
+}
#else /* CONFIG_MMU */
static int
do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
return 0;
}
+
+static int
+do_pabt_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+{
+ return 0;
+}
#endif /* CONFIG_MMU */

/*
diff --git a/arch/arm/mm/fsr-2level.c b/arch/arm/mm/fsr-2level.c
index 18ca74c..4cede9b 100644
--- a/arch/arm/mm/fsr-2level.c
+++ b/arch/arm/mm/fsr-2level.c
@@ -50,7 +50,7 @@ static struct fsr_info ifsr_info[] = {
{ do_bad, SIGBUS, 0, "unknown 4" },
{ do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" },
{ do_bad, SIGSEGV, SEGV_ACCERR, "page access flag fault" },
- { do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" },
+ { do_pabt_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" },
{ do_bad, SIGBUS, 0, "external abort on non-linefetch" },
{ do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" },
{ do_bad, SIGBUS, 0, "unknown 10" },
@@ -58,7 +58,7 @@ static struct fsr_info ifsr_info[] = {
{ do_bad, SIGBUS, 0, "external abort on translation" },
{ do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" },
{ do_bad, SIGBUS, 0, "external abort on translation" },
- { do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" },
+ { do_pabt_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" },
{ do_bad, SIGBUS, 0, "unknown 16" },
{ do_bad, SIGBUS, 0, "unknown 17" },
{ do_bad, SIGBUS, 0, "unknown 18" },
diff --git a/arch/arm/mm/fsr-3level.c b/arch/arm/mm/fsr-3level.c
index ab4409a..2745f7f 100644
--- a/arch/arm/mm/fsr-3level.c
+++ b/arch/arm/mm/fsr-3level.c
@@ -65,4 +65,73 @@ static struct fsr_info fsr_info[] = {
{ do_bad, SIGBUS, 0, "unknown 63" },
};

+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+static struct fsr_info ifsr_info[] = {
+ { do_bad, SIGBUS, 0, "unknown 0" },
+ { do_bad, SIGBUS, 0, "unknown 1" },
+ { do_bad, SIGBUS, 0, "unknown 2" },
+ { do_bad, SIGBUS, 0, "unknown 3" },
+ { do_bad, SIGBUS, 0, "reserved translation fault" },
+ { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" },
+ { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" },
+ { do_pabt_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" },
+ { do_bad, SIGBUS, 0, "reserved access flag fault" },
+ { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" },
+ { do_pabt_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" },
+ { do_pabt_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" },
+ { do_bad, SIGBUS, 0, "reserved permission fault" },
+ { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" },
+ { do_pabt_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" },
+ { do_pabt_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" },
+ { do_bad, SIGBUS, 0, "synchronous external abort" },
+ { do_bad, SIGBUS, 0, "asynchronous external abort" },
+ { do_bad, SIGBUS, 0, "unknown 18" },
+ { do_bad, SIGBUS, 0, "unknown 19" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous parity error" },
+ { do_bad, SIGBUS, 0, "asynchronous parity error" },
+ { do_bad, SIGBUS, 0, "unknown 26" },
+ { do_bad, SIGBUS, 0, "unknown 27" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "unknown 32" },
+ { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" },
+ { do_bad, SIGBUS, 0, "debug event" },
+ { do_bad, SIGBUS, 0, "unknown 35" },
+ { do_bad, SIGBUS, 0, "unknown 36" },
+ { do_bad, SIGBUS, 0, "unknown 37" },
+ { do_bad, SIGBUS, 0, "unknown 38" },
+ { do_bad, SIGBUS, 0, "unknown 39" },
+ { do_bad, SIGBUS, 0, "unknown 40" },
+ { do_bad, SIGBUS, 0, "unknown 41" },
+ { do_bad, SIGBUS, 0, "unknown 42" },
+ { do_bad, SIGBUS, 0, "unknown 43" },
+ { do_bad, SIGBUS, 0, "unknown 44" },
+ { do_bad, SIGBUS, 0, "unknown 45" },
+ { do_bad, SIGBUS, 0, "unknown 46" },
+ { do_bad, SIGBUS, 0, "unknown 47" },
+ { do_bad, SIGBUS, 0, "unknown 48" },
+ { do_bad, SIGBUS, 0, "unknown 49" },
+ { do_bad, SIGBUS, 0, "unknown 50" },
+ { do_bad, SIGBUS, 0, "unknown 51" },
+ { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" },
+ { do_bad, SIGBUS, 0, "unknown 53" },
+ { do_bad, SIGBUS, 0, "unknown 54" },
+ { do_bad, SIGBUS, 0, "unknown 55" },
+ { do_bad, SIGBUS, 0, "unknown 56" },
+ { do_bad, SIGBUS, 0, "unknown 57" },
+ { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" },
+ { do_bad, SIGBUS, 0, "unknown 59" },
+ { do_bad, SIGBUS, 0, "unknown 60" },
+ { do_bad, SIGBUS, 0, "unknown 61" },
+ { do_bad, SIGBUS, 0, "unknown 62" },
+ { do_bad, SIGBUS, 0, "unknown 63" },
+};
+#else
#define ifsr_info fsr_info
+#endif
--
2.7.4

Next message: Alex Shi: "[PATCH 48/52] arm: KVM: Invalidate BTB on guest exit for Cortex-A12/A17"
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