From: Marc Zyngier <marc.zyngier@arm.com>
Date: Thu, 27 Sep 2018 17:15:32 +0100
Subject: arm64: compat: Add CNTVCT trap handler
Git-commit: 50de013d22e4e112d7b0778a0e7d032f16c46778
Patch-mainline: v4.20-rc1
References: jsc#ECO-561
Since people seem to make a point in breaking the userspace visible
counter, we have no choice but to trap the access. We already do this
for 64bit userspace, but this is lacking for compat. Let's provide
the required handler.
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
arch/arm64/include/asm/esr.h | 3 +++
arch/arm64/kernel/traps.c | 16 ++++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 56d32e5557a5..5548712ce6e5 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -315,6 +315,9 @@
ESR_ELx_CP15_64_ISS_CRM_MASK | \
ESR_ELx_CP15_64_ISS_DIR_MASK)
+#define ESR_ELx_CP15_64_ISS_SYS_CNTVCT (ESR_ELx_CP15_64_ISS_SYS_VAL(1, 14) | \
+ ESR_ELx_CP15_64_ISS_DIR_READ)
+
#ifndef __ASSEMBLY__
#include <asm/types.h>
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 76ffb9f42aa4..3602b900ff1c 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -629,7 +629,23 @@ static struct sys64_hook cp15_32_hooks[] = {
{},
};
+static void compat_cntvct_read_handler(unsigned int esr, struct pt_regs *regs)
+{
+ int rt = (esr & ESR_ELx_CP15_64_ISS_RT_MASK) >> ESR_ELx_CP15_64_ISS_RT_SHIFT;
+ int rt2 = (esr & ESR_ELx_CP15_64_ISS_RT2_MASK) >> ESR_ELx_CP15_64_ISS_RT2_SHIFT;
+ u64 val = arch_counter_get_cntvct();
+
+ pt_regs_write_reg(regs, rt, lower_32_bits(val));
+ pt_regs_write_reg(regs, rt2, upper_32_bits(val));
+ arm64_compat_skip_faulting_instruction(regs, 4);
+}
+
static struct sys64_hook cp15_64_hooks[] = {
+ {
+ .esr_mask = ESR_ELx_CP15_64_ISS_SYS_MASK,
+ .esr_val = ESR_ELx_CP15_64_ISS_SYS_CNTVCT,
+ .handler = compat_cntvct_read_handler,
+ },
{},
};
--
2.16.4