arm64: compat: Add CNTVCT trap handler

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>

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 56d32e5557a5e9c6512ce5b0957d6ca4697fe2f1..5548712ce6e54c27f5b981a0b56d6718747a22d8 100644 (file)
--- 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 76ffb9f42aa400dae5d2bc6ad6e1266171f0888f..3602b900ff1c4be90411fb869ac226f2099d09c1 100644 (file)
--- 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,
+       },
        {},
 };