On Mon, Mar 06, 2017 at 11:26:15AM +0000, Marc Zyngier wrote: > Since people seem to make a point in breaking the userspace visible > counter, we have no choice but to trap the access. Add the required > handler. > > Signed-off-by: Marc Zyngier <[email protected]> > --- > arch/arm64/include/asm/esr.h | 2 ++ > arch/arm64/kernel/traps.c | 14 ++++++++++++++ > 2 files changed, 16 insertions(+) > > diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h > index d14c478976d0..ad42e79a5d4d 100644 > --- a/arch/arm64/include/asm/esr.h > +++ b/arch/arm64/include/asm/esr.h > @@ -175,6 +175,8 @@ > #define ESR_ELx_SYS64_ISS_SYS_CTR_READ (ESR_ELx_SYS64_ISS_SYS_CTR | \ > ESR_ELx_SYS64_ISS_DIR_READ) > > +#define ESR_ELx_SYS64_ISS_SYS_CNTVCT (ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 2, 14, > 0) | \ > + ESR_ELx_SYS64_ISS_DIR_READ) > #ifndef __ASSEMBLY__ > #include <asm/types.h> > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > index e52be6aa44ee..1de444e6c669 100644 > --- a/arch/arm64/kernel/traps.c > +++ b/arch/arm64/kernel/traps.c > @@ -505,6 +505,14 @@ static void ctr_read_handler(unsigned int esr, struct > pt_regs *regs) > regs->pc += 4; > } > > +static void cntvct_read_handler(unsigned int esr, struct pt_regs *regs) > +{ > + int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> > ESR_ELx_SYS64_ISS_RT_SHIFT; > + > + pt_regs_write_reg(regs, rt, arch_counter_get_cntvct()); > + regs->pc += 4; > +}
I was going to suggest it'd be worth using AARCH64_INSN_SIZE, but I see most of the other handlers in this file don't, so I guess that's not a big deal. Otherwise, this looks fine to me. FWIW: Acked-by: Mark Rutland <[email protected]> Mark. > + > struct sys64_hook { > unsigned int esr_mask; > unsigned int esr_val; > @@ -523,6 +531,12 @@ static struct sys64_hook sys64_hooks[] = { > .esr_val = ESR_ELx_SYS64_ISS_SYS_CTR_READ, > .handler = ctr_read_handler, > }, > + { > + /* Trap read access to CNTVCT_EL0 */ > + .esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK, > + .esr_val = ESR_ELx_SYS64_ISS_SYS_CNTVCT, > + .handler = cntvct_read_handler, > + }, > {}, > }; > > -- > 2.11.0 >
