[PATCH v9 07/13] arm64: unify native/compat instruction skipping

Mark Brown
2020-03-11T19:33:18Z

Skipping of an instruction on AArch32 works a bit differently from
AArch64, mainly due to the different CPSR/PSTATE semantics.

Currently arm64_skip_faulting_instruction() is only suitable for
AArch64, and arm64_compat_skip_faulting_instruction() handles the IT
state machine but is local to traps.c.

Since manual instruction skipping implies a trap, it's a relatively
slow path.

So, make arm64_skip_faulting_instruction() handle both compat and
native, and get rid of the arm64_compat_skip_faulting_instruction()
special case.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kernel/traps.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index b8c714dda851..bc9f4292bfc3 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -272,6 +272,8 @@ void arm64_notify_die(const char *str, struct pt_regs *regs,
}
}

+static void advance_itstate(struct pt_regs *regs);
+
void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
{
regs->pc += size;
@@ -282,6 +284,9 @@ void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
*/
if (user_mode(regs))
user_fastforward_single_step(current);
+
+ if (regs->pstate & PSR_MODE32_BIT)
+ advance_itstate(regs);
}

static LIST_HEAD(undef_hook);
@@ -644,19 +649,12 @@ static void advance_itstate(struct pt_regs *regs)
compat_set_it_state(regs, it);
}

-static void arm64_compat_skip_faulting_instruction(struct pt_regs *regs,
- unsigned int sz)
-{
- advance_itstate(regs);
- arm64_skip_faulting_instruction(regs, sz);
-}
-
static void compat_cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
{
int reg = (esr & ESR_ELx_CP15_32_ISS_RT_MASK) >> ESR_ELx_CP15_32_ISS_RT_SHIFT;

pt_regs_write_reg(regs, reg, arch_timer_get_rate());
- arm64_compat_skip_faulting_instruction(regs, 4);
+ arm64_skip_faulting_instruction(regs, 4);
}

static const struct sys64_hook cp15_32_hooks[] = {
@@ -676,7 +674,7 @@ static void compat_cntvct_read_handler(unsigned int esr, struct pt_regs *regs)

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);
+ arm64_skip_faulting_instruction(regs, 4);
}

static const struct sys64_hook cp15_64_hooks[] = {
@@ -697,7 +695,7 @@ void do_cp15instr(unsigned int esr, struct pt_regs *regs)
* There is no T16 variant of a CP access, so we
* always advance PC by 4 bytes.
*/
- arm64_compat_skip_faulting_instruction(regs, 4);
+ arm64_skip_faulting_instruction(regs, 4);
return;
}

--
2.20.1