As indicated in the ARMv7 ARM in B1.9.2, an instruction that would cause an UNDEF can trap even if it fails its condition code. Yes, this is annoying.
Add a arm_check_condition call before trying to handle an UNDEF, and move the PC by the right amount if the condition check fails. Signed-off-by: Marc Zyngier <marc.zyng...@arm.com> --- arch/arm/kernel/traps.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index 948c648fea00..ca51e80a60b6 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -462,6 +462,19 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs) instr = __mem_to_opcode_arm(instr); } + /* + * An UNDEF is allowed to trap even when failing its condition + * code (see B1.9.2 in the ARMv7 ARM). + */ + if (arm_check_condition(instr, regs->ARM_cpsr) == ARM_OPCODE_CONDTEST_FAIL) { + if (thumb_mode(regs) && !is_wide_instruction(instr)) + regs->ARM_pc += 2; + else + regs->ARM_pc +=4; + + return; + } + if (call_undef_hook(regs, instr) == 0) return; -- 2.11.0