From 85e7d1e9ff11e5df827cc7b81034b85efae7d315 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 13 Sep 2021 10:54:30 +0100 Subject: target/arm: Enforce that FPDSCR.LTPSIZE is 4 on inbound migration Architecturally, for an M-profile CPU with the LOB feature the LTPSIZE field in FPDSCR is always constant 4. QEMU's implementation enforces this everywhere, except that we don't check that it is true in incoming migration data. We're going to add come in gen_update_fp_context() which relies on the "always 4" property. Since this is TCG-only, we don't actually need to be robust to bogus incoming migration data, and the effect of it being wrong would be wrong code generation rather than a QEMU crash; but if it did ever happen somehow it would be very difficult to track down the cause. Add a check so that we fail the inbound migration if the FPDSCR.LTPSIZE value is incorrect. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20210913095440.13462-3-peter.maydell@linaro.org --- target/arm/machine.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'target') diff --git a/target/arm/machine.c b/target/arm/machine.c index 81e30de824..c74d8c3f4b 100644 --- a/target/arm/machine.c +++ b/target/arm/machine.c @@ -781,6 +781,19 @@ static int cpu_post_load(void *opaque, int version_id) hw_breakpoint_update_all(cpu); hw_watchpoint_update_all(cpu); + /* + * TCG gen_update_fp_context() relies on the invariant that + * FPDSCR.LTPSIZE is constant 4 for M-profile with the LOB extension; + * forbid bogus incoming data with some other value. + */ + if (arm_feature(env, ARM_FEATURE_M) && cpu_isar_feature(aa32_lob, cpu)) { + if (extract32(env->v7m.fpdscr[M_REG_NS], + FPCR_LTPSIZE_SHIFT, FPCR_LTPSIZE_LENGTH) != 4 || + extract32(env->v7m.fpdscr[M_REG_S], + FPCR_LTPSIZE_SHIFT, FPCR_LTPSIZE_LENGTH) != 4) { + return -1; + } + } if (!kvm_enabled()) { pmu_op_finish(&cpu->env); } -- cgit v1.2.3