From 0c317eb3dd407f2ec7fcaccec79be6c3987573e2 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Fri, 23 Jul 2021 17:21:42 +0100 Subject: [PATCH] target/arm: Add missing 'return's after calling v7m_exception_taken() In do_v7m_exception_exit(), we perform various checks as part of performing the exception return. If one of these checks fails, the architecture requires that we take an appropriate exception on the existing stackframe. We implement this by calling v7m_exception_taken() to set up to take the new exception, and then immediately returning from do_v7m_exception_exit() without proceeding any further with the unstack-and-exception-return process. In a couple of checks that are new in v8.1M, we forgot the "return" statement, with the effect that if bad code in the guest tripped over these checks we would set up to take a UsageFault exception but then blunder on trying to also unstack and return from the original exception, with the probable result that the guest would crash. Add the missing return statements. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20210723162146.5167-3-peter.maydell@linaro.org --- target/arm/m_helper.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/target/arm/m_helper.c b/target/arm/m_helper.c index f9a9cb466c..f352346a96 100644 --- a/target/arm/m_helper.c +++ b/target/arm/m_helper.c @@ -1554,6 +1554,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu) qemu_log_mask(CPU_LOG_INT, "...taking UsageFault on existing " "stackframe: NSACR prevents clearing FPU registers\n"); v7m_exception_taken(cpu, excret, true, false); + return; } else if (!cpacr_pass) { armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, exc_secure); @@ -1561,6 +1562,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu) qemu_log_mask(CPU_LOG_INT, "...taking UsageFault on existing " "stackframe: CPACR prevents clearing FPU registers\n"); v7m_exception_taken(cpu, excret, true, false); + return; } } /* Clear s0..s15, FPSCR and VPR */