From a59b1ed618415212c5f0f05abc1192e14ad5fdbb Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 19 Nov 2020 21:56:05 +0000 Subject: target/arm: For v8.1M, always clear R0-R3, R12, APSR, EPSR on exception entry In v8.0M, on exception entry the registers R0-R3, R12, APSR and EPSR are zeroed for an exception taken to Non-secure state; for an exception taken to Secure state they become UNKNOWN, and we chose to leave them at their previous values. In v8.1M the behaviour is specified more tightly and these registers are always zeroed regardless of the security state that the exception targets (see rule R_KPZV). Implement this. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20201119215617.29887-17-peter.maydell@linaro.org --- target/arm/m_helper.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'target') diff --git a/target/arm/m_helper.c b/target/arm/m_helper.c index aad01ea012..721b4b4896 100644 --- a/target/arm/m_helper.c +++ b/target/arm/m_helper.c @@ -897,10 +897,12 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr, bool dotailchain, * Clear registers if necessary to prevent non-secure exception * code being able to see register values from secure code. * Where register values become architecturally UNKNOWN we leave - * them with their previous values. + * them with their previous values. v8.1M is tighter than v8.0M + * here and always zeroes the caller-saved registers regardless + * of the security state the exception is targeting. */ if (arm_feature(env, ARM_FEATURE_M_SECURITY)) { - if (!targets_secure) { + if (!targets_secure || arm_feature(env, ARM_FEATURE_V8_1M)) { /* * Always clear the caller-saved registers (they have been * pushed to the stack earlier in v7m_push_stack()). @@ -909,10 +911,16 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr, bool dotailchain, * v7m_push_callee_stack()). */ int i; + /* + * r4..r11 are callee-saves, zero only if background + * state was Secure (EXCRET.S == 1) and exception + * targets Non-secure state + */ + bool zero_callee_saves = !targets_secure && + (lr & R_V7M_EXCRET_S_MASK); for (i = 0; i < 13; i++) { - /* r4..r11 are callee-saves, zero only if EXCRET.S == 1 */ - if (i < 4 || i > 11 || (lr & R_V7M_EXCRET_S_MASK)) { + if (i < 4 || i > 11 || zero_callee_saves) { env->regs[i] = 0; } } -- cgit v1.2.3-55-g7522