From c32da7aa6205a5ff62ae8d5062f7cad0eae4c1fd Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 8 Oct 2018 14:55:04 +0100 Subject: target/arm: Add v8M stack checks on exception entry MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add checks for breaches of the v8M stack limit when the stack pointer is decremented to push the exception frame for exception entry. Note that the exception-entry case is unique in that the stack pointer is updated to be the limit value if the limit is hit (per rule R_ZLZG). Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Richard Henderson Message-id: 20181002163556.10279-7-peter.maydell@linaro.org --- target/arm/helper.c | 54 +++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 46 insertions(+), 8 deletions(-) diff --git a/target/arm/helper.c b/target/arm/helper.c index 7ffd184044..4cc4369255 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -6867,6 +6867,8 @@ static bool v7m_push_callee_stack(ARMCPU *cpu, uint32_t lr, bool dotailchain, uint32_t frameptr; ARMMMUIdx mmu_idx; bool stacked_ok; + uint32_t limit; + bool want_psp; if (dotailchain) { bool mode = lr & R_V7M_EXCRET_MODE_MASK; @@ -6876,12 +6878,34 @@ static bool v7m_push_callee_stack(ARMCPU *cpu, uint32_t lr, bool dotailchain, mmu_idx = arm_v7m_mmu_idx_for_secstate_and_priv(env, M_REG_S, priv); frame_sp_p = get_v7m_sp_ptr(env, M_REG_S, mode, lr & R_V7M_EXCRET_SPSEL_MASK); + want_psp = mode && (lr & R_V7M_EXCRET_SPSEL_MASK); + if (want_psp) { + limit = env->v7m.psplim[M_REG_S]; + } else { + limit = env->v7m.msplim[M_REG_S]; + } } else { mmu_idx = core_to_arm_mmu_idx(env, cpu_mmu_index(env, false)); frame_sp_p = &env->regs[13]; + limit = v7m_sp_limit(env); } frameptr = *frame_sp_p - 0x28; + if (frameptr < limit) { + /* + * Stack limit failure: set SP to the limit value, and generate + * STKOF UsageFault. Stack pushes below the limit must not be + * performed. It is IMPDEF whether pushes above the limit are + * performed; we choose not to. + */ + qemu_log_mask(CPU_LOG_INT, + "...STKOF during callee-saves register stacking\n"); + env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_STKOF_MASK; + armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, + env->v7m.secure); + *frame_sp_p = limit; + return true; + } /* Write as much of the stack frame as we can. A write failure may * cause us to pend a derived exception. @@ -6905,10 +6929,7 @@ static bool v7m_push_callee_stack(ARMCPU *cpu, uint32_t lr, bool dotailchain, v7m_stack_write(cpu, frameptr + 0x24, env->regs[11], mmu_idx, ignore_faults); - /* Update SP regardless of whether any of the stack accesses failed. - * When we implement v8M stack limit checking then this attempt to - * update SP might also fail and result in a derived exception. - */ + /* Update SP regardless of whether any of the stack accesses failed. */ *frame_sp_p = frameptr; return !stacked_ok; @@ -7056,6 +7077,26 @@ static bool v7m_push_stack(ARMCPU *cpu) frameptr -= 0x20; + if (arm_feature(env, ARM_FEATURE_V8)) { + uint32_t limit = v7m_sp_limit(env); + + if (frameptr < limit) { + /* + * Stack limit failure: set SP to the limit value, and generate + * STKOF UsageFault. Stack pushes below the limit must not be + * performed. It is IMPDEF whether pushes above the limit are + * performed; we choose not to. + */ + qemu_log_mask(CPU_LOG_INT, + "...STKOF during stacking\n"); + env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_STKOF_MASK; + armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, + env->v7m.secure); + env->regs[13] = limit; + return true; + } + } + /* Write as much of the stack frame as we can. If we fail a stack * write this will result in a derived exception being pended * (which may be taken in preference to the one we started with @@ -7071,10 +7112,7 @@ static bool v7m_push_stack(ARMCPU *cpu) v7m_stack_write(cpu, frameptr + 24, env->regs[15], mmu_idx, false) && v7m_stack_write(cpu, frameptr + 28, xpsr, mmu_idx, false); - /* Update SP regardless of whether any of the stack accesses failed. - * When we implement v8M stack limit checking then this attempt to - * update SP might also fail and result in a derived exception. - */ + /* Update SP regardless of whether any of the stack accesses failed. */ env->regs[13] = frameptr; return !stacked_ok; -- cgit v1.2.3