From 6808c4d2d2826920087533f517472c09edc7b0d2 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 29 Apr 2019 17:36:01 +0100 Subject: [PATCH] target/arm: Handle floating point registers in exception return Handle floating point registers in exception return. This corresponds to pseudocode functions ValidateExceptionReturn(), ExceptionReturn(), PopStack() and ConsumeExcStackFrame(). Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20190416125744.27770-16-peter.maydell@linaro.org --- target/arm/helper.c | 142 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 141 insertions(+), 1 deletion(-) diff --git a/target/arm/helper.c b/target/arm/helper.c index c7b1a8d231..14604f49a4 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -8447,6 +8447,8 @@ static void do_v7m_exception_exit(ARMCPU *cpu) bool rettobase = false; bool exc_secure = false; bool return_to_secure; + bool ftype; + bool restore_s16_s31; /* If we're not in Handler mode then jumps to magic exception-exit * addresses don't have magic behaviour. However for the v8M @@ -8484,6 +8486,16 @@ static void do_v7m_exception_exit(ARMCPU *cpu) excret); } + ftype = excret & R_V7M_EXCRET_FTYPE_MASK; + + if (!arm_feature(env, ARM_FEATURE_VFP) && !ftype) { + qemu_log_mask(LOG_GUEST_ERROR, "M profile: zero FTYPE in exception " + "exit PC value 0x%" PRIx32 " is UNPREDICTABLE " + "if FPU not present\n", + excret); + ftype = true; + } + if (arm_feature(env, ARM_FEATURE_M_SECURITY)) { /* EXC_RETURN.ES validation check (R_SMFL). We must do this before * we pick which FAULTMASK to clear. @@ -8584,6 +8596,30 @@ static void do_v7m_exception_exit(ARMCPU *cpu) */ write_v7m_control_spsel_for_secstate(env, return_to_sp_process, exc_secure); + /* + * Clear scratch FP values left in caller saved registers; this + * must happen before any kind of tail chaining. + */ + if ((env->v7m.fpccr[M_REG_S] & R_V7M_FPCCR_CLRONRET_MASK) && + (env->v7m.control[M_REG_S] & R_V7M_CONTROL_FPCA_MASK)) { + if (env->v7m.fpccr[M_REG_S] & R_V7M_FPCCR_LSPACT_MASK) { + env->v7m.sfsr |= R_V7M_SFSR_LSERR_MASK; + armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false); + qemu_log_mask(CPU_LOG_INT, "...taking SecureFault on existing " + "stackframe: error during lazy state deactivation\n"); + v7m_exception_taken(cpu, excret, true, false); + return; + } else { + /* Clear s0..s15 and FPSCR */ + int i; + + for (i = 0; i < 16; i += 2) { + *aa32_vfp_dreg(env, i / 2) = 0; + } + vfp_set_fpscr(env, 0); + } + } + if (sfault) { env->v7m.sfsr |= R_V7M_SFSR_INVER_MASK; armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false); @@ -8745,8 +8781,105 @@ static void do_v7m_exception_exit(ARMCPU *cpu) } } + if (!ftype) { + /* FP present and we need to handle it */ + if (!return_to_secure && + (env->v7m.fpccr[M_REG_S] & R_V7M_FPCCR_LSPACT_MASK)) { + armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false); + env->v7m.sfsr |= R_V7M_SFSR_LSERR_MASK; + qemu_log_mask(CPU_LOG_INT, + "...taking SecureFault on existing stackframe: " + "Secure LSPACT set but exception return is " + "not to secure state\n"); + v7m_exception_taken(cpu, excret, true, false); + return; + } + + restore_s16_s31 = return_to_secure && + (env->v7m.fpccr[M_REG_S] & R_V7M_FPCCR_TS_MASK); + + if (env->v7m.fpccr[return_to_secure] & R_V7M_FPCCR_LSPACT_MASK) { + /* State in FPU is still valid, just clear LSPACT */ + env->v7m.fpccr[return_to_secure] &= ~R_V7M_FPCCR_LSPACT_MASK; + } else { + int i; + uint32_t fpscr; + bool cpacr_pass, nsacr_pass; + + cpacr_pass = v7m_cpacr_pass(env, return_to_secure, + return_to_priv); + nsacr_pass = return_to_secure || + extract32(env->v7m.nsacr, 10, 1); + + if (!cpacr_pass) { + armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, + return_to_secure); + env->v7m.cfsr[return_to_secure] |= R_V7M_CFSR_NOCP_MASK; + qemu_log_mask(CPU_LOG_INT, + "...taking UsageFault on existing " + "stackframe: CPACR.CP10 prevents unstacking " + "FP regs\n"); + v7m_exception_taken(cpu, excret, true, false); + return; + } else if (!nsacr_pass) { + armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, true); + env->v7m.cfsr[M_REG_S] |= R_V7M_CFSR_INVPC_MASK; + qemu_log_mask(CPU_LOG_INT, + "...taking Secure UsageFault on existing " + "stackframe: NSACR.CP10 prevents unstacking " + "FP regs\n"); + v7m_exception_taken(cpu, excret, true, false); + return; + } + + for (i = 0; i < (restore_s16_s31 ? 32 : 16); i += 2) { + uint32_t slo, shi; + uint64_t dn; + uint32_t faddr = frameptr + 0x20 + 4 * i; + + if (i >= 16) { + faddr += 8; /* Skip the slot for the FPSCR */ + } + + pop_ok = pop_ok && + v7m_stack_read(cpu, &slo, faddr, mmu_idx) && + v7m_stack_read(cpu, &shi, faddr + 4, mmu_idx); + + if (!pop_ok) { + break; + } + + dn = (uint64_t)shi << 32 | slo; + *aa32_vfp_dreg(env, i / 2) = dn; + } + pop_ok = pop_ok && + v7m_stack_read(cpu, &fpscr, frameptr + 0x60, mmu_idx); + if (pop_ok) { + vfp_set_fpscr(env, fpscr); + } + if (!pop_ok) { + /* + * These regs are 0 if security extension present; + * otherwise merely UNKNOWN. We zero always. + */ + for (i = 0; i < (restore_s16_s31 ? 32 : 16); i += 2) { + *aa32_vfp_dreg(env, i / 2) = 0; + } + vfp_set_fpscr(env, 0); + } + } + } + env->v7m.control[M_REG_S] = FIELD_DP32(env->v7m.control[M_REG_S], + V7M_CONTROL, FPCA, !ftype); + /* Commit to consuming the stack frame */ frameptr += 0x20; + if (!ftype) { + frameptr += 0x48; + if (restore_s16_s31) { + frameptr += 0x40; + } + } /* Undo stack alignment (the SPREALIGN bit indicates that the original * pre-exception SP was not 8-aligned and we added a padding word to * align it, so we undo this by ORing in the bit that increases it @@ -8759,7 +8892,14 @@ static void do_v7m_exception_exit(ARMCPU *cpu) *frame_sp_p = frameptr; } /* This xpsr_write() will invalidate frame_sp_p as it may switch stack */ - xpsr_write(env, xpsr, ~XPSR_SPREALIGN); + xpsr_write(env, xpsr, ~(XPSR_SPREALIGN | XPSR_SFPA)); + + if (env->v7m.secure) { + bool sfpa = xpsr & XPSR_SFPA; + + env->v7m.control[M_REG_S] = FIELD_DP32(env->v7m.control[M_REG_S], + V7M_CONTROL, SFPA, sfpa); + } /* The restored xPSR exception field will be zero if we're * resuming in Thread mode. If that doesn't match what the