1 /* 2 * Copyright (c) 2021-2024, Arm Limited. All rights reserved. 3 * 4 * SPDX-License-Identifier: BSD-3-Clause 5 */ 6 7 #include <arch.h> 8 #include <arch_features.h> 9 #include <arch_helpers.h> 10 #include <lib/el3_runtime/pubsub.h> 11 #include <lib/extensions/trbe.h> 12 13 static void tsb_csync(void) 14 { 15 /* 16 * The assembler does not yet understand the tsb csync mnemonic 17 * so use the equivalent hint instruction. 18 */ 19 __asm__ volatile("hint #18"); 20 } 21 22 void trbe_enable(cpu_context_t *ctx) 23 { 24 el3_state_t *state = get_el3state_ctx(ctx); 25 u_register_t mdcr_el3_val = read_ctx_reg(state, CTX_MDCR_EL3); 26 27 /* 28 * MDCR_EL3.NSTBE = 0b0 29 * Trace Buffer owning Security state is Non-secure state. If FEAT_RME 30 * is not implemented, this field is RES0. 31 * 32 * MDCR_EL3.NSTB = 0b11 33 * Allow access of trace buffer control registers from NS-EL1 and 34 * NS-EL2, tracing is prohibited in Secure and Realm state (if 35 * implemented). 36 */ 37 mdcr_el3_val |= MDCR_NSTB(MDCR_NSTB_EL1); 38 mdcr_el3_val &= ~(MDCR_NSTBE_BIT); 39 write_ctx_reg(state, CTX_MDCR_EL3, mdcr_el3_val); 40 } 41 42 void trbe_disable(cpu_context_t *ctx) 43 { 44 el3_state_t *state = get_el3state_ctx(ctx); 45 u_register_t mdcr_el3_val = read_ctx_reg(state, CTX_MDCR_EL3); 46 47 /* 48 * MDCR_EL3.NSTBE = 0b0 49 * Trace Buffer owning Security state is secure state. If FEAT_RME 50 * is not implemented, this field is RES0. 51 * 52 * MDCR_EL3.NSTB = 0b00 53 * Clear these bits to disable access of trace buffer control registers 54 * from lower ELs in any security state. 55 */ 56 mdcr_el3_val &= ~(MDCR_NSTB(MDCR_NSTB_EL1)); 57 mdcr_el3_val &= ~(MDCR_NSTBE_BIT); 58 write_ctx_reg(state, CTX_MDCR_EL3, mdcr_el3_val); 59 } 60 61 void trbe_init_el2_unused(void) 62 { 63 /* 64 * MDCR_EL2.E2TB: Set to zero so that the trace Buffer 65 * owning exception level is NS-EL1 and, tracing is 66 * prohibited at NS-EL2. These bits are RES0 when 67 * FEAT_TRBE is not implemented. 68 */ 69 write_mdcr_el2(read_mdcr_el2() & ~MDCR_EL2_E2TB(MDCR_EL2_E2TB_EL1)); 70 } 71 72 static void *trbe_drain_trace_buffers_hook(const void *arg __unused) 73 { 74 if (is_feat_trbe_supported()) { 75 /* 76 * Before switching from normal world to secure world 77 * the trace buffers need to be drained out to memory. This is 78 * required to avoid an invalid memory access when TTBR is switched 79 * for entry to S-EL1. 80 */ 81 tsb_csync(); 82 dsbnsh(); 83 } 84 85 return (void *)0; 86 } 87 88 SUBSCRIBE_TO_EVENT(cm_entering_secure_world, trbe_drain_trace_buffers_hook); 89