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1/* SPDX-License-Identifier: GPL-2.0 */2/* Copyright (C) 2019 ARM Limited */3 4#ifndef __TEST_SIGNALS_UTILS_H__5#define __TEST_SIGNALS_UTILS_H__6 7#include <assert.h>8#include <stdio.h>9#include <string.h>10 11#include <linux/compiler.h>12 13#include "test_signals.h"14 15int test_init(struct tdescr *td);16int test_setup(struct tdescr *td);17void test_cleanup(struct tdescr *td);18int test_run(struct tdescr *td);19void test_result(struct tdescr *td);20 21static inline bool feats_ok(struct tdescr *td)22{23 if (td->feats_incompatible & td->feats_supported)24 return false;25 return (td->feats_required & td->feats_supported) == td->feats_required;26}27 28/*29 * Obtaining a valid and full-blown ucontext_t from userspace is tricky:30 * libc getcontext does() not save all the regs and messes with some of31 * them (pstate value in particular is not reliable).32 *33 * Here we use a service signal to grab the ucontext_t from inside a34 * dedicated signal handler, since there, it is populated by Kernel35 * itself in setup_sigframe(). The grabbed context is then stored and36 * made available in td->live_uc.37 *38 * As service-signal is used a SIGTRAP induced by a 'brk' instruction,39 * because here we have to avoid syscalls to trigger the signal since40 * they would cause any SVE sigframe content (if any) to be removed.41 *42 * Anyway this function really serves a dual purpose:43 *44 * 1. grab a valid sigcontext into td->live_uc for result analysis: in45 * such case it returns 1.46 *47 * 2. detect if, somehow, a previously grabbed live_uc context has been48 * used actively with a sigreturn: in such a case the execution would have49 * magically resumed in the middle of this function itself (seen_already==1):50 * in such a case return 0, since in fact we have not just simply grabbed51 * the context.52 *53 * This latter case is useful to detect when a fake_sigreturn test-case has54 * unexpectedly survived without hitting a SEGV.55 *56 * Note that the case of runtime dynamically sized sigframes (like in SVE57 * context) is still NOT addressed: sigframe size is supposed to be fixed58 * at sizeof(ucontext_t).59 */60static __always_inline bool get_current_context(struct tdescr *td,61 ucontext_t *dest_uc,62 size_t dest_sz)63{64 static volatile bool seen_already;65 int i;66 char *uc = (char *)dest_uc;67 68 assert(td && dest_uc);69 /* it's a genuine invocation..reinit */70 seen_already = 0;71 td->live_uc_valid = 0;72 td->live_sz = dest_sz;73 74 /*75 * This is a memset() but we don't want the compiler to76 * optimise it into either instructions or a library call77 * which might be incompatible with streaming mode.78 */79 for (i = 0; i < td->live_sz; i++) {80 uc[i] = 0;81 OPTIMIZER_HIDE_VAR(uc[0]);82 }83 84 td->live_uc = dest_uc;85 /*86 * Grab ucontext_t triggering a SIGTRAP.87 *88 * Note that:89 * - live_uc_valid is declared volatile sig_atomic_t in90 * struct tdescr since it will be changed inside the91 * sig_copyctx handler92 * - the additional 'memory' clobber is there to avoid possible93 * compiler's assumption on live_uc_valid and the content94 * pointed by dest_uc, which are all changed inside the signal95 * handler96 * - BRK causes a debug exception which is handled by the Kernel97 * and finally causes the SIGTRAP signal to be delivered to this98 * test thread. Since such delivery happens on the ret_to_user()99 * /do_notify_resume() debug exception return-path, we are sure100 * that the registered SIGTRAP handler has been run to completion101 * before the execution path is restored here: as a consequence102 * we can be sure that the volatile sig_atomic_t live_uc_valid103 * carries a meaningful result. Being in a single thread context104 * we'll also be sure that any access to memory modified by the105 * handler (namely ucontext_t) will be visible once returned.106 * - note that since we are using a breakpoint instruction here107 * to cause a SIGTRAP, the ucontext_t grabbed from the signal108 * handler would naturally contain a PC pointing exactly to this109 * BRK line, which means that, on return from the signal handler,110 * or if we place the ucontext_t on the stack to fake a sigreturn,111 * we'll end up in an infinite loop of BRK-SIGTRAP-handler.112 * For this reason we take care to artificially move forward the113 * PC to the next instruction while inside the signal handler.114 */115 asm volatile ("brk #666"116 : "+m" (*dest_uc)117 :118 : "memory");119 120 /*121 * If we were grabbing a streaming mode context then we may122 * have entered streaming mode behind the system's back and123 * libc or compiler generated code might decide to do124 * something invalid in streaming mode, or potentially even125 * the state of ZA. Issue a SMSTOP to exit both now we have126 * grabbed the state.127 */128 if (td->feats_supported & FEAT_SME)129 asm volatile("msr S0_3_C4_C6_3, xzr");130 131 /*132 * If we get here with seen_already==1 it implies the td->live_uc133 * context has been used to get back here....this probably means134 * a test has failed to cause a SEGV...anyway live_uc does not135 * point to a just acquired copy of ucontext_t...so return 0136 */137 if (seen_already) {138 fprintf(stdout,139 "Unexpected successful sigreturn detected: live_uc is stale !\n");140 return 0;141 }142 seen_already = 1;143 144 return td->live_uc_valid;145}146 147int fake_sigreturn(void *sigframe, size_t sz, int misalign_bytes);148#endif149