diff options
Diffstat (limited to 'tools/testing/selftests/arm64/signal/test_signals_utils.h')
| -rw-r--r-- | tools/testing/selftests/arm64/signal/test_signals_utils.h | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/tools/testing/selftests/arm64/signal/test_signals_utils.h b/tools/testing/selftests/arm64/signal/test_signals_utils.h new file mode 100644 index 000000000000..36fc12b3cd60 --- /dev/null +++ b/tools/testing/selftests/arm64/signal/test_signals_utils.h @@ -0,0 +1,187 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2019 ARM Limited */ + +#ifndef __TEST_SIGNALS_UTILS_H__ +#define __TEST_SIGNALS_UTILS_H__ + +#include <assert.h> +#include <stdio.h> +#include <stdint.h> +#include <string.h> + +#include <linux/compiler.h> + +#include "test_signals.h" + +int test_init(struct tdescr *td); +int test_setup(struct tdescr *td); +void test_cleanup(struct tdescr *td); +int test_run(struct tdescr *td); +void test_result(struct tdescr *td); + +#ifndef __NR_prctl +#define __NR_prctl 167 +#endif + +/* + * The prctl takes 1 argument but we need to ensure that the other + * values passed in registers to the syscall are zero since the kernel + * validates them. + */ +#define gcs_set_state(state) \ + ({ \ + register long _num __asm__ ("x8") = __NR_prctl; \ + register long _arg1 __asm__ ("x0") = PR_SET_SHADOW_STACK_STATUS; \ + register long _arg2 __asm__ ("x1") = (long)(state); \ + register long _arg3 __asm__ ("x2") = 0; \ + register long _arg4 __asm__ ("x3") = 0; \ + register long _arg5 __asm__ ("x4") = 0; \ + \ + __asm__ volatile ( \ + "svc #0\n" \ + : "=r"(_arg1) \ + : "r"(_arg1), "r"(_arg2), \ + "r"(_arg3), "r"(_arg4), \ + "r"(_arg5), "r"(_num) \ + : "memory", "cc" \ + ); \ + _arg1; \ + }) + +static inline __attribute__((always_inline)) uint64_t get_gcspr_el0(void) +{ + uint64_t val; + + asm volatile("mrs %0, S3_3_C2_C5_1" : "=r" (val)); + + return val; +} + +static inline bool feats_ok(struct tdescr *td) +{ + if (td->feats_incompatible & td->feats_supported) + return false; + return (td->feats_required & td->feats_supported) == td->feats_required; +} + +/* + * Obtaining a valid and full-blown ucontext_t from userspace is tricky: + * libc getcontext does() not save all the regs and messes with some of + * them (pstate value in particular is not reliable). + * + * Here we use a service signal to grab the ucontext_t from inside a + * dedicated signal handler, since there, it is populated by Kernel + * itself in setup_sigframe(). The grabbed context is then stored and + * made available in td->live_uc. + * + * As service-signal is used a SIGTRAP induced by a 'brk' instruction, + * because here we have to avoid syscalls to trigger the signal since + * they would cause any SVE sigframe content (if any) to be removed. + * + * Anyway this function really serves a dual purpose: + * + * 1. grab a valid sigcontext into td->live_uc for result analysis: in + * such case it returns 1. + * + * 2. detect if, somehow, a previously grabbed live_uc context has been + * used actively with a sigreturn: in such a case the execution would have + * magically resumed in the middle of this function itself (seen_already==1): + * in such a case return 0, since in fact we have not just simply grabbed + * the context. + * + * This latter case is useful to detect when a fake_sigreturn test-case has + * unexpectedly survived without hitting a SEGV. + * + * Note that the case of runtime dynamically sized sigframes (like in SVE + * context) is still NOT addressed: sigframe size is supposed to be fixed + * at sizeof(ucontext_t). + */ +static __always_inline bool get_current_context(struct tdescr *td, + ucontext_t *dest_uc, + size_t dest_sz) +{ + static volatile bool seen_already; + int i; + char *uc = (char *)dest_uc; + + assert(td && dest_uc); + /* it's a genuine invocation..reinit */ + seen_already = 0; + td->live_uc_valid = 0; + td->live_sz = dest_sz; + + /* + * This is a memset() but we don't want the compiler to + * optimise it into either instructions or a library call + * which might be incompatible with streaming mode. + */ + for (i = 0; i < td->live_sz; i++) { + uc[i] = 0; + OPTIMIZER_HIDE_VAR(uc[0]); + } + + td->live_uc = dest_uc; + /* + * Grab ucontext_t triggering a SIGTRAP. + * + * Note that: + * - live_uc_valid is declared volatile sig_atomic_t in + * struct tdescr since it will be changed inside the + * sig_copyctx handler + * - the additional 'memory' clobber is there to avoid possible + * compiler's assumption on live_uc_valid and the content + * pointed by dest_uc, which are all changed inside the signal + * handler + * - BRK causes a debug exception which is handled by the Kernel + * and finally causes the SIGTRAP signal to be delivered to this + * test thread. Since such delivery happens on the ret_to_user() + * /do_notify_resume() debug exception return-path, we are sure + * that the registered SIGTRAP handler has been run to completion + * before the execution path is restored here: as a consequence + * we can be sure that the volatile sig_atomic_t live_uc_valid + * carries a meaningful result. Being in a single thread context + * we'll also be sure that any access to memory modified by the + * handler (namely ucontext_t) will be visible once returned. + * - note that since we are using a breakpoint instruction here + * to cause a SIGTRAP, the ucontext_t grabbed from the signal + * handler would naturally contain a PC pointing exactly to this + * BRK line, which means that, on return from the signal handler, + * or if we place the ucontext_t on the stack to fake a sigreturn, + * we'll end up in an infinite loop of BRK-SIGTRAP-handler. + * For this reason we take care to artificially move forward the + * PC to the next instruction while inside the signal handler. + */ + asm volatile ("brk #666" + : "+m" (*dest_uc) + : + : "memory"); + + /* + * If we were grabbing a streaming mode context then we may + * have entered streaming mode behind the system's back and + * libc or compiler generated code might decide to do + * something invalid in streaming mode, or potentially even + * the state of ZA. Issue a SMSTOP to exit both now we have + * grabbed the state. + */ + if (td->feats_supported & FEAT_SME) + asm volatile("msr S0_3_C4_C6_3, xzr"); + + /* + * If we get here with seen_already==1 it implies the td->live_uc + * context has been used to get back here....this probably means + * a test has failed to cause a SEGV...anyway live_uc does not + * point to a just acquired copy of ucontext_t...so return 0 + */ + if (seen_already) { + fprintf(stdout, + "Unexpected successful sigreturn detected: live_uc is stale !\n"); + return 0; + } + seen_already = 1; + + return td->live_uc_valid; +} + +int fake_sigreturn(void *sigframe, size_t sz, int misalign_bytes); +#endif |