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120 lines
4.4 KiB
120 lines
4.4 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* Copyright (C) 2019 ARM Limited */ |
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#ifndef __TEST_SIGNALS_UTILS_H__ |
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#define __TEST_SIGNALS_UTILS_H__ |
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#include <assert.h> |
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#include <stdio.h> |
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#include <string.h> |
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#include "test_signals.h" |
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int test_init(struct tdescr *td); |
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int test_setup(struct tdescr *td); |
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void test_cleanup(struct tdescr *td); |
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int test_run(struct tdescr *td); |
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void test_result(struct tdescr *td); |
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static inline bool feats_ok(struct tdescr *td) |
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{ |
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return (td->feats_required & td->feats_supported) == td->feats_required; |
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} |
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/* |
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* Obtaining a valid and full-blown ucontext_t from userspace is tricky: |
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* libc getcontext does() not save all the regs and messes with some of |
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* them (pstate value in particular is not reliable). |
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* |
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* Here we use a service signal to grab the ucontext_t from inside a |
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* dedicated signal handler, since there, it is populated by Kernel |
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* itself in setup_sigframe(). The grabbed context is then stored and |
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* made available in td->live_uc. |
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* |
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* As service-signal is used a SIGTRAP induced by a 'brk' instruction, |
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* because here we have to avoid syscalls to trigger the signal since |
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* they would cause any SVE sigframe content (if any) to be removed. |
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* |
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* Anyway this function really serves a dual purpose: |
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* |
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* 1. grab a valid sigcontext into td->live_uc for result analysis: in |
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* such case it returns 1. |
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* |
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* 2. detect if, somehow, a previously grabbed live_uc context has been |
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* used actively with a sigreturn: in such a case the execution would have |
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* magically resumed in the middle of this function itself (seen_already==1): |
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* in such a case return 0, since in fact we have not just simply grabbed |
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* the context. |
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* |
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* This latter case is useful to detect when a fake_sigreturn test-case has |
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* unexpectedly survived without hitting a SEGV. |
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* |
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* Note that the case of runtime dynamically sized sigframes (like in SVE |
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* context) is still NOT addressed: sigframe size is supposed to be fixed |
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* at sizeof(ucontext_t). |
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*/ |
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static __always_inline bool get_current_context(struct tdescr *td, |
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ucontext_t *dest_uc) |
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{ |
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static volatile bool seen_already; |
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assert(td && dest_uc); |
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/* it's a genuine invocation..reinit */ |
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seen_already = 0; |
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td->live_uc_valid = 0; |
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td->live_sz = sizeof(*dest_uc); |
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memset(dest_uc, 0x00, td->live_sz); |
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td->live_uc = dest_uc; |
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/* |
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* Grab ucontext_t triggering a SIGTRAP. |
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* |
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* Note that: |
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* - live_uc_valid is declared volatile sig_atomic_t in |
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* struct tdescr since it will be changed inside the |
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* sig_copyctx handler |
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* - the additional 'memory' clobber is there to avoid possible |
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* compiler's assumption on live_uc_valid and the content |
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* pointed by dest_uc, which are all changed inside the signal |
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* handler |
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* - BRK causes a debug exception which is handled by the Kernel |
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* and finally causes the SIGTRAP signal to be delivered to this |
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* test thread. Since such delivery happens on the ret_to_user() |
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* /do_notify_resume() debug exception return-path, we are sure |
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* that the registered SIGTRAP handler has been run to completion |
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* before the execution path is restored here: as a consequence |
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* we can be sure that the volatile sig_atomic_t live_uc_valid |
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* carries a meaningful result. Being in a single thread context |
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* we'll also be sure that any access to memory modified by the |
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* handler (namely ucontext_t) will be visible once returned. |
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* - note that since we are using a breakpoint instruction here |
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* to cause a SIGTRAP, the ucontext_t grabbed from the signal |
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* handler would naturally contain a PC pointing exactly to this |
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* BRK line, which means that, on return from the signal handler, |
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* or if we place the ucontext_t on the stack to fake a sigreturn, |
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* we'll end up in an infinite loop of BRK-SIGTRAP-handler. |
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* For this reason we take care to artificially move forward the |
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* PC to the next instruction while inside the signal handler. |
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*/ |
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asm volatile ("brk #666" |
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: "+m" (*dest_uc) |
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: |
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: "memory"); |
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/* |
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* If we get here with seen_already==1 it implies the td->live_uc |
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* context has been used to get back here....this probably means |
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* a test has failed to cause a SEGV...anyway live_uc does not |
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* point to a just acquired copy of ucontext_t...so return 0 |
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*/ |
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if (seen_already) { |
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fprintf(stdout, |
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"Unexpected successful sigreturn detected: live_uc is stale !\n"); |
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return 0; |
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} |
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seen_already = 1; |
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return td->live_uc_valid; |
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} |
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int fake_sigreturn(void *sigframe, size_t sz, int misalign_bytes); |
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#endif
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