/* 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 <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);
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
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