kselftest: arm64: add helper get_current_context (34306b05) · Commits · 戴 / test

tools/testing/selftests/arm64/signal/test_signals.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -72,6 +72,10 @@ struct tdescr {
		/* optional sa_flags for the installed handler */
		int sa_flags;
		ucontext_t saved_uc;
		/* used by get_current_ctx() */
		size_t live_sz;
		ucontext_t *live_uc;
		volatile sig_atomic_t live_uc_valid;
		/* optional test private data */
		void *priv;

tools/testing/selftests/arm64/signal/test_signals_utils.c

+31 −0

Original line number	Diff line number	Diff line
		@@ -11,14 +11,19 @@
		#include <linux/auxvec.h>
		#include <ucontext.h>

		#include <asm/unistd.h>

		#include <kselftest.h>

		#include "test_signals.h"
		#include "test_signals_utils.h"
		#include "testcases/testcases.h"


		extern struct tdescr *current;

		static int sig_copyctx = SIGTRAP;

		static char const *const feats_names[FMAX_END] = {
		" SSBS ",
		};
		@@ -154,6 +159,20 @@ static bool handle_signal_ok(struct tdescr *td,
		return true;
		}

		static bool handle_signal_copyctx(struct tdescr *td,
		siginfo_t si, void uc)
		{
		/* Mangling PC to avoid loops on original BRK instr */
		((ucontext_t *)uc)->uc_mcontext.pc += 4;
		memcpy(td->live_uc, uc, td->live_sz);
		ASSERT_GOOD_CONTEXT(td->live_uc);
		td->live_uc_valid = 1;
		fprintf(stderr,
		"GOOD CONTEXT grabbed from sig_copyctx handler\n");

		return true;
		}

		static void default_handler(int signum, siginfo_t si, void uc)
		{
		if (current->sig_unsupp && signum == current->sig_unsupp &&
		@@ -165,6 +184,9 @@ static void default_handler(int signum, siginfo_t si, void uc)
		} else if (current->sig_ok && signum == current->sig_ok &&
		handle_signal_ok(current, si, uc)) {
		fprintf(stderr, "Handled SIG_OK\n");
		} else if (signum == sig_copyctx && current->live_uc &&
		handle_signal_copyctx(current, si, uc)) {
		fprintf(stderr, "Handled SIG_COPYCTX\n");
		} else {
		if (signum == SIGALRM && current->timeout) {
		fprintf(stderr, "-- Timeout !\n");
		@@ -219,6 +241,15 @@ static inline int default_trigger(struct tdescr *td)

		int test_init(struct tdescr *td)
		{
		if (td->sig_trig == sig_copyctx) {
		fprintf(stdout,
		"Signal %d is RESERVED, cannot be used as a trigger. Aborting\n",
		sig_copyctx);
		return 0;
		}
		/* just in case */
		unblock_signal(sig_copyctx);

		td->minsigstksz = getauxval(AT_MINSIGSTKSZ);
		if (!td->minsigstksz)
		td->minsigstksz = MINSIGSTKSZ;

tools/testing/selftests/arm64/signal/test_signals_utils.h

+98 −0

Original line number	Diff line number	Diff line
		@@ -4,6 +4,10 @@
		#ifndef __TEST_SIGNALS_UTILS_H__
		#define __TEST_SIGNALS_UTILS_H__

		#include <assert.h>
		#include <stdio.h>
		#include <string.h>

		#include "test_signals.h"

		int test_init(struct tdescr *td);
		@@ -17,4 +21,98 @@ static inline bool feats_ok(struct tdescr *td)
		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)
		{
		static volatile bool seen_already;

		assert(td && dest_uc);
		/* it's a genuine invocation..reinit */
		seen_already = 0;
		td->live_uc_valid = 0;
		td->live_sz = sizeof(*dest_uc);
		memset(dest_uc, 0x00, td->live_sz);
		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 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;
		}
		#endif

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