tools/testing/selftests/powerpc/tm/tm-trap.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright 2017, Gustavo Romero, IBM Corp.
  *
  * Check if thread endianness is flipped inadvertently to BE on trap
  * caught in TM whilst MSR.FP and MSR.VEC are zero (i.e. just after
  * load_fp and load_vec overflowed).
  *
  * The issue can be checked on LE machines simply by zeroing load_fp
  * and load_vec and then causing a trap in TM. Since the endianness
  * changes to BE on return from the signal handler, 'nop' is
  * thread as an illegal instruction in following sequence:
  *	tbegin.
  *	beq 1f
  *	trap
  *	tend.
  * 1:	nop
  *
  * However, although the issue is also present on BE machines, it's a
  * bit trickier to check it on BE machines because MSR.LE bit is set
  * to zero which determines a BE endianness that is the native
  * endianness on BE machines, so nothing notably critical happens,
  * i.e. no illegal instruction is observed immediately after returning
  * from the signal handler (as it happens on LE machines). Thus to test
  * it on BE machines LE endianness is forced after a first trap and then
  * the endianness is verified on subsequent traps to determine if the
  * endianness "flipped back" to the native endianness (BE).
  */

 #define _GNU_SOURCE
 #include <error.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <htmintrin.h>
 #include <inttypes.h>
 #include <pthread.h>
 #include <sched.h>
 #include <signal.h>
 #include <stdbool.h>

 #include "tm.h"
 #include "utils.h"

 #define pr_error(error_code, format, ...) \
 	error_at_line(1, error_code, __FILE__, __LINE__, format, ##__VA_ARGS__)

 #define MSR_LE 1UL
 #define LE     1UL

 pthread_t t0_ping;
 pthread_t t1_pong;

 int exit_from_pong;

 int trap_event;
 int le;

 bool success;

 void trap_signal_handler(int signo, siginfo_t *si, void *uc)
 {
 	ucontext_t *ucp = uc;
 	uint64_t thread_endianness;

 	/* Get thread endianness: extract bit LE from MSR */
 	thread_endianness = MSR_LE & ucp->uc_mcontext.gp_regs[PT_MSR];

 	/***
 	 * Little-Endian Machine
 	 */

 	if (le) {
 		/* First trap event */
 		if (trap_event == 0) {
 			/* Do nothing. Since it is returning from this trap
 			 * event that endianness is flipped by the bug, so just
 			 * let the process return from the signal handler and
 			 * check on the second trap event if endianness is
 			 * flipped or not.
 			 */
 		}
 		/* Second trap event */
 		else if (trap_event == 1) {
 			/*
 			 * Since trap was caught in TM on first trap event, if
 			 * endianness was still LE (not flipped inadvertently)
 			 * after returning from the signal handler instruction
 			 * (1) is executed (basically a 'nop'), as it's located
 			 * at address of tbegin. +4 (rollback addr). As (1) on
 			 * LE endianness does in effect nothing, instruction (2)
 			 * is then executed again as 'trap', generating a second
 			 * trap event (note that in that case 'trap' is caught
 			 * not in transacional mode). On te other hand, if after
 			 * the return from the signal handler the endianness in-
 			 * advertently flipped, instruction (1) is tread as a
 			 * branch instruction, i.e. b .+8, hence instruction (3)
 			 * and (4) are executed (tbegin.; trap;) and we get sim-
 			 * ilaly on the trap signal handler, but now in TM mode.
 			 * Either way, it's now possible to check the MSR LE bit
 			 * once in the trap handler to verify if endianness was
 			 * flipped or not after the return from the second trap
 			 * event. If endianness is flipped, the bug is present.
 			 * Finally, getting a trap in TM mode or not is just
 			 * worth noting because it affects the math to determine
 			 * the offset added to the NIP on return: the NIP for a
 			 * trap caught in TM is the rollback address, i.e. the
 			 * next instruction after 'tbegin.', whilst the NIP for
 			 * a trap caught in non-transactional mode is the very
 			 * same address of the 'trap' instruction that generated
 			 * the trap event.
 			 */

 			if (thread_endianness == LE) {
 				/* Go to 'success', i.e. instruction (6) */
 				ucp->uc_mcontext.gp_regs[PT_NIP] += 16;
 			} else {
 				/*
 				 * Thread endianness is BE, so it flipped
 				 * inadvertently. Thus we flip back to LE and
 				 * set NIP to go to 'failure', instruction (5).
 				 */
 				ucp->uc_mcontext.gp_regs[PT_MSR] |= 1UL;
 				ucp->uc_mcontext.gp_regs[PT_NIP] += 4;
 			}
 		}
 	}

 	/***
 	 * Big-Endian Machine
 	 */

 	else {
 		/* First trap event */
 		if (trap_event == 0) {
 			/*
 			 * Force thread endianness to be LE. Instructions (1),
 			 * (3), and (4) will be executed, generating a second
 			 * trap in TM mode.
 			 */
 			ucp->uc_mcontext.gp_regs[PT_MSR] |= 1UL;
 		}
 		/* Second trap event */
 		else if (trap_event == 1) {
 			/*
 			 * Do nothing. If bug is present on return from this
 			 * second trap event endianness will flip back "automat-
 			 * ically" to BE, otherwise thread endianness will
 			 * continue to be LE, just as it was set above.
 			 */
 		}
 		/* A third trap event */
 		else {
 			/*
 			 * Once here it means that after returning from the sec-
 			 * ond trap event instruction (4) (trap) was executed
 			 * as LE, generating a third trap event. In that case
 			 * endianness is still LE as set on return from the
 			 * first trap event, hence no bug. Otherwise, bug
 			 * flipped back to BE on return from the second trap
 			 * event and instruction (4) was executed as 'tdi' (so
 			 * basically a 'nop') and branch to 'failure' in
 			 * instruction (5) was taken to indicate failure and we
 			 * never get here.
 			 */

 			/*
 			 * Flip back to BE and go to instruction (6), i.e. go to
 			 * 'success'.
 			 */
 			ucp->uc_mcontext.gp_regs[PT_MSR] &= ~1UL;
 			ucp->uc_mcontext.gp_regs[PT_NIP] += 8;
 		}
 	}

 	trap_event++;
 }

 void usr1_signal_handler(int signo, siginfo_t *si, void *not_used)
 {
 	/* Got a USR1 signal from ping(), so just tell pong() to exit */
 	exit_from_pong = 1;
 }

 void *ping(void *not_used)
 {
 	uint64_t i;

 	trap_event = 0;

 	/*
 	 * Wait an amount of context switches so load_fp and load_vec overflows
 	 * and MSR_[FP|VEC|V] is 0.
 	 */
 	for (i = 0; i < 1024*1024*512; i++)
 		;

 	asm goto(
 		/*
 		 * [NA] means "Native Endianness", i.e. it tells how a
 		 * instruction is executed on machine's native endianness (in
 		 * other words, native endianness matches kernel endianness).
 		 * [OP] means "Opposite Endianness", i.e. on a BE machine, it
 		 * tells how a instruction is executed as a LE instruction; con-
 		 * versely, on a LE machine, it tells how a instruction is
 		 * executed as a BE instruction. When [NA] is omitted, it means
 		 * that the native interpretation of a given instruction is not
 		 * relevant for the test. Likewise when [OP] is omitted.
 		 */

 		" tbegin.        ;" /* (0) tbegin. [NA]                    */
 		" tdi  0, 0, 0x48;" /* (1) nop     [NA]; b (3) [OP]        */
 		" trap           ;" /* (2) trap    [NA]                    */
 		".long 0x1D05007C;" /* (3) tbegin. [OP]                    */
 		".long 0x0800E07F;" /* (4) trap    [OP]; nop   [NA]        */
 		" b %l[failure]  ;" /* (5) b [NA]; MSR.LE flipped (bug)    */
 		" b %l[success]  ;" /* (6) b [NA]; MSR.LE did not flip (ok)*/

 		: : : : failure, success);

 failure:
 	success = false;
 	goto exit_from_ping;

 success:
 	success = true;

 exit_from_ping:
 	/* Tell pong() to exit before leaving */
 	pthread_kill(t1_pong, SIGUSR1);
 	return NULL;
 }

 void *pong(void *not_used)
 {
 	while (!exit_from_pong)
 		/*
 		 * Induce context switches on ping() thread
 		 * until ping() finishes its job and signs
 		 * to exit from this loop.
 		 */
 		sched_yield();

 	return NULL;
 }

 int tm_trap_test(void)
 {
 	uint16_t k = 1;

 	int rc;

 	pthread_attr_t attr;
 	cpu_set_t cpuset;

 	struct sigaction trap_sa;

 	SKIP_IF(!have_htm());

 	trap_sa.sa_flags = SA_SIGINFO;
 	trap_sa.sa_sigaction = trap_signal_handler;
 	sigaction(SIGTRAP, &trap_sa, NULL);

 	struct sigaction usr1_sa;

 	usr1_sa.sa_flags = SA_SIGINFO;
 	usr1_sa.sa_sigaction = usr1_signal_handler;
 	sigaction(SIGUSR1, &usr1_sa, NULL);

 	/* Set only CPU 0 in the mask. Both threads will be bound to cpu 0. */
 	CPU_ZERO(&cpuset);
 	CPU_SET(0, &cpuset);

 	/* Init pthread attribute */
 	rc = pthread_attr_init(&attr);
 	if (rc)
 		pr_error(rc, "pthread_attr_init()");

 	/*
 	 * Bind thread ping() and pong() both to CPU 0 so they ping-pong and
 	 * speed up context switches on ping() thread, speeding up the load_fp
 	 * and load_vec overflow.
 	 */
 	rc = pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);
 	if (rc)
 		pr_error(rc, "pthread_attr_setaffinity()");

 	/* Figure out the machine endianness */
 	le = (int) *(uint8_t *)&k;

 	printf("%s machine detected. Checking if endianness flips %s",
 		le ? "Little-Endian" : "Big-Endian",
 		"inadvertently on trap in TM... ");

 	rc = fflush(0);
 	if (rc)
 		pr_error(rc, "fflush()");

 	/* Launch ping() */
 	rc = pthread_create(&t0_ping, &attr, ping, NULL);
 	if (rc)
 		pr_error(rc, "pthread_create()");

 	exit_from_pong = 0;

 	/* Launch pong() */
 	rc = pthread_create(&t1_pong, &attr, pong, NULL);
 	if (rc)
 		pr_error(rc, "pthread_create()");

 	rc = pthread_join(t0_ping, NULL);
 	if (rc)
 		pr_error(rc, "pthread_join()");

 	rc = pthread_join(t1_pong, NULL);
 	if (rc)
 		pr_error(rc, "pthread_join()");

 	if (success) {
 		printf("no.\n"); /* no, endianness did not flip inadvertently */
 		return EXIT_SUCCESS;
 	}

 	printf("yes!\n"); /* yes, endianness did flip inadvertently */
 	return EXIT_FAILURE;
 }

 int main(int argc, char **argv)
 {
 	return test_harness(tm_trap_test, "tm_trap_test");
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright 2017, Gustavo Romero, IBM Corp.
	*
	* Check if thread endianness is flipped inadvertently to BE on trap
	* caught in TM whilst MSR.FP and MSR.VEC are zero (i.e. just after
	* load_fp and load_vec overflowed).
	*
	* The issue can be checked on LE machines simply by zeroing load_fp
	* and load_vec and then causing a trap in TM. Since the endianness
	* changes to BE on return from the signal handler, 'nop' is
	* thread as an illegal instruction in following sequence:
	* tbegin.
	* beq 1f
	* trap
	* tend.
	* 1: nop
	*
	* However, although the issue is also present on BE machines, it's a
	* bit trickier to check it on BE machines because MSR.LE bit is set
	* to zero which determines a BE endianness that is the native
	* endianness on BE machines, so nothing notably critical happens,
	* i.e. no illegal instruction is observed immediately after returning
	* from the signal handler (as it happens on LE machines). Thus to test
	* it on BE machines LE endianness is forced after a first trap and then
	* the endianness is verified on subsequent traps to determine if the
	* endianness "flipped back" to the native endianness (BE).
	*/

	#define _GNU_SOURCE
	#include <error.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <htmintrin.h>
	#include <inttypes.h>
	#include <pthread.h>
	#include <sched.h>
	#include <signal.h>
	#include <stdbool.h>

	#include "tm.h"
	#include "utils.h"

	#define pr_error(error_code, format, ...) \
	error_at_line(1, error_code, __FILE__, __LINE__, format, ##__VA_ARGS__)

	#define MSR_LE 1UL
	#define LE 1UL

	pthread_t t0_ping;
	pthread_t t1_pong;

	int exit_from_pong;

	int trap_event;
	int le;

	bool success;

	void trap_signal_handler(int signo, siginfo_t si, void uc)
	{
	ucontext_t *ucp = uc;
	uint64_t thread_endianness;

	/* Get thread endianness: extract bit LE from MSR */
	thread_endianness = MSR_LE & ucp->uc_mcontext.gp_regs[PT_MSR];

	/***
	* Little-Endian Machine
	*/

	if (le) {
	/* First trap event */
	if (trap_event == 0) {
	/* Do nothing. Since it is returning from this trap
	* event that endianness is flipped by the bug, so just
	* let the process return from the signal handler and
	* check on the second trap event if endianness is
	* flipped or not.
	*/
	}
	/* Second trap event */
	else if (trap_event == 1) {
	/*
	* Since trap was caught in TM on first trap event, if
	* endianness was still LE (not flipped inadvertently)
	* after returning from the signal handler instruction
	* (1) is executed (basically a 'nop'), as it's located
	* at address of tbegin. +4 (rollback addr). As (1) on
	* LE endianness does in effect nothing, instruction (2)
	* is then executed again as 'trap', generating a second
	* trap event (note that in that case 'trap' is caught
	* not in transacional mode). On te other hand, if after
	* the return from the signal handler the endianness in-
	* advertently flipped, instruction (1) is tread as a
	* branch instruction, i.e. b .+8, hence instruction (3)
	* and (4) are executed (tbegin.; trap;) and we get sim-
	* ilaly on the trap signal handler, but now in TM mode.
	* Either way, it's now possible to check the MSR LE bit
	* once in the trap handler to verify if endianness was
	* flipped or not after the return from the second trap
	* event. If endianness is flipped, the bug is present.
	* Finally, getting a trap in TM mode or not is just
	* worth noting because it affects the math to determine
	* the offset added to the NIP on return: the NIP for a
	* trap caught in TM is the rollback address, i.e. the
	* next instruction after 'tbegin.', whilst the NIP for
	* a trap caught in non-transactional mode is the very
	* same address of the 'trap' instruction that generated
	* the trap event.
	*/

	if (thread_endianness == LE) {
	/* Go to 'success', i.e. instruction (6) */
	ucp->uc_mcontext.gp_regs[PT_NIP] += 16;
	} else {
	/*
	* Thread endianness is BE, so it flipped
	* inadvertently. Thus we flip back to LE and
	* set NIP to go to 'failure', instruction (5).
	*/
	ucp->uc_mcontext.gp_regs[PT_MSR] \|= 1UL;
	ucp->uc_mcontext.gp_regs[PT_NIP] += 4;
	}
	}
	}

	/***
	* Big-Endian Machine
	*/

	else {
	/* First trap event */
	if (trap_event == 0) {
	/*
	* Force thread endianness to be LE. Instructions (1),
	* (3), and (4) will be executed, generating a second
	* trap in TM mode.
	*/
	ucp->uc_mcontext.gp_regs[PT_MSR] \|= 1UL;
	}
	/* Second trap event */
	else if (trap_event == 1) {
	/*
	* Do nothing. If bug is present on return from this
	* second trap event endianness will flip back "automat-
	* ically" to BE, otherwise thread endianness will
	* continue to be LE, just as it was set above.
	*/
	}
	/* A third trap event */
	else {
	/*
	* Once here it means that after returning from the sec-
	* ond trap event instruction (4) (trap) was executed
	* as LE, generating a third trap event. In that case
	* endianness is still LE as set on return from the
	* first trap event, hence no bug. Otherwise, bug
	* flipped back to BE on return from the second trap
	* event and instruction (4) was executed as 'tdi' (so
	* basically a 'nop') and branch to 'failure' in
	* instruction (5) was taken to indicate failure and we
	* never get here.
	*/

	/*
	* Flip back to BE and go to instruction (6), i.e. go to
	* 'success'.
	*/
	ucp->uc_mcontext.gp_regs[PT_MSR] &= ~1UL;
	ucp->uc_mcontext.gp_regs[PT_NIP] += 8;
	}
	}

	trap_event++;
	}

	void usr1_signal_handler(int signo, siginfo_t si, void not_used)
	{
	/* Got a USR1 signal from ping(), so just tell pong() to exit */
	exit_from_pong = 1;
	}

	void ping(void not_used)
	{
	uint64_t i;

	trap_event = 0;

	/*
	* Wait an amount of context switches so load_fp and load_vec overflows
	* and MSR_[FP\|VEC\|V] is 0.
	*/
	for (i = 0; i < 10241024512; i++)
	;

	asm goto(
	/*
	* [NA] means "Native Endianness", i.e. it tells how a
	* instruction is executed on machine's native endianness (in
	* other words, native endianness matches kernel endianness).
	* [OP] means "Opposite Endianness", i.e. on a BE machine, it
	* tells how a instruction is executed as a LE instruction; con-
	* versely, on a LE machine, it tells how a instruction is
	* executed as a BE instruction. When [NA] is omitted, it means
	* that the native interpretation of a given instruction is not
	* relevant for the test. Likewise when [OP] is omitted.
	*/

	" tbegin. ;" /* (0) tbegin. [NA] */
	" tdi 0, 0, 0x48;" /* (1) nop [NA]; b (3) [OP] */
	" trap ;" /* (2) trap [NA] */
	".long 0x1D05007C;" /* (3) tbegin. [OP] */
	".long 0x0800E07F;" /* (4) trap [OP]; nop [NA] */
	" b %l[failure] ;" /* (5) b [NA]; MSR.LE flipped (bug) */
	" b %l[success] ;" /* (6) b [NA]; MSR.LE did not flip (ok)*/

	: : : : failure, success);

	failure:
	success = false;
	goto exit_from_ping;

	success:
	success = true;

	exit_from_ping:
	/* Tell pong() to exit before leaving */
	pthread_kill(t1_pong, SIGUSR1);
	return NULL;
	}

	void pong(void not_used)
	{
	while (!exit_from_pong)
	/*
	* Induce context switches on ping() thread
	* until ping() finishes its job and signs
	* to exit from this loop.
	*/
	sched_yield();

	return NULL;
	}

	int tm_trap_test(void)
	{
	uint16_t k = 1;

	int rc;

	pthread_attr_t attr;
	cpu_set_t cpuset;

	struct sigaction trap_sa;

	SKIP_IF(!have_htm());

	trap_sa.sa_flags = SA_SIGINFO;
	trap_sa.sa_sigaction = trap_signal_handler;
	sigaction(SIGTRAP, &trap_sa, NULL);

	struct sigaction usr1_sa;

	usr1_sa.sa_flags = SA_SIGINFO;
	usr1_sa.sa_sigaction = usr1_signal_handler;
	sigaction(SIGUSR1, &usr1_sa, NULL);

	/* Set only CPU 0 in the mask. Both threads will be bound to cpu 0. */
	CPU_ZERO(&cpuset);
	CPU_SET(0, &cpuset);

	/* Init pthread attribute */
	rc = pthread_attr_init(&attr);
	if (rc)
	pr_error(rc, "pthread_attr_init()");

	/*
	* Bind thread ping() and pong() both to CPU 0 so they ping-pong and
	* speed up context switches on ping() thread, speeding up the load_fp
	* and load_vec overflow.
	*/
	rc = pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);
	if (rc)
	pr_error(rc, "pthread_attr_setaffinity()");

	/* Figure out the machine endianness */
	le = (int) (uint8_t )&k;

	printf("%s machine detected. Checking if endianness flips %s",
	le ? "Little-Endian" : "Big-Endian",
	"inadvertently on trap in TM... ");

	rc = fflush(0);
	if (rc)
	pr_error(rc, "fflush()");

	/* Launch ping() */
	rc = pthread_create(&t0_ping, &attr, ping, NULL);
	if (rc)
	pr_error(rc, "pthread_create()");

	exit_from_pong = 0;

	/* Launch pong() */
	rc = pthread_create(&t1_pong, &attr, pong, NULL);
	if (rc)
	pr_error(rc, "pthread_create()");

	rc = pthread_join(t0_ping, NULL);
	if (rc)
	pr_error(rc, "pthread_join()");

	rc = pthread_join(t1_pong, NULL);
	if (rc)
	pr_error(rc, "pthread_join()");

	if (success) {
	printf("no.\n"); /* no, endianness did not flip inadvertently */
	return EXIT_SUCCESS;
	}

	printf("yes!\n"); /* yes, endianness did flip inadvertently */
	return EXIT_FAILURE;
	}

	int main(int argc, char **argv)
	{
	return test_harness(tm_trap_test, "tm_trap_test");
	}