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Commit a65329aa authored by Breno Leitao's avatar Breno Leitao Committed by Michael Ellerman
Browse files

selftests/powerpc: New TM signal self test 



A new self test that forces MSR[TS] to be set without calling any TM
instruction. This test also tries to cause a page fault at a signal
handler, exactly between MSR[TS] set and tm_recheckpoint(), forcing
thread->texasr to be rewritten with TEXASR[FS] = 0, which will cause a BUG
when tm_recheckpoint() is called.

This test is not deterministic, since it is hard to guarantee that the page
access will cause a page fault. In order to force more page faults at
signal context, the signal handler and the ucontext are being mapped into a
MADV_DONTNEED memory chunks.

Tests have shown that the bug could be exposed with few interactions in a
buggy kernel. This test is configured to loop 5000x, having a good chance
to hit the kernel issue in just one run.  This self test takes less than
two seconds to run.

This test uses set/getcontext because the kernel will recheckpoint
zeroed structures, causing the test to segfault, which is undesired because
the test needs to rerun, so, there is a signal handler for SIGSEGV which
will restart the test.

v2: Uses the MADV_DONTNEED memory advice
v3: Fix memcpy and 32-bits compilation
v4: Does not define unused macros

Signed-off-by: default avatarBreno Leitao <leitao@debian.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 8de7547e

tools/testing/selftests/powerpc/include/reg.h

+8 −0
Original line number Diff line number Diff line
@@ -77,6 +77,14 @@ 
#define TEXASR_TE	0x0000000004000000

#define TEXASR_ROT	0x0000000002000000



/* MSR register bits */

#define MSR_TS_S_LG     33              /* Trans Mem state: Suspended */



#define __MASK(X)       (1UL<<(X))



/* macro to check TM MSR bits */

#define MSR_TS_S        __MASK(MSR_TS_S_LG)   /* Transaction Suspended */



/* Vector Instructions */

#define VSX_XX1(xs, ra, rb)	(((xs) & 0x1f) << 21 | ((ra) << 16) |  \

				 ((rb) << 11) | (((xs) >> 5)))

tools/testing/selftests/powerpc/include/utils.h

+2 −0
Original line number Diff line number Diff line
@@ -102,8 +102,10 @@ do { \ 


#if defined(__powerpc64__)

#define UCONTEXT_NIA(UC)	(UC)->uc_mcontext.gp_regs[PT_NIP]

#define UCONTEXT_MSR(UC)	(UC)->uc_mcontext.gp_regs[PT_MSR]

#elif defined(__powerpc__)

#define UCONTEXT_NIA(UC)	(UC)->uc_mcontext.uc_regs->gregs[PT_NIP]

#define UCONTEXT_MSR(UC)	(UC)->uc_mcontext.uc_regs->gregs[PT_MSR]

#else

#error implement UCONTEXT_NIA

#endif

tools/testing/selftests/powerpc/tm/.gitignore

+1 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ tm-signal-context-chk-fpu 
tm-signal-context-chk-gpr

tm-signal-context-chk-vmx

tm-signal-context-chk-vsx

tm-signal-context-force-tm

tm-signal-sigreturn-nt

tm-vmx-unavail

tm-unavailable

tools/testing/selftests/powerpc/tm/Makefile

+3 −1
Original line number Diff line number Diff line
@@ -4,7 +4,8 @@ SIGNAL_CONTEXT_CHK_TESTS := tm-signal-context-chk-gpr tm-signal-context-chk-fpu 


TEST_GEN_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack \

	tm-vmxcopy tm-fork tm-tar tm-tmspr tm-vmx-unavail tm-unavailable tm-trap \

	$(SIGNAL_CONTEXT_CHK_TESTS) tm-sigreturn tm-signal-sigreturn-nt

	$(SIGNAL_CONTEXT_CHK_TESTS) tm-sigreturn tm-signal-sigreturn-nt \

	tm-signal-context-force-tm



top_srcdir = ../../../../..

include ../../lib.mk
@@ -20,6 +21,7 @@ $(OUTPUT)/tm-vmx-unavail: CFLAGS += -pthread -m64 
$(OUTPUT)/tm-resched-dscr: ../pmu/lib.c

$(OUTPUT)/tm-unavailable: CFLAGS += -O0 -pthread -m64 -Wno-error=uninitialized -mvsx

$(OUTPUT)/tm-trap: CFLAGS += -O0 -pthread -m64

$(OUTPUT)/tm-signal-context-force-tm: CFLAGS += -pthread -m64



SIGNAL_CONTEXT_CHK_TESTS := $(patsubst %,$(OUTPUT)/%,$(SIGNAL_CONTEXT_CHK_TESTS))

$(SIGNAL_CONTEXT_CHK_TESTS): tm-signal.S

tools/testing/selftests/powerpc/tm/tm-signal-context-force-tm.c

0 → 100644
+184 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Copyright 2018, Breno Leitao, Gustavo Romero, IBM Corp.

 *

 * This test raises a SIGUSR1 signal, and toggle the MSR[TS]

 * fields at the signal handler. With MSR[TS] being set, the kernel will

 * force a recheckpoint, which may cause a segfault when returning to

 * user space. Since the test needs to re-run, the segfault needs to be

 * caught and handled.

 *

 * In order to continue the test even after a segfault, the context is

 * saved prior to the signal being raised, and it is restored when there is

 * a segmentation fault. This happens for COUNT_MAX times.

 *

 * This test never fails (as returning EXIT_FAILURE). It either succeeds,

 * or crash the kernel (on a buggy kernel).

 */



#define _GNU_SOURCE

#include <stdio.h>

#include <stdlib.h>

#include <signal.h>

#include <string.h>

#include <ucontext.h>

#include <unistd.h>

#include <sys/mman.h>



#include "tm.h"

#include "utils.h"

#include "reg.h"



#define COUNT_MAX       5000		/* Number of interactions */



/*

 * This test only runs on 64 bits system. Unsetting MSR_TS_S to avoid

 * compilation issue on 32 bits system. There is no side effect, since the

 * whole test will be skipped if it is not running on 64 bits system.

 */

#ifndef __powerpc64__

#undef  MSR_TS_S

#define MSR_TS_S	0

#endif



/* Setting contexts because the test will crash and we want to recover */

ucontext_t init_context, main_context;



static int count, first_time;



void usr_signal_handler(int signo, siginfo_t *si, void *uc)

{

	ucontext_t *ucp = uc;

	int ret;



	/*

	 * Allocating memory in a signal handler, and never freeing it on

	 * purpose, forcing the heap increase, so, the memory leak is what

	 * we want here.

	 */

	ucp->uc_link = mmap(NULL, sizeof(ucontext_t),

			    PROT_READ | PROT_WRITE,

			    MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);

	if (ucp->uc_link == (void *)-1) {

		perror("Mmap failed");

		exit(-1);

	}



	/* Forcing the page to be allocated in a page fault */

	ret = madvise(ucp->uc_link, sizeof(ucontext_t), MADV_DONTNEED);

	if (ret) {

		perror("madvise failed");

		exit(-1);

	}



	memcpy(&ucp->uc_link->uc_mcontext, &ucp->uc_mcontext,

		sizeof(ucp->uc_mcontext));



	/* Forcing to enable MSR[TM] */

	UCONTEXT_MSR(ucp) |= MSR_TS_S;



	/*

	 * A fork inside a signal handler seems to be more efficient than a

	 * fork() prior to the signal being raised.

	 */

	if (fork() == 0) {

		/*

		 * Both child and parent will return, but, child returns

		 * with count set so it will exit in the next segfault.

		 * Parent will continue to loop.

		 */

		count = COUNT_MAX;

	}



	/*

	 * If the change above does not hit the bug, it will cause a

	 * segmentation fault, since the ck structures are NULL.

	 */

}



void seg_signal_handler(int signo, siginfo_t *si, void *uc)

{

	if (count == COUNT_MAX) {

		/* Return to tm_signal_force_msr() and exit */

		setcontext(&main_context);

	}



	count++;



	/* Reexecute the test */

	setcontext(&init_context);

}



void tm_trap_test(void)

{

	struct sigaction usr_sa, seg_sa;

	stack_t ss;



	usr_sa.sa_flags = SA_SIGINFO | SA_ONSTACK;

	usr_sa.sa_sigaction = usr_signal_handler;



	seg_sa.sa_flags = SA_SIGINFO;

	seg_sa.sa_sigaction = seg_signal_handler;



	/*

	 * Set initial context. Will get back here from

	 * seg_signal_handler()

	 */

	getcontext(&init_context);



	/* Allocated an alternative signal stack area */

	ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,

			MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);

	ss.ss_size = SIGSTKSZ;

	ss.ss_flags = 0;



	if (ss.ss_sp == (void *)-1) {

		perror("mmap error\n");

		exit(-1);

	}



	/* Force the allocation through a page fault */

	if (madvise(ss.ss_sp, SIGSTKSZ, MADV_DONTNEED)) {

		perror("madvise\n");

		exit(-1);

	}



	/* Setting an alternative stack to generate a page fault when

	 * the signal is raised.

	 */

	if (sigaltstack(&ss, NULL)) {

		perror("sigaltstack\n");

		exit(-1);

	}



	/* The signal handler will enable MSR_TS */

	sigaction(SIGUSR1, &usr_sa, NULL);

	/* If it does not crash, it will segfault, avoid it to retest */

	sigaction(SIGSEGV, &seg_sa, NULL);



	raise(SIGUSR1);

}



int tm_signal_context_force_tm(void)

{

	SKIP_IF(!have_htm());

	/*

	 * Skipping if not running on 64 bits system, since I think it is

	 * not possible to set mcontext's [MSR] with TS, due to it being 32

	 * bits.

	 */

	SKIP_IF(!is_ppc64le());



	/* Will get back here after COUNT_MAX interactions */

	getcontext(&main_context);



	if (!first_time++)

		tm_trap_test();



	return EXIT_SUCCESS;

}



int main(int argc, char **argv)

{

	test_harness(tm_signal_context_force_tm, "tm_signal_context_force_tm");

}