// 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;

/* count is changed in the signal handler, so it must be volatile */
static volatile int count;

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)
{
        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);

        while (count < COUNT_MAX) {
                /* 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 might segfault, avoid it to retest */
                sigaction(SIGSEGV, &seg_sa, NULL);

                raise(SIGUSR1);
                count++;
        }
}

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());

        tm_trap_test();

        return EXIT_SUCCESS;
}

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