// SPDX-License-Identifier: GPL-2.0+

#include <errno.h>
#include <setjmp.h>
#include <signal.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/wait.h>

#include "dexcr.h"
#include "reg.h"
#include "utils.h"

static jmp_buf generic_signal_jump_buf;

static void generic_signal_handler(int signum, siginfo_t *info, void *context)
{
        longjmp(generic_signal_jump_buf, 0);
}

bool dexcr_exists(void)
{
        struct sigaction old;
        volatile bool exists;

        old = push_signal_handler(SIGILL, generic_signal_handler);
        if (setjmp(generic_signal_jump_buf))
                goto out;

        /*
         * If the SPR is not recognised by the hardware it triggers
         * a hypervisor emulation interrupt. If the kernel does not
         * recognise/try to emulate it, we receive a SIGILL signal.
         *
         * If we do not receive a signal, assume we have the SPR or the
         * kernel is trying to emulate it correctly.
         */
        exists = false;
        mfspr(SPRN_DEXCR_RO);
        exists = true;

out:
        pop_signal_handler(SIGILL, old);
        return exists;
}

unsigned int pr_which_to_aspect(unsigned long which)
{
        switch (which) {
        case PR_PPC_DEXCR_SBHE:
                return DEXCR_PR_SBHE;
        case PR_PPC_DEXCR_IBRTPD:
                return DEXCR_PR_IBRTPD;
        case PR_PPC_DEXCR_SRAPD:
                return DEXCR_PR_SRAPD;
        case PR_PPC_DEXCR_NPHIE:
                return DEXCR_PR_NPHIE;
        default:
                FAIL_IF_EXIT_MSG(true, "unknown PR aspect");
        }
}

int pr_get_dexcr(unsigned long which)
{
        return prctl(PR_PPC_GET_DEXCR, which, 0UL, 0UL, 0UL);
}

int pr_set_dexcr(unsigned long which, unsigned long ctrl)
{
        return prctl(PR_PPC_SET_DEXCR, which, ctrl, 0UL, 0UL);
}

bool pr_dexcr_aspect_supported(unsigned long which)
{
        if (pr_get_dexcr(which) == -1)
                return errno == ENODEV;

        return true;
}

bool pr_dexcr_aspect_editable(unsigned long which)
{
        return pr_get_dexcr(which) & PR_PPC_DEXCR_CTRL_EDITABLE;
}

/*
 * Just test if a bad hashchk triggers a signal, without checking
 * for support or if the NPHIE aspect is enabled.
 */
bool hashchk_triggers(void)
{
        struct sigaction old;
        volatile bool triggers;

        old = push_signal_handler(SIGILL, generic_signal_handler);
        if (setjmp(generic_signal_jump_buf))
                goto out;

        triggers = true;
        do_bad_hashchk();
        triggers = false;

out:
        pop_signal_handler(SIGILL, old);
        return triggers;
}

unsigned int get_dexcr(enum dexcr_source source)
{
        switch (source) {
        case DEXCR:
                return mfspr(SPRN_DEXCR_RO);
        case HDEXCR:
                return mfspr(SPRN_HDEXCR_RO);
        case EFFECTIVE:
                return mfspr(SPRN_DEXCR_RO) | mfspr(SPRN_HDEXCR_RO);
        default:
                FAIL_IF_EXIT_MSG(true, "bad enum dexcr_source");
        }
}

void await_child_success(pid_t pid)
{
        int wstatus;

        FAIL_IF_EXIT_MSG(pid == -1, "fork failed");
        FAIL_IF_EXIT_MSG(waitpid(pid, &wstatus, 0) == -1, "wait failed");
        FAIL_IF_EXIT_MSG(!WIFEXITED(wstatus), "child did not exit cleanly");
        FAIL_IF_EXIT_MSG(WEXITSTATUS(wstatus) != 0, "child exit error");
}

/*
 * Perform a hashst instruction. The following components determine the result
 *
 * 1. The LR value (any register technically)
 * 2. The SP value (also any register, but it must be a valid address)
 * 3. A secret key managed by the kernel
 *
 * The result is stored to the address held in SP.
 */
void hashst(unsigned long lr, void *sp)
{
        asm volatile ("addi 31, %0, 0;"         /* set r31 (pretend LR) to lr */
                      "addi 30, %1, 8;"         /* set r30 (pretend SP) to sp + 8 */
                      PPC_RAW_HASHST(31, -8, 30)        /* compute hash into stack location */
                      : : "r" (lr), "r" (sp) : "r31", "r30", "memory");
}

/*
 * Perform a hashchk instruction. A hash is computed as per hashst(),
 * however the result is not stored to memory. Instead the existing
 * value is read and compared against the computed hash.
 *
 * If they match, execution continues.
 * If they differ, an interrupt triggers.
 */
void hashchk(unsigned long lr, void *sp)
{
        asm volatile ("addi 31, %0, 0;"         /* set r31 (pretend LR) to lr */
                      "addi 30, %1, 8;"         /* set r30 (pretend SP) to sp + 8 */
                      PPC_RAW_HASHCHK(31, -8, 30)       /* check hash at stack location */
                      : : "r" (lr), "r" (sp) : "r31", "r30", "memory");
}

void do_bad_hashchk(void)
{
        unsigned long hash = 0;

        hashst(0, &hash);
        hash += 1;
        hashchk(0, &hash);
}