// SPDX-License-Identifier: GPL-2.0-only
#include "linux/types.h"
#include "linux/bitmap.h"
#include "linux/atomic.h"

#include "kvm_util.h"
#include "ucall_common.h"


#define GUEST_UCALL_FAILED -1

struct ucall_header {
        DECLARE_BITMAP(in_use, KVM_MAX_VCPUS);
        struct ucall ucalls[KVM_MAX_VCPUS];
};

int ucall_nr_pages_required(uint64_t page_size)
{
        return align_up(sizeof(struct ucall_header), page_size) / page_size;
}

/*
 * ucall_pool holds per-VM values (global data is duplicated by each VM), it
 * must not be accessed from host code.
 */
static struct ucall_header *ucall_pool;

void ucall_init(struct kvm_vm *vm, vm_paddr_t mmio_gpa)
{
        struct ucall_header *hdr;
        struct ucall *uc;
        vm_vaddr_t vaddr;
        int i;

        vaddr = vm_vaddr_alloc_shared(vm, sizeof(*hdr), KVM_UTIL_MIN_VADDR,
                                      MEM_REGION_DATA);
        hdr = (struct ucall_header *)addr_gva2hva(vm, vaddr);
        memset(hdr, 0, sizeof(*hdr));

        for (i = 0; i < KVM_MAX_VCPUS; ++i) {
                uc = &hdr->ucalls[i];
                uc->hva = uc;
        }

        write_guest_global(vm, ucall_pool, (struct ucall_header *)vaddr);

        ucall_arch_init(vm, mmio_gpa);
}

static struct ucall *ucall_alloc(void)
{
        struct ucall *uc;
        int i;

        if (!ucall_pool)
                goto ucall_failed;

        for (i = 0; i < KVM_MAX_VCPUS; ++i) {
                if (!test_and_set_bit(i, ucall_pool->in_use)) {
                        uc = &ucall_pool->ucalls[i];
                        memset(uc->args, 0, sizeof(uc->args));
                        return uc;
                }
        }

ucall_failed:
        /*
         * If the vCPU cannot grab a ucall structure, make a bare ucall with a
         * magic value to signal to get_ucall() that things went sideways.
         * GUEST_ASSERT() depends on ucall_alloc() and so cannot be used here.
         */
        ucall_arch_do_ucall(GUEST_UCALL_FAILED);
        return NULL;
}

static void ucall_free(struct ucall *uc)
{
        /* Beware, here be pointer arithmetic.  */
        clear_bit(uc - ucall_pool->ucalls, ucall_pool->in_use);
}

void ucall_assert(uint64_t cmd, const char *exp, const char *file,
                  unsigned int line, const char *fmt, ...)
{
        struct ucall *uc;
        va_list va;

        uc = ucall_alloc();
        uc->cmd = cmd;

        WRITE_ONCE(uc->args[GUEST_ERROR_STRING], (uint64_t)(exp));
        WRITE_ONCE(uc->args[GUEST_FILE], (uint64_t)(file));
        WRITE_ONCE(uc->args[GUEST_LINE], line);

        va_start(va, fmt);
        guest_vsnprintf(uc->buffer, UCALL_BUFFER_LEN, fmt, va);
        va_end(va);

        ucall_arch_do_ucall((vm_vaddr_t)uc->hva);

        ucall_free(uc);
}

void ucall_fmt(uint64_t cmd, const char *fmt, ...)
{
        struct ucall *uc;
        va_list va;

        uc = ucall_alloc();
        uc->cmd = cmd;

        va_start(va, fmt);
        guest_vsnprintf(uc->buffer, UCALL_BUFFER_LEN, fmt, va);
        va_end(va);

        ucall_arch_do_ucall((vm_vaddr_t)uc->hva);

        ucall_free(uc);
}

void ucall(uint64_t cmd, int nargs, ...)
{
        struct ucall *uc;
        va_list va;
        int i;

        uc = ucall_alloc();

        WRITE_ONCE(uc->cmd, cmd);

        nargs = min(nargs, UCALL_MAX_ARGS);

        va_start(va, nargs);
        for (i = 0; i < nargs; ++i)
                WRITE_ONCE(uc->args[i], va_arg(va, uint64_t));
        va_end(va);

        ucall_arch_do_ucall((vm_vaddr_t)uc->hva);

        ucall_free(uc);
}

uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
{
        struct ucall ucall;
        void *addr;

        if (!uc)
                uc = &ucall;

        addr = ucall_arch_get_ucall(vcpu);
        if (addr) {
                TEST_ASSERT(addr != (void *)GUEST_UCALL_FAILED,
                            "Guest failed to allocate ucall struct");

                memcpy(uc, addr, sizeof(*uc));
                vcpu_run_complete_io(vcpu);
        } else {
                memset(uc, 0, sizeof(*uc));
        }

        return uc->cmd;
}