// SPDX-License-Identifier: GPL-2.0
#include "util/copyfile.h"
#include "util/namespaces.h"
#include <internal/lib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static int slow_copyfile(const char *from, const char *to, struct nsinfo *nsi)
{
        int err = -1;
        char *line = NULL;
        size_t n;
        FILE *from_fp, *to_fp;
        struct nscookie nsc;

        nsinfo__mountns_enter(nsi, &nsc);
        from_fp = fopen(from, "r");
        nsinfo__mountns_exit(&nsc);
        if (from_fp == NULL)
                goto out;

        to_fp = fopen(to, "w");
        if (to_fp == NULL)
                goto out_fclose_from;

        while (getline(&line, &n, from_fp) > 0)
                if (fputs(line, to_fp) == EOF)
                        goto out_fclose_to;
        err = 0;
out_fclose_to:
        fclose(to_fp);
        free(line);
out_fclose_from:
        fclose(from_fp);
out:
        return err;
}

int copyfile_offset(int ifd, loff_t off_in, int ofd, loff_t off_out, u64 size)
{
        void *ptr;
        loff_t pgoff;

        pgoff = off_in & ~(page_size - 1);
        off_in -= pgoff;

        ptr = mmap(NULL, off_in + size, PROT_READ, MAP_PRIVATE, ifd, pgoff);
        if (ptr == MAP_FAILED)
                return -1;

        while (size) {
                ssize_t ret = pwrite(ofd, ptr + off_in, size, off_out);
                if (ret < 0 && errno == EINTR)
                        continue;
                if (ret <= 0)
                        break;

                size -= ret;
                off_in += ret;
                off_out += ret;
        }
        munmap(ptr, off_in + size);

        return size ? -1 : 0;
}

static int copyfile_mode_ns(const char *from, const char *to, mode_t mode,
                            struct nsinfo *nsi)
{
        int fromfd, tofd;
        struct stat st;
        int err;
        char *tmp = NULL, *ptr = NULL;
        struct nscookie nsc;

        nsinfo__mountns_enter(nsi, &nsc);
        err = stat(from, &st);
        nsinfo__mountns_exit(&nsc);
        if (err)
                goto out;
        err = -1;

        /* extra 'x' at the end is to reserve space for '.' */
        if (asprintf(&tmp, "%s.XXXXXXx", to) < 0) {
                tmp = NULL;
                goto out;
        }
        ptr = strrchr(tmp, '/');
        if (!ptr)
                goto out;
        ptr = memmove(ptr + 1, ptr, strlen(ptr) - 1);
        *ptr = '.';

        tofd = mkstemp(tmp);
        if (tofd < 0)
                goto out;

        if (st.st_size == 0) { /* /proc? do it slowly... */
                err = slow_copyfile(from, tmp, nsi);
                if (!err && fchmod(tofd, mode))
                        err = -1;
                goto out_close_to;
        }

        if (fchmod(tofd, mode))
                goto out_close_to;

        nsinfo__mountns_enter(nsi, &nsc);
        fromfd = open(from, O_RDONLY);
        nsinfo__mountns_exit(&nsc);
        if (fromfd < 0)
                goto out_close_to;

        err = copyfile_offset(fromfd, 0, tofd, 0, st.st_size);

        close(fromfd);
out_close_to:
        close(tofd);
        if (!err)
                err = link(tmp, to);
        unlink(tmp);
out:
        free(tmp);
        return err;
}

int copyfile_ns(const char *from, const char *to, struct nsinfo *nsi)
{
        return copyfile_mode_ns(from, to, 0755, nsi);
}

int copyfile_mode(const char *from, const char *to, mode_t mode)
{
        return copyfile_mode_ns(from, to, mode, NULL);
}

int copyfile(const char *from, const char *to)
{
        return copyfile_mode(from, to, 0755);
}