system/uapp/sysconfig/sysconfig.c

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <ddk/debug.h>
#include <kvstore/kvstore.h>
#include <zircon/boot/sysconfig.h>
#include <zircon/device/block.h>
#include <zircon/hw/gpt.h>
#include <dirent.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define DEV_BLOCK "/dev/class/block"

typedef enum {
    OP_READ,
    OP_WRITE,
    OP_EDIT,
} sysconfig_op_t;

static const uint8_t sysconfig_guid[GPT_GUID_LEN] = GUID_SYS_CONFIG_VALUE;

static void usage(void) {
    fprintf(stderr,
            "Usage:\n"
            "    sysconfig read <section> [key]*\n"
            "    sysconfig write <section> [key=value]*\n"
            "    sysconfig edit <section> [key=value]*\n"
            "\n"
            "Where <section> is one of: {version-a, version-b, boot-default, boot-oneshot}\n"
            "\n"
            "read:    Print values for the specified keys. If no keys are provided after \"read\",\n"
            "         then all key/value pairs are printed.\n"
            "write:   Write the provided key/value pairs to the specified section.\n"
            "edit:    Write the provided key/value pairs to the specified section,\n"
            "         preserving any existing key/value pairs already in the partition\n");
}

// returns a file descriptor to the raw sysconfig partition
static int open_sysconfig(void) {
    struct dirent* de;
    DIR* dir = opendir(DEV_BLOCK);
    if (!dir) {
        printf("Error opening %s\n", DEV_BLOCK);
        return -1;
    }
    while ((de = readdir(dir)) != NULL) {
        if (!strcmp(de->d_name, ".") || !strcmp(de->d_name, "..")) {
            continue;
        }
        char path[PATH_MAX];
        snprintf(path, sizeof(path), "%s/%s", DEV_BLOCK, de->d_name);
        int fd = open(path, O_RDWR);
        if (fd < 0) {
            fprintf(stderr, "Error opening %s\n", path);
            continue;
        }

        uint8_t guid[GPT_GUID_LEN];
        if (ioctl_block_get_type_guid(fd, &guid, sizeof(guid)) < 0) {
            close(fd);
            continue;
        }
        if (memcmp(guid, sysconfig_guid, sizeof(sysconfig_guid))) {
            close(fd);
            continue;
        }

        return fd;
    }
    closedir(dir);
    return -1;
}

static int print_func(void *cookie, const char* key, const char* value) {
    printf("%s=%s\n", key, value);
    return 0;
}

static int copy_func(void *cookie, const char* key, const char* value) {
    struct kvstore* kvs = cookie;

    // copy values to kvs if they aren't set already
    const char* new_value = kvs_get(kvs, key, NULL);
    if (new_value) {
        return 0;
    } else {
        return kvs_add(kvs, key, value);
    }
}

int main(int argc, char **argv) {
    int ret = 0;

    if (argc < 3) {
        usage();
        return -1;
    }

    // skip "sysconfig"
    argv++;
    argc--;

    const char* op_name = *argv++;
    argc--;
    sysconfig_op_t op;

    if (!strcmp(op_name, "read")) {
        op = OP_READ;
    } else if (!strcmp(op_name, "write")) {
        op = OP_WRITE;
    } else if (!strcmp(op_name, "edit")) {
        op = OP_EDIT;
    } else {
        usage();
        return -1;
    }

    off_t section_offset;
    const char* section = *argv++;
    argc--;
    if (!strcmp(section, "version-a")) {
        section_offset = ZX_SYSCONFIG_VERSION_A_OFFSET;
    } else if (!strcmp(section, "version-b")) {
        section_offset = ZX_SYSCONFIG_VERSION_B_OFFSET;
    } else if (!strcmp(section, "boot-default")) {
        section_offset = ZX_SYSCONFIG_BOOT_DEFAULT_OFFSET;
    } else if (!strcmp(section, "boot-oneshot")) {
        section_offset = ZX_SYSCONFIG_BOOT_ONESHOT_OFFSET;
    } else {
        usage();
        return -1;
    }

    int fd = open_sysconfig();
    if (fd < 0) {
        fprintf(stderr, "could not find sysconfig partition\n");
        return -1;
    }

    ret = lseek(fd, section_offset, SEEK_SET);
    if (ret < 0) {
        fprintf(stderr, "lseek failed\n");
        goto done;
    }

    uint8_t old_buffer[ZX_SYSCONFIG_KVSTORE_SIZE];
    uint8_t new_buffer[ZX_SYSCONFIG_KVSTORE_SIZE];

    if ((ret = read(fd, old_buffer, sizeof(old_buffer))) != sizeof(old_buffer)) {
        fprintf(stderr, "could not read sysconfig partition: %d\n", ret);
        goto done;
    }

    // we will read the current section into old_kvs and write new section from new_kvs
    struct kvstore old_kvs, new_kvs;

    ret = kvs_load(&old_kvs, old_buffer, sizeof(old_buffer));
    if (ret == KVS_ERR_PARSE_HDR) {
        if (op == OP_WRITE || op == OP_EDIT) {
            printf("initializing empty or corrupt sysconfig partition\n");
            kvs_init(&old_kvs, old_buffer, sizeof(old_buffer));
        } else {
            fprintf(stderr, "kvs_load failed: %d\n", ret);
            goto done;
        }
    } else if (ret < 0) {
        fprintf(stderr, "unexpected error %d from kvs_load\n", ret);
        goto done;
    }

    if (op == OP_WRITE || op == OP_EDIT) {
        kvs_init(&new_kvs, new_buffer, sizeof(new_buffer));
    }

    if (argc == 0 && op == OP_READ) {
        // print all key/value pairs
        kvs_foreach(&old_kvs, NULL, print_func);
        goto done;
    }

    while (argc > 0) {
        const char* arg = *argv++;
        argc--;
        char* equals = strchr(arg, '=');
        // we should only find an '=' if we are writing or editing
        if (!!equals == (op == OP_READ)) {
            usage();
            ret = -1;
            goto done;
        }

        if (op == OP_WRITE || op == OP_EDIT) {
            // separate arg into key and value strings
            *equals = 0;
            const char* key = arg;
            const char* value = equals + 1;
            ret = kvs_add(&new_kvs, key, value);
            if (ret < 0) {
                fprintf(stderr, "kvs_add failed: %d\n", ret);
                goto done;
            }
        } else {
            const char* key = arg;
            const char* value = kvs_get(&old_kvs, key, "");
            printf("%s=%s\n", key, value);
        }
    }

    if (op == OP_EDIT) {
        // copy the other key/value pairs from old_kvs to new_kvs
        ret = kvs_foreach(&old_kvs, &new_kvs, copy_func);
        if (ret < 0) {
            fprintf(stderr, "failed to copy existing values to new kvs: %d\n", ret);
            goto done;
        }
    }
    if (op == OP_WRITE || op == OP_EDIT) {
        kvs_save(&new_kvs);
        ret = lseek(fd, section_offset, SEEK_SET);
        if (ret < 0) {
            fprintf(stderr, "lseek failed\n");
            goto done;
        }
        if ((ret = write(fd, new_buffer, sizeof(new_buffer))) != sizeof(new_buffer)) {
            fprintf(stderr, "could not write sysconfig partition: %d\n", ret);
            goto done;
        }
    }

done:
    close(fd);
    return ret;
}