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hw/uefi: add var-service-json.c + qapi for NV vars.
Define qapi schema for the uefi variable store state. Use it and the generated visitor helper functions to store persistent (EFI_VARIABLE_NON_VOLATILE) variables in JSON format on disk. Acked-by: Markus Armbruster <[email protected]> Signed-off-by: Gerd Hoffmann <[email protected]> Message-ID: <[email protected]> [ incremental fix squashed in ] Message-ID: <pji24p6oag7cn2rovus7rquo7q2c6tokuquobfro2sqorky7vu@tk7cxud6jw7f>
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‎hw/uefi/var-service-json.c‎

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/*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*
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* uefi vars device - serialize non-volatile varstore from/to json,
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* using qapi
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*
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* tools which can read/write these json files:
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* - https://gitlab.com/kraxel/virt-firmware
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* - https://github.com/awslabs/python-uefivars
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*/
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#include "qemu/osdep.h"
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#include "qemu/cutils.h"
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#include "qemu/error-report.h"
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#include "system/dma.h"
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#include "hw/uefi/var-service.h"
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#include "qobject/qobject.h"
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#include "qobject/qjson.h"
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#include "qapi/dealloc-visitor.h"
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#include "qapi/qobject-input-visitor.h"
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#include "qapi/qobject-output-visitor.h"
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#include "qapi/qapi-types-uefi.h"
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#include "qapi/qapi-visit-uefi.h"
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static char *generate_hexstr(void *data, size_t len)
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{
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static const char hex[] = {
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'0', '1', '2', '3', '4', '5', '6', '7',
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'8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
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};
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uint8_t *src = data;
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char *dest;
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size_t i;
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dest = g_malloc(len * 2 + 1);
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for (i = 0; i < len * 2;) {
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dest[i++] = hex[*src >> 4];
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dest[i++] = hex[*src & 15];
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src++;
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}
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dest[i++] = 0;
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return dest;
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}
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static UefiVarStore *uefi_vars_to_qapi(uefi_vars_state *uv)
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{
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UefiVarStore *vs;
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UefiVariableList **tail;
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UefiVariable *v;
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QemuUUID be;
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uefi_variable *var;
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vs = g_new0(UefiVarStore, 1);
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vs->version = 2;
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tail = &vs->variables;
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QTAILQ_FOREACH(var, &uv->variables, next) {
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if (!(var->attributes & EFI_VARIABLE_NON_VOLATILE)) {
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continue;
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}
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v = g_new0(UefiVariable, 1);
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be = qemu_uuid_bswap(var->guid);
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v->guid = qemu_uuid_unparse_strdup(&be);
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v->name = uefi_ucs2_to_ascii(var->name, var->name_size);
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v->attr = var->attributes;
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v->data = generate_hexstr(var->data, var->data_size);
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if (var->attributes &
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EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) {
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v->time = generate_hexstr(&var->time, sizeof(var->time));
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if (var->digest && var->digest_size) {
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v->digest = generate_hexstr(var->digest, var->digest_size);
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}
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}
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QAPI_LIST_APPEND(tail, v);
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}
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return vs;
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}
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static unsigned parse_hexchar(char c)
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{
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switch (c) {
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case '0' ... '9': return c - '0';
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case 'a' ... 'f': return c - 'a' + 0xa;
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case 'A' ... 'F': return c - 'A' + 0xA;
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default: return 0;
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}
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}
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static void parse_hexstr(void *dest, char *src, int len)
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{
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uint8_t *data = dest;
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size_t i;
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for (i = 0; i < len; i += 2) {
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*(data++) =
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parse_hexchar(src[i]) << 4 |
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parse_hexchar(src[i + 1]);
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}
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}
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static void uefi_vars_from_qapi(uefi_vars_state *uv, UefiVarStore *vs)
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{
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UefiVariableList *item;
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UefiVariable *v;
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QemuUUID be;
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uefi_variable *var;
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uint8_t *data;
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size_t i, len;
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for (item = vs->variables; item != NULL; item = item->next) {
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v = item->value;
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var = g_new0(uefi_variable, 1);
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var->attributes = v->attr;
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qemu_uuid_parse(v->guid, &be);
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var->guid = qemu_uuid_bswap(be);
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len = strlen(v->name);
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var->name_size = len * 2 + 2;
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var->name = g_malloc(var->name_size);
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for (i = 0; i <= len; i++) {
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var->name[i] = v->name[i];
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}
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len = strlen(v->data);
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var->data_size = len / 2;
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var->data = data = g_malloc(var->data_size);
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parse_hexstr(var->data, v->data, len);
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if (v->time && strlen(v->time) == 32) {
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parse_hexstr(&var->time, v->time, 32);
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}
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if (v->digest) {
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len = strlen(v->digest);
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var->digest_size = len / 2;
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var->digest = g_malloc(var->digest_size);
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parse_hexstr(var->digest, v->digest, len);
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}
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QTAILQ_INSERT_TAIL(&uv->variables, var, next);
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}
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}
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static GString *uefi_vars_to_json(uefi_vars_state *uv)
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{
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UefiVarStore *vs = uefi_vars_to_qapi(uv);
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QObject *qobj = NULL;
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Visitor *v;
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GString *gstr;
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v = qobject_output_visitor_new(&qobj);
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if (visit_type_UefiVarStore(v, NULL, &vs, NULL)) {
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visit_complete(v, &qobj);
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}
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visit_free(v);
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qapi_free_UefiVarStore(vs);
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gstr = qobject_to_json_pretty(qobj, true);
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qobject_unref(qobj);
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return gstr;
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}
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void uefi_vars_json_init(uefi_vars_state *uv, Error **errp)
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{
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if (uv->jsonfile) {
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uv->jsonfd = qemu_create(uv->jsonfile, O_RDWR, 0666, errp);
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}
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}
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void uefi_vars_json_save(uefi_vars_state *uv)
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{
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GString *gstr;
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int rc;
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if (uv->jsonfd == -1) {
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return;
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}
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gstr = uefi_vars_to_json(uv);
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lseek(uv->jsonfd, 0, SEEK_SET);
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rc = ftruncate(uv->jsonfd, 0);
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if (rc != 0) {
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warn_report("%s: ftruncate error", __func__);
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}
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rc = write(uv->jsonfd, gstr->str, gstr->len);
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if (rc != gstr->len) {
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warn_report("%s: write error", __func__);
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}
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fsync(uv->jsonfd);
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g_string_free(gstr, true);
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}
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void uefi_vars_json_load(uefi_vars_state *uv, Error **errp)
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{
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UefiVarStore *vs;
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QObject *qobj;
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Visitor *v;
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char *str;
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size_t len;
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int rc;
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if (uv->jsonfd == -1) {
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return;
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}
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len = lseek(uv->jsonfd, 0, SEEK_END);
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if (len == 0) {
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return;
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}
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str = g_malloc(len + 1);
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lseek(uv->jsonfd, 0, SEEK_SET);
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rc = read(uv->jsonfd, str, len);
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if (rc != len) {
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warn_report("%s: read error", __func__);
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}
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str[len] = 0;
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qobj = qobject_from_json(str, errp);
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v = qobject_input_visitor_new(qobj);
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visit_type_UefiVarStore(v, NULL, &vs, errp);
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visit_free(v);
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if (!(*errp)) {
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uefi_vars_from_qapi(uv, vs);
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uefi_vars_update_storage(uv);
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}
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qapi_free_UefiVarStore(vs);
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qobject_unref(qobj);
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g_free(str);
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}

‎qapi/meson.build‎

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'pci',
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'rocker',
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'tpm',
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'uefi',
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]
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endif
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if have_system or have_tools

‎qapi/qapi-schema.json‎

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{ 'include': 'vfio.json' }
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{ 'include': 'cryptodev.json' }
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{ 'include': 'cxl.json' }
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{ 'include': 'uefi.json' }

‎qapi/uefi.json‎

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# -*- Mode: Python -*-
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# vim: filetype=python
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#
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##
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# = UEFI Variable Store
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#
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# The qemu efi variable store implementation (hw/uefi/) uses this to
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# store non-volatile variables in json format on disk.
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#
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# This is an existing format already supported by (at least) two other
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# projects, specifically https://gitlab.com/kraxel/virt-firmware and
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# https://github.com/awslabs/python-uefivars.
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##
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##
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# @UefiVariable:
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#
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# UEFI Variable. Check the UEFI specifification for more detailed
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# information on the fields.
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#
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# @guid: variable namespace GUID
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#
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# @name: variable name, in UTF-8 encoding.
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#
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# @attr: variable attributes.
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#
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# @data: variable value, encoded as hex string.
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#
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# @time: variable modification time. EFI_TIME struct, encoded as hex
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# string. Used only for authenticated variables, where the
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# EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS attribute bit
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# is set.
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#
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# @digest: variable certificate digest. Used to verify the signature
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# of updates for authenticated variables. UEFI has two kinds of
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# authenticated variables. The secure boot variables ('PK',
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# 'KEK', 'db' and 'dbx') have hard coded signature checking rules.
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# For other authenticated variables the firmware stores a digest
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# of the signing certificate at variable creation time, and any
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# updates must be signed with the same certificate.
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#
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# Since: 10.0
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##
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{ 'struct' : 'UefiVariable',
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'data' : { 'guid' : 'str',
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'name' : 'str',
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'attr' : 'int',
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'data' : 'str',
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'*time' : 'str',
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'*digest' : 'str'}}
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##
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# @UefiVarStore:
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#
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# @version: currently always 2
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#
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# @variables: list of UEFI variables
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#
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# Since: 10.0
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##
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{ 'struct' : 'UefiVarStore',
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'data' : { 'version' : 'int',
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'variables' : [ 'UefiVariable' ] }}

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