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// SPDX-License-Identifier: GPL-2.0
/*
* Verified Boot for Embedded (VBE) OS request (device tree fixup) functions
*
* Copyright 2022 Google LLC
* Written by Simon Glass <sjg@chromium.org>
*/
#define LOG_CATEGORY LOGC_BOOT
#include <dm.h>
#include <event.h>
#include <image.h>
#include <malloc.h>
#include <rng.h>
#include <dm/ofnode.h>
#define VBE_PREFIX "vbe,"
#define VBE_PREFIX_LEN (sizeof(VBE_PREFIX) - 1)
#define VBE_ERR_STR_LEN 128
#define VBE_MAX_RAND_SIZE 256
struct vbe_result {
int errnum;
char err_str[VBE_ERR_STR_LEN];
};
typedef int (*vbe_req_func)(ofnode node, struct vbe_result *result);
static int handle_random_req(ofnode node, int default_size,
struct vbe_result *result)
{
char buf[VBE_MAX_RAND_SIZE];
struct udevice *dev;
u32 size;
int ret;
if (!CONFIG_IS_ENABLED(DM_RNG))
return -ENOTSUPP;
if (ofnode_read_u32(node, "vbe,size", &size)) {
if (!default_size) {
snprintf(result->err_str, VBE_ERR_STR_LEN,
"Missing vbe,size property");
return log_msg_ret("byt", -EINVAL);
}
size = default_size;
}
if (size > VBE_MAX_RAND_SIZE) {
snprintf(result->err_str, VBE_ERR_STR_LEN,
"vbe,size %#x exceeds max size %#x", size,
VBE_MAX_RAND_SIZE);
return log_msg_ret("siz", -E2BIG);
}
ret = uclass_first_device_err(UCLASS_RNG, &dev);
if (ret) {
snprintf(result->err_str, VBE_ERR_STR_LEN,
"Cannot find random-number device (err=%d)", ret);
return log_msg_ret("wr", ret);
}
ret = dm_rng_read(dev, buf, size);
if (ret) {
snprintf(result->err_str, VBE_ERR_STR_LEN,
"Failed to read random-number device (err=%d)", ret);
return log_msg_ret("rd", ret);
}
ret = ofnode_write_prop(node, "data", buf, size, true);
if (ret)
return log_msg_ret("wr", -EINVAL);
return 0;
}
static int vbe_req_random_seed(ofnode node, struct vbe_result *result)
{
return handle_random_req(node, 0, result);
}
static int vbe_req_aslr_move(ofnode node, struct vbe_result *result)
{
return -ENOTSUPP;
}
static int vbe_req_aslr_rand(ofnode node, struct vbe_result *result)
{
return handle_random_req(node, 4, result);
}
static int vbe_req_efi_runtime_rand(ofnode node, struct vbe_result *result)
{
return handle_random_req(node, 4, result);
}
static struct vbe_req {
const char *compat;
vbe_req_func func;
} vbe_reqs[] = {
/* address space layout randomization - move the OS in memory */
{ "aslr-move", vbe_req_aslr_move },
/* provide random data for address space layout randomization */
{ "aslr-rand", vbe_req_aslr_rand },
/* provide random data for EFI-runtime-services address */
{ "efi-runtime-rand", vbe_req_efi_runtime_rand },
/* generate random data bytes to see the OS's rand generator */
{ "random-rand", vbe_req_random_seed },
};
static int vbe_process_request(ofnode node, struct vbe_result *result)
{
const char *compat, *req_name;
int i;
compat = ofnode_read_string(node, "compatible");
if (!compat)
return 0;
if (strlen(compat) <= VBE_PREFIX_LEN ||
strncmp(compat, VBE_PREFIX, VBE_PREFIX_LEN))
return -EINVAL;
req_name = compat + VBE_PREFIX_LEN; /* drop "vbe," prefix */
for (i = 0; i < ARRAY_SIZE(vbe_reqs); i++) {
if (!strcmp(vbe_reqs[i].compat, req_name)) {
int ret;
ret = vbe_reqs[i].func(node, result);
if (ret)
return log_msg_ret("req", ret);
return 0;
}
}
snprintf(result->err_str, VBE_ERR_STR_LEN, "Unknown request: %s",
req_name);
return -ENOTSUPP;
}
/**
* bootmeth_vbe_ft_fixup() - Process VBE OS requests and do device tree fixups
*
* If there are no images provided, this does nothing and returns 0.
*
* @ctx: Context for event
* @event: Event to process
* @return 0 if OK, -ve on error
*/
static int bootmeth_vbe_ft_fixup(void *ctx, struct event *event)
{
const struct event_ft_fixup *fixup = &event->data.ft_fixup;
const struct bootm_headers *images = fixup->images;
ofnode parent, dest_parent, root, node;
oftree fit;
if (!images || !images->fit_hdr_os)
return 0;
/* Get the image node with requests in it */
log_debug("fit=%p, noffset=%d\n", images->fit_hdr_os,
images->fit_noffset_os);
fit = oftree_from_fdt(images->fit_hdr_os);
root = oftree_root(fit);
if (of_live_active()) {
log_warning("Cannot fix up live tree\n");
return 0;
}
if (!ofnode_valid(root))
return log_msg_ret("rt", -EINVAL);
parent = noffset_to_ofnode(root, images->fit_noffset_os);
if (!ofnode_valid(parent))
return log_msg_ret("img", -EINVAL);
dest_parent = oftree_path(fixup->tree, "/chosen");
if (!ofnode_valid(dest_parent))
return log_msg_ret("dst", -EINVAL);
ofnode_for_each_subnode(node, parent) {
const char *name = ofnode_get_name(node);
struct vbe_result result;
ofnode dest;
int ret;
log_debug("copy subnode: %s\n", name);
ret = ofnode_add_subnode(dest_parent, name, &dest);
if (ret && ret != -EEXIST)
return log_msg_ret("add", ret);
ret = ofnode_copy_props(dest, node);
if (ret)
return log_msg_ret("cp", ret);
*result.err_str = '\0';
ret = vbe_process_request(dest, &result);
if (ret) {
result.errnum = ret;
log_warning("Failed to process VBE request %s (err=%d)\n",
ofnode_get_name(dest), ret);
if (*result.err_str) {
char *msg = strdup(result.err_str);
if (!msg)
return log_msg_ret("msg", -ENOMEM);
ret = ofnode_write_string(dest, "vbe,error",
msg);
if (ret) {
free(msg);
return log_msg_ret("str", -ENOMEM);
}
}
if (result.errnum) {
ret = ofnode_write_u32(dest, "vbe,errnum",
result.errnum);
if (ret)
return log_msg_ret("num", -ENOMEM);
if (result.errnum != -ENOTSUPP)
return log_msg_ret("pro",
result.errnum);
if (result.errnum == -ENOTSUPP &&
ofnode_read_bool(dest, "vbe,required")) {
log_err("Cannot handle required request: %s\n",
ofnode_get_name(dest));
return log_msg_ret("req",
result.errnum);
}
}
}
}
return 0;
}
EVENT_SPY_FULL(EVT_FT_FIXUP, bootmeth_vbe_ft_fixup);
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