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/* SPDX-License-Identifier: GPL-2.0-only */
/* This file is part of the coreboot project. */
#include <commonlib/region.h>
#include <console/console.h>
#include <fmap.h>
#include <string.h>
#include <vb2_api.h>
#include <security/vboot/vboot_common.h>
#include <security/vboot/vbnv.h>
#include <security/vboot/vbnv_layout.h>
#define BLOB_SIZE VB2_NVDATA_SIZE
struct vbnv_flash_ctx {
/* VBNV flash is initialized */
int initialized;
/* Offset of the current nvdata in flash */
int blob_offset;
/* Offset of the topmost nvdata blob in flash */
int top_offset;
/* Region to store and retrieve the VBNV contents. */
struct region_device vbnv_dev;
/* Cache of the current nvdata */
uint8_t cache[BLOB_SIZE];
};
static struct vbnv_flash_ctx vbnv_flash;
/*
* This code assumes that flash is erased to 1-bits, and write operations can
* only change 1-bits to 0-bits. So if the new contents only change 1-bits to
* 0-bits, we can reuse the current blob.
*/
static inline uint8_t erase_value(void)
{
return 0xff;
}
static inline int can_overwrite(uint8_t current, uint8_t new)
{
return (current & new) == new;
}
static int init_vbnv(void)
{
struct vbnv_flash_ctx *ctx = &vbnv_flash;
struct region_device *rdev = &ctx->vbnv_dev;
uint8_t buf[BLOB_SIZE];
uint8_t empty_blob[BLOB_SIZE];
int used_below, empty_above;
int offset;
int i;
if (fmap_locate_area_as_rdev_rw("RW_NVRAM", rdev) ||
region_device_sz(rdev) < BLOB_SIZE) {
printk(BIOS_ERR, "%s: failed to locate NVRAM\n", __func__);
return 1;
}
/* Prepare an empty blob to compare against. */
for (i = 0; i < BLOB_SIZE; i++)
empty_blob[i] = erase_value();
ctx->top_offset = region_device_sz(rdev) - BLOB_SIZE;
/* Binary search for the border between used and empty */
used_below = 0;
empty_above = region_device_sz(rdev) / BLOB_SIZE;
while (used_below + 1 < empty_above) {
int guess = (used_below + empty_above) / 2;
if (rdev_readat(rdev, buf, guess * BLOB_SIZE, BLOB_SIZE) < 0) {
printk(BIOS_ERR, "failed to read nvdata\n");
return 1;
}
if (!memcmp(buf, empty_blob, BLOB_SIZE))
empty_above = guess;
else
used_below = guess;
}
/*
* Offset points to the last non-empty blob. Or if all blobs are empty
* (nvram is totally erased), point to the first blob.
*/
offset = used_below * BLOB_SIZE;
/* reread the nvdata and write it to the cache */
if (rdev_readat(rdev, ctx->cache, offset, BLOB_SIZE) < 0) {
printk(BIOS_ERR, "failed to read nvdata\n");
return 1;
}
ctx->blob_offset = offset;
ctx->initialized = 1;
return 0;
}
static int erase_nvram(void)
{
struct vbnv_flash_ctx *ctx = &vbnv_flash;
const struct region_device *rdev = &ctx->vbnv_dev;
if (rdev_eraseat(rdev, 0, region_device_sz(rdev)) < 0) {
printk(BIOS_ERR, "failed to erase nvram\n");
return 1;
}
printk(BIOS_INFO, "nvram is cleared\n");
return 0;
}
void read_vbnv_flash(uint8_t *vbnv_copy)
{
struct vbnv_flash_ctx *ctx = &vbnv_flash;
if (!ctx->initialized)
if (init_vbnv())
return; /* error */
memcpy(vbnv_copy, ctx->cache, BLOB_SIZE);
}
void save_vbnv_flash(const uint8_t *vbnv_copy)
{
struct vbnv_flash_ctx *ctx = &vbnv_flash;
int new_offset;
int i;
const struct region_device *rdev = &ctx->vbnv_dev;
if (!ctx->initialized)
if (init_vbnv())
return; /* error */
/* Bail out if there have been no changes. */
if (!memcmp(vbnv_copy, ctx->cache, BLOB_SIZE))
return;
new_offset = ctx->blob_offset;
/* See if we can overwrite the current blob with the new one */
for (i = 0; i < BLOB_SIZE; i++) {
if (!can_overwrite(ctx->cache[i], vbnv_copy[i])) {
/* unable to overwrite. need to use the next blob */
new_offset += BLOB_SIZE;
if (new_offset > ctx->top_offset) {
if (erase_nvram())
return; /* error */
new_offset = 0;
}
break;
}
}
if (rdev_writeat(rdev, vbnv_copy, new_offset, BLOB_SIZE) == BLOB_SIZE) {
/* write was successful. safely move pointer forward */
ctx->blob_offset = new_offset;
memcpy(ctx->cache, vbnv_copy, BLOB_SIZE);
} else {
printk(BIOS_ERR, "failed to save nvdata\n");
}
}
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