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/* Copyright 2016 The Chromium OS 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 "common.h"
#include "console.h"
#include "flash.h"
#include "nvmem.h"
#include "task.h"
#include "timer.h"
#include "util.h"
#define CPRINTF(format, args...) cprintf(CC_COMMAND, format, ## args)
#define CPRINTS(format, args...) cprints(CC_COMMAND, format, ## args)
#define NVMEM_NOT_INITIALIZED (-1)
/*
* The NVMEM contents are stored in flash memory. At run time there is an SRAM
* cache and two instances of the contents in the flash in two partitions.
*
* Each instance is protected by a 16 bytes hash and has a 'generation' value
* associated with it. When NVMEM module is initialized it checks the flash
* stored instances. If both of them are valid, it considers the newer one
* (younger generation) to be the proper NVMEM contents and copies it to the
* SRAM cache. If only one instance is valid, it is used, and if no instances
* are valid - a new valid partition is created and copied into the SRAM
* cache.
*
* When stored in flash, the contents are encrypted, the hash value is used as
* the IV for the encryption routine.
*
* There is a mutex controlling access to the NVMEM. There are two levels
* of protection - for read only accesses and for write accesses. When the
* module is initialized the mutex is opened.
*
* If there are no pending writes, each read access locks the mutex, reads out
* the data and unlocks the mutex, thus multiple tasks could be reading NVMEM,
* blocking access momentarily.
*
* If a write access ever occurs things get more complicated. The write access
* leaves the mutex locked and stores the flag, indicating that the
* contents have changed and need to be saved, and stores the task id of the
* task performing the write access.
*
* The mutex remains locked in this case. Next time a read access happens,
* if it comes from the same task, the unlock in the end of the read is
* bypassed because the 'write in progress' flag is set. If a read or write
* request comes from another task, they will be blocked until the first
* task to write commits.
*
* nvmem_commit() calls the nvmem_save() function which checks if the cache
* contents indeed changed (by calculating the hash again). If there is no
* change - the mutex is released and the function exits. If there is a
* change, the new generation value is set, the new hash is calculated
* and the copy is saved in the least recently used flash partition, and
* then the lock is released.
*/
/* Table of start addresses for each partition */
static const uintptr_t nvmem_base_addr[NVMEM_NUM_PARTITIONS] = {
CONFIG_FLASH_NVMEM_BASE_A,
CONFIG_FLASH_NVMEM_BASE_B
};
/* NvMem user buffer start offset table */
static uint32_t nvmem_user_start_offset[NVMEM_NUM_USERS];
/* A/B partion that is most up to date */
static int nvmem_act_partition;
/* NvMem cache memory structure */
struct nvmem_mutex_ {
task_id_t task;
int write_in_progress;
struct mutex mtx;
};
static struct nvmem_mutex_ nvmem_mutex = { .task = TASK_ID_COUNT };
static uint8_t nvmem_cache[NVMEM_PARTITION_SIZE] __aligned(4);
static uint8_t commits_enabled;
/* NvMem error state */
static int nvmem_error_state;
/* Flag to track if an Nv write/move is not completed */
static int nvmem_write_error;
static void nvmem_release_cache(void);
/*
* Given the nvmem tag address calculate the sha value of the nvmem buffer and
* save it in the provided space. The caller is expected to provide enough
* space to store CIPHER_SALT_SIZE bytes.
*/
static void nvmem_compute_sha(struct nvmem_tag *tag, void *sha_buf)
{
app_compute_hash(tag->padding, NVMEM_PARTITION_SIZE - NVMEM_SHA_SIZE,
sha_buf, sizeof(tag->sha));
}
static int nvmem_save(void)
{
struct nvmem_partition *part;
size_t nvmem_offset;
int dest_partition;
uint8_t sha_comp[NVMEM_SHA_SIZE];
int rv = EC_SUCCESS;
part = (struct nvmem_partition *)nvmem_cache;
/* Has anything changed in the cache? */
nvmem_compute_sha(&part->tag, sha_comp);
if (!memcmp(part->tag.sha, sha_comp, sizeof(part->tag.sha))) {
CPRINTF("%s: Nothing changed, skipping flash write\n",
__func__);
goto release_cache;
}
/* Get flash offset of the partition to save to. */
dest_partition = (nvmem_act_partition + 1) % NVMEM_NUM_PARTITIONS;
nvmem_offset = nvmem_base_addr[dest_partition] -
CONFIG_PROGRAM_MEMORY_BASE;
/* Erase partition */
rv = flash_physical_erase(nvmem_offset, NVMEM_PARTITION_SIZE);
if (rv != EC_SUCCESS) {
CPRINTF("%s flash erase failed\n", __func__);
goto release_cache;
}
part->tag.layout_version = NVMEM_LAYOUT_VERSION;
part->tag.generation++;
/* Calculate sha of the whole thing. */
nvmem_compute_sha(&part->tag, part->tag.sha);
/* Encrypt actual payload. */
if (!app_cipher(part->tag.sha, part->buffer, part->buffer,
sizeof(part->buffer))) {
CPRINTF("%s encryption failed\n", __func__);
rv = EC_ERROR_UNKNOWN;
goto release_cache;
}
rv = flash_physical_write(nvmem_offset,
NVMEM_PARTITION_SIZE,
nvmem_cache);
if (rv != EC_SUCCESS) {
CPRINTF("%s flash write failed\n", __func__);
goto release_cache;
}
/* Restore payload. */
if (!app_cipher(part->tag.sha, part->buffer, part->buffer,
sizeof(part->buffer))) {
CPRINTF("%s decryption failed\n", __func__);
rv = EC_ERROR_UNKNOWN;
goto release_cache;
}
nvmem_act_partition = dest_partition;
release_cache:
nvmem_mutex.write_in_progress = 0;
nvmem_release_cache();
return rv;
}
/*
* Read from flash and verify partition.
*
* @param index - index of the partition to verify
*
* Returns EC_SUCCESS on verification success
* EC_ERROR_BUSY in case of malloc failure
* EC_ERROR_UNKNOWN on failure to decrypt of verify.
*/
static int nvmem_partition_read_verify(int index)
{
uint8_t sha_comp[NVMEM_SHA_SIZE];
struct nvmem_partition *p_part;
struct nvmem_partition *p_copy;
int ret;
p_part = (struct nvmem_partition *)nvmem_base_addr[index];
p_copy = (struct nvmem_partition *)nvmem_cache;
memcpy(p_copy, p_part, NVMEM_PARTITION_SIZE);
/* Then decrypt it. */
if (!app_cipher(p_copy->tag.sha, &p_copy->tag + 1,
&p_copy->tag + 1,
NVMEM_PARTITION_SIZE - sizeof(struct nvmem_tag))) {
CPRINTF("%s: decryption failure\n", __func__);
return EC_ERROR_UNKNOWN;
}
/*
* Check if computed value matches stored value. Nonzero 'ret' value
* means there was a match.
*/
nvmem_compute_sha(&p_copy->tag, sha_comp);
ret = !memcmp(p_copy->tag.sha, sha_comp, NVMEM_SHA_SIZE);
return ret ? EC_SUCCESS : EC_ERROR_UNKNOWN;
}
static void nvmem_lock_cache(void)
{
/*
* Need to protect the cache contents value from other tasks
* attempting to do nvmem write operations. However, since this
* function may be called mutliple times prior to the mutex lock being
* released, there is a check first to see if the current task holds
* the lock. If it does then the task number will equal the value in
* cache.task, no need to wait.
*
* If the lock is held by a different task then mutex_lock function
* will operate as normal.
*/
if (nvmem_mutex.task == task_get_current())
return;
mutex_lock(&nvmem_mutex.mtx);
nvmem_mutex.task = task_get_current();
}
static void nvmem_release_cache(void)
{
if (nvmem_mutex.write_in_progress || !commits_enabled)
return; /* It will have to be saved first. */
/* Reset task number to max value */
nvmem_mutex.task = TASK_ID_COUNT;
/* Release mutex lock here */
mutex_unlock(&nvmem_mutex.mtx);
}
static int nvmem_reinitialize(void)
{
nvmem_lock_cache(); /* Unlocked by nvmem_save() below. */
/*
* NvMem is not properly initialized. Let's just erase everything and
* start over, so that at least 1 partition is ready to be used.
*/
nvmem_act_partition = 0;
memset(nvmem_cache, 0xff, NVMEM_PARTITION_SIZE);
/* Start with generation zero in the current active partition. */
return nvmem_save();
}
static int nvmem_compare_generation(void)
{
struct nvmem_partition *p_part;
uint16_t ver0, ver1;
uint32_t delta;
p_part = (struct nvmem_partition *)nvmem_base_addr[0];
ver0 = p_part->tag.generation;
p_part = (struct nvmem_partition *)nvmem_base_addr[1];
ver1 = p_part->tag.generation;
/* Compute generation difference accounting for wrap condition */
delta = (ver0 - ver1 + (1<<NVMEM_GENERATION_BITS)) &
NVMEM_GENERATION_MASK;
/*
* If generation number delta is positive in a circular sense then
* partition 0 has the newest generation number. Otherwise, it's
* partition 1.
*/
return delta < (1<<(NVMEM_GENERATION_BITS-1)) ? 0 : 1;
}
static int nvmem_find_partition(void)
{
int n;
/* Don't know which partition to use yet */
nvmem_act_partition = NVMEM_NOT_INITIALIZED;
/*
* Check each partition to determine if the sha is good. If both
* partitions have valid sha(s), then compare generation numbers to
* select the most recent one.
*/
for (n = 0; n < NVMEM_NUM_PARTITIONS; n++)
if (nvmem_partition_read_verify(n) == EC_SUCCESS) {
if (nvmem_act_partition == NVMEM_NOT_INITIALIZED)
nvmem_act_partition = n;
else
nvmem_act_partition =
nvmem_compare_generation();
} else {
ccprintf("%s:%d partiton %d verification FAILED\n",
__func__, __LINE__, n);
}
if (nvmem_act_partition != NVMEM_NOT_INITIALIZED)
return EC_SUCCESS;
/*
* If active_partition is still not selected, then neither partition
* is valid. Let's reinitialize the NVMEM - there is nothing else we
* can do.
*/
CPRINTS("%s: No Valid Partition found, will reinitialize!", __func__);
if (nvmem_reinitialize() != EC_SUCCESS) {
CPRINTS("%s: Reinitialization failed!!");
return EC_ERROR_UNKNOWN;
}
return EC_SUCCESS;
}
static int nvmem_generate_offset_table(void)
{
int n;
uint32_t start_offset;
/*
* Create table of starting offsets within partition for each user
* buffer that's been defined.
*/
start_offset = sizeof(struct nvmem_tag);
for (n = 0; n < NVMEM_NUM_USERS; n++) {
nvmem_user_start_offset[n] = start_offset;
start_offset += nvmem_user_sizes[n];
}
/* Verify that all defined user buffers fit within the partition */
if (start_offset > NVMEM_PARTITION_SIZE)
return EC_ERROR_OVERFLOW;
return EC_SUCCESS;
}
static int nvmem_get_partition_off(int user, uint32_t offset,
uint32_t len, uint32_t *p_buf_offset)
{
uint32_t start_offset;
/* Sanity check for user */
if (user >= NVMEM_NUM_USERS)
return EC_ERROR_OVERFLOW;
/* Get offset within the partition for the start of user buffer */
start_offset = nvmem_user_start_offset[user];
/*
* Ensure that read/write operation that is calling this function
* doesn't exceed the end of its buffer.
*/
if (offset + len > nvmem_user_sizes[user])
return EC_ERROR_OVERFLOW;
/* Compute offset within the partition for the rd/wr operation */
*p_buf_offset = start_offset + offset;
return EC_SUCCESS;
}
int nvmem_setup(void)
{
int part;
int ret;
CPRINTS("Configuring NVMEM Flash Partition");
part = nvmem_act_partition;
nvmem_act_partition = 0;
ret = EC_SUCCESS;
for (part = 0; part < NVMEM_NUM_PARTITIONS; part++) {
int rv;
memset(nvmem_cache, 0xff, NVMEM_PARTITION_SIZE);
/*
* Make sure the contents change between runs of
* nvmem_save() so that both flash partitions are
* written with empty contents and different
* generation numbers.
*/
((struct nvmem_partition *)nvmem_cache)->tag.generation = part;
/* Lock the cache buffer (unlocked by nvmem_save() */
nvmem_lock_cache();
rv = nvmem_save();
/* Even if one partition saving failed, let's keep going. */
if (rv != EC_SUCCESS)
ret = rv;
}
return ret;
}
int nvmem_init(void)
{
int ret;
/* Generate start offsets within partiion for user buffers */
ret = nvmem_generate_offset_table();
if (ret) {
CPRINTF("%s:%d\n", __func__, __LINE__);
return ret;
}
/* Initialize error state, assume everything is good */
nvmem_error_state = EC_SUCCESS;
nvmem_write_error = 0;
/*
* Default policy is to allow all commits. This ensures reinitialization
* succeeds to bootstrap the nvmem area.
*/
commits_enabled = 1;
ret = nvmem_find_partition();
if (ret != EC_SUCCESS) {
/* Change error state to non-zero */
nvmem_error_state = ret;
CPRINTF("%s:%d\n", __func__, __LINE__);
return ret;
}
CPRINTS("Active Nvmem partition set to %d", nvmem_act_partition);
return EC_SUCCESS;
}
int nvmem_get_error_state(void)
{
return nvmem_error_state;
}
int nvmem_is_different(uint32_t offset, uint32_t size, void *data,
enum nvmem_users user)
{
int ret;
uint32_t src_offset;
nvmem_lock_cache();
/* Get partition offset for this read operation */
ret = nvmem_get_partition_off(user, offset, size, &src_offset);
if (ret != EC_SUCCESS)
return ret;
/* Advance to the correct byte within the data buffer */
/* Compare NvMem with data */
ret = memcmp(nvmem_cache + src_offset, data, size);
nvmem_release_cache();
return ret;
}
int nvmem_read(uint32_t offset, uint32_t size,
void *data, enum nvmem_users user)
{
int ret;
uint32_t src_offset;
nvmem_lock_cache();
/* Get partition offset for this read operation */
ret = nvmem_get_partition_off(user, offset, size, &src_offset);
if (ret == EC_SUCCESS)
/* Copy from src into the caller's destination buffer */
memcpy(data, nvmem_cache + src_offset, size);
nvmem_release_cache();
return ret;
}
int nvmem_write(uint32_t offset, uint32_t size,
void *data, enum nvmem_users user)
{
int ret;
uint8_t *p_dest;
uint32_t dest_offset;
/* Make sure that the cache buffer is active */
nvmem_lock_cache();
nvmem_mutex.write_in_progress = 1;
/* Compute partition offset for this write operation */
ret = nvmem_get_partition_off(user, offset, size, &dest_offset);
if (ret != EC_SUCCESS) {
nvmem_write_error = 1;
return ret;
}
/* Advance to correct offset within data buffer */
p_dest = nvmem_cache + dest_offset;
/* Copy data from caller into destination buffer */
memcpy(p_dest, data, size);
return EC_SUCCESS;
}
int nvmem_move(uint32_t src_offset, uint32_t dest_offset, uint32_t size,
enum nvmem_users user)
{
int ret;
uint8_t *p_src, *p_dest;
uintptr_t base_addr;
uint32_t s_buff_offset, d_buff_offset;
/* Make sure that the cache buffer is active */
nvmem_lock_cache();
nvmem_mutex.write_in_progress = 1;
/* Compute partition offset for source */
ret = nvmem_get_partition_off(user, src_offset, size, &s_buff_offset);
if (ret != EC_SUCCESS) {
nvmem_write_error = 1;
return ret;
}
/* Compute partition offset for destination */
ret = nvmem_get_partition_off(user, dest_offset, size, &d_buff_offset);
if (ret != EC_SUCCESS) {
nvmem_write_error = 1;
return ret;
}
base_addr = (uintptr_t)nvmem_cache;
/* Create pointer to src location within partition */
p_src = (uint8_t *)(base_addr + s_buff_offset);
/* Create pointer to dest location within partition */
p_dest = (uint8_t *)(base_addr + d_buff_offset);
/* Move the data block in NvMem */
memmove(p_dest, p_src, size);
return EC_SUCCESS;
}
int nvmem_enable_commits(void)
{
if (commits_enabled)
return EC_SUCCESS;
if (nvmem_mutex.task != task_get_current()) {
CPRINTF("%s: locked by task %d, attempt to unlock by task %d\n",
__func__, nvmem_mutex.task, task_get_current());
return EC_ERROR_INVAL;
}
commits_enabled = 1;
CPRINTS("Committing NVMEM changes.");
return nvmem_commit();
}
void nvmem_disable_commits(void)
{
/* Will be unlocked when nvmem_enable_commits() is called. */
nvmem_lock_cache();
commits_enabled = 0;
}
int nvmem_commit(void)
{
if (nvmem_mutex.task == TASK_ID_COUNT) {
CPRINTF("%s: attempt to commit in unlocked state\n",
__func__, nvmem_mutex.task);
return EC_ERROR_OVERFLOW; /* Noting to commit. */
}
if (nvmem_mutex.task != task_get_current()) {
CPRINTF("%s: locked by task %d, attempt to unlock by task %d\n",
__func__, nvmem_mutex.task, task_get_current());
return EC_ERROR_INVAL;
}
/* Ensure that all writes/moves prior to commit call succeeded */
if (nvmem_write_error) {
CPRINTS("%s: Write Error, commit abandoned", __func__);
/* Clear error state */
nvmem_write_error = 0;
commits_enabled = 1;
nvmem_release_cache();
return EC_ERROR_UNKNOWN;
}
if (!commits_enabled) {
CPRINTS("Skipping commit");
return EC_SUCCESS;
}
/* Write active partition to NvMem */
return nvmem_save();
}
|