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author | Patrick Georgi <pgeorgi@google.com> | 2018-03-14 21:11:21 +0100 |
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committer | Patrick Georgi <pgeorgi@google.com> | 2018-10-08 09:46:30 +0000 |
commit | 9360feaf5121fb0b4b2d63e3168effe066650071 (patch) | |
tree | dae8bcba4a33a3920e1b57e5f2d9033fa763b32d /src/drivers/smmstore/store.c | |
parent | 88607a4b1002ed6acc7f316f274feea2fd861095 (diff) | |
download | coreboot-9360feaf5121fb0b4b2d63e3168effe066650071.tar.xz |
smmstore: Add a key/val store facility in flash, mediated through SMM
It exposes an interface that is as generic as possible, so payloads
and/or kernels can use it for their data.
Change-Id: I9553922f9dfa60b9d4b3576973ad4b84d3fe2fb5
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/25182
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Diffstat (limited to 'src/drivers/smmstore/store.c')
-rw-r--r-- | src/drivers/smmstore/store.c | 225 |
1 files changed, 225 insertions, 0 deletions
diff --git a/src/drivers/smmstore/store.c b/src/drivers/smmstore/store.c new file mode 100644 index 0000000000..67d38ee143 --- /dev/null +++ b/src/drivers/smmstore/store.c @@ -0,0 +1,225 @@ +/* + * This file is part of the coreboot project. + * + * Copyright (C) 2018 The Chromium OS Authors. All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; version 2 of the License. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <boot_device.h> +#include <cbfs.h> +#include <commonlib/region.h> +#include <console/console.h> +#include <smmstore.h> +#include <string.h> + +/* + * The region format is still not finalized, but so far it looks like this: + * ( + * uint32le_t key_sz + * uint32le_t value_sz + * uint8_t key[key_sz] + * uint8_t value[value_sz] + * uint8_t active + * align to 4 bytes + * )* + * uint32le_t endmarker = 0xffffffff + * + * active needs to be set to 0x00 for the entry to be valid. This satisfies + * the constraint that entries are either complete or will be ignored, as long + * as flash is written sequentially and into a fully erased block. + * + * Future additions to the format will split the region in half with an active + * block marker to allow safe compaction (ie. write the new data in the unused + * region, mark it active after the write completed). Otherwise a well-timed + * crash/reboot could clear out all variables. + */ + +/* + * Return a region device that points into the store file. + * + * It's the image builder's responsibility to make it block aligned so that + * erase works without destroying other data. + * + * It doesn't cache the location to cope with flash changing underneath (eg + * due to an update) + * + * returns 0 on success, -1 on failure + * outputs the valid store rdev in rstore + */ +static int lookup_store(struct region_device *rstore) +{ + struct cbfsf file; + if (cbfs_locate_file_in_region(&file, + CONFIG_SMMSTORE_REGION, CONFIG_SMMSTORE_FILENAME, NULL) < 0) { + printk(BIOS_WARNING, "smm store: " + "Unable to find SMM store file in region '%s'\n", + CONFIG_SMMSTORE_REGION); + return -1; + } + + cbfs_file_data(rstore, &file); + + return 0; +} + +/* + * Read entire store into user provided buffer + * + * returns 0 on success, -1 on failure + * writes up to `*bufsize` bytes into `buf` and updates `*bufsize` + */ +int smmstore_read_region(void *buf, ssize_t *bufsize) +{ + struct region_device store; + + if (bufsize == NULL) + return -1; + + *bufsize = 0; + if (lookup_store(&store) < 0) { + printk(BIOS_WARNING, "reading region failed\n"); + return -1; + } + + ssize_t tx = min(*bufsize, region_device_sz(&store)); + *bufsize = rdev_readat(&store, buf, 0, tx); + + if (*bufsize < 0) + return -1; + + return 0; +} + +/* + * Append data to region + * + * Returns 0 on success, -1 on failure + */ +int smmstore_append_data(void *key, uint32_t key_sz, + void *value, uint32_t value_sz) +{ + struct region_device store; + + if (lookup_store(&store) < 0) { + printk(BIOS_WARNING, "reading region failed\n"); + return -1; + } + + ssize_t data_sz = region_device_sz(&store); + + /* scan for end */ + ssize_t end = 0; + uint32_t k_sz, v_sz; + while (end < data_sz) { + /* make odd corner cases identifiable, eg. invalid v_sz */ + k_sz = 0; + + if (rdev_readat(&store, &k_sz, end, sizeof(k_sz)) < 0) { + printk(BIOS_WARNING, "failed reading key size\n"); + return -1; + } + + /* found the end */ + if (k_sz == 0xffffffff) + break; + + /* something is fishy here: + * Avoid wrapping (since data_size < MAX_UINT32_T / 2) while + * other problems are covered by the loop condition + */ + if (k_sz > data_sz) { + printk(BIOS_WARNING, "key size out of bounds\n"); + return -1; + } + + if (rdev_readat(&store, &v_sz, end + 4, sizeof(v_sz)) < 0) { + printk(BIOS_WARNING, "failed reading value size\n"); + return -1; + } + + if (v_sz > data_sz) { + printk(BIOS_WARNING, "value size out of bounds\n"); + return -1; + } + + end += 8 + k_sz + v_sz + 1; + end = ALIGN_UP(end, sizeof(uint32_t)); + } + + printk(BIOS_WARNING, "used smm store size might be 0x%zx bytes\n", end); + + if (k_sz != 0xffffffff) { + printk(BIOS_WARNING, + "eof of data marker looks invalid: 0x%x\n", k_sz); + return -1; + } + + printk(BIOS_WARNING, "used size looks legit\n"); + + printk(BIOS_WARNING, "open (%zx, %zx) for writing\n", + region_device_offset(&store), region_device_sz(&store)); + if (boot_device_rw_subregion(&store.region, &store) < 0) { + printk(BIOS_WARNING, "couldn't open store for writing\n"); + return -1; + } + + uint32_t record_sz = 8 + key_sz + value_sz + 1; + if (end + record_sz >= data_sz) { + printk(BIOS_WARNING, "not enough space for new data\n"); + return -1; + } + + if (rdev_writeat(&store, &key_sz, end, 4) != 4) { + printk(BIOS_WARNING, "failed writing key size\n"); + } + end += 4; + if (rdev_writeat(&store, &value_sz, end, 4) != 4) { + printk(BIOS_WARNING, "failed writing value size\n"); + } + end += 4; + if (rdev_writeat(&store, key, end, key_sz) != key_sz) { + printk(BIOS_WARNING, "failed writing key data\n"); + } + end += key_sz; + if (rdev_writeat(&store, value, end, value_sz) != value_sz) { + printk(BIOS_WARNING, "failed writing value data\n"); + } + end += value_sz; + uint8_t nul = 0; + if (rdev_writeat(&store, &nul, end, 1) != 1) { + printk(BIOS_WARNING, "failed writing termination\n"); + } + + return 0; +} + +/* + * Clear region + * + * Returns 0 on success, -1 on failure, including partial erase + */ +int smmstore_clear_region(void) +{ + struct region_device store; + + if (lookup_store(&store) < 0) { + printk(BIOS_WARNING, "smm store: reading region failed\n"); + return -1; + } + + ssize_t res = rdev_eraseat(&store, 0, region_device_sz(&store)); + if (res != region_device_sz(&store)) { + printk(BIOS_WARNING, "smm store: erasing region failed\n"); + return -1; + } + + return 0; +} |