Fail immediately when trying to write/erase wp regions

This patch introduces chipset-level protections and adds checks that
abort writing to flash if any of the requested regions are
write-protected by chip, dynamically by a chipset, or are defined as
read-only.

This change is done so it's harder for user to brick his own platform.
Information about read-only regions can easily be missed as flashrom
can output a lot of information on screen. Even if you notice you might
not know if one of the regions you requested falls inside read-only
range, especially if using different names for those regions.
If you are flashing multiple regions or ones that partially overlap with
read-only parts then that could result in flashrom failing in the
middle leaving you in unknown state.

This patch was tested with multiple combinations of
unprotected/protected regions:

- dummy programmer

```sh
flashrom -p dummy:hwwp=yes,emulate=S25FL128L --wp-enable \
  --wp-range 0x00040000,0x00fc0000 \
  -l <(echo '00000000:0004ffff part1') -i part1 -E
```

- internal programmer on Protectli VP6670 with Dasharo UEFI firmware
with locked BIOS boot medium (PR0, part of bios region)

```sh
flashrom -p internal --ifd -i me -i bios -w test.rom
```

Normal reads and flashing non-protected regions was also tested.

Change-Id: Ia0dd847923e20ff0081ceae68984369e98952c2f
Signed-off-by: Michał Iwanicki <michal.iwanicki@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/89222
Reviewed-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>

doc/release_notes/devel.rst

@@ -23,3 +23,18 @@ Added support
 * Intel Wildcat Lake chipset
 * Eon EN25QX128A
 * PUYA P25D80H
+
+New features
+============
+
+Fail immediately when trying to write/erase wp regions
+------------------------------------------------------
+
+This change is done so it's harder for user to brick his own platform.
+Information about read-only regions can easily be missed as flashrom
+can output a lot of information on screen. Even if you notice you might
+not know if one of the regions you requested falls inside read-only
+range, especially if using different names for those regions.
+If you are flashing multiple regions or ones that partially overlap with
+read-only parts then that could result in flashrom failing in the
+middle, leaving you in unknown state.

flashrom.c

@@ -384,6 +384,22 @@ void get_flash_region(const struct flashctx *flash, int addr, struct flash_regio
 	}
 }
 
+void get_protected_ranges(const struct flashctx *flash, struct protected_ranges *ranges) {
+	if ((flash->mst->buses_supported & BUS_PROG) && flash->mst->opaque.get_protected_ranges) {
+		flash->mst->opaque.get_protected_ranges(ranges);
+	} else {
+		*ranges = (const struct protected_ranges){ 0 };
+	}
+}
+
+void release_protected_ranges(const struct flashctx *flash, struct protected_ranges *ranges) {
+	for (int i = 0; i < ranges->count; ++i) {
+		free(ranges->ranges[i].name);
+	}
+	free(ranges->ranges);
+	*ranges = (const struct protected_ranges){ 0 };
+}
+
 int check_for_unwritable_regions(const struct flashctx *flash, unsigned int start, unsigned int len)
 {
 	struct flash_region region;
@@ -1817,6 +1833,58 @@ warn_out:
 	return ret;
 }
 
+static bool can_change_target_regions(struct flashctx *flash) {
+	bool check_wp = false;
+	size_t wp_start, wp_len;
+	enum flashrom_wp_mode mode;
+	struct flashrom_wp_cfg *cfg = NULL;
+	const struct romentry *entry = NULL;
+	const struct flashrom_layout *const layout = get_layout(flash);
+	struct protected_ranges ranges;
+	get_protected_ranges(flash, &ranges);
+
+	if (flashrom_wp_cfg_new(&cfg) == FLASHROM_WP_OK &&
+		flashrom_wp_read_cfg(cfg, flash) == FLASHROM_WP_OK)
+	{
+		flashrom_wp_get_range(&wp_start, &wp_len, cfg);
+		mode = flashrom_wp_get_mode(cfg);
+		if (mode != FLASHROM_WP_MODE_DISABLED && wp_len != 0)
+			check_wp = true;
+	}
+	flashrom_wp_cfg_release(cfg);
+
+	while ((entry = layout_next_included(layout, entry))) {
+		if (!flash->flags.skip_unwritable_regions &&
+			check_for_unwritable_regions(flash, entry->region.start,
+						     entry->region.end - entry->region.start + 1))
+		{
+			release_protected_ranges(flash, &ranges);
+			return false;
+		}
+		if (check_wp && entry->region.start < wp_start + wp_len && wp_start <= entry->region.end) {
+			msg_gerr("%s: cannot fully update %s region (%#08"PRIx32"..%#08"PRIx32")"
+				 " due to chip's write-protection.\n", __func__,
+				 entry->region.name, entry->region.start, entry->region.end);
+			release_protected_ranges(flash, &ranges);
+			return false;
+		}
+		for (int i = 0; i < ranges.count; ++i) {
+			struct flash_region prot = ranges.ranges[i];
+			if (prot.write_prot && prot.start <= entry->region.end &&
+			    prot.end >= entry->region.start) {
+				msg_gerr("%s: cannot fully update %s region (%#08"PRIx32"..%#08"PRIx32")"
+					 " due to chipset write-protection.\n", __func__,
+					 entry->region.name, entry->region.start, entry->region.end);
+				release_protected_ranges(flash, &ranges);
+				return false;
+			}
+		}
+	}
+
+	release_protected_ranges(flash, &ranges);
+	return true;
+}
+
 int prepare_flash_access(struct flashctx *const flash,
 			 const bool read_it, const bool write_it,
 			 const bool erase_it, const bool verify_it)
@@ -1831,6 +1899,13 @@ int prepare_flash_access(struct flashctx *const flash,
 		return 1;
 	}
 
+	if ((write_it || erase_it) && !flash->flags.force) {
+		if (!can_change_target_regions(flash)) {
+			msg_cerr("At least one target region is not fully writable. Aborting.\n");
+			return 1;
+		}
+	}
+
 	if (map_flash(flash) != 0)
 		return 1;
 

ichspi.c

@@ -1287,6 +1287,13 @@ struct hwseq_data {
 	struct fd_region fd_regions[MAX_FD_REGIONS];
 };
 
+#define MAX_PR_REGISTERS 6
+struct flash_region ranges_data[MAX_PR_REGISTERS];
+struct protected_ranges ranges = {
+	.count = 0,
+	.ranges = ranges_data,
+};
+
 static struct hwseq_data *get_hwseq_data_from_context(const struct flashctx *flash)
 {
 	return flash->mst->opaque.data;
@@ -1469,6 +1476,21 @@ static void ich_get_region(const struct flashctx *flash, unsigned int addr, stru
 	region->name = strdup(name);
 }
 
+static void ich_get_protected_ranges(struct protected_ranges *protected_ranges) {
+	protected_ranges->count = ranges.count;
+	protected_ranges->ranges = malloc(sizeof(*ranges.ranges) * ranges.count);
+	for (int i = 0; i < ranges.count; ++i) {
+		if (ranges.ranges[i].name == NULL)
+			protected_ranges->ranges[i].name = strdup("");
+		else
+			protected_ranges->ranges[i].name = strdup(ranges.ranges[i].name);
+		protected_ranges->ranges[i].start = ranges.ranges[i].start;
+		protected_ranges->ranges[i].end = ranges.ranges[i].end;
+		protected_ranges->ranges[i].read_prot = ranges.ranges[i].read_prot;
+		protected_ranges->ranges[i].write_prot = ranges.ranges[i].write_prot;
+	}
+}
+
 /* Given RDID info, return pointer to entry in flashchips[] */
 static const struct flashchip *flash_id_to_entry(uint32_t mfg_id, uint32_t model_id)
 {
@@ -1952,13 +1974,19 @@ static enum ich_access_protection ich9_handle_region_access(struct fd_region *fd
 #define ICH_PR_PERMS(pr)	(((~((pr) >> PR_RP_OFF) & 1) << 0) | \
 				 ((~((pr) >> PR_WP_OFF) & 1) << 1))
 
-static enum ich_access_protection ich9_handle_pr(const size_t reg_pr0, unsigned int i)
+static enum ich_access_protection ich9_handle_pr(const size_t reg_pr0, unsigned int i, struct flash_region *prot)
 {
 	uint8_t off = reg_pr0 + (i * 4);
 	uint32_t pr = mmio_readl(ich_spibar + off);
 	unsigned int rwperms_idx = ICH_PR_PERMS(pr);
 	enum ich_access_protection rwperms = access_perms_to_protection[rwperms_idx];
 
+	prot->name = NULL;
+	prot->start = ICH_FREG_BASE(pr);
+	prot->end = ICH_FREG_LIMIT(pr);
+	prot->write_prot = (rwperms == WRITE_PROT) || (rwperms == LOCKED);
+	prot->read_prot = (rwperms == READ_PROT) || (rwperms == LOCKED);
+
 	/* From 5 on we have GPR registers and start from 0 again. */
 	const char *const prefix = i >= 5 ? "G" : "";
 	if (i >= 5)
@@ -2012,16 +2040,17 @@ static const struct spi_master spi_master_ich = {
 };
 
 static const struct opaque_master opaque_master_ich_hwseq = {
-	.max_data_read	= 64,
-	.max_data_write	= 64,
-	.probe		= ich_hwseq_probe,
-	.read		= ich_hwseq_read,
-	.write		= ich_hwseq_write,
-	.erase		= ich_hwseq_block_erase,
-	.read_register	= ich_hwseq_read_status,
-	.write_register	= ich_hwseq_write_status,
-	.get_region	= ich_get_region,
-	.shutdown	= ich_hwseq_shutdown,
+	.max_data_read		= 64,
+	.max_data_write		= 64,
+	.probe			= ich_hwseq_probe,
+	.read			= ich_hwseq_read,
+	.write			= ich_hwseq_write,
+	.erase			= ich_hwseq_block_erase,
+	.read_register		= ich_hwseq_read_status,
+	.write_register		= ich_hwseq_write_status,
+	.get_region		= ich_get_region,
+	.get_protected_ranges	= ich_get_protected_ranges,
+	.shutdown		= ich_hwseq_shutdown,
 };
 
 static int init_ich7_spi(void *spibar, enum ich_chipset ich_gen)
@@ -2248,7 +2277,13 @@ static int init_ich_default(const struct programmer_cfg *cfg, void *spibar, enum
 		/* if not locked down try to disable PR locks first */
 		if (!ichspi_lock)
 			ich9_set_pr(reg_pr0, i, 0, 0);
-		ich_spi_rw_restricted |= ich9_handle_pr(reg_pr0, i);
+		struct flash_region pr_region = { 0 };
+		enum ich_access_protection rwperms = ich9_handle_pr(reg_pr0, i, &pr_region);
+		ich_spi_rw_restricted |= rwperms;
+		if (rwperms != NO_PROT) {
+			ranges_data[ranges.count] = pr_region;
+			ranges.count += 1;
+		}
 	}
 
 	switch (ich_spi_rw_restricted) {

include/layout.h

@@ -57,6 +57,11 @@ struct romentry {
 	struct flash_region region;
 };
 
+struct protected_ranges {
+	int count;
+	struct flash_region *ranges;
+};
+
 struct flashrom_layout;
 
 struct layout_include_args;
@@ -80,5 +85,11 @@ void prepare_layout_for_extraction(struct flashrom_flashctx *);
 int layout_sanity_checks(const struct flashrom_flashctx *);
 int check_for_unwritable_regions(const struct flashrom_flashctx *flash, unsigned int start, unsigned int len);
 void get_flash_region(const struct flashrom_flashctx *flash, int addr, struct flash_region *region);
+/*
+ * Return chipset-level protections.
+ * ranges parameter has to be freed by the caller with release_protected_ranges
+ */
+void get_protected_ranges(const struct flashrom_flashctx *flash, struct protected_ranges *ranges);
+void release_protected_ranges(const struct flashrom_flashctx *flash, struct protected_ranges *ranges);
 
 #endif /* !__LAYOUT_H__ */

include/programmer.h

@@ -397,6 +397,12 @@ struct opaque_master {
 	enum flashrom_wp_result (*wp_read_cfg)(struct flashrom_wp_cfg *, struct flashctx *);
 	enum flashrom_wp_result (*wp_get_ranges)(struct flashrom_wp_ranges **, struct flashctx *);
 	void (*get_region)(const struct flashctx *flash, unsigned int addr, struct flash_region *region);
+	/*
+	 * Returns chipset-level protections (e.g., when SPI controller refuses
+	 * to pass read/write commands to the flash chip based on chipset's
+	 * configuration)
+	 */
+	void (*get_protected_ranges)(struct protected_ranges *);
 	int (*shutdown)(void *data);
 	void (*delay) (const struct flashctx *flash, unsigned int usecs);
 	void *data;