libflashrom,writeprotect: add functions for reading/writing WP configs

New functions are exposed through the libflashrom API for
reading/writing chip's WP settins: `flashrom_wp_{read,write}_cfg()`.

They read/write an opaque `struct flashrom_wp_cfg` instance, which
includes the flash protection range and status register protection mode.

This commit also adds `{read,write}_wp_bits()` helper functions that
read/write chip-specific WP configuration bits.

BUG=b:195381327,b:153800563
BRANCH=none
TEST=flashrom --wp-{enable,disable,range,list,status} at end of patch series

Change-Id: I3ad25708c3321b8fb0216c3eaf6ffc07616537ad
Signed-off-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/58479
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

1 files changed, 188 insertions, 0 deletions

diff --git a/writeprotect.c b/writeprotect.c
index cfcb13c2..20b5afcc 100644
--- a/writeprotect.c
+++ b/writeprotect.c
@@ -23,3 +23,191 @@
 #include "libflashrom.h"
 #include "chipdrivers.h"
 #include "writeprotect.h"
+
+/** Read and extract a single bit from the chip's registers */
+static enum flashrom_wp_result read_bit(uint8_t *value, bool *present, struct flashctx *flash, struct reg_bit_info bit)
+{
+	*present = bit.reg != INVALID_REG;
+	if (*present) {
+		if (spi_read_register(flash, bit.reg, value))
+			return FLASHROM_WP_ERR_READ_FAILED;
+		*value = (*value >> bit.bit_index) & 1;
+	} else {
+		/* Zero bit, it may be used by compare_ranges(). */
+		*value = 0;
+	}
+
+	return FLASHROM_WP_OK;
+}
+
+/** Read all WP configuration bits from the chip's registers. */
+static enum flashrom_wp_result read_wp_bits(struct wp_bits *bits, struct flashctx *flash)
+{
+	/*
+	 * For each WP bit that is included in the chip's register layout, read
+	 * the register that contains it, extracts the bit's value, and assign
+	 * it to the appropriate field in the wp_bits structure.
+	 */
+	const struct reg_bit_map *bit_map = &flash->chip->reg_bits;
+	bool ignored;
+	size_t i;
+	enum flashrom_wp_result ret;
+
+	ret = read_bit(&bits->tb,  &bits->tb_bit_present,  flash, bit_map->tb);
+	if (ret != FLASHROM_WP_OK)
+		return ret;
+
+	ret = read_bit(&bits->sec, &bits->sec_bit_present, flash, bit_map->sec);
+	if (ret != FLASHROM_WP_OK)
+		return ret;
+
+	ret = read_bit(&bits->cmp, &bits->cmp_bit_present, flash, bit_map->cmp);
+	if (ret != FLASHROM_WP_OK)
+		return ret;
+
+	ret = read_bit(&bits->srp, &bits->srp_bit_present, flash, bit_map->srp);
+	if (ret != FLASHROM_WP_OK)
+		return ret;
+
+	ret = read_bit(&bits->srl, &bits->srl_bit_present, flash, bit_map->srl);
+	if (ret != FLASHROM_WP_OK)
+		return ret;
+
+	for (i = 0; i < ARRAY_SIZE(bits->bp); i++) {
+		if (bit_map->bp[i].reg == INVALID_REG)
+			break;
+
+		bits->bp_bit_count = i + 1;
+		ret = read_bit(&bits->bp[i], &ignored, flash, bit_map->bp[i]);
+		if (ret != FLASHROM_WP_OK)
+			return ret;
+	}
+
+	return ret;
+}
+
+/** Helper function for write_wp_bits(). */
+static void set_reg_bit(
+		uint8_t *reg_values, uint8_t *write_masks,
+		struct reg_bit_info bit, uint8_t value)
+{
+	if (bit.reg != INVALID_REG) {
+		reg_values[bit.reg] |= value << bit.bit_index;
+		write_masks[bit.reg] |= 1 << bit.bit_index;
+	}
+}
+
+/** Write WP configuration bits to the flash's registers. */
+static enum flashrom_wp_result write_wp_bits(struct flashctx *flash, struct wp_bits bits)
+{
+	size_t i;
+	const struct reg_bit_map *reg_bits = &flash->chip->reg_bits;
+
+	/* Convert wp_bits to register values and write masks */
+	uint8_t reg_values[MAX_REGISTERS] = {0};
+	uint8_t write_masks[MAX_REGISTERS] = {0};
+
+	for (i = 0; i < bits.bp_bit_count; i++)
+		set_reg_bit(reg_values, write_masks, reg_bits->bp[i], bits.bp[i]);
+
+	set_reg_bit(reg_values, write_masks, reg_bits->tb,  bits.tb);
+	set_reg_bit(reg_values, write_masks, reg_bits->sec, bits.sec);
+	set_reg_bit(reg_values, write_masks, reg_bits->cmp, bits.cmp);
+	set_reg_bit(reg_values, write_masks, reg_bits->srp, bits.srp);
+	set_reg_bit(reg_values, write_masks, reg_bits->srl, bits.srl);
+
+	/* Write each register */
+	for (enum flash_reg reg = STATUS1; reg < MAX_REGISTERS; reg++) {
+		if (!write_masks[reg])
+			continue;
+
+		uint8_t value;
+		if (spi_read_register(flash, reg, &value))
+			return FLASHROM_WP_ERR_READ_FAILED;
+
+		value = (value & ~write_masks[reg]) | (reg_values[reg] & write_masks[reg]);
+
+		if (spi_write_register(flash, reg, value))
+			return FLASHROM_WP_ERR_WRITE_FAILED;
+	}
+
+	/* Verify each register */
+	for (enum flash_reg reg = STATUS1; reg < MAX_REGISTERS; reg++) {
+		if (!write_masks[reg])
+			continue;
+
+		uint8_t value;
+		if (spi_read_register(flash, reg, &value))
+			return FLASHROM_WP_ERR_READ_FAILED;
+
+		uint8_t actual = value & write_masks[reg];
+		uint8_t expected = reg_values[reg] & write_masks[reg];
+
+		if (actual != expected)
+			return FLASHROM_WP_ERR_VERIFY_FAILED;
+	}
+
+	return FLASHROM_WP_OK;
+}
+
+static bool chip_supported(struct flashctx *flash)
+{
+	return false;
+}
+
+enum flashrom_wp_result wp_read_cfg(struct flashrom_wp_cfg *cfg, struct flashctx *flash)
+{
+	struct wp_bits bits;
+	enum flashrom_wp_result ret = FLASHROM_WP_OK;
+
+	if (!chip_supported(flash))
+		ret = FLASHROM_WP_ERR_CHIP_UNSUPPORTED;
+
+	if (ret == FLASHROM_WP_OK)
+		ret = read_wp_bits(&bits, flash);
+
+	/* TODO: implement get_wp_range() and get_wp_mode() and call them */
+	/*
+	if (ret == FLASHROM_WP_OK)
+		ret = get_wp_range(&cfg->range, flash, &bits);
+
+	if (ret == FLASHROM_WP_OK)
+		ret = get_wp_mode(&cfg->mode, &bits);
+	*/
+
+	return ret;
+}
+
+enum flashrom_wp_result wp_write_cfg(struct flashctx *flash, const struct flashrom_wp_cfg *cfg)
+{
+	struct wp_bits bits;
+	enum flashrom_wp_result ret = FLASHROM_WP_OK;
+
+	if (!chip_supported(flash))
+		ret = FLASHROM_WP_ERR_CHIP_UNSUPPORTED;
+
+	if (ret == FLASHROM_WP_OK)
+		ret = read_wp_bits(&bits, flash);
+
+	/* Set protection range */
+	/* TODO: implement set_wp_range() and use it */
+	/*
+	if (ret == FLASHROM_WP_OK)
+		ret = set_wp_range(&bits, flash, cfg->range);
+	if (ret == FLASHROM_WP_OK)
+		ret = write_wp_bits(flash, bits);
+	*/
+
+	/* Set protection mode */
+	/* TODO: implement set_wp_mode() and use it */
+	/*
+	if (ret == FLASHROM_WP_OK)
+		ret = set_wp_mode(&bits, cfg->mode);
+	*/
+	if (ret == FLASHROM_WP_OK)
+		ret = write_wp_bits(flash, bits);
+
+	return ret;
+}
+
+/** @} */ /* end flashrom-wp */