[Skiboot] [RFC 1/6] core/flash.c: add SECBOOT read and write support

[Eric Richter]

From: Claudio Carvalho <cclaudio at linux.ibm.com>

In secure boot enabled systems, the petitboot linux kernel verifies the
OS kernel against x509 certificates that are wrapped in secure variables
controlled by OPAL. These secure variables are stored in the PNOR SECBOOT
partition, as well as the updates submitted for them using userspace
tools.

This patch adds read and write support to the PNOR SECBOOT partition so
that OPAL can handle the secure variables.

CC: Jeremy Kerr <jk at ozlabs.org>
Signed-off-by: Claudio Carvalho <cclaudio at linux.ibm.com>
---
 core/flash.c       | 130 +++++++++++++++++++++++++++++++++++++++++++++
 include/platform.h |   4 ++
 2 files changed, 134 insertions(+)

diff --git a/core/flash.c b/core/flash.c
index 90189dd6..4de52e3f 100644
--- a/core/flash.c
+++ b/core/flash.c
@@ -50,6 +50,10 @@ static struct lock flash_lock;
 static struct flash *nvram_flash;
 static u32 nvram_offset, nvram_size;
 
+/* secboot-on-flash support */
+static struct flash *secboot_flash;
+static u32 secboot_offset, secboot_size;
+
 bool flash_reserve(void)
 {
 	bool rc = false;
@@ -73,6 +77,91 @@ void flash_release(void)
 	unlock(&flash_lock);
 }
 
+static int flash_secboot_info(uint32_t *total_size)
+{
+	int rc;
+
+	lock(&flash_lock);
+	if (!secboot_flash) {
+		rc = OPAL_HARDWARE;
+	} else if (secboot_flash->busy) {
+		rc = OPAL_BUSY;
+	} else {
+		*total_size = secboot_size;
+		rc = OPAL_SUCCESS;
+	}
+	unlock(&flash_lock);
+
+	return rc;
+}
+
+static int flash_secboot_read(void *dst, uint32_t src, uint32_t len)
+{
+	int rc;
+
+	if (!try_lock(&flash_lock))
+		return OPAL_BUSY;
+
+	if (!secboot_flash) {
+		rc = OPAL_HARDWARE;
+		goto out;
+	}
+
+	if (secboot_flash->busy) {
+		rc = OPAL_BUSY;
+		goto out;
+	}
+
+	if ((src + len) > secboot_size) {
+		prerror("FLASH_SECBOOT: read out of bound (0x%x,0x%x)\n",
+			src, len);
+		rc = OPAL_PARAMETER;
+		goto out;
+	}
+
+	secboot_flash->busy = true;
+	unlock(&flash_lock);
+
+	rc = blocklevel_read(secboot_flash->bl, secboot_offset + src, dst, len);
+
+	lock(&flash_lock);
+	secboot_flash->busy = false;
+out:
+	unlock(&flash_lock);
+	return rc;
+}
+
+static int flash_secboot_write(uint32_t dst, void *src, uint32_t len)
+{
+	int rc;
+
+	if (!try_lock(&flash_lock))
+		return OPAL_BUSY;
+
+	if (secboot_flash->busy) {
+		rc = OPAL_BUSY;
+		goto out;
+	}
+
+	if ((dst + len) > secboot_size) {
+		prerror("FLASH_SECBOOT: write out of bound (0x%x,0x%x)\n",
+			dst, len);
+		rc = OPAL_PARAMETER;
+		goto out;
+	}
+
+	secboot_flash->busy = true;
+	unlock(&flash_lock);
+
+	rc = blocklevel_write(secboot_flash->bl, secboot_offset + dst, src, len);
+
+	lock(&flash_lock);
+	secboot_flash->busy = false;
+out:
+	unlock(&flash_lock);
+	return rc;
+}
+
 static int flash_nvram_info(uint32_t *total_size)
 {
 	int rc;
@@ -162,6 +251,46 @@ out:
 	return rc;
 }
 
+
+static int flash_secboot_probe(struct flash *flash, struct ffs_handle *ffs)
+{
+	uint32_t start, size, part;
+	bool ecc;
+	int rc;
+
+	prlog(PR_INFO, "FLASH: probing for SECBOOT\n");
+
+	rc = ffs_lookup_part(ffs, "SECBOOT", &part);
+	if (rc) {
+		prlog(PR_WARNING, "FLASH: no SECBOOT partition found\n");
+		return OPAL_HARDWARE;
+	}
+
+	rc = ffs_part_info(ffs, part, NULL,
+			   &start, &size, NULL, &ecc);
+	if (rc) {
+		/**
+		 * @fwts-label SECBOOTNoPartition
+		 * @fwts-advice OPAL could not find an SECBOOT partition
+		 *     on the system flash. Check that the system flash
+		 *     has a valid partition table, and that the firmware
+		 *     build process has added a SECBOOT partition.
+		 */
+		prlog(PR_ERR, "FLASH: Can't parse ffs info for SECBOOT\n");
+		return OPAL_HARDWARE;
+	}
+
+	secboot_flash = flash;
+	secboot_offset = start;
+	secboot_size = ecc ? ecc_buffer_size_minus_ecc(size) : size;
+
+	platform.secboot_info = flash_secboot_info;
+	platform.secboot_read = flash_secboot_read;
+	platform.secboot_write = flash_secboot_write;
+
+	return 0;
+}
+
 static int flash_nvram_probe(struct flash *flash, struct ffs_handle *ffs)
 {
 	uint32_t start, size, part;
@@ -255,6 +384,7 @@ static void setup_system_flash(struct flash *flash, struct dt_node *node,
 	prlog(PR_INFO, "FLASH: registered system flash device %s\n", name);
 
 	flash_nvram_probe(flash, ffs);
+	flash_secboot_probe(flash, ffs);
 }
 
 static int num_flashes(void)
diff --git a/include/platform.h b/include/platform.h
index de4638f3..0cc9c234 100644
--- a/include/platform.h
+++ b/include/platform.h
@@ -181,6 +181,10 @@ struct platform {
 					    uint32_t len);
 	int		(*nvram_write)(uint32_t dst, void *src, uint32_t len);
 
+	int (*secboot_info)(uint32_t *total_size);
+	int (*secboot_read)(void *dst, uint32_t src, uint32_t len);
+	int (*secboot_write)(uint32_t dst, void *src, uint32_t len);
+
 	/*
 	 * OCC timeout. This return how long we should wait for the OCC
 	 * before timing out. This lets us use a high value on larger FSP
-- 
2.17.2