What: /sys/firmware/secvar/vars/<variable name>
Date: August 2019
diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c
b/arch/powerpc/platforms/pseries/plpks-secvar.c
index 257fd1f8bc19..767e5e8c6990 100644
--- a/arch/powerpc/platforms/pseries/plpks-secvar.c
+++ b/arch/powerpc/platforms/pseries/plpks-secvar.c
@@ -152,39 +152,55 @@ static int plpks_set_variable(const char *key,
u64 key_len, u8 *data,
return rc;
}
-// PLPKS dynamic secure boot doesn't give us a format string in the
same way OPAL does.
-// Instead, report the format using the SB_VERSION variable in the
keystore.
-// The string is made up by us, and takes the form "ibm,plpks-sb-
v<n>" (or "ibm,plpks-sb-unknown"
-// if the SB_VERSION variable doesn't exist). Hypervisor defines the
SB_VERSION variable as a
-// "1 byte unsigned integer value".
-static ssize_t plpks_secvar_format(char *buf, size_t bufsize)
+/*
+ * Return the key management mode.
+ *
+ * SB_VERSION is defined as a "1 byte unsigned integer value",
taking values
+ * starting from 1. It is owned by the Partition Firmware and its
presence
+ * indicates that the key management mode is dynamic. Any failure in
+ * reading SB_VERSION defaults the key management mode to static.
The error
+ * codes -ENOENT or -EPERM are expected in static key management
mode. An
+ * unexpected error code will have to be investigated. Only signed
variables
+ * have null bytes in their names, SB_VERSION does not.
+ *
+ * Return 0 to indicate that the key management mode is static.
Otherwise
+ * return the SB_VERSION value to indicate that the key management
mode is
+ * dynamic.
+ */
+static u8 plpks_get_sb_keymgmt_mode(void)
{
- struct plpks_var var = {0};
- ssize_t ret;
- u8 version;
-
- var.component = NULL;
- // Only the signed variables have null bytes in their names,
this one doesn't
- var.name = "SB_VERSION";
- var.namelen = strlen(var.name);
- var.datalen = 1;
- var.data = &version;
-
- // Unlike the other vars, SB_VERSION is owned by firmware
instead of the OS
- ret = plpks_read_fw_var(&var);
- if (ret) {
- if (ret == -ENOENT) {
- ret = snprintf(buf, bufsize, "ibm,plpks-sb-
unknown");
- } else {
- pr_err("Error %ld reading SB_VERSION from
firmware\n", ret);
- ret = -EIO;
- }
- goto err;
+ u8 mode;
+ ssize_t rc;
+ struct plpks_var var = {
+ .component = NULL,
+ .name = "SB_VERSION",
+ .namelen = 10,
+ .datalen = 1,
+ .data = &mode,
+ };
+
+ rc = plpks_read_fw_var(&var);
+ if (rc) {
+ if (rc != -ENOENT && rc != -EPERM)
+ pr_info("Error %ld reading SB_VERSION from
firmware\n", rc);
+ mode = 0;
}
+ return mode;
+}
- ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version);
-err:
- return ret;
+/*
+ * PLPKS dynamic secure boot doesn't give us a format string in the
same way
+ * OPAL does. Instead, report the format using the SB_VERSION
variable in the
+ * keystore. The string, made up by us, takes the form of either
+ * "ibm,plpks-sb-v<n>" or "ibm,plpks-sb-v0", based on the key
management mode,
+ * and return the length of the secvar format property.
+ */
+static ssize_t plpks_secvar_format(char *buf, size_t bufsize)
+{
+ u8 mode;
+
+ mode = plpks_get_sb_keymgmt_mode();
+ return snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", mode);
}
static int plpks_max_size(u64 *max_size)
