powerpc/pseries: Implement signed update for PLPKS objects

The Platform Keystore provides a signed update interface which can be used
to create, replace or append to certain variables in the PKS in a secure
fashion, with the hypervisor requiring that the update be signed using the
Platform Key.

Implement an interface to the H_PKS_SIGNED_UPDATE hcall in the plpks
driver to allow signed updates to PKS objects.

(The plpks driver doesn't need to do any cryptography or otherwise handle
the actual signed variable contents - that will be handled by userspace
tooling.)
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
[ajd: split patch, add timeout handling and misc cleanups]
Co-developed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230210080401.345462-18-ajd@linux.ibm.com

arch/powerpc/include/asm/hvcall.h

@@ -335,6 +335,7 @@
 #define H_RPT_INVALIDATE	0x448
 #define H_SCM_FLUSH		0x44C
 #define H_GET_ENERGY_SCALE_INFO	0x450
+#define H_PKS_SIGNED_UPDATE	0x454
 #define H_WATCHDOG		0x45C
 #define MAX_HCALL_OPCODE	H_WATCHDOG
 

arch/powerpc/include/asm/plpks.h

@@ -68,6 +68,11 @@ struct plpks_var_name_list {
 	struct plpks_var_name varlist[];
 };
 
+/**
+ * Updates the authenticated variable. It expects NULL as the component.
+ */
+int plpks_signed_update_var(struct plpks_var *var, u64 flags);
+
 /**
  * Writes the specified var and its data to PKS.
  * Any caller of PKS driver should present a valid component type for

arch/powerpc/platforms/pseries/plpks.c

@@ -81,6 +81,12 @@ static int pseries_status_to_err(int rc)
 		err = -ENOENT;
 		break;
 	case H_BUSY:
+	case H_LONG_BUSY_ORDER_1_MSEC:
+	case H_LONG_BUSY_ORDER_10_MSEC:
+	case H_LONG_BUSY_ORDER_100_MSEC:
+	case H_LONG_BUSY_ORDER_1_SEC:
+	case H_LONG_BUSY_ORDER_10_SEC:
+	case H_LONG_BUSY_ORDER_100_SEC:
 		err = -EBUSY;
 		break;
 	case H_AUTHORITY:
@@ -184,14 +190,17 @@ static struct label *construct_label(char *component, u8 varos, u8 *name,
 				     u16 namelen)
 {
 	struct label *label;
-	size_t slen;
+	size_t slen = 0;
 
 	if (!name || namelen > PLPKS_MAX_NAME_SIZE)
 		return ERR_PTR(-EINVAL);
 
-	slen = strlen(component);
-	if (component && slen > sizeof(label->attr.prefix))
-		return ERR_PTR(-EINVAL);
+	// Support NULL component for signed updates
+	if (component) {
+		slen = strlen(component);
+		if (slen > sizeof(label->attr.prefix))
+			return ERR_PTR(-EINVAL);
+	}
 
 	// The label structure must not cross a page boundary, so we align to the next power of 2
 	label = kzalloc(roundup_pow_of_two(sizeof(*label)), GFP_KERNEL);
@@ -397,6 +406,61 @@ static int plpks_confirm_object_flushed(struct label *label,
 	return pseries_status_to_err(rc);
 }
 
+int plpks_signed_update_var(struct plpks_var *var, u64 flags)
+{
+	unsigned long retbuf[PLPAR_HCALL9_BUFSIZE] = {0};
+	int rc;
+	struct label *label;
+	struct plpks_auth *auth;
+	u64 continuetoken = 0;
+	u64 timeout = 0;
+
+	if (!var->data || var->datalen <= 0 || var->namelen > PLPKS_MAX_NAME_SIZE)
+		return -EINVAL;
+
+	if (!(var->policy & PLPKS_SIGNEDUPDATE))
+		return -EINVAL;
+
+	// Signed updates need the component to be NULL.
+	if (var->component)
+		return -EINVAL;
+
+	auth = construct_auth(PLPKS_OS_OWNER);
+	if (IS_ERR(auth))
+		return PTR_ERR(auth);
+
+	label = construct_label(var->component, var->os, var->name, var->namelen);
+	if (IS_ERR(label)) {
+		rc = PTR_ERR(label);
+		goto out;
+	}
+
+	do {
+		rc = plpar_hcall9(H_PKS_SIGNED_UPDATE, retbuf,
+				  virt_to_phys(auth), virt_to_phys(label),
+				  label->size, var->policy, flags,
+				  virt_to_phys(var->data), var->datalen,
+				  continuetoken);
+
+		continuetoken = retbuf[0];
+		if (pseries_status_to_err(rc) == -EBUSY) {
+			int delay_ms = get_longbusy_msecs(rc);
+			mdelay(delay_ms);
+			timeout += delay_ms;
+		}
+		rc = pseries_status_to_err(rc);
+	} while (rc == -EBUSY && timeout < PLPKS_MAX_TIMEOUT);
+
+	if (!rc)
+		rc = plpks_confirm_object_flushed(label, auth);
+
+	kfree(label);
+out:
+	kfree(auth);
+
+	return rc;
+}
+
 int plpks_write_var(struct plpks_var var)
 {
 	unsigned long retbuf[PLPAR_HCALL_BUFSIZE] = { 0 };
@@ -443,7 +507,7 @@ int plpks_remove_var(char *component, u8 varos, struct plpks_var_name vname)
 	struct label *label;
 	int rc;
 
-	if (!component || vname.namelen > PLPKS_MAX_NAME_SIZE)
+	if (vname.namelen > PLPKS_MAX_NAME_SIZE)
 		return -EINVAL;
 
 	auth = construct_auth(PLPKS_OS_OWNER);