powerpc/pseries: Pass PLPKS password on kexec

Before interacting with the PLPKS, we ask the hypervisor to generate a
password for the current boot, which is then required for most further
PLPKS operations.

If we kexec into a new kernel, the new kernel will try and fail to
generate a new password, as the password has already been set.

Pass the password through to the new kernel via the device tree, in
/chosen/ibm,plpks-pw. Check for the presence of this property before
trying to generate a new password - if it exists, use the existing
password and remove it from the device tree.

This only works with the kexec_file_load() syscall, not the older
kexec_load() syscall, however if you're using Secure Boot then you want
to be using kexec_file_load() anyway.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230210080401.345462-24-ajd@linux.ibm.com

1 files changed, 13 insertions, 5 deletions

diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index 9be3e818a240..ab80c492da31 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -28,6 +28,7 @@
 #include <asm/crashdump-ppc64.h>
 #include <asm/mmzone.h>
 #include <asm/prom.h>
+#include <asm/plpks.h>
 
 struct umem_info {
 	u64 *buf;		/* data buffer for usable-memory property */
@@ -978,12 +979,17 @@ static unsigned int cpu_node_size(void)
  */
 unsigned int kexec_extra_fdt_size_ppc64(struct kimage *image)
 {
-	unsigned int cpu_nodes, extra_size;
+	unsigned int cpu_nodes, extra_size = 0;
 	struct device_node *dn;
 	u64 usm_entries;
 
+	// Budget some space for the password blob. There's already extra space
+	// for the key name
+	if (plpks_is_available())
+		extra_size += (unsigned int)plpks_get_passwordlen();
+
 	if (image->type != KEXEC_TYPE_CRASH)
-		return 0;
+		return extra_size;
 
 	/*
 	 * For kdump kernel, account for linux,usable-memory and
@@ -993,9 +999,7 @@ unsigned int kexec_extra_fdt_size_ppc64(struct kimage *image)
 	if (drmem_lmb_size()) {
 		usm_entries = ((memory_hotplug_max() / drmem_lmb_size()) +
 			       (2 * (resource_size(&crashk_res) / drmem_lmb_size())));
-		extra_size = (unsigned int)(usm_entries * sizeof(u64));
-	} else {
-		extra_size = 0;
+		extra_size += (unsigned int)(usm_entries * sizeof(u64));
 	}
 
 	/*
@@ -1234,6 +1238,10 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt,
 		}
 	}
 
+	// If we have PLPKS active, we need to provide the password to the new kernel
+	if (plpks_is_available())
+		ret = plpks_populate_fdt(fdt);
+
 out:
 	kfree(rmem);
 	kfree(umem);