[PATCH 5.12 308/384] powerpc/kexec_file: Use current CPU info while setting up FDT

From: Greg Kroah-Hartman
Date: Mon May 10 2021 - 08:41:19 EST


From: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>

commit 40c753993e3aad51a12c21233486e2037417a4d6 upstream.

kexec_file_load() uses initial_boot_params in setting up the device tree
for the kernel to be loaded. Though initial_boot_params holds info about
CPUs at the time of boot, it doesn't account for hot added CPUs.

So, kexec'ing with kexec_file_load() syscall leaves the kexec'ed kernel
with inaccurate CPU info.

If kdump kernel is loaded with kexec_file_load() syscall and the system
crashes on a hot added CPU, the capture kernel hangs failing to identify
the boot CPU, with no output.

To avoid this from happening, extract current CPU info from of_root
device node and use it for setting up the fdt in kexec_file_load case.

Fixes: 6ecd0163d360 ("powerpc/kexec_file: Add appropriate regions for memory reserve map")
Cc: stable@xxxxxxxxxxxxxxx # v5.9+
Signed-off-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
Reviewed-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210429060256.199714-1-sourabhjain@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kexec/file_load_64.c | 92 ++++++++++++++++++++++++++++++++++++++
1 file changed, 92 insertions(+)

--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -961,6 +961,93 @@ unsigned int kexec_fdt_totalsize_ppc64(s
}

/**
+ * add_node_props - Reads node properties from device node structure and add
+ * them to fdt.
+ * @fdt: Flattened device tree of the kernel
+ * @node_offset: offset of the node to add a property at
+ * @dn: device node pointer
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int add_node_props(void *fdt, int node_offset, const struct device_node *dn)
+{
+ int ret = 0;
+ struct property *pp;
+
+ if (!dn)
+ return -EINVAL;
+
+ for_each_property_of_node(dn, pp) {
+ ret = fdt_setprop(fdt, node_offset, pp->name, pp->value, pp->length);
+ if (ret < 0) {
+ pr_err("Unable to add %s property: %s\n", pp->name, fdt_strerror(ret));
+ return ret;
+ }
+ }
+ return ret;
+}
+
+/**
+ * update_cpus_node - Update cpus node of flattened device tree using of_root
+ * device node.
+ * @fdt: Flattened device tree of the kernel.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int update_cpus_node(void *fdt)
+{
+ struct device_node *cpus_node, *dn;
+ int cpus_offset, cpus_subnode_offset, ret = 0;
+
+ cpus_offset = fdt_path_offset(fdt, "/cpus");
+ if (cpus_offset < 0 && cpus_offset != -FDT_ERR_NOTFOUND) {
+ pr_err("Malformed device tree: error reading /cpus node: %s\n",
+ fdt_strerror(cpus_offset));
+ return cpus_offset;
+ }
+
+ if (cpus_offset > 0) {
+ ret = fdt_del_node(fdt, cpus_offset);
+ if (ret < 0) {
+ pr_err("Error deleting /cpus node: %s\n", fdt_strerror(ret));
+ return -EINVAL;
+ }
+ }
+
+ /* Add cpus node to fdt */
+ cpus_offset = fdt_add_subnode(fdt, fdt_path_offset(fdt, "/"), "cpus");
+ if (cpus_offset < 0) {
+ pr_err("Error creating /cpus node: %s\n", fdt_strerror(cpus_offset));
+ return -EINVAL;
+ }
+
+ /* Add cpus node properties */
+ cpus_node = of_find_node_by_path("/cpus");
+ ret = add_node_props(fdt, cpus_offset, cpus_node);
+ of_node_put(cpus_node);
+ if (ret < 0)
+ return ret;
+
+ /* Loop through all subnodes of cpus and add them to fdt */
+ for_each_node_by_type(dn, "cpu") {
+ cpus_subnode_offset = fdt_add_subnode(fdt, cpus_offset, dn->full_name);
+ if (cpus_subnode_offset < 0) {
+ pr_err("Unable to add %s subnode: %s\n", dn->full_name,
+ fdt_strerror(cpus_subnode_offset));
+ ret = cpus_subnode_offset;
+ goto out;
+ }
+
+ ret = add_node_props(fdt, cpus_subnode_offset, dn);
+ if (ret < 0)
+ goto out;
+ }
+out:
+ of_node_put(dn);
+ return ret;
+}
+
+/**
* setup_new_fdt_ppc64 - Update the flattend device-tree of the kernel
* being loaded.
* @image: kexec image being loaded.
@@ -1020,6 +1107,11 @@ int setup_new_fdt_ppc64(const struct kim
}
}

+ /* Update cpus nodes information to account hotplug CPUs. */
+ ret = update_cpus_node(fdt);
+ if (ret < 0)
+ goto out;
+
/* Update memory reserve map */
ret = get_reserved_memory_ranges(&rmem);
if (ret)