powerpc/kexec_file: Restrict memory usage of kdump kernel

Kdump kernel, used for capturing the kernel core image, is supposed
to use only specific memory regions to avoid corrupting the image to
be captured. The regions are crashkernel range - the memory reserved
explicitly for kdump kernel, memory used for the tce-table, the OPAL
region and RTAS region as applicable. Restrict kdump kernel memory
to use only these regions by setting up usable-memory DT property.
Also, tell the kdump kernel to run at the loaded address by setting
the magic word at 0x5c.
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Tested-by: Pingfan Liu <piliu@redhat.com>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/159602284284.575379.6962016255404325493.stgit@hbathini

arch/powerpc/kexec/file_load_64.c

@@ -17,9 +17,23 @@
 #include <linux/kexec.h>
 #include <linux/of_fdt.h>
 #include <linux/libfdt.h>
+#include <linux/of_device.h>
 #include <linux/memblock.h>
+#include <linux/slab.h>
+#include <asm/drmem.h>
 #include <asm/kexec_ranges.h>
 
+struct umem_info {
+	u64 *buf;		/* data buffer for usable-memory property */
+	u32 size;		/* size allocated for the data buffer */
+	u32 max_entries;	/* maximum no. of entries */
+	u32 idx;		/* index of current entry */
+
+	/* usable memory ranges to look up */
+	unsigned int nr_ranges;
+	const struct crash_mem_range *ranges;
+};
+
 const struct kexec_file_ops * const kexec_file_loaders[] = {
 	&kexec_elf64_ops,
 	NULL
@@ -74,6 +88,44 @@ static int get_exclude_memory_ranges(struct crash_mem **mem_ranges)
 	return ret;
 }
 
+/**
+ * get_usable_memory_ranges - Get usable memory ranges. This list includes
+ *                            regions like crashkernel, opal/rtas & tce-table,
+ *                            that kdump kernel could use.
+ * @mem_ranges:               Range list to add the memory ranges to.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int get_usable_memory_ranges(struct crash_mem **mem_ranges)
+{
+	int ret;
+
+	/*
+	 * Early boot failure observed on guests when low memory (first memory
+	 * block?) is not added to usable memory. So, add [0, crashk_res.end]
+	 * instead of [crashk_res.start, crashk_res.end] to workaround it.
+	 * Also, crashed kernel's memory must be added to reserve map to
+	 * avoid kdump kernel from using it.
+	 */
+	ret = add_mem_range(mem_ranges, 0, crashk_res.end + 1);
+	if (ret)
+		goto out;
+
+	ret = add_rtas_mem_range(mem_ranges);
+	if (ret)
+		goto out;
+
+	ret = add_opal_mem_range(mem_ranges);
+	if (ret)
+		goto out;
+
+	ret = add_tce_mem_ranges(mem_ranges);
+out:
+	if (ret)
+		pr_err("Failed to setup usable memory ranges\n");
+	return ret;
+}
+
 /**
  * __locate_mem_hole_top_down - Looks top down for a large enough memory hole
  *                              in the memory regions between buf_min & buf_max
@@ -273,6 +325,286 @@ static int locate_mem_hole_bottom_up_ppc64(struct kexec_buf *kbuf,
 	return ret;
 }
 
+/**
+ * check_realloc_usable_mem - Reallocate buffer if it can't accommodate entries
+ * @um_info:                  Usable memory buffer and ranges info.
+ * @cnt:                      No. of entries to accommodate.
+ *
+ * Frees up the old buffer if memory reallocation fails.
+ *
+ * Returns buffer on success, NULL on error.
+ */
+static u64 *check_realloc_usable_mem(struct umem_info *um_info, int cnt)
+{
+	u32 new_size;
+	u64 *tbuf;
+
+	if ((um_info->idx + cnt) <= um_info->max_entries)
+		return um_info->buf;
+
+	new_size = um_info->size + MEM_RANGE_CHUNK_SZ;
+	tbuf = krealloc(um_info->buf, new_size, GFP_KERNEL);
+	if (tbuf) {
+		um_info->buf = tbuf;
+		um_info->size = new_size;
+		um_info->max_entries = (um_info->size / sizeof(u64));
+	}
+
+	return tbuf;
+}
+
+/**
+ * add_usable_mem - Add the usable memory ranges within the given memory range
+ *                  to the buffer
+ * @um_info:        Usable memory buffer and ranges info.
+ * @base:           Base address of memory range to look for.
+ * @end:            End address of memory range to look for.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int add_usable_mem(struct umem_info *um_info, u64 base, u64 end)
+{
+	u64 loc_base, loc_end;
+	bool add;
+	int i;
+
+	for (i = 0; i < um_info->nr_ranges; i++) {
+		add = false;
+		loc_base = um_info->ranges[i].start;
+		loc_end = um_info->ranges[i].end;
+		if (loc_base >= base && loc_end <= end)
+			add = true;
+		else if (base < loc_end && end > loc_base) {
+			if (loc_base < base)
+				loc_base = base;
+			if (loc_end > end)
+				loc_end = end;
+			add = true;
+		}
+
+		if (add) {
+			if (!check_realloc_usable_mem(um_info, 2))
+				return -ENOMEM;
+
+			um_info->buf[um_info->idx++] = cpu_to_be64(loc_base);
+			um_info->buf[um_info->idx++] =
+					cpu_to_be64(loc_end - loc_base + 1);
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * kdump_setup_usable_lmb - This is a callback function that gets called by
+ *                          walk_drmem_lmbs for every LMB to set its
+ *                          usable memory ranges.
+ * @lmb:                    LMB info.
+ * @usm:                    linux,drconf-usable-memory property value.
+ * @data:                   Pointer to usable memory buffer and ranges info.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int kdump_setup_usable_lmb(struct drmem_lmb *lmb, const __be32 **usm,
+				  void *data)
+{
+	struct umem_info *um_info;
+	int tmp_idx, ret;
+	u64 base, end;
+
+	/*
+	 * kdump load isn't supported on kernels already booted with
+	 * linux,drconf-usable-memory property.
+	 */
+	if (*usm) {
+		pr_err("linux,drconf-usable-memory property already exists!");
+		return -EINVAL;
+	}
+
+	um_info = data;
+	tmp_idx = um_info->idx;
+	if (!check_realloc_usable_mem(um_info, 1))
+		return -ENOMEM;
+
+	um_info->idx++;
+	base = lmb->base_addr;
+	end = base + drmem_lmb_size() - 1;
+	ret = add_usable_mem(um_info, base, end);
+	if (!ret) {
+		/*
+		 * Update the no. of ranges added. Two entries (base & size)
+		 * for every range added.
+		 */
+		um_info->buf[tmp_idx] =
+				cpu_to_be64((um_info->idx - tmp_idx - 1) / 2);
+	}
+
+	return ret;
+}
+
+#define NODE_PATH_LEN		256
+/**
+ * add_usable_mem_property - Add usable memory property for the given
+ *                           memory node.
+ * @fdt:                     Flattened device tree for the kdump kernel.
+ * @dn:                      Memory node.
+ * @um_info:                 Usable memory buffer and ranges info.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int add_usable_mem_property(void *fdt, struct device_node *dn,
+				   struct umem_info *um_info)
+{
+	int n_mem_addr_cells, n_mem_size_cells, node;
+	char path[NODE_PATH_LEN];
+	int i, len, ranges, ret;
+	const __be32 *prop;
+	u64 base, end;
+
+	of_node_get(dn);
+
+	if (snprintf(path, NODE_PATH_LEN, "%pOF", dn) > (NODE_PATH_LEN - 1)) {
+		pr_err("Buffer (%d) too small for memory node: %pOF\n",
+		       NODE_PATH_LEN, dn);
+		return -EOVERFLOW;
+	}
+	pr_debug("Memory node path: %s\n", path);
+
+	/* Now that we know the path, find its offset in kdump kernel's fdt */
+	node = fdt_path_offset(fdt, path);
+	if (node < 0) {
+		pr_err("Malformed device tree: error reading %s\n", path);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Get the address & size cells */
+	n_mem_addr_cells = of_n_addr_cells(dn);
+	n_mem_size_cells = of_n_size_cells(dn);
+	pr_debug("address cells: %d, size cells: %d\n", n_mem_addr_cells,
+		 n_mem_size_cells);
+
+	um_info->idx  = 0;
+	if (!check_realloc_usable_mem(um_info, 2)) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	prop = of_get_property(dn, "reg", &len);
+	if (!prop || len <= 0) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * "reg" property represents sequence of (addr,size) tuples
+	 * each representing a memory range.
+	 */
+	ranges = (len >> 2) / (n_mem_addr_cells + n_mem_size_cells);
+
+	for (i = 0; i < ranges; i++) {
+		base = of_read_number(prop, n_mem_addr_cells);
+		prop += n_mem_addr_cells;
+		end = base + of_read_number(prop, n_mem_size_cells) - 1;
+		prop += n_mem_size_cells;
+
+		ret = add_usable_mem(um_info, base, end);
+		if (ret)
+			goto out;
+	}
+
+	/*
+	 * No kdump kernel usable memory found in this memory node.
+	 * Write (0,0) tuple in linux,usable-memory property for
+	 * this region to be ignored.
+	 */
+	if (um_info->idx == 0) {
+		um_info->buf[0] = 0;
+		um_info->buf[1] = 0;
+		um_info->idx = 2;
+	}
+
+	ret = fdt_setprop(fdt, node, "linux,usable-memory", um_info->buf,
+			  (um_info->idx * sizeof(u64)));
+
+out:
+	of_node_put(dn);
+	return ret;
+}
+
+
+/**
+ * update_usable_mem_fdt - Updates kdump kernel's fdt with linux,usable-memory
+ *                         and linux,drconf-usable-memory DT properties as
+ *                         appropriate to restrict its memory usage.
+ * @fdt:                   Flattened device tree for the kdump kernel.
+ * @usable_mem:            Usable memory ranges for kdump kernel.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int update_usable_mem_fdt(void *fdt, struct crash_mem *usable_mem)
+{
+	struct umem_info um_info;
+	struct device_node *dn;
+	int node, ret = 0;
+
+	if (!usable_mem) {
+		pr_err("Usable memory ranges for kdump kernel not found\n");
+		return -ENOENT;
+	}
+
+	node = fdt_path_offset(fdt, "/ibm,dynamic-reconfiguration-memory");
+	if (node == -FDT_ERR_NOTFOUND)
+		pr_debug("No dynamic reconfiguration memory found\n");
+	else if (node < 0) {
+		pr_err("Malformed device tree: error reading /ibm,dynamic-reconfiguration-memory.\n");
+		return -EINVAL;
+	}
+
+	um_info.buf  = NULL;
+	um_info.size = 0;
+	um_info.max_entries = 0;
+	um_info.idx  = 0;
+	/* Memory ranges to look up */
+	um_info.ranges = &(usable_mem->ranges[0]);
+	um_info.nr_ranges = usable_mem->nr_ranges;
+
+	dn = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
+	if (dn) {
+		ret = walk_drmem_lmbs(dn, &um_info, kdump_setup_usable_lmb);
+		of_node_put(dn);
+
+		if (ret) {
+			pr_err("Could not setup linux,drconf-usable-memory property for kdump\n");
+			goto out;
+		}
+
+		ret = fdt_setprop(fdt, node, "linux,drconf-usable-memory",
+				  um_info.buf, (um_info.idx * sizeof(u64)));
+		if (ret) {
+			pr_err("Failed to update fdt with linux,drconf-usable-memory property");
+			goto out;
+		}
+	}
+
+	/*
+	 * Walk through each memory node and set linux,usable-memory property
+	 * for the corresponding node in kdump kernel's fdt.
+	 */
+	for_each_node_by_type(dn, "memory") {
+		ret = add_usable_mem_property(fdt, dn, &um_info);
+		if (ret) {
+			pr_err("Failed to set linux,usable-memory property for %s node",
+			       dn->full_name);
+			goto out;
+		}
+	}
+
+out:
+	kfree(um_info.buf);
+	return ret;
+}
+
 /**
  * setup_purgatory_ppc64 - initialize PPC64 specific purgatory's global
  *                         variables and call setup_purgatory() to initialize
@@ -293,6 +625,25 @@ int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
 
 	ret = setup_purgatory(image, slave_code, fdt, kernel_load_addr,
 			      fdt_load_addr);
+	if (ret)
+		goto out;
+
+	if (image->type == KEXEC_TYPE_CRASH) {
+		u32 my_run_at_load = 1;
+
+		/*
+		 * Tell relocatable kernel to run at load address
+		 * via the word meant for that at 0x5c.
+		 */
+		ret = kexec_purgatory_get_set_symbol(image, "run_at_load",
+						     &my_run_at_load,
+						     sizeof(my_run_at_load),
+						     false);
+		if (ret)
+			goto out;
+	}
+
+out:
 	if (ret)
 		pr_err("Failed to setup purgatory symbols");
 	return ret;
@@ -314,7 +665,40 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt,
 			unsigned long initrd_load_addr,
 			unsigned long initrd_len, const char *cmdline)
 {
-	return setup_new_fdt(image, fdt, initrd_load_addr, initrd_len, cmdline);
+	struct crash_mem *umem = NULL;
+	int ret;
+
+	ret = setup_new_fdt(image, fdt, initrd_load_addr, initrd_len, cmdline);
+	if (ret)
+		goto out;
+
+	/*
+	 * Restrict memory usage for kdump kernel by setting up
+	 * usable memory ranges.
+	 */
+	if (image->type == KEXEC_TYPE_CRASH) {
+		ret = get_usable_memory_ranges(&umem);
+		if (ret)
+			goto out;
+
+		ret = update_usable_mem_fdt(fdt, umem);
+		if (ret) {
+			pr_err("Error setting up usable-memory property for kdump kernel\n");
+			goto out;
+		}
+
+		/* Ensure we don't touch crashed kernel's memory */
+		ret = fdt_add_mem_rsv(fdt, 0, crashk_res.start);
+		if (ret) {
+			pr_err("Error reserving crash memory: %s\n",
+			       fdt_strerror(ret));
+			goto out;
+		}
+	}
+
+out:
+	kfree(umem);
+	return ret;
 }
 
 /**