powerpc/kexec_file: Add helper functions for getting memory ranges

In kexec case, the kernel to be loaded uses the same memory layout as
the running kernel. So, passing on the DT of the running kernel would
be good enough.

But in case of kdump, different memory ranges are needed to manage
loading the kdump kernel, booting into it and exporting the elfcore of
the crashing kernel. The ranges are exclude memory ranges, usable
memory ranges, reserved memory ranges and crash memory ranges.

Exclude memory ranges specify the list of memory ranges to avoid while
loading kdump segments. Usable memory ranges list the memory ranges
that could be used for booting kdump kernel. Reserved memory ranges
list the memory regions for the loading kernel's reserve map. Crash
memory ranges list the memory ranges to be exported as the crashing
kernel's elfcore.

Add helper functions for setting up the above mentioned memory ranges.
This helpers facilitate in understanding the subsequent changes better
and make it easy to setup the different memory ranges listed above, as
and when appropriate.

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/159602279194.575379.8526552316948643550.stgit@hbathini

2 files changed, 236 insertions, 1 deletions

diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
index 67c355329457..4aff6846c772 100644
--- a/arch/powerpc/kexec/Makefile
+++ b/arch/powerpc/kexec/Makefile
@@ -7,7 +7,7 @@ obj-y				+= core.o crash.o core_$(BITS).o
 
 obj-$(CONFIG_PPC32)		+= relocate_32.o
 
-obj-$(CONFIG_KEXEC_FILE)	+= file_load.o file_load_$(BITS).o elf_$(BITS).o
+obj-$(CONFIG_KEXEC_FILE)	+= file_load.o ranges.o file_load_$(BITS).o elf_$(BITS).o
 
 ifdef CONFIG_HAVE_IMA_KEXEC
 ifdef CONFIG_IMA
diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
new file mode 100644
index 000000000000..dc3ce036f416
--- /dev/null
+++ b/arch/powerpc/kexec/ranges.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * powerpc code to implement the kexec_file_load syscall
+ *
+ * Copyright (C) 2004  Adam Litke (agl@us.ibm.com)
+ * Copyright (C) 2004  IBM Corp.
+ * Copyright (C) 2004,2005  Milton D Miller II, IBM Corporation
+ * Copyright (C) 2005  R Sharada (sharada@in.ibm.com)
+ * Copyright (C) 2006  Mohan Kumar M (mohan@in.ibm.com)
+ * Copyright (C) 2020  IBM Corporation
+ *
+ * Based on kexec-tools' kexec-ppc64.c, fs2dt.c.
+ * Heavily modified for the kernel by
+ * Hari Bathini, IBM Corporation.
+ */
+
+#define pr_fmt(fmt) "kexec ranges: " fmt
+
+#include <linux/sort.h>
+#include <linux/kexec.h>
+#include <linux/of_device.h>
+#include <linux/slab.h>
+#include <asm/sections.h>
+#include <asm/kexec_ranges.h>
+
+/**
+ * get_max_nr_ranges - Get the max no. of ranges crash_mem structure
+ *                     could hold, given the size allocated for it.
+ * @size:              Allocation size of crash_mem structure.
+ *
+ * Returns the maximum no. of ranges.
+ */
+static inline unsigned int get_max_nr_ranges(size_t size)
+{
+	return ((size - sizeof(struct crash_mem)) /
+		sizeof(struct crash_mem_range));
+}
+
+/**
+ * get_mem_rngs_size - Get the allocated size of mem_rngs based on
+ *                     max_nr_ranges and chunk size.
+ * @mem_rngs:          Memory ranges.
+ *
+ * Returns the maximum size of @mem_rngs.
+ */
+static inline size_t get_mem_rngs_size(struct crash_mem *mem_rngs)
+{
+	size_t size;
+
+	if (!mem_rngs)
+		return 0;
+
+	size = (sizeof(struct crash_mem) +
+		(mem_rngs->max_nr_ranges * sizeof(struct crash_mem_range)));
+
+	/*
+	 * Memory is allocated in size multiple of MEM_RANGE_CHUNK_SZ.
+	 * So, align to get the actual length.
+	 */
+	return ALIGN(size, MEM_RANGE_CHUNK_SZ);
+}
+
+/**
+ * __add_mem_range - add a memory range to memory ranges list.
+ * @mem_ranges:      Range list to add the memory range to.
+ * @base:            Base address of the range to add.
+ * @size:            Size of the memory range to add.
+ *
+ * (Re)allocates memory, if needed.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int __add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size)
+{
+	struct crash_mem *mem_rngs = *mem_ranges;
+
+	if (!mem_rngs || (mem_rngs->nr_ranges == mem_rngs->max_nr_ranges)) {
+		mem_rngs = realloc_mem_ranges(mem_ranges);
+		if (!mem_rngs)
+			return -ENOMEM;
+	}
+
+	mem_rngs->ranges[mem_rngs->nr_ranges].start = base;
+	mem_rngs->ranges[mem_rngs->nr_ranges].end = base + size - 1;
+	pr_debug("Added memory range [%#016llx - %#016llx] at index %d\n",
+		 base, base + size - 1, mem_rngs->nr_ranges);
+	mem_rngs->nr_ranges++;
+	return 0;
+}
+
+/**
+ * __merge_memory_ranges - Merges the given memory ranges list.
+ * @mem_rngs:              Range list to merge.
+ *
+ * Assumes a sorted range list.
+ *
+ * Returns nothing.
+ */
+static void __merge_memory_ranges(struct crash_mem *mem_rngs)
+{
+	struct crash_mem_range *ranges;
+	int i, idx;
+
+	if (!mem_rngs)
+		return;
+
+	idx = 0;
+	ranges = &(mem_rngs->ranges[0]);
+	for (i = 1; i < mem_rngs->nr_ranges; i++) {
+		if (ranges[i].start <= (ranges[i-1].end + 1))
+			ranges[idx].end = ranges[i].end;
+		else {
+			idx++;
+			if (i == idx)
+				continue;
+
+			ranges[idx] = ranges[i];
+		}
+	}
+	mem_rngs->nr_ranges = idx + 1;
+}
+
+/* cmp_func_t callback to sort ranges with sort() */
+static int rngcmp(const void *_x, const void *_y)
+{
+	const struct crash_mem_range *x = _x, *y = _y;
+
+	if (x->start > y->start)
+		return 1;
+	if (x->start < y->start)
+		return -1;
+	return 0;
+}
+
+/**
+ * sort_memory_ranges - Sorts the given memory ranges list.
+ * @mem_rngs:           Range list to sort.
+ * @merge:              If true, merge the list after sorting.
+ *
+ * Returns nothing.
+ */
+void sort_memory_ranges(struct crash_mem *mem_rngs, bool merge)
+{
+	int i;
+
+	if (!mem_rngs)
+		return;
+
+	/* Sort the ranges in-place */
+	sort(&(mem_rngs->ranges[0]), mem_rngs->nr_ranges,
+	     sizeof(mem_rngs->ranges[0]), rngcmp, NULL);
+
+	if (merge)
+		__merge_memory_ranges(mem_rngs);
+
+	/* For debugging purpose */
+	pr_debug("Memory ranges:\n");
+	for (i = 0; i < mem_rngs->nr_ranges; i++) {
+		pr_debug("\t[%03d][%#016llx - %#016llx]\n", i,
+			 mem_rngs->ranges[i].start,
+			 mem_rngs->ranges[i].end);
+	}
+}
+
+/**
+ * realloc_mem_ranges - reallocate mem_ranges with size incremented
+ *                      by MEM_RANGE_CHUNK_SZ. Frees up the old memory,
+ *                      if memory allocation fails.
+ * @mem_ranges:         Memory ranges to reallocate.
+ *
+ * Returns pointer to reallocated memory on success, NULL otherwise.
+ */
+struct crash_mem *realloc_mem_ranges(struct crash_mem **mem_ranges)
+{
+	struct crash_mem *mem_rngs = *mem_ranges;
+	unsigned int nr_ranges;
+	size_t size;
+
+	size = get_mem_rngs_size(mem_rngs);
+	nr_ranges = mem_rngs ? mem_rngs->nr_ranges : 0;
+
+	size += MEM_RANGE_CHUNK_SZ;
+	mem_rngs = krealloc(*mem_ranges, size, GFP_KERNEL);
+	if (!mem_rngs) {
+		kfree(*mem_ranges);
+		*mem_ranges = NULL;
+		return NULL;
+	}
+
+	mem_rngs->nr_ranges = nr_ranges;
+	mem_rngs->max_nr_ranges = get_max_nr_ranges(size);
+	*mem_ranges = mem_rngs;
+
+	return mem_rngs;
+}
+
+/**
+ * add_mem_range - Updates existing memory range, if there is an overlap.
+ *                 Else, adds a new memory range.
+ * @mem_ranges:    Range list to add the memory range to.
+ * @base:          Base address of the range to add.
+ * @size:          Size of the memory range to add.
+ *
+ * (Re)allocates memory, if needed.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size)
+{
+	struct crash_mem *mem_rngs = *mem_ranges;
+	u64 mstart, mend, end;
+	unsigned int i;
+
+	if (!size)
+		return 0;
+
+	end = base + size - 1;
+
+	if (!mem_rngs || !(mem_rngs->nr_ranges))
+		return __add_mem_range(mem_ranges, base, size);
+
+	for (i = 0; i < mem_rngs->nr_ranges; i++) {
+		mstart = mem_rngs->ranges[i].start;
+		mend = mem_rngs->ranges[i].end;
+		if (base < mend && end > mstart) {
+			if (base < mstart)
+				mem_rngs->ranges[i].start = base;
+			if (end > mend)
+				mem_rngs->ranges[i].end = end;
+			return 0;
+		}
+	}
+
+	return __add_mem_range(mem_ranges, base, size);
+}