[RESEND,v5,03/11] 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>
---

v4 -> v5:
* Added Reviewed-by tag from Thiago.
* Added the missing "#ifdef CONFIG_PPC_BOOK3S_64" around add_htab_mem_range()
  function in arch/powerpc/kexec/ranges.c file.
* add_tce_mem_ranges() function returned error when tce table is not found
  in a pci node. This is wrong as pci nodes may not always have tce tables
  (KVM guests, for example). Fixed it by ignoring error in reading tce
  table base/size while returning from the function.

v3 -> v4:
* Updated sort_memory_ranges() function to reuse sort() from lib/sort.c
  and addressed other review comments from Thiago.

v2 -> v3:
* Unchanged. Added Tested-by tag from Pingfan.

v1 -> v2:
* Added an option to merge ranges while sorting to minimize reallocations
  for memory ranges list.
* Dropped within_crashkernel option for add_opal_mem_range() &
  add_rtas_mem_range() as it is not really needed.


 arch/powerpc/include/asm/kexec_ranges.h |   25 ++
 arch/powerpc/kexec/Makefile             |    2 
 arch/powerpc/kexec/ranges.c             |  417 +++++++++++++++++++++++++++++++
 3 files changed, 443 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/include/asm/kexec_ranges.h
 create mode 100644 arch/powerpc/kexec/ranges.c

Hi Hari,

Some comments inline ...

Hari Bathini <hbathini@linux.ibm.com> writes:
> diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
> new file mode 100644
> index 000000000000..21bea1b78443
> --- /dev/null
> +++ b/arch/powerpc/kexec/ranges.c
> @@ -0,0 +1,417 @@
> +// 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 <hbathini@linux.ibm.com>.

Please just use your name, email addresses bit rot. It's in the commit
log anyway.

> + */
> +
> +#undef DEBUG
    ^
Dont do that in new code please.

> +#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 mrngs based on
> + *                     max_nr_ranges and chunk size.
> + * @mrngs:             Memory ranges.

mrngs is not a great name, what about memory_ranges or ranges?

Ditto everywhere else you use mrngs.

> + *
> + * Returns the maximum size of @mrngs.
> + */
> +static inline size_t get_mem_rngs_size(struct crash_mem *mrngs)
> +{
> +	size_t size;
> +
> +	if (!mrngs)
> +		return 0;
> +
> +	size = (sizeof(struct crash_mem) +
> +		(mrngs->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 *mrngs = *mem_ranges;
> +
> +	if ((mrngs == NULL) || (mrngs->nr_ranges == mrngs->max_nr_ranges)) {

(mrngs == NULL) should just be !mrngs.

> +		mrngs = realloc_mem_ranges(mem_ranges);
> +		if (!mrngs)
> +			return -ENOMEM;
> +	}
> +
> +	mrngs->ranges[mrngs->nr_ranges].start = base;
> +	mrngs->ranges[mrngs->nr_ranges].end = base + size - 1;
> +	pr_debug("Added memory range [%#016llx - %#016llx] at index %d\n",
> +		 base, base + size - 1, mrngs->nr_ranges);
> +	mrngs->nr_ranges++;
> +	return 0;
> +}
> +
> +/**
> + * __merge_memory_ranges - Merges the given memory ranges list.
> + * @mem_ranges:            Range list to merge.
> + *
> + * Assumes a sorted range list.
> + *
> + * Returns nothing.
> + */

A lot of this code is annoyingly similar to the memblock code, though
the internals of that are all static these days.

I guess for now we'll just have to add all this. Maybe in future it can
be consolidated.

> +static void __merge_memory_ranges(struct crash_mem *mrngs)
> +{
> +	struct crash_mem_range *rngs;
> +	int i, idx;
> +
> +	if (!mrngs)
> +		return;
> +
> +	idx = 0;
> +	rngs = &mrngs->ranges[0];
> +	for (i = 1; i < mrngs->nr_ranges; i++) {
> +		if (rngs[i].start <= (rngs[i-1].end + 1))
> +			rngs[idx].end = rngs[i].end;
> +		else {
> +			idx++;
> +			if (i == idx)
> +				continue;
> +
> +			rngs[idx] = rngs[i];
> +		}
> +	}
> +	mrngs->nr_ranges = idx + 1;
> +}
> +
> +/**
> + * 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 *mrngs = *mem_ranges;
> +	unsigned int nr_ranges;
> +	size_t size;
> +
> +	size = get_mem_rngs_size(mrngs);
> +	nr_ranges = mrngs ? mrngs->nr_ranges : 0;
> +
> +	size += MEM_RANGE_CHUNK_SZ;
> +	mrngs = krealloc(*mem_ranges, size, GFP_KERNEL);
> +	if (!mrngs) {
> +		kfree(*mem_ranges);
> +		*mem_ranges = NULL;
> +		return NULL;
> +	}
> +
> +	mrngs->nr_ranges = nr_ranges;
> +	mrngs->max_nr_ranges = get_max_nr_ranges(size);
> +	*mem_ranges = mrngs;
> +
> +	return mrngs;
> +}
> +
> +/**
> + * 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 *mrngs = *mem_ranges;
> +	u64 mstart, mend, end;
> +	unsigned int i;
> +
> +	if (!size)
> +		return 0;
> +
> +	end = base + size - 1;
> +
> +	if ((mrngs == NULL) || (mrngs->nr_ranges == 0))
> +		return __add_mem_range(mem_ranges, base, size);
> +
> +	for (i = 0; i < mrngs->nr_ranges; i++) {
> +		mstart = mrngs->ranges[i].start;
> +		mend = mrngs->ranges[i].end;
> +		if (base < mend && end > mstart) {
> +			if (base < mstart)
> +				mrngs->ranges[i].start = base;
> +			if (end > mend)
> +				mrngs->ranges[i].end = end;
> +			return 0;
> +		}
> +	}
> +
> +	return __add_mem_range(mem_ranges, base, size);
> +}
> +
> +/**
> + * add_tce_mem_ranges - Adds tce-table range to the given memory ranges list.
> + * @mem_ranges:         Range list to add the memory range(s) to.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int add_tce_mem_ranges(struct crash_mem **mem_ranges)

Not sure this and the other add_foo_mem_ranges() really belong in this patch.

> +{
> +	struct device_node *dn;
> +	int ret = 0;
> +
> +	for_each_node_by_type(dn, "pci") {
> +		u64 base;
> +		u32 size;
> +		int rc;

Do you really need ret and rc?

> +		/*
> +		 * It is ok to have pci nodes without tce. So, ignore
> +		 * any read errors here.
> +		 */
> +		rc = of_property_read_u64(dn, "linux,tce-base", &base);
> +		rc |= of_property_read_u32(dn, "linux,tce-size", &size);
> +		if (rc)
> +			continue;
> +
> +		ret = add_mem_range(mem_ranges, base, size);
> +		if (ret)
> +			break;
                        ^
                        dn leaked.
> +	}
> +
> +	return ret;
> +}
> +
> +/**
> + * add_initrd_mem_range - Adds initrd range to the given memory ranges list,
> + *                        if the initrd was retained.
> + * @mem_ranges:           Range list to add the memory range to.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int add_initrd_mem_range(struct crash_mem **mem_ranges)
> +{
> +	u64 base, end;
> +	char *str;
> +	int ret;
> +
> +	/* This range means something only if initrd was retained */
> +	str = strstr(saved_command_line, "retain_initrd");
> +	if (!str)
> +		return 0;

Unfortunate that we have to go and scan the command line again. But I
don't see a better way ATM.

Could be more concise:

	if (!strstr(saved_command_line, "retain_initrd"))
		return 0;

> +
> +	ret = of_property_read_u64(of_chosen, "linux,initrd-start", &base);
> +	ret |= of_property_read_u64(of_chosen, "linux,initrd-end", &end);
> +	if (!ret)
> +		ret = add_mem_range(mem_ranges, base, end - base + 1);
> +	return ret;
> +}
> +
> +#ifdef CONFIG_PPC_BOOK3S_64
> +/**
> + * add_htab_mem_range - Adds htab range to the given memory ranges list,
> + *                      if it exists
> + * @mem_ranges:         Range list to add the memory range to.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int add_htab_mem_range(struct crash_mem **mem_ranges)
> +{
> +	if (!htab_address)
> +		return 0;
> +
> +	return add_mem_range(mem_ranges, __pa(htab_address), htab_size_bytes);
> +}
> +#endif
> +
> +/**
> + * add_kernel_mem_range - Adds kernel text region to the given
> + *                        memory ranges list.
> + * @mem_ranges:           Range list to add the memory range to.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int add_kernel_mem_range(struct crash_mem **mem_ranges)
> +{
> +	return add_mem_range(mem_ranges, 0, __pa(_end));
> +}
> +
> +/**
> + * add_rtas_mem_range - Adds RTAS region to the given memory ranges list.
> + * @mem_ranges:         Range list to add the memory range to.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int add_rtas_mem_range(struct crash_mem **mem_ranges)
> +{
> +	struct device_node *dn;
> +	int ret = 0;
> +
> +	dn = of_find_node_by_path("/rtas");
> +	if (dn) {
> +		u32 base, size;
> +
> +		ret = of_property_read_u32(dn, "linux,rtas-base", &base);
> +		ret |= of_property_read_u32(dn, "rtas-size", &size);
> +		if (ret)
> +			goto out;
> +
> +		ret = add_mem_range(mem_ranges, base, size);
> +	}
> +
> +out:
> +	of_node_put(dn);
> +	return ret;
> +}

Or:
	struct device_node *dn;
        u32 base, size;
	int rc;

	dn = of_find_node_by_path("/rtas");
	if (!dn)
        	return 0;

	rc  = of_property_read_u32(dn, "linux,rtas-base", &base);
	rc |= of_property_read_u32(dn, "rtas-size", &size);
	if (rc == 0)
		rc = add_mem_range(mem_ranges, base, size);

	of_node_put(dn);
	return rc;
}


> +
> +/**
> + * add_opal_mem_range - Adds OPAL region to the given memory ranges list.
> + * @mem_ranges:         Range list to add the memory range to.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int add_opal_mem_range(struct crash_mem **mem_ranges)
> +{
> +	struct device_node *dn;
> +	int ret = 0;
> +
> +	dn = of_find_node_by_path("/ibm,opal");
> +	if (dn) {
> +		u64 base, size;
> +
> +		ret = of_property_read_u64(dn, "opal-base-address", &base);
> +		ret |= of_property_read_u64(dn, "opal-runtime-size", &size);
> +		if (ret)
> +			goto out;
> +
> +		ret = add_mem_range(mem_ranges, base, size);
> +	}
> +
> +out:
> +	of_node_put(dn);
> +	return ret;
> +}
> +
> +/**
> + * add_reserved_ranges - Adds "/reserved-ranges" regions exported by f/w
> + *                       to the given memory ranges list.
> + * @mem_ranges:          Range list to add the memory ranges to.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int add_reserved_ranges(struct crash_mem **mem_ranges)
> +{
> +	int n_mem_addr_cells, n_mem_size_cells, i, len, cells, ret = 0;
> +	const __be32 *prop;
> +
> +	prop = of_get_property(of_root, "reserved-ranges", &len);
> +	if (!prop)
> +		return 0;
> +
> +	of_node_get(of_root);

You shouldn't need to get the root node, you already used it above anyway.

> +	n_mem_addr_cells = of_n_addr_cells(of_root);
> +	n_mem_size_cells = of_n_size_cells(of_root);
> +	cells = n_mem_addr_cells + n_mem_size_cells;
> +
> +	/* Each reserved range is an (address,size) pair */
> +	for (i = 0; i < (len / (sizeof(*prop) * cells)); i++) {
                                       ^
                                       just u32 would be clearer I think.



cheers