Re: [RESEND PATCH v5 03/11] powerpc/kexec_file: add helper functions for getting memory ranges

Michael Ellerman
2020-07-28T12:58:29Z

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