Hari Bathini <hbath...@linux.ibm.com> writes:
> @@ -968,7 +1040,7 @@ int setup_new_fdt_ppc64(const struct kimage *image, void
> *fdt,
>
> /*
> * Restrict memory usage for kdump kernel by setting up
> - * usable memory ranges.
> + * usable memory ranges and memory reserve map.
> */
> if (image->type == KEXEC_TYPE_CRASH) {
> ret = get_usable_memory_ranges(&umem);
> @@ -980,6 +1052,24 @@ int setup_new_fdt_ppc64(const struct kimage *image,
> void *fdt,
> pr_err("Error setting up usable-memory property for
> kdump kernel\n");
> goto out;
> }
> +
> + ret = fdt_add_mem_rsv(fdt, BACKUP_SRC_START + BACKUP_SRC_SIZE,
> + crashk_res.start - BACKUP_SRC_SIZE);
I believe this answers my question from the other email about how the
crashkernel is prevented from stomping in the crashed kernel's memory,
right? I needed to think for a bit to understand what the above
reservation was protecting. I think it's worth adding a comment.
> + if (ret) {
> + pr_err("Error reserving crash memory: %s\n",
> + fdt_strerror(ret));
> + goto out;
> + }
> + }
> +
> + if (image->arch.backup_start) {
> + ret = fdt_add_mem_rsv(fdt, image->arch.backup_start,
> + BACKUP_SRC_SIZE);
> + if (ret) {
> + pr_err("Error reserving memory for backup: %s\n",
> + fdt_strerror(ret));
> + goto out;
> + }
> }
This is only true for KEXEC_TYPE_CRASH, if I'm following the code
correctly. I think it would be clearer to put the if above inside the if
for KEXEC_TYPE_CRASH to make it clearer.
>
> ret = setup_new_fdt(image, fdt, initrd_load_addr, initrd_len,
<snip>
> diff --git a/arch/powerpc/purgatory/purgatory_64.c
> b/arch/powerpc/purgatory/purgatory_64.c
> new file mode 100644
> index 0000000..1eca74c
> --- /dev/null
> +++ b/arch/powerpc/purgatory/purgatory_64.c
> @@ -0,0 +1,36 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * purgatory: Runs between two kernels
> + *
> + * Copyright 2020, Hari Bathini, IBM Corporation.
> + */
> +
> +#include <asm/purgatory.h>
> +#include <asm/crashdump-ppc64.h>
> +
> +extern unsigned long backup_start;
> +
> +static void *__memcpy(void *dest, const void *src, unsigned long n)
> +{
> + unsigned long i;
> + unsigned char *d;
> + const unsigned char *s;
> +
> + d = dest;
> + s = src;
> + for (i = 0; i < n; i++)
> + d[i] = s[i];
> +
> + return dest;
> +}
> +
> +void purgatory(void)
> +{
> + void *dest, *src;
> +
> + src = (void *)BACKUP_SRC_START;
> + if (backup_start) {
> + dest = (void *)backup_start;
> + __memcpy(dest, src, BACKUP_SRC_SIZE);
> + }
> +}
In general I'm in favor of using C code over assembly, but having to
bring in that relocation support just for the above makes me wonder if
it's worth it in this case.
--
Thiago Jung Bauermann
IBM Linux Technology Center
