[PATCH v4 1/3] crash: Exclude crash kernel memory in crash core
Jinjie Ruan
ruanjinjie at huawei.com
Wed Feb 11 19:28:42 PST 2026
On 2026/2/10 20:30, Sourabh Jain wrote:
> Hello Jinjie,
>
> On 09/02/26 15:29, Jinjie Ruan wrote:
>> The exclude of crashk_res, crashk_low_res and crashk_cma memory
>> are almost identical across different architectures, handling them
>> in the crash core would eliminate a lot of duplication, so do
>> them in the common code.
>>
>> And move the size calculation (and the realloc if needed) into the
>> generic crash core so that:
>>
>> - New CMA regions or future crash-memory types can automatically
>> accounted for in crash core;
>>
>> - Each architecture no longer has to play whack-a-mole with
>> its private array size.
>>
>> To achieve the above goal, 4 architecture-specific functions are
>> introduced:
>>
>> - arch_get_system_nr_ranges() and arch_prepare_elf64_ram_headers().
>> The 1st function pre-counts the number of memory ranges, and
>> the 2st function fill the memory ranges into the cmem->ranges[] array,
>> and count the actual number of ranges filled. The default
>> implementation
>> is consistent with arm64 and loongson.
>>
>> - arch_crash_exclude_mem_range(). Realloc for powerpc. The default
>> implementation is crash_exclude_mem_range(), and use
>> crash_exclude_mem_range_guarded() to implement the arch version
>> for powerpc.
>>
>> - arch_get_crash_memory_ranges(). Get crash memory ranges for arch and
>> the default implementation is generic across x86, arm64, riscv, and
>> loongson by using the first two arch functions above. powerpc has its
>> own implementation by calling get_crash_memory_ranges().
>>
>> Tested on x86, arm64 and riscv with QEMU.
>>
>> Signed-off-by: Jinjie Ruan <ruanjinjie at huawei.com>
>> ---
>> arch/arm64/kernel/machine_kexec_file.c | 47 +--------
>> arch/loongarch/kernel/machine_kexec_file.c | 45 +-------
>> arch/powerpc/include/asm/kexec.h | 13 +++
>> arch/powerpc/kexec/crash.c | 52 ++++++----
>> arch/powerpc/kexec/file_load_64.c | 17 ++-
>> arch/powerpc/kexec/ranges.c | 18 +---
>> arch/riscv/include/asm/kexec.h | 10 ++
>> arch/riscv/kernel/machine_kexec_file.c | 37 ++-----
>> arch/x86/include/asm/kexec.h | 10 ++
>> arch/x86/kernel/crash.c | 104 ++-----------------
>> include/linux/crash_core.h | 114 +++++++++++++++++++--
>> kernel/crash_core.c | 71 +++++++++++--
>> 12 files changed, 269 insertions(+), 269 deletions(-)
>>
[...]
>> extern void crash_ipi_callback(struct pt_regs *regs);
>> diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
>> index a325c1c02f96..5ade9a853fb0 100644
>> --- a/arch/powerpc/kexec/crash.c
>> +++ b/arch/powerpc/kexec/crash.c
>> @@ -419,30 +419,21 @@ unsigned int arch_crash_get_elfcorehdr_size(void)
>> return sizeof(struct elfhdr) + (phdr_cnt * sizeof(Elf64_Phdr));
>> }
>> -/**
>> - * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it
>> with old
>> - * elfcorehdr in the kexec segment array.
>> - * @image: the active struct kimage
>> - * @mn: struct memory_notify data handler
>> - */
>> -static void update_crash_elfcorehdr(struct kimage *image, struct
>> memory_notify *mn)
>> +int arch_get_crash_memory_ranges(struct crash_mem **cmem, unsigned
>> long *nr_mem_ranges,
>> + struct kimage *image, struct memory_notify *mn)
>> {
>> + unsigned long base_addr, size;
>> int ret;
>> - struct crash_mem *cmem = NULL;
>> - struct kexec_segment *ksegment;
>> - void *ptr, *mem, *elfbuf = NULL;
>> - unsigned long elfsz, memsz, base_addr, size;
>> - ksegment = &image->segment[image->elfcorehdr_index];
>> - mem = (void *) ksegment->mem;
>> - memsz = ksegment->memsz;
>> -
>> - ret = get_crash_memory_ranges(&cmem);
>> + ret = get_crash_memory_ranges(cmem);
>> if (ret) {
>> pr_err("Failed to get crash mem range\n");
>> - return;
>> + return ret;
>> }
>> + if (!image || !mn)
>> + return 0;
>> +
>> /*
>> * The hot unplugged memory is part of crash memory ranges,
>> * remove it here.
>> @@ -450,14 +441,34 @@ static void update_crash_elfcorehdr(struct
>> kimage *image, struct memory_notify *
>> if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
>> base_addr = PFN_PHYS(mn->start_pfn);
>> size = mn->nr_pages * PAGE_SIZE;
>> - ret = remove_mem_range(&cmem, base_addr, size);
>> + ret = remove_mem_range(cmem, base_addr, size);
>
> I like the overall design for handling crashkernel memory exclusion
> in this patch series, especially the way you managed to free the
> crash_mem object (mem) in the generic code (crash_prepare_elf64_headers()).
Thanks for the review.
>
> However, the way crash memory is prepared after a memory hotplug
> event on powerpc by calling remove_mem_range(), can leave the crash
> memory ranges unsorted. This can cause issues in the generic code
> when excluding crashkernel memory, because crash_exclude_mem_range()
> expects crash_mem to be sorted.
You are absolutely correct.
>
> So I wrote a simple patch to cover this scenario. Including the
> patch below as the first patch in this series would be helpful.
> https://lore.kernel.org/all/20260210120803.433978-1-sourabhjain@linux.ibm.com/
Thanks for the additional patch. I'll add it as the first patch in the
next revision to ensure crash_mem remains sorted after memory hotplug
events on powerpc.
Best regards,
Jinjie
>
> Jinjie, will it be possible for you to include the above patch in this
> patch series?
My pleasure.
>> if (ret) {
>> pr_err("Failed to remove hot-unplugged memory from crash
>> memory ranges\n");
>> - goto out;
>> + return ret;
>> }
>> }
>> - ret = crash_prepare_elf64_headers(cmem, false, &elfbuf, &elfsz);
>> + return 0;
>> +}
>> +
>> +/**
>> + * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it
>> with old
>> + * elfcorehdr in the kexec segment array.
>> + * @image: the active struct kimage
>> + * @mn: struct memory_notify data handler
>> + */
>> +static void update_crash_elfcorehdr(struct kimage *image, struct
>> memory_notify *mn)
>> +{
>> + void *ptr, *mem, *elfbuf = NULL;
>> + struct kexec_segment *ksegment;
>> + unsigned long elfsz, memsz;
>> + int ret;
>> +
>> + ksegment = &image->segment[image->elfcorehdr_index];
>> + mem = (void *) ksegment->mem;
>> + memsz = ksegment->memsz;
>> +
>> + ret = crash_prepare_elf64_headers(false, &elfbuf, &elfsz, NULL,
>> image, mn);
>> if (ret) {
>> pr_err("Failed to prepare elf header\n");
>> goto out;
>> @@ -486,7 +497,6 @@ static void update_crash_elfcorehdr(struct kimage
>> *image, struct memory_notify *
>> xchg(&kexec_crash_image, image);
>> }
>> out:
>> - kvfree(cmem);
>> kvfree(elfbuf);
>> }
[...]
>> +int crash_prepare_elf64_headers(int need_kernel_map, void **addr,
>> + unsigned long *sz, unsigned long *nr_mem_ranges,
>> + struct kimage *image, struct memory_notify *mn)
>> {
>> - Elf64_Ehdr *ehdr;
>> - Elf64_Phdr *phdr;
>> unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
>> - unsigned char *buf;
>> - unsigned int cpu, i;
>> unsigned long long notes_addr;
>> + struct crash_mem *mem = NULL;
>> unsigned long mstart, mend;
>> + unsigned int cpu, i;
>> + unsigned char *buf;
>> + Elf64_Ehdr *ehdr;
>> + Elf64_Phdr *phdr;
>> + int ret = 0;
>> +
>> + ret = arch_get_crash_memory_ranges(&mem, nr_mem_ranges, image, mn);
>> + if (ret)
>> + return ret;
>> +
>> + if (mem) {
>> + ret = crash_exclude_mem_ranges(mem, nr_mem_ranges);
>> + if (ret)
>> + goto out;
>> + }
>> /* extra phdr for vmcoreinfo ELF note */
>> nr_phdr = nr_cpus + 1;
>> @@ -192,8 +240,10 @@ int crash_prepare_elf64_headers(struct crash_mem
>> *mem, int need_kernel_map,
>> elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
>> buf = vzalloc(elf_sz);
>> - if (!buf)
>> - return -ENOMEM;
>> + if (!buf) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> ehdr = (Elf64_Ehdr *)buf;
>> phdr = (Elf64_Phdr *)(ehdr + 1);
>> @@ -262,7 +312,10 @@ int crash_prepare_elf64_headers(struct crash_mem
>> *mem, int need_kernel_map,
>> *addr = buf;
>> *sz = elf_sz;
>> - return 0;
>> +
>> +out:
>> + kvfree(mem);
>> + return ret;
>> }
>> /**
>
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