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charset="utf-8" At the outcome of this patch set, the crash_prepare_elf64_headers() is utilized on both the kexec_file_load() and kexec_load() paths. As such, need to move this function out of kexec_file.c and into a common location crash_core.c. No functionality change. Signed-off-by: Eric DeVolder Acked-by: Baoquan He --- kernel/crash_core.c | 100 ++++++++++++++++++++++++++++++++++++++++++++ kernel/kexec_file.c | 99 ------------------------------------------- 2 files changed, 100 insertions(+), 99 deletions(-) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index a0eb4d5cf557..46c160d14045 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -10,6 +10,7 @@ #include #include #include +#include =20 #include #include @@ -314,6 +315,105 @@ static int __init parse_crashkernel_dummy(char *arg) } early_param("crashkernel", parse_crashkernel_dummy); =20 +int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map, + void **addr, unsigned long *sz) +{ + Elf64_Ehdr *ehdr; + Elf64_Phdr *phdr; + unsigned long nr_cpus =3D num_possible_cpus(), nr_phdr, elf_sz; + unsigned char *buf; + unsigned int cpu, i; + unsigned long long notes_addr; + unsigned long mstart, mend; + + /* extra phdr for vmcoreinfo ELF note */ + nr_phdr =3D nr_cpus + 1; + nr_phdr +=3D mem->nr_ranges; + + /* + * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping + * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64). + * I think this is required by tools like gdb. So same physical + * memory will be mapped in two ELF headers. One will contain kernel + * text virtual addresses and other will have __va(physical) addresses. + */ + + nr_phdr++; + elf_sz =3D sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr); + elf_sz =3D ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN); + + buf =3D vzalloc(elf_sz); + if (!buf) + return -ENOMEM; + + ehdr =3D (Elf64_Ehdr *)buf; + phdr =3D (Elf64_Phdr *)(ehdr + 1); + memcpy(ehdr->e_ident, ELFMAG, SELFMAG); + ehdr->e_ident[EI_CLASS] =3D ELFCLASS64; + ehdr->e_ident[EI_DATA] =3D ELFDATA2LSB; + ehdr->e_ident[EI_VERSION] =3D EV_CURRENT; + ehdr->e_ident[EI_OSABI] =3D ELF_OSABI; + memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD); + ehdr->e_type =3D ET_CORE; + ehdr->e_machine =3D ELF_ARCH; + ehdr->e_version =3D EV_CURRENT; + ehdr->e_phoff =3D sizeof(Elf64_Ehdr); + ehdr->e_ehsize =3D sizeof(Elf64_Ehdr); + ehdr->e_phentsize =3D sizeof(Elf64_Phdr); + + /* Prepare one phdr of type PT_NOTE for each present CPU */ + for_each_present_cpu(cpu) { + phdr->p_type =3D PT_NOTE; + notes_addr =3D per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu)); + phdr->p_offset =3D phdr->p_paddr =3D notes_addr; + phdr->p_filesz =3D phdr->p_memsz =3D sizeof(note_buf_t); + (ehdr->e_phnum)++; + phdr++; + } + + /* Prepare one PT_NOTE header for vmcoreinfo */ + phdr->p_type =3D PT_NOTE; + phdr->p_offset =3D phdr->p_paddr =3D paddr_vmcoreinfo_note(); + phdr->p_filesz =3D phdr->p_memsz =3D VMCOREINFO_NOTE_SIZE; + (ehdr->e_phnum)++; + phdr++; + + /* Prepare PT_LOAD type program header for kernel text region */ + if (need_kernel_map) { + phdr->p_type =3D PT_LOAD; + phdr->p_flags =3D PF_R|PF_W|PF_X; + phdr->p_vaddr =3D (unsigned long) _text; + phdr->p_filesz =3D phdr->p_memsz =3D _end - _text; + phdr->p_offset =3D phdr->p_paddr =3D __pa_symbol(_text); + ehdr->e_phnum++; + phdr++; + } + + /* Go through all the ranges in mem->ranges[] and prepare phdr */ + for (i =3D 0; i < mem->nr_ranges; i++) { + mstart =3D mem->ranges[i].start; + mend =3D mem->ranges[i].end; + + phdr->p_type =3D PT_LOAD; + phdr->p_flags =3D PF_R|PF_W|PF_X; + phdr->p_offset =3D mstart; + + phdr->p_paddr =3D mstart; + phdr->p_vaddr =3D (unsigned long) __va(mstart); + phdr->p_filesz =3D phdr->p_memsz =3D mend - mstart + 1; + phdr->p_align =3D 0; + ehdr->e_phnum++; + pr_debug("Crash PT_LOAD ELF header. phdr=3D%p vaddr=3D0x%llx, paddr=3D0x= %llx, sz=3D0x%llx e_phnum=3D%d p_offset=3D0x%llx\n", + phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz, + ehdr->e_phnum, phdr->p_offset); + phdr++; + } + + *addr =3D buf; + *sz =3D elf_sz; + return 0; +} + Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type, void *data, size_t data_len) { diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index 45637511e0de..f98d1742872b 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -1217,102 +1217,3 @@ int crash_exclude_mem_range(struct crash_mem *mem, mem->nr_ranges++; return 0; } - -int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map, - void **addr, unsigned long *sz) -{ - Elf64_Ehdr *ehdr; - Elf64_Phdr *phdr; - unsigned long nr_cpus =3D num_possible_cpus(), nr_phdr, elf_sz; - unsigned char *buf; - unsigned int cpu, i; - unsigned long long notes_addr; - unsigned long mstart, mend; - - /* extra phdr for vmcoreinfo ELF note */ - nr_phdr =3D nr_cpus + 1; - nr_phdr +=3D mem->nr_ranges; - - /* - * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping - * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64). - * I think this is required by tools like gdb. So same physical - * memory will be mapped in two ELF headers. One will contain kernel - * text virtual addresses and other will have __va(physical) addresses. - */ - - nr_phdr++; - elf_sz =3D sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr); - elf_sz =3D ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN); - - buf =3D vzalloc(elf_sz); - if (!buf) - return -ENOMEM; - - ehdr =3D (Elf64_Ehdr *)buf; - phdr =3D (Elf64_Phdr *)(ehdr + 1); - memcpy(ehdr->e_ident, ELFMAG, SELFMAG); - ehdr->e_ident[EI_CLASS] =3D ELFCLASS64; - ehdr->e_ident[EI_DATA] =3D ELFDATA2LSB; - ehdr->e_ident[EI_VERSION] =3D EV_CURRENT; - ehdr->e_ident[EI_OSABI] =3D ELF_OSABI; - memset(ehdr->e_ident + EI_PAD, 0, EI_NIDENT - EI_PAD); - ehdr->e_type =3D ET_CORE; - ehdr->e_machine =3D ELF_ARCH; - ehdr->e_version =3D EV_CURRENT; - ehdr->e_phoff =3D sizeof(Elf64_Ehdr); - ehdr->e_ehsize =3D sizeof(Elf64_Ehdr); - ehdr->e_phentsize =3D sizeof(Elf64_Phdr); - - /* Prepare one phdr of type PT_NOTE for each present CPU */ - for_each_present_cpu(cpu) { - phdr->p_type =3D PT_NOTE; - notes_addr =3D per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu)); - phdr->p_offset =3D phdr->p_paddr =3D notes_addr; - phdr->p_filesz =3D phdr->p_memsz =3D sizeof(note_buf_t); - (ehdr->e_phnum)++; - phdr++; - } - - /* Prepare one PT_NOTE header for vmcoreinfo */ - phdr->p_type =3D PT_NOTE; - phdr->p_offset =3D phdr->p_paddr =3D paddr_vmcoreinfo_note(); - phdr->p_filesz =3D phdr->p_memsz =3D VMCOREINFO_NOTE_SIZE; - (ehdr->e_phnum)++; - phdr++; - - /* Prepare PT_LOAD type program header for kernel text region */ - if (need_kernel_map) { - phdr->p_type =3D PT_LOAD; - phdr->p_flags =3D PF_R|PF_W|PF_X; - phdr->p_vaddr =3D (unsigned long) _text; - phdr->p_filesz =3D phdr->p_memsz =3D _end - _text; - phdr->p_offset =3D phdr->p_paddr =3D __pa_symbol(_text); - ehdr->e_phnum++; - phdr++; - } - - /* Go through all the ranges in mem->ranges[] and prepare phdr */ - for (i =3D 0; i < mem->nr_ranges; i++) { - mstart =3D mem->ranges[i].start; - mend =3D mem->ranges[i].end; - - phdr->p_type =3D PT_LOAD; - phdr->p_flags =3D PF_R|PF_W|PF_X; - phdr->p_offset =3D mstart; - - phdr->p_paddr =3D mstart; - phdr->p_vaddr =3D (unsigned long) __va(mstart); - phdr->p_filesz =3D phdr->p_memsz =3D mend - mstart + 1; - phdr->p_align =3D 0; - ehdr->e_phnum++; - pr_debug("Crash PT_LOAD ELF header. phdr=3D%p vaddr=3D0x%llx, paddr=3D0x= %llx, sz=3D0x%llx e_phnum=3D%d p_offset=3D0x%llx\n", - phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz, - ehdr->e_phnum, phdr->p_offset); - phdr++; - } - - *addr =3D buf; - *sz =3D elf_sz; - return 0; -} --=20 2.31.1 From nobody Thu Sep 18 04:17:11 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D0A4C4332F for ; Fri, 9 Dec 2022 15:37:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229824AbiLIPhv (ORCPT ); Fri, 9 Dec 2022 10:37:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230153AbiLIPhh (ORCPT ); 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charset="utf-8" From within crash_prepare_elf64_headers() there is a need to reference the struct kimage hotplug members. As such, this change passes the struct kimage as a parameter to the crash_prepare_elf64_headers(). The hotplug members are added in "crash: add generic infrastructure for crash hotplug support". This is preparation for later patch, no functionality change. Signed-off-by: Eric DeVolder Acked-by: Baoquan He Acked-by: David Hildenbrand --- arch/arm64/kernel/machine_kexec_file.c | 6 +++--- arch/powerpc/kexec/file_load_64.c | 2 +- arch/riscv/kernel/elf_kexec.c | 7 ++++--- arch/x86/kernel/crash.c | 2 +- include/linux/kexec.h | 7 +++++-- kernel/crash_core.c | 4 ++-- 6 files changed, 16 insertions(+), 12 deletions(-) diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/mac= hine_kexec_file.c index a11a6e14ba89..2f7b773a83bb 100644 --- a/arch/arm64/kernel/machine_kexec_file.c +++ b/arch/arm64/kernel/machine_kexec_file.c @@ -39,7 +39,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *ima= ge) return kexec_image_post_load_cleanup_default(image); } =20 -static int prepare_elf_headers(void **addr, unsigned long *sz) +static int prepare_elf_headers(struct kimage *image, void **addr, unsigned= long *sz) { struct crash_mem *cmem; unsigned int nr_ranges; @@ -64,7 +64,7 @@ static int prepare_elf_headers(void **addr, unsigned long= *sz) } =20 /* Exclude crashkernel region */ - ret =3D crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end); + ret =3D crash_exclude_mem_range(image, cmem, crashk_res.start, crashk_res= .end); if (ret) goto out; =20 @@ -74,7 +74,7 @@ static int prepare_elf_headers(void **addr, unsigned long= *sz) goto out; } =20 - ret =3D crash_prepare_elf64_headers(cmem, true, addr, sz); + ret =3D crash_prepare_elf64_headers(image, cmem, true, addr, sz); =20 out: kfree(cmem); diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_lo= ad_64.c index 349a781cea0b..a0af9966a8f0 100644 --- a/arch/powerpc/kexec/file_load_64.c +++ b/arch/powerpc/kexec/file_load_64.c @@ -798,7 +798,7 @@ static int load_elfcorehdr_segment(struct kimage *image= , struct kexec_buf *kbuf) goto out; =20 /* Setup elfcorehdr segment */ - ret =3D crash_prepare_elf64_headers(cmem, false, &headers, &headers_sz); + ret =3D crash_prepare_elf64_headers(image, cmem, false, &headers, &header= s_sz); if (ret) { pr_err("Failed to prepare elf headers for the core\n"); goto out; diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c index 0cb94992c15b..ffde73228108 100644 --- a/arch/riscv/kernel/elf_kexec.c +++ b/arch/riscv/kernel/elf_kexec.c @@ -118,7 +118,8 @@ static int prepare_elf64_ram_headers_callback(struct re= source *res, void *arg) return 0; } =20 -static int prepare_elf_headers(void **addr, unsigned long *sz) +static int prepare_elf_headers(struct kimage *image, + void **addr, unsigned long *sz) { struct crash_mem *cmem; unsigned int nr_ranges; @@ -140,7 +141,7 @@ static int prepare_elf_headers(void **addr, unsigned lo= ng *sz) /* Exclude crashkernel region */ ret =3D crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end); if (!ret) - ret =3D crash_prepare_elf64_headers(cmem, true, addr, sz); + ret =3D crash_prepare_elf64_headers(image, cmem, true, addr, sz); =20 out: kfree(cmem); @@ -212,7 +213,7 @@ static void *elf_kexec_load(struct kimage *image, char = *kernel_buf, =20 /* Add elfcorehdr */ if (image->type =3D=3D KEXEC_TYPE_CRASH) { - ret =3D prepare_elf_headers(&headers, &headers_sz); + ret =3D prepare_elf_headers(image, &headers, &headers_sz); if (ret) { pr_err("Preparing elf core header failed\n"); goto out; diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 9730c88530fc..9ceb93c176a6 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -265,7 +265,7 @@ static int prepare_elf_headers(struct kimage *image, vo= id **addr, goto out; =20 /* By default prepare 64bit headers */ - ret =3D crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), add= r, sz); + ret =3D crash_prepare_elf64_headers(image, cmem, IS_ENABLED(CONFIG_X86_6= 4), addr, sz); =20 out: vfree(cmem); diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 41a686996aaa..ebf46c3b8f8b 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -253,8 +253,11 @@ struct crash_mem { extern int crash_exclude_mem_range(struct crash_mem *mem, unsigned long long mstart, unsigned long long mend); -extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_ker= nel_map, - void **addr, unsigned long *sz); +extern int crash_prepare_elf64_headers(struct kimage *image, + struct crash_mem *mem, + int need_kernel_map, + void **addr, + unsigned long *sz); =20 #ifndef arch_kexec_apply_relocations_add /* diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 46c160d14045..8c648fd5897a 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -315,8 +315,8 @@ static int __init parse_crashkernel_dummy(char *arg) } early_param("crashkernel", parse_crashkernel_dummy); 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charset="utf-8" CPU and memory change notifications are received in order to regenerate the elfcorehdr. To support cpu hotplug, a callback is registered to capture the CPUHP_AP_ONLINE_DYN online and offline events via cpuhp_setup_state_nocalls(). To support memory hotplug, a notifier is registered to capture the MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier(). The cpu callback and memory notifiers call handle_hotplug_event() which performs needed tasks and then dispatches the event to the architecture specific arch_crash_handle_hotplug_event(). During the process, the kexec_lock is held. Signed-off-by: Eric DeVolder Acked-by: Baoquan He --- include/linux/crash_core.h | 8 +++ include/linux/kexec.h | 12 ++++ kernel/crash_core.c | 138 +++++++++++++++++++++++++++++++++++++ 3 files changed, 158 insertions(+) diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h index de62a722431e..a270f8660538 100644 --- a/include/linux/crash_core.h +++ b/include/linux/crash_core.h @@ -84,4 +84,12 @@ int parse_crashkernel_high(char *cmdline, unsigned long = long system_ram, int parse_crashkernel_low(char *cmdline, unsigned long long system_ram, unsigned long long *crash_size, unsigned long long *crash_base); =20 +#define KEXEC_CRASH_HP_REMOVE_CPU 0 +#define KEXEC_CRASH_HP_ADD_CPU 1 +#define KEXEC_CRASH_HP_REMOVE_MEMORY 2 +#define KEXEC_CRASH_HP_ADD_MEMORY 3 +#define KEXEC_CRASH_HP_INVALID_CPU -1U + +struct kimage; + #endif /* LINUX_CRASH_CORE_H */ diff --git a/include/linux/kexec.h b/include/linux/kexec.h index ebf46c3b8f8b..389444cb03cc 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -32,6 +32,7 @@ extern note_buf_t __percpu *crash_notes; #include #include #include +#include #include =20 /* Verify architecture specific macros are defined */ @@ -374,6 +375,13 @@ struct kimage { struct purgatory_info purgatory_info; #endif =20 +#ifdef CONFIG_CRASH_HOTPLUG + bool hotplug_event; + unsigned int offlinecpu; + bool elfcorehdr_index_valid; + int elfcorehdr_index; +#endif + #ifdef CONFIG_IMA_KEXEC /* Virtual address of IMA measurement buffer for kexec syscall */ void *ima_buffer; @@ -503,6 +511,10 @@ static inline int arch_kexec_post_alloc_pages(void *va= ddr, unsigned int pages, g static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pag= es) { } #endif =20 +#ifndef arch_crash_handle_hotplug_event +static inline void arch_crash_handle_hotplug_event(struct kimage *image) {= } +#endif + #else /* !CONFIG_KEXEC_CORE */ struct pt_regs; struct task_struct; diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 8c648fd5897a..fcb642a03d7b 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -11,6 +11,8 @@ #include #include #include +#include +#include =20 #include #include @@ -18,6 +20,7 @@ #include =20 #include "kallsyms_internal.h" +#include "kexec_internal.h" =20 /* vmcoreinfo stuff */ unsigned char *vmcoreinfo_data; @@ -612,3 +615,138 @@ static int __init crash_save_vmcoreinfo_init(void) } =20 subsys_initcall(crash_save_vmcoreinfo_init); + +#ifdef CONFIG_CRASH_HOTPLUG +#undef pr_fmt +#define pr_fmt(fmt) "crash hp: " fmt +/* + * To accurately reflect hot un/plug changes, the elfcorehdr (which + * is passed to the crash kernel via the elfcorehdr=3D parameter) + * must be updated with the new list of CPUs and memories. + * + * In order to make changes to elfcorehdr, two conditions are needed: + * First, the segment containing the elfcorehdr must be large enough + * to permit a growing number of resources; the elfcorehdr memory size + * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES. + * Second, purgatory must explicitly exclude the elfcorehdr from the + * list of segments it checks (since the elfcorehdr changes and thus + * would require an update to purgatory itself to update the digest). + */ +static void handle_hotplug_event(unsigned int hp_action, unsigned int cpu) +{ + /* Obtain lock while changing crash information */ + if (kexec_trylock()) { + + /* Check kdump is loaded */ + if (kexec_crash_image) { + struct kimage *image =3D kexec_crash_image; + + if (hp_action =3D=3D KEXEC_CRASH_HP_ADD_CPU || + hp_action =3D=3D KEXEC_CRASH_HP_REMOVE_CPU) + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu); + else + pr_debug("hp_action %u\n", hp_action); + + /* + * When the struct kimage is allocated, it is wiped to zero, so + * the elfcorehdr_index_valid defaults to false. Find the + * segment containing the elfcorehdr, if not already found. + * This works for both the kexec_load and kexec_file_load paths. + */ + if (!image->elfcorehdr_index_valid) { + unsigned long mem; + unsigned char *ptr; + unsigned int n; + + for (n =3D 0; n < image->nr_segments; n++) { + mem =3D image->segment[n].mem; + ptr =3D kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT)); + if (ptr) { + /* The segment containing elfcorehdr */ + if (memcmp(ptr, ELFMAG, SELFMAG) =3D=3D 0) { + image->elfcorehdr_index =3D (int)n; + image->elfcorehdr_index_valid =3D true; + } + kunmap_local(ptr); + } + } + } + + if (!image->elfcorehdr_index_valid) { + pr_err("unable to locate elfcorehdr segment"); + goto out; + } + + /* Needed in order for the segments to be updated */ + arch_kexec_unprotect_crashkres(); + + /* Flag to differentiate between normal load and hotplug */ + image->hotplug_event =3D true; + + /* Now invoke arch-specific update handler */ + arch_crash_handle_hotplug_event(image); + + /* No longer handling a hotplug event */ + image->hotplug_event =3D false; + + /* Change back to read-only */ + arch_kexec_protect_crashkres(); + } + +out: + /* Release lock now that update complete */ + kexec_unlock(); + } +} + +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long v= al, void *v) +{ + switch (val) { + case MEM_ONLINE: + handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY, + KEXEC_CRASH_HP_INVALID_CPU); + break; + + case MEM_OFFLINE: + handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY, + KEXEC_CRASH_HP_INVALID_CPU); + break; + } + return NOTIFY_OK; +} + +static struct notifier_block crash_memhp_nb =3D { + .notifier_call =3D crash_memhp_notifier, + .priority =3D 0 +}; + +static int crash_cpuhp_online(unsigned int cpu) +{ + handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu); + return 0; +} + +static int crash_cpuhp_offline(unsigned int cpu) +{ + handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu); + return 0; +} + +static int __init crash_hotplug_init(void) +{ + int result =3D 0; + + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) + register_memory_notifier(&crash_memhp_nb); + + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) + result =3D cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, + "crash/cpuhp", + crash_cpuhp_online, + crash_cpuhp_offline); + + return result; +} + +subsys_initcall(crash_hotplug_init); +#endif --=20 2.31.1 From nobody Thu Sep 18 04:17:11 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AADFBC4332F for ; Fri, 9 Dec 2022 15:38:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229961AbiLIPiA (ORCPT ); Fri, 9 Dec 2022 10:38:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230240AbiLIPhl (ORCPT ); Fri, 9 Dec 2022 10:37:41 -0500 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 062902B2 for ; 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charset="utf-8" When a crash kernel is loaded via the kexec_file_load() syscall, the kernel places the various segments (ie crash kernel, crash initrd, boot_params, elfcorehdr, purgatory, etc) in memory. For those architectures that utilize purgatory, a hash digest of the segments is calculated for integrity checking. This digest is embedded into the purgatory image prior to placing purgatory in memory. Since hotplug events cause changes to the elfcorehdr, purgatory integrity checking fails (at crash time, and no kdump created). As a result, this change explicitly excludes the elfcorehdr segment from the list of segments used to create the digest. By doing so, this permits changes to the elfcorehdr in response to hotplug events, without having to also reload purgatory due to the change to the digest. Signed-off-by: Eric DeVolder Acked-by: Baoquan He --- kernel/kexec_file.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index f98d1742872b..cc976948f17e 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -723,6 +723,12 @@ static int kexec_calculate_store_digests(struct kimage= *image) for (j =3D i =3D 0; i < image->nr_segments; i++) { struct kexec_segment *ksegment; =20 +#ifdef CONFIG_CRASH_HOTPLUG + /* Exclude elfcorehdr segment to allow future changes via hotplug */ + if (image->elfcorehdr_index_valid && (j =3D=3D image->elfcorehdr_index)) + continue; +#endif + ksegment =3D &image->segment[i]; /* * Skip purgatory as it will be modified once we put digest --=20 2.31.1 From nobody Thu Sep 18 04:17:11 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA752C4332F for ; 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Fri, 9 Dec 2022 15:37:18 +0000 From: Eric DeVolder To: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, david@redhat.com, sourabhjain@linux.ibm.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, eric.devolder@oracle.com Subject: [PATCH v15 5/7] kexec: exclude hot remove cpu from elfcorehdr notes Date: Fri, 9 Dec 2022 10:36:54 -0500 Message-Id: <20221209153656.3284-6-eric.devolder@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20221209153656.3284-1-eric.devolder@oracle.com> References: <20221209153656.3284-1-eric.devolder@oracle.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SA0PR13CA0016.namprd13.prod.outlook.com (2603:10b6:806:130::21) To CO1PR10MB4531.namprd10.prod.outlook.com (2603:10b6:303:6c::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PR10MB4531:EE_|SA2PR10MB4666:EE_ X-MS-Office365-Filtering-Correlation-Id: a4f5889e-0726-4507-cb5c-08dad9fb417f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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charset="utf-8" Due to use of CPUHP_AP_ONLINE_DYN, upon CPU unplug, the CPU is still in the for_each_present_cpu() list when within the handle_hotplug_event(). Thus the CPU must be explicitly excluded when building the new list of CPUs. This change identifies in handle_hotplug_event() the CPU to be excluded, and the check for excluding the CPU in crash_prepare_elf64_headers(). Signed-off-by: Eric DeVolder Acked-by: Baoquan He --- kernel/crash_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index fcb642a03d7b..189065afd04f 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -366,6 +366,13 @@ int crash_prepare_elf64_headers(struct kimage *image, = struct crash_mem *mem, =20 /* Prepare one phdr of type PT_NOTE for each present CPU */ for_each_present_cpu(cpu) { +#ifdef CONFIG_CRASH_HOTPLUG + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) { + /* Skip the soon-to-be offlined cpu */ + if (image->hotplug_event && (cpu =3D=3D image->offlinecpu)) + continue; + } +#endif phdr->p_type =3D PT_NOTE; notes_addr =3D per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu)); phdr->p_offset =3D phdr->p_paddr =3D notes_addr; @@ -683,6 +690,16 @@ static void handle_hotplug_event(unsigned int hp_actio= n, unsigned int cpu) /* Flag to differentiate between normal load and hotplug */ image->hotplug_event =3D true; =20 + /* + * Due to use of CPUHP_AP_ONLINE_DYN, upon unplug and during + * this callback, the CPU is still in the for_each_present_cpu() + * list. Must explicitly look to exclude this CPU when building + * new list. + */ + image->offlinecpu =3D + (hp_action =3D=3D KEXEC_CRASH_HP_REMOVE_CPU) ? + cpu : KEXEC_CRASH_HP_INVALID_CPU; + /* Now invoke arch-specific update handler */ arch_crash_handle_hotplug_event(image); =20 --=20 2.31.1 From nobody Thu Sep 18 04:17:11 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2630AC4332F for ; Fri, 9 Dec 2022 15:38:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229724AbiLIPiU (ORCPT ); Fri, 9 Dec 2022 10:38:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57320 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230363AbiLIPhv (ORCPT ); Fri, 9 Dec 2022 10:37:51 -0500 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 412EA15FC6 for ; 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charset="utf-8" This introduces the crash_hotplug attribute for memory and CPUs for use by userspace. This change directly facilitates the udev rule for managing userspace re-loading of the crash kernel upon hot un/plug changes. For memory, this changeset introduces the crash_hotplug attribute to the /sys/devices/system/memory directory. For example: # udevadm info --attribute-walk /sys/devices/system/memory/memory81 looking at device '/devices/system/memory/memory81': KERNEL=3D=3D"memory81" SUBSYSTEM=3D=3D"memory" DRIVER=3D=3D"" ATTR{online}=3D=3D"1" ATTR{phys_device}=3D=3D"0" ATTR{phys_index}=3D=3D"00000051" ATTR{removable}=3D=3D"1" ATTR{state}=3D=3D"online" ATTR{valid_zones}=3D=3D"Movable" looking at parent device '/devices/system/memory': KERNELS=3D=3D"memory" SUBSYSTEMS=3D=3D"" DRIVERS=3D=3D"" ATTRS{auto_online_blocks}=3D=3D"offline" ATTRS{block_size_bytes}=3D=3D"8000000" ATTRS{crash_hotplug}=3D=3D"1" For CPUs, this changeset introduces the crash_hotplug attribute to the /sys/devices/system/cpu directory. For example: # udevadm info --attribute-walk /sys/devices/system/cpu/cpu0 looking at device '/devices/system/cpu/cpu0': KERNEL=3D=3D"cpu0" SUBSYSTEM=3D=3D"cpu" DRIVER=3D=3D"processor" ATTR{crash_notes}=3D=3D"277c38600" ATTR{crash_notes_size}=3D=3D"368" ATTR{online}=3D=3D"1" looking at parent device '/devices/system/cpu': KERNELS=3D=3D"cpu" SUBSYSTEMS=3D=3D"" DRIVERS=3D=3D"" ATTRS{crash_hotplug}=3D=3D"1" ATTRS{isolated}=3D=3D"" ATTRS{kernel_max}=3D=3D"8191" ATTRS{nohz_full}=3D=3D" (null)" ATTRS{offline}=3D=3D"4-7" ATTRS{online}=3D=3D"0-3" ATTRS{possible}=3D=3D"0-7" ATTRS{present}=3D=3D"0-3" With these sysfs attributes in place, it is possible to efficiently instruct the udev rule to skip crash kernel reloading. For example, the following is the proposed udev rule change for RHEL system 98-kexec.rules (as the first lines of the rule file): # The kernel handles updates to crash elfcorehdr for cpu and memory changes SUBSYSTEM=3D=3D"cpu", ATTRS{crash_hotplug}=3D=3D"1", GOTO=3D"kdump_reload_= end" SUBSYSTEM=3D=3D"memory", ATTRS{crash_hotplug}=3D=3D"1", GOTO=3D"kdump_relo= ad_end" When examined in the context of 98-kexec.rules, the above change tests if crash_hotplug is set, and if so, it skips the userspace initiated unload-then-reload of the crash kernel. Cpu and memory checks are separated in accordance with CONFIG_HOTPLUG_CPU and CONFIG_MEMORY_HOTPLUG kernel config options. If an architecture supports, for example, memory hotplug but not CPU hotplug, then the /sys/devices/system/memory/crash_hotplug attribute file is present, but the /sys/devices/system/cpu/crash_hotplug attribute file will NOT be present. Thus the udev rule will skip userspace processing of memory hot un/plug events, but the udev rule will fail for CPU events, thus allowing userspace to process cpu hot un/plug events (ie the unload-then-reload of the kdump capture kernel). Signed-off-by: Eric DeVolder Acked-by: Baoquan He --- .../admin-guide/mm/memory-hotplug.rst | 8 ++++++++ Documentation/core-api/cpu_hotplug.rst | 18 ++++++++++++++++++ drivers/base/cpu.c | 14 ++++++++++++++ drivers/base/memory.c | 13 +++++++++++++ include/linux/kexec.h | 8 ++++++++ 5 files changed, 61 insertions(+) diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentatio= n/admin-guide/mm/memory-hotplug.rst index a3c9e8ad8fa0..15fd1751a63c 100644 --- a/Documentation/admin-guide/mm/memory-hotplug.rst +++ b/Documentation/admin-guide/mm/memory-hotplug.rst @@ -293,6 +293,14 @@ The following files are currently defined: Availability depends on the CONFIG_ARCH_MEMORY_PROBE kernel configuration option. ``uevent`` read-write: generic udev file for device subsystems. +``crash_hotplug`` read-only: when changes to the system memory map + occur due to hot un/plug of memory, this file contains + '1' if the kernel updates the kdump capture kernel memory + map itself (via elfcorehdr), or '0' if userspace must update + the kdump capture kernel memory map. + + Availability depends on the CONFIG_MEMORY_HOTPLUG kernel + configuration option. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D =20 .. note:: diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-ap= i/cpu_hotplug.rst index f75778d37488..0c8dc3fe5f94 100644 --- a/Documentation/core-api/cpu_hotplug.rst +++ b/Documentation/core-api/cpu_hotplug.rst @@ -750,6 +750,24 @@ will receive all events. A script like:: =20 can process the event further. =20 +When changes to the CPUs in the system occur, the sysfs file +/sys/devices/system/cpu/crash_hotplug contains '1' if the kernel +updates the kdump capture kernel list of CPUs itself (via elfcorehdr), +or '0' if userspace must update the kdump capture kernel list of CPUs. + +The availability depends on the CONFIG_HOTPLUG_CPU kernel configuration +option. + +To skip userspace processing of CPU hot un/plug events for kdump +(ie the unload-then-reload to obtain a current list of CPUs), this sysfs +file can be used in a udev rule as follows: + + SUBSYSTEM=3D=3D"cpu", ATTRS{crash_hotplug}=3D=3D"1", GOTO=3D"kdump_reload= _end" + +For a cpu hot un/plug event, if the architecture supports kernel updates +of the elfcorehdr (which contains the list of CPUs), then the rule skips +the unload-then-reload of the kdump capture kernel. + Kernel Inline Documentations Reference =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 4c98849577d4..fedbf87f9d13 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -293,6 +293,17 @@ static ssize_t print_cpus_nohz_full(struct device *dev, static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL); #endif =20 +#ifdef CONFIG_HOTPLUG_CPU +#include +static ssize_t crash_hotplug_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + return sprintf(buf, "%d\n", crash_hotplug_cpu_support()); +} +static DEVICE_ATTR_ADMIN_RO(crash_hotplug); +#endif + static void cpu_device_release(struct device *dev) { /* @@ -469,6 +480,9 @@ static struct attribute *cpu_root_attrs[] =3D { #ifdef CONFIG_NO_HZ_FULL &dev_attr_nohz_full.attr, #endif +#ifdef CONFIG_HOTPLUG_CPU + &dev_attr_crash_hotplug.attr, +#endif #ifdef CONFIG_GENERIC_CPU_AUTOPROBE &dev_attr_modalias.attr, #endif diff --git a/drivers/base/memory.c b/drivers/base/memory.c index 9aa0da991cfb..226be3134ffe 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c @@ -483,6 +483,16 @@ static ssize_t auto_online_blocks_store(struct device = *dev, =20 static DEVICE_ATTR_RW(auto_online_blocks); =20 +#ifdef CONFIG_MEMORY_HOTPLUG +#include +static ssize_t crash_hotplug_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "%d\n", crash_hotplug_memory_support()); +} +static DEVICE_ATTR_RO(crash_hotplug); +#endif + /* * Some architectures will have custom drivers to do this, and * will not need to do it from userspace. The fake hot-add code @@ -881,6 +891,9 @@ static struct attribute *memory_root_attrs[] =3D { =20 &dev_attr_block_size_bytes.attr, &dev_attr_auto_online_blocks.attr, +#ifdef CONFIG_MEMORY_HOTPLUG + &dev_attr_crash_hotplug.attr, +#endif NULL }; =20 diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 389444cb03cc..4d096bc97597 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -515,6 +515,14 @@ static inline void arch_kexec_pre_free_pages(void *vad= dr, unsigned int pages) { static inline void arch_crash_handle_hotplug_event(struct kimage *image) {= } #endif =20 +#ifndef crash_hotplug_cpu_support +static inline int crash_hotplug_cpu_support(void) { return 0; } +#endif + +#ifndef crash_hotplug_memory_support +static inline int crash_hotplug_memory_support(void) { return 0; } +#endif + #else /* !CONFIG_KEXEC_CORE */ struct pt_regs; struct task_struct; --=20 2.31.1 From nobody Thu Sep 18 04:17:11 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EAB8CC4332F for ; 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Fri, 9 Dec 2022 15:37:24 +0000 From: Eric DeVolder To: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, david@redhat.com, sourabhjain@linux.ibm.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, eric.devolder@oracle.com Subject: [PATCH v15 7/7] x86/crash: add x86 crash hotplug support Date: Fri, 9 Dec 2022 10:36:56 -0500 Message-Id: <20221209153656.3284-8-eric.devolder@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20221209153656.3284-1-eric.devolder@oracle.com> References: <20221209153656.3284-1-eric.devolder@oracle.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: SN6PR2101CA0006.namprd21.prod.outlook.com (2603:10b6:805:106::16) To CO1PR10MB4531.namprd10.prod.outlook.com (2603:10b6:303:6c::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PR10MB4531:EE_|BL3PR10MB6116:EE_ X-MS-Office365-Filtering-Correlation-Id: 7fcefd9f-d6a0-430d-bcbc-08dad9fb448d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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charset="utf-8" When CPU or memory is hot un/plugged, the crash elfcorehdr, which describes the CPUs and memory in the system, must also be updated. A new elfcorehdr is generated from the available CPUs and memory into a buffer, and then installed over the top of the existing elfcorehdr. The segment containing the elfcorehdr is identified at run time in crash_core:handle_hotplug_event(), which works for both the kexec_load() and kexec_file_load() syscalls. In the patch 'kexec: exclude elfcorehdr from the segment digest' the need to update purgatory due to the change in elfcorehdr was eliminated. As a result, no changes to purgatory or boot_params (as the elfcorehdr=3D kernel command line parameter pointer remains unchanged and correct) are needed, just elfcorehdr. To accommodate a growing number of resources via hotplug, the elfcorehdr segment must be sufficiently large enough to accommodate changes, see the CRASH_MAX_MEMORY_RANGES description. Signed-off-by: Eric DeVolder --- arch/x86/Kconfig | 12 ++++ arch/x86/include/asm/kexec.h | 15 +++++ arch/x86/kernel/crash.c | 114 ++++++++++++++++++++++++++++++++++- 3 files changed, 138 insertions(+), 3 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 67745ceab0db..d1990a83e8f0 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2072,6 +2072,18 @@ config CRASH_DUMP (CONFIG_RELOCATABLE=3Dy). For more details see Documentation/admin-guide/kdump/kdump.rst =20 +config CRASH_HOTPLUG + bool "Update the crash elfcorehdr on system configuration changes" + default n + depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG) + help + Enable direct update to the crash elfcorehdr (which contains + the list of CPUs and memory regions to be dumped upon a crash) + in response to hot plug/unplug of CPUs or memory. This is a much + more advanced approach than userspace attempting that. + + If unsure, say Y. + config KEXEC_JUMP bool "kexec jump" depends on KEXEC && HIBERNATION diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h index a3760ca796aa..1bc852ce347d 100644 --- a/arch/x86/include/asm/kexec.h +++ b/arch/x86/include/asm/kexec.h @@ -212,6 +212,21 @@ typedef void crash_vmclear_fn(void); extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; extern void kdump_nmi_shootdown_cpus(void); =20 +#ifdef CONFIG_CRASH_HOTPLUG +void arch_crash_handle_hotplug_event(struct kimage *image); +#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event + +#ifdef CONFIG_HOTPLUG_CPU +static inline int crash_hotplug_cpu_support(void) { return 1; } +#define crash_hotplug_cpu_support crash_hotplug_cpu_support +#endif + +#ifdef CONFIG_MEMORY_HOTPLUG +static inline int crash_hotplug_memory_support(void) { return 1; } +#define crash_hotplug_memory_support crash_hotplug_memory_support +#endif +#endif + #endif /* __ASSEMBLY__ */ =20 #endif /* _ASM_X86_KEXEC_H */ diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 9ceb93c176a6..5186df48ce6c 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -42,6 +42,21 @@ #include #include =20 +/* + * For the kexec_file_load() syscall path, specify the maximum number of + * memory regions that the elfcorehdr buffer/segment can accommodate. + * These regions are obtained via walk_system_ram_res(); eg. the + * 'System RAM' entries in /proc/iomem. + * This value is combined with NR_CPUS_DEFAULT and multiplied by + * sizeof(Elf64_Phdr) to determine the final elfcorehdr memory buffer/ + * segment size. + * The value 8192, for example, covers a (sparsely populated) 1TiB system + * consisting of 128MiB memblocks, while resulting in an elfcorehdr + * memory buffer/segment size under 1MiB. This represents a sane choice + * to accommodate both baremetal and virtual machine configurations. + */ +#define CRASH_MAX_MEMORY_RANGES 8192 + /* Used while preparing memory map entries for second kernel */ struct crash_memmap_data { struct boot_params *params; @@ -394,10 +409,39 @@ int crash_load_segments(struct kimage *image) if (ret) return ret; =20 - image->elf_headers =3D kbuf.buffer; - image->elf_headers_sz =3D kbuf.bufsz; + image->elf_headers =3D kbuf.buffer; + image->elf_headers_sz =3D kbuf.bufsz; + kbuf.memsz =3D kbuf.bufsz; + +#ifdef CONFIG_CRASH_HOTPLUG + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) { + /* + * Ensure the elfcorehdr segment large enough for hotplug changes. + * Start with VMCOREINFO and kernel_map. + */ + unsigned long pnum =3D 2; + + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) + pnum +=3D CONFIG_NR_CPUS_DEFAULT; + + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) + pnum +=3D CRASH_MAX_MEMORY_RANGES; + + if (pnum < (unsigned long)PN_XNUM) { + kbuf.memsz =3D pnum * sizeof(Elf64_Phdr); + kbuf.memsz +=3D sizeof(Elf64_Ehdr); + + image->elfcorehdr_index =3D image->nr_segments; + image->elfcorehdr_index_valid =3D true; + + /* Mark as usable to crash kernel, else crash kernel fails on boot */ + image->elf_headers_sz =3D kbuf.memsz; + } else { + pr_err("number of Phdrs %lu exceeds max\n", pnum); + } + } +#endif =20 - kbuf.memsz =3D kbuf.bufsz; kbuf.buf_align =3D ELF_CORE_HEADER_ALIGN; kbuf.mem =3D KEXEC_BUF_MEM_UNKNOWN; ret =3D kexec_add_buffer(&kbuf); @@ -412,3 +456,67 @@ int crash_load_segments(struct kimage *image) return ret; } #endif /* CONFIG_KEXEC_FILE */ + +#ifdef CONFIG_CRASH_HOTPLUG + +#undef pr_fmt +#define pr_fmt(fmt) "crash hp: " fmt + +/** + * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes + * @image: the active struct kimage + * + * To accurately reflect hot un/plug changes, the new elfcorehdr + * is prepared in a kernel buffer, and then it is written on top + * of the existing/old elfcorehdr. + */ +void arch_crash_handle_hotplug_event(struct kimage *image) +{ + void *elfbuf =3D NULL, *old_elfcorehdr; + unsigned long mem, memsz; + unsigned long elfsz =3D 0; + + /* + * Create the new elfcorehdr reflecting the changes to CPU and/or + * memory resources. + */ + if (prepare_elf_headers(image, &elfbuf, &elfsz)) { + pr_err("unable to prepare elfcore headers"); + goto out; + } + + /* + * Obtain address and size of the elfcorehdr segment, and + * check it against the new elfcorehdr buffer. + */ + mem =3D image->segment[image->elfcorehdr_index].mem; + memsz =3D image->segment[image->elfcorehdr_index].memsz; + if (elfsz > memsz) { + pr_err("update elfcorehdr elfsz %lu > memsz %lu", + elfsz, memsz); + goto out; + } + + /* + * Copy new elfcorehdr over the old elfcorehdr at destination. + */ + old_elfcorehdr =3D kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT)); + if (old_elfcorehdr) { + pr_err("updating elfcorehdr failed\n"); + goto out; + } + + /* + * Temporarily invalidate the crash image while the + * elfcorehdr is updated. + */ + xchg(&kexec_crash_image, NULL); + memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz); + xchg(&kexec_crash_image, image); + kunmap_local(old_elfcorehdr); + pr_debug("updated elfcorehdr\n"); + +out: + vfree(elfbuf); +} +#endif --=20 2.31.1