linux/arch/x86/kernel/crash.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Architecture specific (i386/x86_64) functions for kexec based crash dumps.
 *
 * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 *
 * Copyright (C) IBM Corporation, 2004. All rights reserved.
 * Copyright (C) Red Hat Inc., 2014. All rights reserved.
 * Authors:
 *      Vivek Goyal <vgoyal@redhat.com>
 *
 */

#define pr_fmt(fmt)	"kexec: " fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/delay.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/memblock.h>

#include <asm/bootparam.h>
#include <asm/processor.h>
#include <asm/hardirq.h>
#include <asm/nmi.h>
#include <asm/hw_irq.h>
#include <asm/apic.h>
#include <asm/e820/types.h>
#include <asm/io_apic.h>
#include <asm/hpet.h>
#include <linux/kdebug.h>
#include <asm/cpu.h>
#include <asm/reboot.h>
#include <asm/intel_pt.h>
#include <asm/crash.h>
#include <asm/cmdline.h>
#include <asm/sev.h>

/* Used while preparing memory map entries for second kernel */
struct crash_memmap_data {
	struct boot_params *params;
	/* Type of memory */
	unsigned int type;
};

#if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)

static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
{
	crash_save_cpu(regs, cpu);

	/*
	 * Disable Intel PT to stop its logging
	 */
	cpu_emergency_stop_pt();

	kdump_sev_callback();

	disable_local_APIC();
}

void kdump_nmi_shootdown_cpus(void)
{
	nmi_shootdown_cpus(kdump_nmi_callback);

	disable_local_APIC();
}

/* Override the weak function in kernel/panic.c */
void crash_smp_send_stop(void)
{
	static int cpus_stopped;

	if (cpus_stopped)
		return;

	if (smp_ops.crash_stop_other_cpus)
		smp_ops.crash_stop_other_cpus();
	else
		smp_send_stop();

	cpus_stopped = 1;
}

#else
void crash_smp_send_stop(void)
{
	/* There are no cpus to shootdown */
}
#endif

void native_machine_crash_shutdown(struct pt_regs *regs)
{
	/* This function is only called after the system
	 * has panicked or is otherwise in a critical state.
	 * The minimum amount of code to allow a kexec'd kernel
	 * to run successfully needs to happen here.
	 *
	 * In practice this means shooting down the other cpus in
	 * an SMP system.
	 */
	/* The kernel is broken so disable interrupts */
	local_irq_disable();

	crash_smp_send_stop();

	cpu_emergency_disable_virtualization();

	/*
	 * Disable Intel PT to stop its logging
	 */
	cpu_emergency_stop_pt();

#ifdef CONFIG_X86_IO_APIC
	/* Prevent crash_kexec() from deadlocking on ioapic_lock. */
	ioapic_zap_locks();
	clear_IO_APIC();
#endif
	lapic_shutdown();
	restore_boot_irq_mode();
#ifdef CONFIG_HPET_TIMER
	hpet_disable();
#endif

	/*
	 * Non-crash kexec calls enc_kexec_begin() while scheduling is still
	 * active. This allows the callback to wait until all in-flight
	 * shared<->private conversions are complete. In a crash scenario,
	 * enc_kexec_begin() gets called after all but one CPU have been shut
	 * down and interrupts have been disabled. This allows the callback to
	 * detect a race with the conversion and report it.
	 */
	x86_platform.guest.enc_kexec_begin();
	x86_platform.guest.enc_kexec_finish();

	crash_save_cpu(regs, safe_smp_processor_id());
}

#if defined(CONFIG_KEXEC_FILE) || defined(CONFIG_CRASH_HOTPLUG)
static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
{
	unsigned int *nr_ranges = arg;

	(*nr_ranges)++;
	return 0;
}

/* Gather all the required information to prepare elf headers for ram regions */
static struct crash_mem *fill_up_crash_elf_data(void)
{
	unsigned int nr_ranges = 0;
	struct crash_mem *cmem;

	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
	if (!nr_ranges)
		return NULL;

	/*
	 * Exclusion of crash region and/or crashk_low_res may cause
	 * another range split. So add extra two slots here.
	 */
	nr_ranges += 2;
	cmem = vzalloc(struct_size(cmem, ranges, nr_ranges));
	if (!cmem)
		return NULL;

	cmem->max_nr_ranges = nr_ranges;
	cmem->nr_ranges = 0;

	return cmem;
}

/*
 * Look for any unwanted ranges between mstart, mend and remove them. This
 * might lead to split and split ranges are put in cmem->ranges[] array
 */
static int elf_header_exclude_ranges(struct crash_mem *cmem)
{
	int ret = 0;

	/* Exclude the low 1M because it is always reserved */
	ret = crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
	if (ret)
		return ret;

	/* Exclude crashkernel region */
	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
	if (ret)
		return ret;

	if (crashk_low_res.end)
		ret = crash_exclude_mem_range(cmem, crashk_low_res.start,
					      crashk_low_res.end);

	return ret;
}

static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
{
	struct crash_mem *cmem = arg;

	cmem->ranges[cmem->nr_ranges].start = res->start;
	cmem->ranges[cmem->nr_ranges].end = res->end;
	cmem->nr_ranges++;

	return 0;
}

/* Prepare elf headers. Return addr and size */
static int prepare_elf_headers(void **addr, unsigned long *sz,
			       unsigned long *nr_mem_ranges)
{
	struct crash_mem *cmem;
	int ret;

	cmem = fill_up_crash_elf_data();
	if (!cmem)
		return -ENOMEM;

	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
	if (ret)
		goto out;

	/* Exclude unwanted mem ranges */
	ret = elf_header_exclude_ranges(cmem);
	if (ret)
		goto out;

	/* Return the computed number of memory ranges, for hotplug usage */
	*nr_mem_ranges = cmem->nr_ranges;

	/* By default prepare 64bit headers */
	ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);

out:
	vfree(cmem);
	return ret;
}
#endif

#ifdef CONFIG_KEXEC_FILE
static int add_e820_entry(struct boot_params *params, struct e820_entry *entry)
{
	unsigned int nr_e820_entries;

	nr_e820_entries = params->e820_entries;
	if (nr_e820_entries >= E820_MAX_ENTRIES_ZEROPAGE)
		return 1;

	memcpy(&params->e820_table[nr_e820_entries], entry, sizeof(struct e820_entry));
	params->e820_entries++;
	return 0;
}

static int memmap_entry_callback(struct resource *res, void *arg)
{
	struct crash_memmap_data *cmd = arg;
	struct boot_params *params = cmd->params;
	struct e820_entry ei;

	ei.addr = res->start;
	ei.size = resource_size(res);
	ei.type = cmd->type;
	add_e820_entry(params, &ei);

	return 0;
}

static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
				 unsigned long long mstart,
				 unsigned long long mend)
{
	unsigned long start, end;

	cmem->ranges[0].start = mstart;
	cmem->ranges[0].end = mend;
	cmem->nr_ranges = 1;

	/* Exclude elf header region */
	start = image->elf_load_addr;
	end = start + image->elf_headers_sz - 1;
	return crash_exclude_mem_range(cmem, start, end);
}

/* Prepare memory map for crash dump kernel */
int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
{
	int i, ret = 0;
	unsigned long flags;
	struct e820_entry ei;
	struct crash_memmap_data cmd;
	struct crash_mem *cmem;

	cmem = vzalloc(struct_size(cmem, ranges, 1));
	if (!cmem)
		return -ENOMEM;

	memset(&cmd, 0, sizeof(struct crash_memmap_data));
	cmd.params = params;

	/* Add the low 1M */
	cmd.type = E820_TYPE_RAM;
	flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
	walk_iomem_res_desc(IORES_DESC_NONE, flags, 0, (1<<20)-1, &cmd,
			    memmap_entry_callback);

	/* Add ACPI tables */
	cmd.type = E820_TYPE_ACPI;
	flags = IORESOURCE_MEM | IORESOURCE_BUSY;
	walk_iomem_res_desc(IORES_DESC_ACPI_TABLES, flags, 0, -1, &cmd,
			    memmap_entry_callback);

	/* Add ACPI Non-volatile Storage */
	cmd.type = E820_TYPE_NVS;
	walk_iomem_res_desc(IORES_DESC_ACPI_NV_STORAGE, flags, 0, -1, &cmd,
			    memmap_entry_callback);

	/* Add e820 reserved ranges */
	cmd.type = E820_TYPE_RESERVED;
	flags = IORESOURCE_MEM;
	walk_iomem_res_desc(IORES_DESC_RESERVED, flags, 0, -1, &cmd,
			    memmap_entry_callback);

	/* Add crashk_low_res region */
	if (crashk_low_res.end) {
		ei.addr = crashk_low_res.start;
		ei.size = resource_size(&crashk_low_res);
		ei.type = E820_TYPE_RAM;
		add_e820_entry(params, &ei);
	}

	/* Exclude some ranges from crashk_res and add rest to memmap */
	ret = memmap_exclude_ranges(image, cmem, crashk_res.start, crashk_res.end);
	if (ret)
		goto out;

	for (i = 0; i < cmem->nr_ranges; i++) {
		ei.size = cmem->ranges[i].end - cmem->ranges[i].start + 1;

		/* If entry is less than a page, skip it */
		if (ei.size < PAGE_SIZE)
			continue;
		ei.addr = cmem->ranges[i].start;
		ei.type = E820_TYPE_RAM;
		add_e820_entry(params, &ei);
	}

out:
	vfree(cmem);
	return ret;
}

int crash_load_segments(struct kimage *image)
{
	int ret;
	unsigned long pnum = 0;
	struct kexec_buf kbuf = { .image = image, .buf_min = 0,
				  .buf_max = ULONG_MAX, .top_down = false };

	/* Prepare elf headers and add a segment */
	ret = prepare_elf_headers(&kbuf.buffer, &kbuf.bufsz, &pnum);
	if (ret)
		return ret;

	image->elf_headers	= kbuf.buffer;
	image->elf_headers_sz	= kbuf.bufsz;
	kbuf.memsz		= kbuf.bufsz;

#ifdef CONFIG_CRASH_HOTPLUG
	/*
	 * The elfcorehdr segment size accounts for VMCOREINFO, kernel_map,
	 * maximum CPUs and maximum memory ranges.
	 */
	if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
		pnum = 2 + CONFIG_NR_CPUS_DEFAULT + CONFIG_CRASH_MAX_MEMORY_RANGES;
	else
		pnum += 2 + CONFIG_NR_CPUS_DEFAULT;

	if (pnum < (unsigned long)PN_XNUM) {
		kbuf.memsz = pnum * sizeof(Elf64_Phdr);
		kbuf.memsz += sizeof(Elf64_Ehdr);

		image->elfcorehdr_index = image->nr_segments;

		/* Mark as usable to crash kernel, else crash kernel fails on boot */
		image->elf_headers_sz = kbuf.memsz;
	} else {
		pr_err("number of Phdrs %lu exceeds max\n", pnum);
	}
#endif

	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
	ret = kexec_add_buffer(&kbuf);
	if (ret)
		return ret;
	image->elf_load_addr = kbuf.mem;
	kexec_dprintk("Loaded ELF headers at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
		      image->elf_load_addr, kbuf.bufsz, kbuf.memsz);

	return ret;
}
#endif /* CONFIG_KEXEC_FILE */

#ifdef CONFIG_CRASH_HOTPLUG

#undef pr_fmt
#define pr_fmt(fmt) "crash hp: " fmt

int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags)
{

#ifdef CONFIG_KEXEC_FILE
	if (image->file_mode)
		return 1;
#endif
	/*
	 * Initially, crash hotplug support for kexec_load was added
	 * with the KEXEC_UPDATE_ELFCOREHDR flag. Later, this
	 * functionality was expanded to accommodate multiple kexec
	 * segment updates, leading to the introduction of the
	 * KEXEC_CRASH_HOTPLUG_SUPPORT kexec flag bit. Consequently,
	 * when the kexec tool sends either of these flags, it indicates
	 * that the required kexec segment (elfcorehdr) is excluded from
	 * the SHA calculation.
	 */
	return (kexec_flags & KEXEC_UPDATE_ELFCOREHDR ||
		kexec_flags & KEXEC_CRASH_HOTPLUG_SUPPORT);
}

unsigned int arch_crash_get_elfcorehdr_size(void)
{
	unsigned int sz;

	/* kernel_map, VMCOREINFO and maximum CPUs */
	sz = 2 + CONFIG_NR_CPUS_DEFAULT;
	if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
		sz += CONFIG_CRASH_MAX_MEMORY_RANGES;
	sz *= sizeof(Elf64_Phdr);
	return sz;
}

/**
 * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
 * @image: a pointer to kexec_crash_image
 * @arg: struct memory_notify handler for memory hotplug case and
 *       NULL for CPU hotplug case.
 *
 * Prepare the new elfcorehdr and replace the existing elfcorehdr.
 */
void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
{
	void *elfbuf = NULL, *old_elfcorehdr;
	unsigned long nr_mem_ranges;
	unsigned long mem, memsz;
	unsigned long elfsz = 0;

	/*
	 * As crash_prepare_elf64_headers() has already described all
	 * possible CPUs, there is no need to update the elfcorehdr
	 * for additional CPU changes.
	 */
	if ((image->file_mode || image->elfcorehdr_updated) &&
		((image->hp_action == KEXEC_CRASH_HP_ADD_CPU) ||
		(image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)))
		return;

	/*
	 * Create the new elfcorehdr reflecting the changes to CPU and/or
	 * memory resources.
	 */
	if (prepare_elf_headers(&elfbuf, &elfsz, &nr_mem_ranges)) {
		pr_err("unable to create new elfcorehdr");
		goto out;
	}

	/*
	 * Obtain address and size of the elfcorehdr segment, and
	 * check it against the new elfcorehdr buffer.
	 */
	mem = image->segment[image->elfcorehdr_index].mem;
	memsz = 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 = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
	if (!old_elfcorehdr) {
		pr_err("mapping elfcorehdr segment 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