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![Sourabh Jain](/assets/img/avatar_default.png)
Commit a72bbec70d
("crash: hotplug support for kexec_load()")
introduced a new kexec flag, `KEXEC_UPDATE_ELFCOREHDR`. Kexec tool uses
this flag to indicate to the kernel that it is safe to modify the
elfcorehdr of the kdump image loaded using the kexec_load system call.
However, it is possible that architectures may need to update kexec
segments other then elfcorehdr. For example, FDT (Flatten Device Tree)
on PowerPC. Introducing a new kexec flag for every new kexec segment
may not be a good solution. Hence, a generic kexec flag bit,
`KEXEC_CRASH_HOTPLUG_SUPPORT`, is introduced to share the CPU/Memory
hotplug support intent between the kexec tool and the kernel for the
kexec_load system call.
Now we have two kexec flags that enables crash hotplug support for
kexec_load system call. First is KEXEC_UPDATE_ELFCOREHDR (only used in
x86), and second is KEXEC_CRASH_HOTPLUG_SUPPORT (for all architectures).
To simplify the process of finding and reporting the crash hotplug
support the following changes are introduced.
1. Define arch specific function to process the kexec flags and
determine crash hotplug support
2. Rename the @update_elfcorehdr member of struct kimage to
@hotplug_support and populate it for both kexec_load and
kexec_file_load syscalls, because architecture can update more than
one kexec segment
3. Let generic function crash_check_hotplug_support report hotplug
support for loaded kdump image based on value of @hotplug_support
To bring the x86 crash hotplug support in line with the above points,
the following changes have been made:
- Introduce the arch_crash_hotplug_support function to process kexec
flags and determine crash hotplug support
- Remove the arch_crash_hotplug_[cpu|memory]_support functions
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240326055413.186534-3-sourabhjain@linux.ibm.com
310 lines
7.6 KiB
C
310 lines
7.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* kexec.c - kexec_load system call
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* Copyright (C) 2002-2004 Eric Biederman <ebiederm@xmission.com>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/capability.h>
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#include <linux/mm.h>
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#include <linux/file.h>
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#include <linux/security.h>
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#include <linux/kexec.h>
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#include <linux/mutex.h>
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#include <linux/list.h>
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#include <linux/syscalls.h>
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#include <linux/vmalloc.h>
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#include <linux/slab.h>
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#include "kexec_internal.h"
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static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
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unsigned long nr_segments,
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struct kexec_segment *segments,
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unsigned long flags)
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{
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int ret;
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struct kimage *image;
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bool kexec_on_panic = flags & KEXEC_ON_CRASH;
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#ifdef CONFIG_CRASH_DUMP
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if (kexec_on_panic) {
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/* Verify we have a valid entry point */
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if ((entry < phys_to_boot_phys(crashk_res.start)) ||
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(entry > phys_to_boot_phys(crashk_res.end)))
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return -EADDRNOTAVAIL;
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}
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#endif
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/* Allocate and initialize a controlling structure */
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image = do_kimage_alloc_init();
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if (!image)
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return -ENOMEM;
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image->start = entry;
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image->nr_segments = nr_segments;
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memcpy(image->segment, segments, nr_segments * sizeof(*segments));
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#ifdef CONFIG_CRASH_DUMP
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if (kexec_on_panic) {
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/* Enable special crash kernel control page alloc policy. */
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image->control_page = crashk_res.start;
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image->type = KEXEC_TYPE_CRASH;
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}
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#endif
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ret = sanity_check_segment_list(image);
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if (ret)
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goto out_free_image;
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/*
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* Find a location for the control code buffer, and add it
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* the vector of segments so that it's pages will also be
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* counted as destination pages.
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*/
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ret = -ENOMEM;
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image->control_code_page = kimage_alloc_control_pages(image,
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get_order(KEXEC_CONTROL_PAGE_SIZE));
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if (!image->control_code_page) {
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pr_err("Could not allocate control_code_buffer\n");
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goto out_free_image;
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}
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if (!kexec_on_panic) {
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image->swap_page = kimage_alloc_control_pages(image, 0);
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if (!image->swap_page) {
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pr_err("Could not allocate swap buffer\n");
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goto out_free_control_pages;
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}
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}
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*rimage = image;
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return 0;
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out_free_control_pages:
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kimage_free_page_list(&image->control_pages);
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out_free_image:
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kfree(image);
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return ret;
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}
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static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
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struct kexec_segment *segments, unsigned long flags)
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{
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struct kimage **dest_image, *image;
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unsigned long i;
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int ret;
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/*
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* Because we write directly to the reserved memory region when loading
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* crash kernels we need a serialization here to prevent multiple crash
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* kernels from attempting to load simultaneously.
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*/
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if (!kexec_trylock())
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return -EBUSY;
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#ifdef CONFIG_CRASH_DUMP
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if (flags & KEXEC_ON_CRASH) {
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dest_image = &kexec_crash_image;
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if (kexec_crash_image)
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arch_kexec_unprotect_crashkres();
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} else
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#endif
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dest_image = &kexec_image;
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if (nr_segments == 0) {
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/* Uninstall image */
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kimage_free(xchg(dest_image, NULL));
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ret = 0;
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goto out_unlock;
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}
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if (flags & KEXEC_ON_CRASH) {
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/*
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* Loading another kernel to switch to if this one
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* crashes. Free any current crash dump kernel before
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* we corrupt it.
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*/
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kimage_free(xchg(&kexec_crash_image, NULL));
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}
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ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
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if (ret)
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goto out_unlock;
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if (flags & KEXEC_PRESERVE_CONTEXT)
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image->preserve_context = 1;
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#ifdef CONFIG_CRASH_HOTPLUG
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if ((flags & KEXEC_ON_CRASH) && arch_crash_hotplug_support(image, flags))
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image->hotplug_support = 1;
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#endif
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ret = machine_kexec_prepare(image);
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if (ret)
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goto out;
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/*
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* Some architecture(like S390) may touch the crash memory before
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* machine_kexec_prepare(), we must copy vmcoreinfo data after it.
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*/
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ret = kimage_crash_copy_vmcoreinfo(image);
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if (ret)
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goto out;
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for (i = 0; i < nr_segments; i++) {
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ret = kimage_load_segment(image, &image->segment[i]);
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if (ret)
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goto out;
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}
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kimage_terminate(image);
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ret = machine_kexec_post_load(image);
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if (ret)
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goto out;
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/* Install the new kernel and uninstall the old */
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image = xchg(dest_image, image);
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out:
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#ifdef CONFIG_CRASH_DUMP
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if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
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arch_kexec_protect_crashkres();
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#endif
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kimage_free(image);
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out_unlock:
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kexec_unlock();
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return ret;
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}
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/*
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* Exec Kernel system call: for obvious reasons only root may call it.
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*
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* This call breaks up into three pieces.
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* - A generic part which loads the new kernel from the current
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* address space, and very carefully places the data in the
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* allocated pages.
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*
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* - A generic part that interacts with the kernel and tells all of
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* the devices to shut down. Preventing on-going dmas, and placing
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* the devices in a consistent state so a later kernel can
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* reinitialize them.
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*
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* - A machine specific part that includes the syscall number
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* and then copies the image to it's final destination. And
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* jumps into the image at entry.
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*
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* kexec does not sync, or unmount filesystems so if you need
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* that to happen you need to do that yourself.
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*/
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static inline int kexec_load_check(unsigned long nr_segments,
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unsigned long flags)
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{
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int image_type = (flags & KEXEC_ON_CRASH) ?
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KEXEC_TYPE_CRASH : KEXEC_TYPE_DEFAULT;
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int result;
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/* We only trust the superuser with rebooting the system. */
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if (!kexec_load_permitted(image_type))
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return -EPERM;
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/* Permit LSMs and IMA to fail the kexec */
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result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
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if (result < 0)
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return result;
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/*
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* kexec can be used to circumvent module loading restrictions, so
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* prevent loading in that case
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*/
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result = security_locked_down(LOCKDOWN_KEXEC);
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if (result)
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return result;
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/*
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* Verify we have a legal set of flags
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* This leaves us room for future extensions.
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*/
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if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
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return -EINVAL;
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/* Put an artificial cap on the number
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* of segments passed to kexec_load.
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*/
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if (nr_segments > KEXEC_SEGMENT_MAX)
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return -EINVAL;
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return 0;
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}
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SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
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struct kexec_segment __user *, segments, unsigned long, flags)
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{
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struct kexec_segment *ksegments;
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unsigned long result;
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result = kexec_load_check(nr_segments, flags);
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if (result)
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return result;
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/* Verify we are on the appropriate architecture */
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if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
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((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
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return -EINVAL;
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ksegments = memdup_array_user(segments, nr_segments, sizeof(ksegments[0]));
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if (IS_ERR(ksegments))
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return PTR_ERR(ksegments);
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result = do_kexec_load(entry, nr_segments, ksegments, flags);
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kfree(ksegments);
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return result;
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}
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#ifdef CONFIG_COMPAT
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COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
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compat_ulong_t, nr_segments,
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struct compat_kexec_segment __user *, segments,
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compat_ulong_t, flags)
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{
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struct compat_kexec_segment in;
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struct kexec_segment *ksegments;
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unsigned long i, result;
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result = kexec_load_check(nr_segments, flags);
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if (result)
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return result;
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/* Don't allow clients that don't understand the native
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* architecture to do anything.
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*/
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if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
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return -EINVAL;
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ksegments = kmalloc_array(nr_segments, sizeof(ksegments[0]),
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GFP_KERNEL);
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if (!ksegments)
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return -ENOMEM;
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for (i = 0; i < nr_segments; i++) {
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result = copy_from_user(&in, &segments[i], sizeof(in));
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if (result)
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goto fail;
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ksegments[i].buf = compat_ptr(in.buf);
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ksegments[i].bufsz = in.bufsz;
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ksegments[i].mem = in.mem;
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ksegments[i].memsz = in.memsz;
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}
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result = do_kexec_load(entry, nr_segments, ksegments, flags);
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fail:
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kfree(ksegments);
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return result;
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}
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#endif
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