309 lines
8.7 KiB
C
309 lines
8.7 KiB
C
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/*
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* EFI capsule support.
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*
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* Copyright 2013 Intel Corporation; author Matt Fleming
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*/
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#define pr_fmt(fmt) "efi: " fmt
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#include <linux/slab.h>
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#include <linux/mutex.h>
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#include <linux/highmem.h>
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#include <linux/efi.h>
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#include <linux/vmalloc.h>
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#include <asm/io.h>
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typedef struct {
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u64 length;
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u64 data;
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} efi_capsule_block_desc_t;
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static bool capsule_pending;
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static bool stop_capsules;
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static int efi_reset_type = -1;
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/*
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* capsule_mutex serialises access to both capsule_pending and
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* efi_reset_type and stop_capsules.
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*/
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static DEFINE_MUTEX(capsule_mutex);
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/**
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* efi_capsule_pending - has a capsule been passed to the firmware?
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* @reset_type: store the type of EFI reset if capsule is pending
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*
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* To ensure that the registered capsule is processed correctly by the
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* firmware we need to perform a specific type of reset. If a capsule is
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* pending return the reset type in @reset_type.
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*
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* This function will race with callers of efi_capsule_update(), for
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* example, calling this function while somebody else is in
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* efi_capsule_update() but hasn't reached efi_capsue_update_locked()
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* will miss the updates to capsule_pending and efi_reset_type after
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* efi_capsule_update_locked() completes.
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*
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* A non-racy use is from platform reboot code because we use
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* system_state to ensure no capsules can be sent to the firmware once
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* we're at SYSTEM_RESTART. See efi_capsule_update_locked().
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*/
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bool efi_capsule_pending(int *reset_type)
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{
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if (!capsule_pending)
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return false;
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if (reset_type)
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*reset_type = efi_reset_type;
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return true;
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}
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/*
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* Whitelist of EFI capsule flags that we support.
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*
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* We do not handle EFI_CAPSULE_INITIATE_RESET because that would
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* require us to prepare the kernel for reboot. Refuse to load any
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* capsules with that flag and any other flags that we do not know how
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* to handle.
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*/
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#define EFI_CAPSULE_SUPPORTED_FLAG_MASK \
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(EFI_CAPSULE_PERSIST_ACROSS_RESET | EFI_CAPSULE_POPULATE_SYSTEM_TABLE)
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/**
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* efi_capsule_supported - does the firmware support the capsule?
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* @guid: vendor guid of capsule
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* @flags: capsule flags
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* @size: size of capsule data
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* @reset: the reset type required for this capsule
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*
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* Check whether a capsule with @flags is supported by the firmware
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* and that @size doesn't exceed the maximum size for a capsule.
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*
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* No attempt is made to check @reset against the reset type required
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* by any pending capsules because of the races involved.
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*/
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int efi_capsule_supported(efi_guid_t guid, u32 flags, size_t size, int *reset)
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{
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efi_capsule_header_t capsule;
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efi_capsule_header_t *cap_list[] = { &capsule };
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efi_status_t status;
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u64 max_size;
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if (flags & ~EFI_CAPSULE_SUPPORTED_FLAG_MASK)
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return -EINVAL;
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capsule.headersize = capsule.imagesize = sizeof(capsule);
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memcpy(&capsule.guid, &guid, sizeof(efi_guid_t));
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capsule.flags = flags;
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status = efi.query_capsule_caps(cap_list, 1, &max_size, reset);
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if (status != EFI_SUCCESS)
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return efi_status_to_err(status);
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if (size > max_size)
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return -ENOSPC;
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return 0;
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}
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EXPORT_SYMBOL_GPL(efi_capsule_supported);
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/*
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* Every scatter gather list (block descriptor) page must end with a
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* continuation pointer. The last continuation pointer of the last
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* page must be zero to mark the end of the chain.
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*/
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#define SGLIST_PER_PAGE ((PAGE_SIZE / sizeof(efi_capsule_block_desc_t)) - 1)
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/*
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* How many scatter gather list (block descriptor) pages do we need
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* to map @count pages?
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*/
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static inline unsigned int sg_pages_num(unsigned int count)
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{
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return DIV_ROUND_UP(count, SGLIST_PER_PAGE);
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}
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/**
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* efi_capsule_update_locked - pass a single capsule to the firmware
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* @capsule: capsule to send to the firmware
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* @sg_pages: array of scatter gather (block descriptor) pages
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* @reset: the reset type required for @capsule
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*
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* Since this function must be called under capsule_mutex check
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* whether efi_reset_type will conflict with @reset, and atomically
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* set it and capsule_pending if a capsule was successfully sent to
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* the firmware.
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*
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* We also check to see if the system is about to restart, and if so,
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* abort. This avoids races between efi_capsule_update() and
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* efi_capsule_pending().
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*/
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static int
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efi_capsule_update_locked(efi_capsule_header_t *capsule,
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struct page **sg_pages, int reset)
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{
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efi_physical_addr_t sglist_phys;
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efi_status_t status;
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lockdep_assert_held(&capsule_mutex);
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/*
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* If someone has already registered a capsule that requires a
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* different reset type, we're out of luck and must abort.
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*/
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if (efi_reset_type >= 0 && efi_reset_type != reset) {
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pr_err("Conflicting capsule reset type %d (%d).\n",
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reset, efi_reset_type);
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return -EINVAL;
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}
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/*
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* If the system is getting ready to restart it may have
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* called efi_capsule_pending() to make decisions (such as
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* whether to force an EFI reboot), and we're racing against
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* that call. Abort in that case.
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*/
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if (unlikely(stop_capsules)) {
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pr_warn("Capsule update raced with reboot, aborting.\n");
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return -EINVAL;
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}
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sglist_phys = page_to_phys(sg_pages[0]);
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status = efi.update_capsule(&capsule, 1, sglist_phys);
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if (status == EFI_SUCCESS) {
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capsule_pending = true;
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efi_reset_type = reset;
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}
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return efi_status_to_err(status);
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}
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/**
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* efi_capsule_update - send a capsule to the firmware
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* @capsule: capsule to send to firmware
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* @pages: an array of capsule data pages
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*
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* Build a scatter gather list with EFI capsule block descriptors to
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* map the capsule described by @capsule with its data in @pages and
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* send it to the firmware via the UpdateCapsule() runtime service.
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*
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* @capsule must be a virtual mapping of the complete capsule update in the
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* kernel address space, as the capsule can be consumed immediately.
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* A capsule_header_t that describes the entire contents of the capsule
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* must be at the start of the first data page.
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*
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* Even though this function will validate that the firmware supports
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* the capsule guid, users will likely want to check that
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* efi_capsule_supported() returns true before calling this function
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* because it makes it easier to print helpful error messages.
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*
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* If the capsule is successfully submitted to the firmware, any
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* subsequent calls to efi_capsule_pending() will return true. @pages
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* must not be released or modified if this function returns
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* successfully.
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*
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* Callers must be prepared for this function to fail, which can
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* happen if we raced with system reboot or if there is already a
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* pending capsule that has a reset type that conflicts with the one
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* required by @capsule. Do NOT use efi_capsule_pending() to detect
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* this conflict since that would be racy. Instead, submit the capsule
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* to efi_capsule_update() and check the return value.
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*
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* Return 0 on success, a converted EFI status code on failure.
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*/
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int efi_capsule_update(efi_capsule_header_t *capsule, struct page **pages)
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{
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u32 imagesize = capsule->imagesize;
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efi_guid_t guid = capsule->guid;
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unsigned int count, sg_count;
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u32 flags = capsule->flags;
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struct page **sg_pages;
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int rv, reset_type;
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int i, j;
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rv = efi_capsule_supported(guid, flags, imagesize, &reset_type);
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if (rv)
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return rv;
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count = DIV_ROUND_UP(imagesize, PAGE_SIZE);
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sg_count = sg_pages_num(count);
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sg_pages = kzalloc(sg_count * sizeof(*sg_pages), GFP_KERNEL);
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if (!sg_pages)
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return -ENOMEM;
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for (i = 0; i < sg_count; i++) {
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sg_pages[i] = alloc_page(GFP_KERNEL);
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if (!sg_pages[i]) {
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rv = -ENOMEM;
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goto out;
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}
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}
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for (i = 0; i < sg_count; i++) {
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efi_capsule_block_desc_t *sglist;
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sglist = kmap(sg_pages[i]);
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if (!sglist) {
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rv = -ENOMEM;
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goto out;
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}
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for (j = 0; j < SGLIST_PER_PAGE && count > 0; j++) {
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u64 sz = min_t(u64, imagesize, PAGE_SIZE);
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sglist[j].length = sz;
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sglist[j].data = page_to_phys(*pages++);
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imagesize -= sz;
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count--;
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}
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/* Continuation pointer */
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sglist[j].length = 0;
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if (i + 1 == sg_count)
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sglist[j].data = 0;
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else
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sglist[j].data = page_to_phys(sg_pages[i + 1]);
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kunmap(sg_pages[i]);
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}
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mutex_lock(&capsule_mutex);
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rv = efi_capsule_update_locked(capsule, sg_pages, reset_type);
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mutex_unlock(&capsule_mutex);
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out:
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for (i = 0; rv && i < sg_count; i++) {
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if (sg_pages[i])
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__free_page(sg_pages[i]);
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}
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kfree(sg_pages);
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return rv;
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}
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EXPORT_SYMBOL_GPL(efi_capsule_update);
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static int capsule_reboot_notify(struct notifier_block *nb, unsigned long event, void *cmd)
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{
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mutex_lock(&capsule_mutex);
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stop_capsules = true;
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mutex_unlock(&capsule_mutex);
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return NOTIFY_DONE;
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}
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static struct notifier_block capsule_reboot_nb = {
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.notifier_call = capsule_reboot_notify,
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};
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static int __init capsule_reboot_register(void)
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{
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return register_reboot_notifier(&capsule_reboot_nb);
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}
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core_initcall(capsule_reboot_register);
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