// SPDX-License-Identifier: GPL-2.0-only
/* adi_64.c: support for ADI (Application Data Integrity) feature on
 * sparc m7 and newer processors. This feature is also known as
 * SSM (Silicon Secured Memory).
 *
 * Copyright (C) 2016 Oracle and/or its affiliates. All rights reserved.
 * Author: Khalid Aziz (khalid.aziz@oracle.com)
 */
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/mm_types.h>
#include <asm/mdesc.h>
#include <asm/adi_64.h>
#include <asm/mmu_64.h>
#include <asm/pgtable_64.h>

/* Each page of storage for ADI tags can accommodate tags for 128
 * pages. When ADI enabled pages are being swapped out, it would be
 * prudent to allocate at least enough tag storage space to accommodate
 * SWAPFILE_CLUSTER number of pages. Allocate enough tag storage to
 * store tags for four SWAPFILE_CLUSTER pages to reduce need for
 * further allocations for same vma.
 */
#define TAG_STORAGE_PAGES       8

struct adi_config adi_state;
EXPORT_SYMBOL(adi_state);

/* mdesc_adi_init() : Parse machine description provided by the
 *      hypervisor to detect ADI capabilities
 *
 * Hypervisor reports ADI capabilities of platform in "hwcap-list" property
 * for "cpu" node. If the platform supports ADI, "hwcap-list" property
 * contains the keyword "adp". If the platform supports ADI, "platform"
 * node will contain "adp-blksz", "adp-nbits" and "ue-on-adp" properties
 * to describe the ADI capabilities.
 */
void __init mdesc_adi_init(void)
{
        struct mdesc_handle *hp = mdesc_grab();
        const char *prop;
        u64 pn, *val;
        int len;

        if (!hp)
                goto adi_not_found;

        pn = mdesc_node_by_name(hp, MDESC_NODE_NULL, "cpu");
        if (pn == MDESC_NODE_NULL)
                goto adi_not_found;

        prop = mdesc_get_property(hp, pn, "hwcap-list", &len);
        if (!prop)
                goto adi_not_found;

        /*
         * Look for "adp" keyword in hwcap-list which would indicate
         * ADI support
         */
        adi_state.enabled = false;
        while (len) {
                int plen;

                if (!strcmp(prop, "adp")) {
                        adi_state.enabled = true;
                        break;
                }

                plen = strlen(prop) + 1;
                prop += plen;
                len -= plen;
        }

        if (!adi_state.enabled)
                goto adi_not_found;

        /* Find the ADI properties in "platform" node. If all ADI
         * properties are not found, ADI support is incomplete and
         * do not enable ADI in the kernel.
         */
        pn = mdesc_node_by_name(hp, MDESC_NODE_NULL, "platform");
        if (pn == MDESC_NODE_NULL)
                goto adi_not_found;

        val = (u64 *) mdesc_get_property(hp, pn, "adp-blksz", &len);
        if (!val)
                goto adi_not_found;
        adi_state.caps.blksz = *val;

        val = (u64 *) mdesc_get_property(hp, pn, "adp-nbits", &len);
        if (!val)
                goto adi_not_found;
        adi_state.caps.nbits = *val;

        val = (u64 *) mdesc_get_property(hp, pn, "ue-on-adp", &len);
        if (!val)
                goto adi_not_found;
        adi_state.caps.ue_on_adi = *val;

        /* Some of the code to support swapping ADI tags is written
         * assumption that two ADI tags can fit inside one byte. If
         * this assumption is broken by a future architecture change,
         * that code will have to be revisited. If that were to happen,
         * disable ADI support so we do not get unpredictable results
         * with programs trying to use ADI and their pages getting
         * swapped out
         */
        if (adi_state.caps.nbits > 4) {
                pr_warn("WARNING: ADI tag size >4 on this platform. Disabling AADI support\n");
                adi_state.enabled = false;
        }

        mdesc_release(hp);
        return;

adi_not_found:
        adi_state.enabled = false;
        adi_state.caps.blksz = 0;
        adi_state.caps.nbits = 0;
        if (hp)
                mdesc_release(hp);
}

static tag_storage_desc_t *find_tag_store(struct mm_struct *mm,
                                          struct vm_area_struct *vma,
                                          unsigned long addr)
{
        tag_storage_desc_t *tag_desc = NULL;
        unsigned long i, max_desc, flags;

        /* Check if this vma already has tag storage descriptor
         * allocated for it.
         */
        max_desc = PAGE_SIZE/sizeof(tag_storage_desc_t);
        if (mm->context.tag_store) {
                tag_desc = mm->context.tag_store;
                spin_lock_irqsave(&mm->context.tag_lock, flags);
                for (i = 0; i < max_desc; i++) {
                        if ((addr >= tag_desc->start) &&
                            ((addr + PAGE_SIZE - 1) <= tag_desc->end))
                                break;
                        tag_desc++;
                }
                spin_unlock_irqrestore(&mm->context.tag_lock, flags);

                /* If no matching entries were found, this must be a
                 * freshly allocated page
                 */
                if (i >= max_desc)
                        tag_desc = NULL;
        }

        return tag_desc;
}

static tag_storage_desc_t *alloc_tag_store(struct mm_struct *mm,
                                           struct vm_area_struct *vma,
                                           unsigned long addr)
{
        unsigned char *tags;
        unsigned long i, size, max_desc, flags;
        tag_storage_desc_t *tag_desc, *open_desc;
        unsigned long end_addr, hole_start, hole_end;

        max_desc = PAGE_SIZE/sizeof(tag_storage_desc_t);
        open_desc = NULL;
        hole_start = 0;
        hole_end = ULONG_MAX;
        end_addr = addr + PAGE_SIZE - 1;

        /* Check if this vma already has tag storage descriptor
         * allocated for it.
         */
        spin_lock_irqsave(&mm->context.tag_lock, flags);
        if (mm->context.tag_store) {
                tag_desc = mm->context.tag_store;

                /* Look for a matching entry for this address. While doing
                 * that, look for the first open slot as well and find
                 * the hole in already allocated range where this request
                 * will fit in.
                 */
                for (i = 0; i < max_desc; i++) {
                        if (tag_desc->tag_users == 0) {
                                if (open_desc == NULL)
                                        open_desc = tag_desc;
                        } else {
                                if ((addr >= tag_desc->start) &&
                                    (tag_desc->end >= (addr + PAGE_SIZE - 1))) {
                                        tag_desc->tag_users++;
                                        goto out;
                                }
                        }
                        if ((tag_desc->start > end_addr) &&
                            (tag_desc->start < hole_end))
                                hole_end = tag_desc->start;
                        if ((tag_desc->end < addr) &&
                            (tag_desc->end > hole_start))
                                hole_start = tag_desc->end;
                        tag_desc++;
                }

        } else {
                size = sizeof(tag_storage_desc_t)*max_desc;
                mm->context.tag_store = kzalloc(size, GFP_NOWAIT);
                if (mm->context.tag_store == NULL) {
                        tag_desc = NULL;
                        goto out;
                }
                tag_desc = mm->context.tag_store;
                for (i = 0; i < max_desc; i++, tag_desc++)
                        tag_desc->tag_users = 0;
                open_desc = mm->context.tag_store;
                i = 0;
        }

        /* Check if we ran out of tag storage descriptors */
        if (open_desc == NULL) {
                tag_desc = NULL;
                goto out;
        }

        /* Mark this tag descriptor slot in use and then initialize it */
        tag_desc = open_desc;
        tag_desc->tag_users = 1;

        /* Tag storage has not been allocated for this vma and space
         * is available in tag storage descriptor. Since this page is
         * being swapped out, there is high probability subsequent pages
         * in the VMA will be swapped out as well. Allocate pages to
         * store tags for as many pages in this vma as possible but not
         * more than TAG_STORAGE_PAGES. Each byte in tag space holds
         * two ADI tags since each ADI tag is 4 bits. Each ADI tag
         * covers adi_blksize() worth of addresses. Check if the hole is
         * big enough to accommodate full address range for using
         * TAG_STORAGE_PAGES number of tag pages.
         */
        size = TAG_STORAGE_PAGES * PAGE_SIZE;
        end_addr = addr + (size*2*adi_blksize()) - 1;
        /* Check for overflow. If overflow occurs, allocate only one page */
        if (end_addr < addr) {
                size = PAGE_SIZE;
                end_addr = addr + (size*2*adi_blksize()) - 1;
                /* If overflow happens with the minimum tag storage
                 * allocation as well, adjust ending address for this
                 * tag storage.
                 */
                if (end_addr < addr)
                        end_addr = ULONG_MAX;
        }
        if (hole_end < end_addr) {
                /* Available hole is too small on the upper end of
                 * address. Can we expand the range towards the lower
                 * address and maximize use of this slot?
                 */
                unsigned long tmp_addr;

                end_addr = hole_end - 1;
                tmp_addr = end_addr - (size*2*adi_blksize()) + 1;
                /* Check for underflow. If underflow occurs, allocate
                 * only one page for storing ADI tags
                 */
                if (tmp_addr > addr) {
                        size = PAGE_SIZE;
                        tmp_addr = end_addr - (size*2*adi_blksize()) - 1;
                        /* If underflow happens with the minimum tag storage
                         * allocation as well, adjust starting address for
                         * this tag storage.
                         */
                        if (tmp_addr > addr)
                                tmp_addr = 0;
                }
                if (tmp_addr < hole_start) {
                        /* Available hole is restricted on lower address
                         * end as well
                         */
                        tmp_addr = hole_start + 1;
                }
                addr = tmp_addr;
                size = (end_addr + 1 - addr)/(2*adi_blksize());
                size = (size + (PAGE_SIZE-adi_blksize()))/PAGE_SIZE;
                size = size * PAGE_SIZE;
        }
        tags = kzalloc(size, GFP_NOWAIT);
        if (tags == NULL) {
                tag_desc->tag_users = 0;
                tag_desc = NULL;
                goto out;
        }
        tag_desc->start = addr;
        tag_desc->tags = tags;
        tag_desc->end = end_addr;

out:
        spin_unlock_irqrestore(&mm->context.tag_lock, flags);
        return tag_desc;
}

static void del_tag_store(tag_storage_desc_t *tag_desc, struct mm_struct *mm)
{
        unsigned long flags;
        unsigned char *tags = NULL;

        spin_lock_irqsave(&mm->context.tag_lock, flags);
        tag_desc->tag_users--;
        if (tag_desc->tag_users == 0) {
                tag_desc->start = tag_desc->end = 0;
                /* Do not free up the tag storage space allocated
                 * by the first descriptor. This is persistent
                 * emergency tag storage space for the task.
                 */
                if (tag_desc != mm->context.tag_store) {
                        tags = tag_desc->tags;
                        tag_desc->tags = NULL;
                }
        }
        spin_unlock_irqrestore(&mm->context.tag_lock, flags);
        kfree(tags);
}

#define tag_start(addr, tag_desc)               \
        ((tag_desc)->tags + ((addr - (tag_desc)->start)/(2*adi_blksize())))

/* Retrieve any saved ADI tags for the page being swapped back in and
 * restore these tags to the newly allocated physical page.
 */
void adi_restore_tags(struct mm_struct *mm, struct vm_area_struct *vma,
                      unsigned long addr, pte_t pte)
{
        unsigned char *tag;
        tag_storage_desc_t *tag_desc;
        unsigned long paddr, tmp, version1, version2;

        /* Check if the swapped out page has an ADI version
         * saved. If yes, restore version tag to the newly
         * allocated page.
         */
        tag_desc = find_tag_store(mm, vma, addr);
        if (tag_desc == NULL)
                return;

        tag = tag_start(addr, tag_desc);
        paddr = pte_val(pte) & _PAGE_PADDR_4V;
        for (tmp = paddr; tmp < (paddr+PAGE_SIZE); tmp += adi_blksize()) {
                version1 = (*tag) >> 4;
                version2 = (*tag) & 0x0f;
                *tag++ = 0;
                asm volatile("stxa %0, [%1] %2\n\t"
                        :
                        : "r" (version1), "r" (tmp),
                          "i" (ASI_MCD_REAL));
                tmp += adi_blksize();
                asm volatile("stxa %0, [%1] %2\n\t"
                        :
                        : "r" (version2), "r" (tmp),
                          "i" (ASI_MCD_REAL));
        }
        asm volatile("membar #Sync\n\t");

        /* Check and mark this tag space for release later if
         * the swapped in page was the last user of tag space
         */
        del_tag_store(tag_desc, mm);
}

/* A page is about to be swapped out. Save any ADI tags associated with
 * this physical page so they can be restored later when the page is swapped
 * back in.
 */
int adi_save_tags(struct mm_struct *mm, struct vm_area_struct *vma,
                  unsigned long addr, pte_t oldpte)
{
        unsigned char *tag;
        tag_storage_desc_t *tag_desc;
        unsigned long version1, version2, paddr, tmp;

        tag_desc = alloc_tag_store(mm, vma, addr);
        if (tag_desc == NULL)
                return -1;

        tag = tag_start(addr, tag_desc);
        paddr = pte_val(oldpte) & _PAGE_PADDR_4V;
        for (tmp = paddr; tmp < (paddr+PAGE_SIZE); tmp += adi_blksize()) {
                asm volatile("ldxa [%1] %2, %0\n\t"
                                : "=r" (version1)
                                : "r" (tmp), "i" (ASI_MCD_REAL));
                tmp += adi_blksize();
                asm volatile("ldxa [%1] %2, %0\n\t"
                                : "=r" (version2)
                                : "r" (tmp), "i" (ASI_MCD_REAL));
                *tag = (version1 << 4) | version2;
                tag++;
        }

        return 0;
}