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Linux/arch/sparc/kernel/adi_64.c

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  1 /* adi_64.c: support for ADI (Application Data Integrity) feature on
  2  * sparc m7 and newer processors. This feature is also known as
  3  * SSM (Silicon Secured Memory).
  4  *
  5  * Copyright (C) 2016 Oracle and/or its affiliates. All rights reserved.
  6  * Author: Khalid Aziz (khalid.aziz@oracle.com)
  7  *
  8  * This work is licensed under the terms of the GNU GPL, version 2.
  9  */
 10 #include <linux/init.h>
 11 #include <linux/slab.h>
 12 #include <linux/mm_types.h>
 13 #include <asm/mdesc.h>
 14 #include <asm/adi_64.h>
 15 #include <asm/mmu_64.h>
 16 #include <asm/pgtable_64.h>
 17 
 18 /* Each page of storage for ADI tags can accommodate tags for 128
 19  * pages. When ADI enabled pages are being swapped out, it would be
 20  * prudent to allocate at least enough tag storage space to accommodate
 21  * SWAPFILE_CLUSTER number of pages. Allocate enough tag storage to
 22  * store tags for four SWAPFILE_CLUSTER pages to reduce need for
 23  * further allocations for same vma.
 24  */
 25 #define TAG_STORAGE_PAGES       8
 26 
 27 struct adi_config adi_state;
 28 EXPORT_SYMBOL(adi_state);
 29 
 30 /* mdesc_adi_init() : Parse machine description provided by the
 31  *      hypervisor to detect ADI capabilities
 32  *
 33  * Hypervisor reports ADI capabilities of platform in "hwcap-list" property
 34  * for "cpu" node. If the platform supports ADI, "hwcap-list" property
 35  * contains the keyword "adp". If the platform supports ADI, "platform"
 36  * node will contain "adp-blksz", "adp-nbits" and "ue-on-adp" properties
 37  * to describe the ADI capabilities.
 38  */
 39 void __init mdesc_adi_init(void)
 40 {
 41         struct mdesc_handle *hp = mdesc_grab();
 42         const char *prop;
 43         u64 pn, *val;
 44         int len;
 45 
 46         if (!hp)
 47                 goto adi_not_found;
 48 
 49         pn = mdesc_node_by_name(hp, MDESC_NODE_NULL, "cpu");
 50         if (pn == MDESC_NODE_NULL)
 51                 goto adi_not_found;
 52 
 53         prop = mdesc_get_property(hp, pn, "hwcap-list", &len);
 54         if (!prop)
 55                 goto adi_not_found;
 56 
 57         /*
 58          * Look for "adp" keyword in hwcap-list which would indicate
 59          * ADI support
 60          */
 61         adi_state.enabled = false;
 62         while (len) {
 63                 int plen;
 64 
 65                 if (!strcmp(prop, "adp")) {
 66                         adi_state.enabled = true;
 67                         break;
 68                 }
 69 
 70                 plen = strlen(prop) + 1;
 71                 prop += plen;
 72                 len -= plen;
 73         }
 74 
 75         if (!adi_state.enabled)
 76                 goto adi_not_found;
 77 
 78         /* Find the ADI properties in "platform" node. If all ADI
 79          * properties are not found, ADI support is incomplete and
 80          * do not enable ADI in the kernel.
 81          */
 82         pn = mdesc_node_by_name(hp, MDESC_NODE_NULL, "platform");
 83         if (pn == MDESC_NODE_NULL)
 84                 goto adi_not_found;
 85 
 86         val = (u64 *) mdesc_get_property(hp, pn, "adp-blksz", &len);
 87         if (!val)
 88                 goto adi_not_found;
 89         adi_state.caps.blksz = *val;
 90 
 91         val = (u64 *) mdesc_get_property(hp, pn, "adp-nbits", &len);
 92         if (!val)
 93                 goto adi_not_found;
 94         adi_state.caps.nbits = *val;
 95 
 96         val = (u64 *) mdesc_get_property(hp, pn, "ue-on-adp", &len);
 97         if (!val)
 98                 goto adi_not_found;
 99         adi_state.caps.ue_on_adi = *val;
100 
101         /* Some of the code to support swapping ADI tags is written
102          * assumption that two ADI tags can fit inside one byte. If
103          * this assumption is broken by a future architecture change,
104          * that code will have to be revisited. If that were to happen,
105          * disable ADI support so we do not get unpredictable results
106          * with programs trying to use ADI and their pages getting
107          * swapped out
108          */
109         if (adi_state.caps.nbits > 4) {
110                 pr_warn("WARNING: ADI tag size >4 on this platform. Disabling AADI support\n");
111                 adi_state.enabled = false;
112         }
113 
114         mdesc_release(hp);
115         return;
116 
117 adi_not_found:
118         adi_state.enabled = false;
119         adi_state.caps.blksz = 0;
120         adi_state.caps.nbits = 0;
121         if (hp)
122                 mdesc_release(hp);
123 }
124 
125 tag_storage_desc_t *find_tag_store(struct mm_struct *mm,
126                                    struct vm_area_struct *vma,
127                                    unsigned long addr)
128 {
129         tag_storage_desc_t *tag_desc = NULL;
130         unsigned long i, max_desc, flags;
131 
132         /* Check if this vma already has tag storage descriptor
133          * allocated for it.
134          */
135         max_desc = PAGE_SIZE/sizeof(tag_storage_desc_t);
136         if (mm->context.tag_store) {
137                 tag_desc = mm->context.tag_store;
138                 spin_lock_irqsave(&mm->context.tag_lock, flags);
139                 for (i = 0; i < max_desc; i++) {
140                         if ((addr >= tag_desc->start) &&
141                             ((addr + PAGE_SIZE - 1) <= tag_desc->end))
142                                 break;
143                         tag_desc++;
144                 }
145                 spin_unlock_irqrestore(&mm->context.tag_lock, flags);
146 
147                 /* If no matching entries were found, this must be a
148                  * freshly allocated page
149                  */
150                 if (i >= max_desc)
151                         tag_desc = NULL;
152         }
153 
154         return tag_desc;
155 }
156 
157 tag_storage_desc_t *alloc_tag_store(struct mm_struct *mm,
158                                     struct vm_area_struct *vma,
159                                     unsigned long addr)
160 {
161         unsigned char *tags;
162         unsigned long i, size, max_desc, flags;
163         tag_storage_desc_t *tag_desc, *open_desc;
164         unsigned long end_addr, hole_start, hole_end;
165 
166         max_desc = PAGE_SIZE/sizeof(tag_storage_desc_t);
167         open_desc = NULL;
168         hole_start = 0;
169         hole_end = ULONG_MAX;
170         end_addr = addr + PAGE_SIZE - 1;
171 
172         /* Check if this vma already has tag storage descriptor
173          * allocated for it.
174          */
175         spin_lock_irqsave(&mm->context.tag_lock, flags);
176         if (mm->context.tag_store) {
177                 tag_desc = mm->context.tag_store;
178 
179                 /* Look for a matching entry for this address. While doing
180                  * that, look for the first open slot as well and find
181                  * the hole in already allocated range where this request
182                  * will fit in.
183                  */
184                 for (i = 0; i < max_desc; i++) {
185                         if (tag_desc->tag_users == 0) {
186                                 if (open_desc == NULL)
187                                         open_desc = tag_desc;
188                         } else {
189                                 if ((addr >= tag_desc->start) &&
190                                     (tag_desc->end >= (addr + PAGE_SIZE - 1))) {
191                                         tag_desc->tag_users++;
192                                         goto out;
193                                 }
194                         }
195                         if ((tag_desc->start > end_addr) &&
196                             (tag_desc->start < hole_end))
197                                 hole_end = tag_desc->start;
198                         if ((tag_desc->end < addr) &&
199                             (tag_desc->end > hole_start))
200                                 hole_start = tag_desc->end;
201                         tag_desc++;
202                 }
203 
204         } else {
205                 size = sizeof(tag_storage_desc_t)*max_desc;
206                 mm->context.tag_store = kzalloc(size, GFP_NOWAIT|__GFP_NOWARN);
207                 if (mm->context.tag_store == NULL) {
208                         tag_desc = NULL;
209                         goto out;
210                 }
211                 tag_desc = mm->context.tag_store;
212                 for (i = 0; i < max_desc; i++, tag_desc++)
213                         tag_desc->tag_users = 0;
214                 open_desc = mm->context.tag_store;
215                 i = 0;
216         }
217 
218         /* Check if we ran out of tag storage descriptors */
219         if (open_desc == NULL) {
220                 tag_desc = NULL;
221                 goto out;
222         }
223 
224         /* Mark this tag descriptor slot in use and then initialize it */
225         tag_desc = open_desc;
226         tag_desc->tag_users = 1;
227 
228         /* Tag storage has not been allocated for this vma and space
229          * is available in tag storage descriptor. Since this page is
230          * being swapped out, there is high probability subsequent pages
231          * in the VMA will be swapped out as well. Allocate pages to
232          * store tags for as many pages in this vma as possible but not
233          * more than TAG_STORAGE_PAGES. Each byte in tag space holds
234          * two ADI tags since each ADI tag is 4 bits. Each ADI tag
235          * covers adi_blksize() worth of addresses. Check if the hole is
236          * big enough to accommodate full address range for using
237          * TAG_STORAGE_PAGES number of tag pages.
238          */
239         size = TAG_STORAGE_PAGES * PAGE_SIZE;
240         end_addr = addr + (size*2*adi_blksize()) - 1;
241         /* Check for overflow. If overflow occurs, allocate only one page */
242         if (end_addr < addr) {
243                 size = PAGE_SIZE;
244                 end_addr = addr + (size*2*adi_blksize()) - 1;
245                 /* If overflow happens with the minimum tag storage
246                  * allocation as well, adjust ending address for this
247                  * tag storage.
248                  */
249                 if (end_addr < addr)
250                         end_addr = ULONG_MAX;
251         }
252         if (hole_end < end_addr) {
253                 /* Available hole is too small on the upper end of
254                  * address. Can we expand the range towards the lower
255                  * address and maximize use of this slot?
256                  */
257                 unsigned long tmp_addr;
258 
259                 end_addr = hole_end - 1;
260                 tmp_addr = end_addr - (size*2*adi_blksize()) + 1;
261                 /* Check for underflow. If underflow occurs, allocate
262                  * only one page for storing ADI tags
263                  */
264                 if (tmp_addr > addr) {
265                         size = PAGE_SIZE;
266                         tmp_addr = end_addr - (size*2*adi_blksize()) - 1;
267                         /* If underflow happens with the minimum tag storage
268                          * allocation as well, adjust starting address for
269                          * this tag storage.
270                          */
271                         if (tmp_addr > addr)
272                                 tmp_addr = 0;
273                 }
274                 if (tmp_addr < hole_start) {
275                         /* Available hole is restricted on lower address
276                          * end as well
277                          */
278                         tmp_addr = hole_start + 1;
279                 }
280                 addr = tmp_addr;
281                 size = (end_addr + 1 - addr)/(2*adi_blksize());
282                 size = (size + (PAGE_SIZE-adi_blksize()))/PAGE_SIZE;
283                 size = size * PAGE_SIZE;
284         }
285         tags = kzalloc(size, GFP_NOWAIT|__GFP_NOWARN);
286         if (tags == NULL) {
287                 tag_desc->tag_users = 0;
288                 tag_desc = NULL;
289                 goto out;
290         }
291         tag_desc->start = addr;
292         tag_desc->tags = tags;
293         tag_desc->end = end_addr;
294 
295 out:
296         spin_unlock_irqrestore(&mm->context.tag_lock, flags);
297         return tag_desc;
298 }
299 
300 void del_tag_store(tag_storage_desc_t *tag_desc, struct mm_struct *mm)
301 {
302         unsigned long flags;
303         unsigned char *tags = NULL;
304 
305         spin_lock_irqsave(&mm->context.tag_lock, flags);
306         tag_desc->tag_users--;
307         if (tag_desc->tag_users == 0) {
308                 tag_desc->start = tag_desc->end = 0;
309                 /* Do not free up the tag storage space allocated
310                  * by the first descriptor. This is persistent
311                  * emergency tag storage space for the task.
312                  */
313                 if (tag_desc != mm->context.tag_store) {
314                         tags = tag_desc->tags;
315                         tag_desc->tags = NULL;
316                 }
317         }
318         spin_unlock_irqrestore(&mm->context.tag_lock, flags);
319         kfree(tags);
320 }
321 
322 #define tag_start(addr, tag_desc)               \
323         ((tag_desc)->tags + ((addr - (tag_desc)->start)/(2*adi_blksize())))
324 
325 /* Retrieve any saved ADI tags for the page being swapped back in and
326  * restore these tags to the newly allocated physical page.
327  */
328 void adi_restore_tags(struct mm_struct *mm, struct vm_area_struct *vma,
329                       unsigned long addr, pte_t pte)
330 {
331         unsigned char *tag;
332         tag_storage_desc_t *tag_desc;
333         unsigned long paddr, tmp, version1, version2;
334 
335         /* Check if the swapped out page has an ADI version
336          * saved. If yes, restore version tag to the newly
337          * allocated page.
338          */
339         tag_desc = find_tag_store(mm, vma, addr);
340         if (tag_desc == NULL)
341                 return;
342 
343         tag = tag_start(addr, tag_desc);
344         paddr = pte_val(pte) & _PAGE_PADDR_4V;
345         for (tmp = paddr; tmp < (paddr+PAGE_SIZE); tmp += adi_blksize()) {
346                 version1 = (*tag) >> 4;
347                 version2 = (*tag) & 0x0f;
348                 *tag++ = 0;
349                 asm volatile("stxa %0, [%1] %2\n\t"
350                         :
351                         : "r" (version1), "r" (tmp),
352                           "i" (ASI_MCD_REAL));
353                 tmp += adi_blksize();
354                 asm volatile("stxa %0, [%1] %2\n\t"
355                         :
356                         : "r" (version2), "r" (tmp),
357                           "i" (ASI_MCD_REAL));
358         }
359         asm volatile("membar #Sync\n\t");
360 
361         /* Check and mark this tag space for release later if
362          * the swapped in page was the last user of tag space
363          */
364         del_tag_store(tag_desc, mm);
365 }
366 
367 /* A page is about to be swapped out. Save any ADI tags associated with
368  * this physical page so they can be restored later when the page is swapped
369  * back in.
370  */
371 int adi_save_tags(struct mm_struct *mm, struct vm_area_struct *vma,
372                   unsigned long addr, pte_t oldpte)
373 {
374         unsigned char *tag;
375         tag_storage_desc_t *tag_desc;
376         unsigned long version1, version2, paddr, tmp;
377 
378         tag_desc = alloc_tag_store(mm, vma, addr);
379         if (tag_desc == NULL)
380                 return -1;
381 
382         tag = tag_start(addr, tag_desc);
383         paddr = pte_val(oldpte) & _PAGE_PADDR_4V;
384         for (tmp = paddr; tmp < (paddr+PAGE_SIZE); tmp += adi_blksize()) {
385                 asm volatile("ldxa [%1] %2, %0\n\t"
386                                 : "=r" (version1)
387                                 : "r" (tmp), "i" (ASI_MCD_REAL));
388                 tmp += adi_blksize();
389                 asm volatile("ldxa [%1] %2, %0\n\t"
390                                 : "=r" (version2)
391                                 : "r" (tmp), "i" (ASI_MCD_REAL));
392                 *tag = (version1 << 4) | version2;
393                 tag++;
394         }
395 
396         return 0;
397 }
398 

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