1 #include "mc_page_store.h"
3 #include "mc_private.h"
5 #include <xbt/mmalloc.h>
7 #define SOFT_DIRTY_BIT_NUMBER 55
8 #define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
12 // ***** Region management:
14 /** @brief Take a per-page snapshot of a region
16 * @param data The start of the region (must be at the beginning of a page)
17 * @param pag_count Number of pages of the region
18 * @param pagemap Linux kernel pagemap values fot this region (or NULL)
19 * @param reference_pages Snapshot page numbers of the previous soft_dirty_reset (or NULL)
20 * @return Snapshot page numbers of this new snapshot
22 size_t* mc_take_page_snapshot_region(void* data, size_t page_count, uint64_t* pagemap, size_t* reference_pages)
24 size_t* pagenos = (size_t*) malloc(page_count * sizeof(size_t));
26 for (size_t i=0; i!=page_count; ++i) {
27 bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
28 if (softclean && reference_pages) {
29 // The page is softclean, it is the same page as the reference page:
30 pagenos[i] = reference_pages[i];
31 mc_model_checker->pages->ref_page(reference_pages[i]);
33 // Otherwise, we need to store the page the hard way
34 // (by reading its content):
35 void* page = (char*) data + (i << xbt_pagebits);
36 pagenos[i] = mc_model_checker->pages->store_page(page);
43 void mc_free_page_snapshot_region(size_t* pagenos, size_t page_count)
45 for (size_t i=0; i!=page_count; ++i) {
46 mc_model_checker->pages->unref_page(pagenos[i]);
50 /** @brief Restore a snapshot of a region
52 * If possible, the restoration will be incremental
53 * (the modified pages will not be touched).
55 * @param data The start of the region (must be at the beginning of a page)
56 * @param pag_count Number of pages of the region
57 * @param pagemap Linux kernel pagemap values fot this region (or NULL)
58 * @param reference_pages Snapshot page numbers of the previous soft_dirty_reset (or NULL)
60 void mc_restore_page_snapshot_region(mc_mem_region_t region, size_t page_count, uint64_t* pagemap, mc_mem_region_t reference_region)
62 for (size_t i=0; i!=page_count; ++i) {
64 bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
65 if (softclean && reference_region && reference_region->page_numbers[i] == region->page_numbers[i]) {
66 // The page is softclean and is the same as the reference one:
67 // the page is already in the target state.
71 // Otherwise, copy the page:
72 void* target_page = mc_page_from_number(region->start_addr, i);
73 const void* source_page = mc_model_checker->pages->get_page(region->page_numbers[i]);
74 memcpy(target_page, source_page, xbt_pagesize);
78 // ***** Soft dirty tracking
80 /** @brief Like pread() but without partial reads */
81 static size_t pread_whole(int fd, void* buf, size_t count, off_t offset) {
84 char* data = (char*) buf;
86 ssize_t n = pread(fd, buf, count, offset);
99 // It might be a partial read:
109 static inline __attribute__ ((always_inline))
110 void mc_ensure_fd(int* fd, const char* path, int flags) {
113 *fd = open(path, flags);
115 xbt_die("Could not open file %s", path);
119 /** @brief Reset the soft-dirty bits
121 * This is done after checkpointing and after checkpoint restoration
122 * (if per page checkpoiting is used) in order to know which pages were
125 * See https://www.kernel.org/doc/Documentation/vm/soft-dirty.txt
127 void mc_softdirty_reset() {
128 mc_ensure_fd(&mc_model_checker->fd_clear_refs, "/proc/self/clear_refs", O_WRONLY|O_CLOEXEC);
129 if( ::write(mc_model_checker->fd_clear_refs, "4\n", 2) != 2) {
130 xbt_die("Could not reset softdirty bits");
134 /** @brief Read memory page informations
136 * For each virtual memory page of the process,
137 * /proc/self/pagemap provides a 64 bit field of information.
138 * We are interested in the soft-dirty bit: with this we can track which
139 * pages were modified between snapshots/restorations and avoid
140 * copying data which was not modified.
142 * See https://www.kernel.org/doc/Documentation/vm/pagemap.txt
144 * @param pagemap Output buffer for pagemap informations
145 * @param start_addr Address of the first page
146 * @param page_count Number of pages
148 static void mc_read_pagemap(uint64_t* pagemap, size_t page_start, size_t page_count)
150 mc_ensure_fd(&mc_model_checker->fd_pagemap, "/proc/self/pagemap", O_RDONLY|O_CLOEXEC);
151 size_t bytesize = sizeof(uint64_t) * page_count;
152 off_t offset = sizeof(uint64_t) * page_start;
153 if (pread_whole(mc_model_checker->fd_pagemap, pagemap, bytesize, offset) != bytesize) {
154 xbt_die("Could not read pagemap");
158 // ***** High level API
160 mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc_mem_region_t ref_reg)
162 mc_mem_region_t new_reg = xbt_new(s_mc_mem_region_t, 1);
164 new_reg->start_addr = start_addr;
165 new_reg->data = NULL;
166 new_reg->size = size;
167 new_reg->page_numbers = NULL;
169 xbt_assert((((uintptr_t)start_addr) & (xbt_pagesize-1)) == 0,
170 "Not at the beginning of a page");
171 size_t page_count = mc_page_count(size);
173 uint64_t* pagemap = NULL;
174 if (_sg_mc_soft_dirty && mc_model_checker->parent_snapshot) {
175 pagemap = (uint64_t*) mmalloc_no_memset((xbt_mheap_t) mc_heap, sizeof(uint64_t) * page_count);
176 mc_read_pagemap(pagemap, mc_page_number(NULL, start_addr), page_count);
179 // Take incremental snapshot:
180 new_reg->page_numbers = mc_take_page_snapshot_region(start_addr, page_count, pagemap,
181 ref_reg==NULL ? NULL : ref_reg->page_numbers);
184 mfree((xbt_mheap_t) mc_heap, pagemap);
189 void mc_region_restore_sparse(mc_mem_region_t reg, mc_mem_region_t ref_reg)
191 xbt_assert((((uintptr_t)reg->start_addr) & (xbt_pagesize-1)) == 0,
192 "Not at the beginning of a page");
193 size_t page_count = mc_page_count(reg->size);
195 uint64_t* pagemap = NULL;
197 // Read soft-dirty bits if necessary in order to know which pages have changed:
198 if (_sg_mc_soft_dirty && mc_model_checker->parent_snapshot) {
199 pagemap = (uint64_t*) mmalloc_no_memset((xbt_mheap_t) mc_heap, sizeof(uint64_t) * page_count);
200 mc_read_pagemap(pagemap, mc_page_number(NULL, reg->start_addr), page_count);
203 // Incremental per-page snapshot restoration:
204 mc_restore_page_snapshot_region(reg, page_count, pagemap, ref_reg);
206 // This is funny, the restoration can restore the state of the current heap,
207 // if this happen free(pagemap) would free from the wrong heap:
209 mfree((xbt_mheap_t) mc_heap, pagemap);