1 #include "mc_page_store.h"
4 #include <xbt/mmalloc.h>
6 #define SOFT_DIRTY_BIT_NUMBER 55
7 #define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
11 // ***** Region management:
13 size_t* mc_take_page_snapshot_region(void* data, size_t page_count, uint64_t* pagemap, size_t* reference_pages)
15 size_t* pagenos = (size_t*) malloc(page_count * sizeof(size_t));
17 for (size_t i=0; i!=page_count; ++i) {
18 bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
20 // The page is softclean, it is the same page as the reference page:
21 pagenos[i] = reference_pages[i];
22 mc_model_checker->pages->ref_page(reference_pages[i]);
24 // Otherwise, we need to store the page the hard hard
25 // (by reading its content):
26 void* page = (char*) data + (i << xbt_pagebits);
27 pagenos[i] = mc_model_checker->pages->store_page(page);
34 void mc_free_page_snapshot_region(size_t* pagenos, size_t page_count)
36 for (size_t i=0; i!=page_count; ++i) {
37 mc_model_checker->pages->unref_page(pagenos[i]);
41 void mc_restore_page_snapshot_region(mc_mem_region_t region, size_t page_count, uint64_t* pagemap, mc_mem_region_t reference_region)
43 for (size_t i=0; i!=page_count; ++i) {
45 bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
46 if (softclean && reference_region && reference_region->page_numbers[i] == region->page_numbers[i]) {
47 // The page is softclean and is the same as the reference one:
48 // the page is already in the target state.
52 // Otherwise, copy the page:
53 void* target_page = mc_page_from_number(region->start_addr, i);
54 const void* source_page = mc_model_checker->pages->get_page(region->page_numbers[i]);
55 memcpy(target_page, source_page, xbt_pagesize);
59 // ***** Soft dirty tracking
61 /** @brief Like pread() but without partial reads */
62 static size_t pread_whole(int fd, void* buf, size_t count, off_t offset) {
65 char* data = (char*) buf;
67 ssize_t n = pread(fd, buf, count, offset);
80 // It might be a partial read:
90 static inline void mc_ensure_fd(int* fd, const char* path, int flags) {
93 *fd = open(path, flags);
95 xbt_die("Could not open file %s", path);
99 /** @brief Reset the soft-dirty bits
101 * This is done after checkpointing and after checkpoint restoration
102 * (if per page checkpoiting is used) in order to know which pages were
105 * See https://www.kernel.org/doc/Documentation/vm/soft-dirty.txt
107 void mc_softdirty_reset() {
108 mc_ensure_fd(&mc_model_checker->fd_clear_refs, "/proc/self/clear_refs", O_WRONLY|O_CLOEXEC);
109 if( ::write(mc_model_checker->fd_clear_refs, "4\n", 2) != 2) {
110 xbt_die("Could not reset softdirty bits");
114 /** @brief Read memory page informations
116 * For each virtual memory page of the process,
117 * /proc/self/pagemap provides a 64 bit field of information.
118 * We are interested in the soft-dirty bit: with this we can track which
119 * pages were modified between snapshots/restorations and avoid
120 * copying data which was not modified.
122 * See https://www.kernel.org/doc/Documentation/vm/pagemap.txt
124 * @param pagemap Output buffer for pagemap informations
125 * @param start_addr Address of the first page
126 * @param page_count Number of pages
128 static void mc_read_pagemap(uint64_t* pagemap, size_t page_start, size_t page_count)
130 mc_ensure_fd(&mc_model_checker->fd_pagemap, "/proc/self/pagemap", O_RDONLY|O_CLOEXEC);
131 size_t bytesize = sizeof(uint64_t) * page_count;
132 off_t offset = sizeof(uint64_t) * page_start;
133 if (pread_whole(mc_model_checker->fd_pagemap, pagemap, bytesize, offset) != bytesize) {
134 xbt_die("Could not read pagemap");
138 // ***** High level API
140 mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc_mem_region_t ref_reg)
142 mc_mem_region_t new_reg = xbt_new(s_mc_mem_region_t, 1);
144 new_reg->start_addr = start_addr;
145 new_reg->data = NULL;
146 new_reg->size = size;
147 new_reg->page_numbers = NULL;
149 xbt_assert((((uintptr_t)start_addr) & (xbt_pagesize-1)) == 0,
150 "Not at the beginning of a page");
151 size_t page_count = mc_page_count(size);
153 uint64_t* pagemap = NULL;
154 if (_sg_mc_soft_dirty && mc_model_checker->parent_snapshot) {
155 pagemap = (uint64_t*) mmalloc_no_memset((xbt_mheap_t) mc_heap, sizeof(uint64_t) * page_count);
156 mc_read_pagemap(pagemap, mc_page_number(NULL, start_addr), page_count);
159 // Take incremental snapshot:
160 new_reg->page_numbers = mc_take_page_snapshot_region(start_addr, page_count, pagemap,
161 ref_reg==NULL ? NULL : ref_reg->page_numbers);
164 mfree((xbt_mheap_t) mc_heap, pagemap);
169 void mc_region_restore_sparse(mc_mem_region_t reg, mc_mem_region_t ref_reg)
171 xbt_assert((((uintptr_t)reg->start_addr) & (xbt_pagesize-1)) == 0,
172 "Not at the beginning of a page");
173 size_t page_count = mc_page_count(reg->size);
175 uint64_t* pagemap = NULL;
177 // Read soft-dirty bits if necessary in order to know which pages have changed:
178 if (_sg_mc_soft_dirty && mc_model_checker->parent_snapshot) {
179 pagemap = (uint64_t*) mmalloc_no_memset((xbt_mheap_t) mc_heap, sizeof(uint64_t) * page_count);
180 mc_read_pagemap(pagemap, mc_page_number(NULL, reg->start_addr), page_count);
183 // Incremental per-page snapshot restoration:
184 mc_restore_page_snapshot_region(reg, page_count, pagemap, ref_reg);
186 // This is funny, the restoration can restore the state of the current heap,
187 // if this happen free(pagemap) would free from the wrong heap:
189 mfree((xbt_mheap_t) mc_heap, pagemap);