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u3: enforce snapshot invariants on segment truncation

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This commit is contained in:
Joe Bryan 2022-12-02 09:58:32 -05:00
parent c111129a5e
commit a7022e75a0
1 changed files with 52 additions and 42 deletions
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94
pkg/urbit/noun/events.c
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@ -747,34 +747,6 @@ _ce_patch_apply(u3_ce_patch* pat_u)
}
}
/* _ce_loom_pure_north(): track clean pages at the bottom of memory.
*/
static inline void
_ce_loom_pure_north(c3_w pgs_w)
{
c3_w blk_w = pgs_w >> 5;
c3_w bit_w = pgs_w & 31;
memset((void*)u3P.dit_w, 0, blk_w << 2);
u3P.dit_w[blk_w] &= 0xffffffff << bit_w;
}
/* _ce_loom_pure_south(): track clean pages at the top of memory.
*/
static inline void
_ce_loom_pure_south(c3_w pgs_w)
{
c3_w blk_w = pgs_w >> 5;
c3_w bit_w = pgs_w & 31;
c3_w bas_w = ((u3P.pag_w - pgs_w) + 31) >> 5;
memset((void*)(u3P.dit_w + bas_w), 0, blk_w << 2);
// this is safe so long as the south segment never includes all pages
//
u3P.dit_w[bas_w - 1] &= 0xffffffff >> bit_w;
}
/* _ce_loom_track_north(): [pgs_w] clean, followed by [dif_w] dirty.
*/
void
@ -863,39 +835,71 @@ _ce_loom_track_south(c3_w pgs_w, c3_w dif_w)
/* _ce_loom_protect_north(): protect/track pages from the bottom of memory.
*/
static void
_ce_loom_protect_north(c3_w pgs_w)
_ce_loom_protect_north(c3_w pgs_w, c3_w old_w)
{
if ( pgs_w ) {
if ( 0 != mprotect((void*)u3_Loom,
(size_t)pgs_w << (u3a_page + 2),
PROT_READ) )
{
fprintf(stderr, "loom: protect north (%u pages): %s\r\n",
fprintf(stderr, "loom: pure north (%u pages): %s\r\n",
pgs_w, strerror(errno));
c3_assert(0);
}
}
_ce_loom_pure_north(pgs_w);
if ( old_w > pgs_w ) {
c3_w dif_w = old_w - pgs_w;
if ( 0 != mprotect((void*)(u3_Loom + (pgs_w << u3a_page)),
(size_t)dif_w << (u3a_page + 2),
(PROT_READ | PROT_WRITE)) )
{
fprintf(stderr, "loom: foul north (%u pages, %u old): %s\r\n",
pgs_w, old_w, strerror(errno));
c3_assert(0);
}
_ce_loom_track_north(pgs_w, dif_w);
}
else {
_ce_loom_track_north(pgs_w, 0);
}
}
/* _ce_loom_protect_south(): protect/track pages from the top of memory.
*/
static void
_ce_loom_protect_south(c3_w pgs_w)
_ce_loom_protect_south(c3_w pgs_w, c3_w old_w)
{
if ( pgs_w ) {
if ( 0 != mprotect((void*)(u3_Loom + ((u3P.pag_w - pgs_w) << u3a_page)),
(size_t)pgs_w << (u3a_page + 2),
PROT_READ) )
{
fprintf(stderr, "loom: protect south (%u pages): %s\r\n",
fprintf(stderr, "loom: pure south (%u pages): %s\r\n",
pgs_w, strerror(errno));
c3_assert(0);
}
}
_ce_loom_pure_south(pgs_w);
if ( old_w > pgs_w ) {
c3_w dif_w = old_w - pgs_w;
if ( 0 != mprotect((void*)(u3_Loom + ((u3P.pag_w - old_w) << u3a_page)),
(size_t)dif_w << (u3a_page + 2),
(PROT_READ | PROT_WRITE)) )
{
fprintf(stderr, "loom: foul south (%u pages, %u old): %s\r\n",
pgs_w, old_w, strerror(errno));
c3_assert(0);
}
_ce_loom_track_south(pgs_w, dif_w);
}
else {
_ce_loom_track_south(pgs_w, 0);
}
}
/* _ce_loom_mapf_north(): map [pgs_w] of [fid_i] into the bottom of memory
@ -926,8 +930,10 @@ _ce_loom_mapf_north(c3_i fid_i, c3_w pgs_w, c3_w old_w)
}
if ( old_w > pgs_w ) {
c3_w dif_w = old_w - pgs_w;
if ( MAP_FAILED == mmap((void*)(u3_Loom + (pgs_w << u3a_page)),
(size_t)(old_w - pgs_w) << (u3a_page + 2),
(size_t)dif_w << (u3a_page + 2),
(PROT_READ | PROT_WRITE),
(MAP_ANON | MAP_FIXED | MAP_PRIVATE),
-1, 0) )
@ -936,9 +942,12 @@ _ce_loom_mapf_north(c3_i fid_i, c3_w pgs_w, c3_w old_w)
pgs_w, old_w, strerror(errno));
c3_assert(0);
}
}
_ce_loom_pure_north(pgs_w);
_ce_loom_track_north(pgs_w, dif_w);
}
else {
_ce_loom_track_north(pgs_w, 0);
}
}
/* _ce_loom_blit_north(): apply pages, in order, from the bottom of memory.
@ -962,7 +971,7 @@ _ce_loom_blit_north(c3_i fid_i, c3_w pgs_w)
}
}
_ce_loom_protect_north(pgs_w);
_ce_loom_protect_north(pgs_w, 0);
}
/* _ce_loom_blit_south(): apply pages, reversed, from the top of memory.
@ -991,7 +1000,7 @@ _ce_loom_blit_south(c3_i fid_i, c3_w pgs_w)
}
}
_ce_loom_protect_south(pgs_w);
_ce_loom_protect_south(pgs_w, 0);
}
#ifdef U3_SNAPSHOT_VALIDATION
@ -1157,7 +1166,7 @@ void
u3e_save(void)
{
u3_ce_patch* pat_u;
c3_w nod_w;
c3_w nod_w, sod_w;
if ( u3C.wag_w & u3o_dryrun ) {
return;
@ -1168,6 +1177,7 @@ u3e_save(void)
}
nod_w = u3P.nor_u.pgs_w;
sod_w = u3P.sou_u.pgs_w;
_ce_patch_sync(pat_u);
@ -1193,13 +1203,13 @@ u3e_save(void)
#endif
if ( u3C.wag_w & u3o_no_demand ) {
_ce_loom_protect_north(u3P.nor_u.pgs_w);
_ce_loom_protect_north(u3P.nor_u.pgs_w, nod_w);
}
else {
_ce_loom_mapf_north(u3P.nor_u.fid_i, u3P.nor_u.pgs_w, nod_w);
}
_ce_loom_protect_south(u3P.sou_u.pgs_w);
_ce_loom_protect_south(u3P.sou_u.pgs_w, sod_w);
_ce_image_sync(&u3P.nor_u);
_ce_image_sync(&u3P.sou_u);