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dart: Fix L2 table allocation & half-fix carnage from stage1

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We were assuming L2 tables were always allocated consecutively at low
IOVAs. 14.5 broke this, causing all kinds of explosions.

The new code looks for the first unused L2 PT, and also checks whether
the first 2 entries are aliased to latter entries (which is what the old
code caused). If so, it clears them and reallocates them. This doesn't
undo the PT wipe from stage1 though, so downstream code has to redo any
missing mappings...

Signed-off-by: Hector Martin <marcan@marcan.st>
This commit is contained in:
Hector Martin 2024-05-17 01:54:30 +09:00
parent 0c64b6b4c1
commit 58090bb58c
1 changed files with 47 additions and 22 deletions
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69
src/dart.c
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@ -417,32 +417,57 @@ int dart_setup_pt_region(dart_dev_t *dart, const char *path, int device, u64 vm_
tbl_count);
return -1;
}
/* first index is the l1 table, cap at 2 or else macOS hates it */
tbl_count = min(2, tbl_count - 1);
u64 l2_start = region[0] + SZ_16K;
/* first index may or may not be the l1 table? */
u64 l2_free = region[0] + SZ_16K;
u64 l2_free_end = region[1];
/* find the lowest unused L2 PT address */
u64 vmstart = vm_base >> (14 + 11);
for (u64 index = 0; index < tbl_count; index++) {
int ttbr = (vmstart + index) >> 11;
int idx = (vmstart + index) & 0x7ff;
u64 l2tbl = l2_start + index * SZ_16K;
if (dart->l1[ttbr][idx] & DART_PTE_VALID) {
u64 off = FIELD_GET(dart->params->offset_mask, dart->l1[ttbr][idx])
<< DART_PTE_OFFSET_SHIFT;
if (off != l2tbl)
printf("dart: unexpected L2 tbl at index:%lu. 0x%016lx != 0x%016lx\n", index,
off, l2tbl);
int ttbr = (vmstart >> 11) & 3;
for (u64 index = 0; index < 2048; index++) {
if (!(dart->l1[ttbr][index] & DART_PTE_VALID))
continue;
} else {
printf("dart: allocating L2 tbl at %d, %d to 0x%lx\n", ttbr, idx, l2tbl);
memset((void *)l2tbl, 0, SZ_16K);
}
u64 offset = FIELD_PREP(dart->params->offset_mask, l2tbl >> DART_PTE_OFFSET_SHIFT);
dart->l1[ttbr][idx] = offset | DART_PTE_VALID;
u64 off = FIELD_GET(dart->params->offset_mask, dart->l1[ttbr][index])
<< DART_PTE_OFFSET_SHIFT;
if (off >= l2_free && off < l2_free_end)
l2_free = off + SZ_16K;
}
u64 l2_tt[2] = {region[0], tbl_count};
/* ensure the first 2 L2 tables are initialized */
tbl_count = min(2, tbl_count - 1);
for (u64 index = 0; index < tbl_count; index++) {
int ttbr = ((vmstart + index) >> 11) & 3;
int idx = (vmstart + index) & 0x7ff;
if (dart->l1[ttbr][idx] & DART_PTE_VALID) {
/* m1n1 bug fixup: old versions used to clobber PTs */
for (int j = 0; j < 2048; j++) {
if (j != idx && dart->l1[ttbr][j] == dart->l1[ttbr][idx]) {
printf("dart: clearing clobbered L1 PTE at %d, %d\n", ttbr, idx);
dart->l1[ttbr][idx] = 0;
break;
}
}
continue;
}
printf("dart: allocating L2 tbl at %d, %d to 0x%lx\n", ttbr, idx, l2_free);
if (l2_free >= l2_free_end) {
printf("dart: out of prealloc page tables\n");
return -1;
}
memset((void *)l2_free, 0, SZ_16K);
u64 offset = FIELD_PREP(dart->params->offset_mask, l2_free >> DART_PTE_OFFSET_SHIFT);
dart->l1[ttbr][idx] = offset | DART_PTE_VALID;
l2_free += SZ_16K;
}
u64 l2_tt[2] = {region[0], 2};
int ret = adt_setprop(adt, node, l2_tt_str, &l2_tt, sizeof(l2_tt));
if (ret < 0) {
printf("dart: failed to update '%s/%s'\n", path, l2_tt_str);