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Set NX on some non-leaf direct map page table entries.

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The direct map is never used for execution of code, so we might as well
set NX in the direct map's PML4Es.  Also clarify the intent of the code
in create_pagetables() that restricts access protections on the region
of the direct map mapping the kernel text.

Reviewed by:	alc, kib (previous version)
MFC after:	1 week
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D21759
This commit is contained in:
Mark Johnston 2019-09-23 14:19:41 +00:00
parent 38dae42c26
commit 2ff730191d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=352624
1 changed files with 5 additions and 5 deletions
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10
sys/amd64/amd64/pmap.c
View file

@ -1539,13 +1539,13 @@ create_pagetables(vm_paddr_t *firstaddr)
}
for (j = 0; i < ndmpdp; i++, j++) {
pdp_p[i] = DMPDphys + ptoa(j);
pdp_p[i] |= X86_PG_RW | X86_PG_V;
pdp_p[i] |= X86_PG_RW | X86_PG_V | pg_nx;
}
/*
* Instead of using a 1G page for the memory containing the kernel,
* use 2M pages with appropriate permissions. (If using 1G pages,
* this will partially overwrite the PDPEs above.)
* use 2M pages with read-only and no-execute permissions. (If using 1G
* pages, this will partially overwrite the PDPEs above.)
*/
if (ndm1g) {
pd_p = (pd_entry_t *)DMPDkernphys;
@ -1555,7 +1555,7 @@ create_pagetables(vm_paddr_t *firstaddr)
bootaddr_rwx(i << PDRSHIFT);
for (i = 0; i < nkdmpde; i++)
pdp_p[i] = (DMPDkernphys + ptoa(i)) | X86_PG_RW |
X86_PG_V;
X86_PG_V | pg_nx;
}
/* And recursively map PML4 to itself in order to get PTmap */
@ -1566,7 +1566,7 @@ create_pagetables(vm_paddr_t *firstaddr)
/* Connect the Direct Map slot(s) up to the PML4. */
for (i = 0; i < ndmpdpphys; i++) {
p4_p[DMPML4I + i] = DMPDPphys + ptoa(i);
p4_p[DMPML4I + i] |= X86_PG_RW | X86_PG_V;
p4_p[DMPML4I + i] |= X86_PG_RW | X86_PG_V | pg_nx;
}
/* Connect the KVA slots up to the PML4 */