Author: alc
Date: Tue Oct 1 15:33:47 2019
New Revision: 352930
URL: https://svnweb.freebsd.org/changeset/base/352930
Log:
In short, pmap_enter_quick_locked("user space", ..., VM_PROT_READ) doesn't
work. More precisely, it doesn't set ATTR_AP(ATTR_AP_USER) in the page
table entry, so any attempt to read from the mapped page by user space
generates a page fault. This problem has gone unnoticed because the page
fault handler, vm_fault(), will ultimately call pmap_enter(), which
replaces the non-working page table entry with one that has
ATTR_AP(ATTR_AP_USER) set.
This change reduces the number of page faults during a "buildworld" by
about 19.4%.
Reviewed by: andrew, markj
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D21841
Modified:
head/sys/arm64/arm64/pmap.c
Modified: head/sys/arm64/arm64/pmap.c
==============================================================================
--- head/sys/arm64/arm64/pmap.c Tue Oct 1 15:10:35 2019 (r352929)
+++ head/sys/arm64/arm64/pmap.c Tue Oct 1 15:33:47 2019 (r352930)
@@ -3752,8 +3752,8 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, v
ATTR_AP(ATTR_AP_RO) | L3_PAGE;
if ((prot & VM_PROT_EXECUTE) == 0 || m->md.pv_memattr == DEVICE_MEMORY)
l3_val |= ATTR_XN;
- else if (va < VM_MAXUSER_ADDRESS)
- l3_val |= ATTR_PXN;
+ if (va < VM_MAXUSER_ADDRESS)
+ l3_val |= ATTR_AP(ATTR_AP_USER) | ATTR_PXN;
/*
* Now validate mapping with RO protection
_______________________________________________
svn-src-head@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
