Author: ian
Date: Sat Jan 2 23:14:52 2016
New Revision: 293065
URL: https://svnweb.freebsd.org/changeset/base/293065
Log:
Reword the comment to better describe what I found while researching the
problem that led to this temporary workaround (and also so I can properly
cite the PR in the commit this time).
In general this is intended to be a temporary workaround until we can figure
out why including any ram from the last megabyte of the physical address
space leads to a NULL pointer deref. Debugging that is made trickier by the
fact that I couldn't even get a backtrace in ddb.
PR: 201614
Modified:
head/sys/arm/arm/physmem.c
Modified: head/sys/arm/arm/physmem.c
==============================================================================
--- head/sys/arm/arm/physmem.c Sat Jan 2 22:55:59 2016 (r293064)
+++ head/sys/arm/arm/physmem.c Sat Jan 2 23:14:52 2016 (r293065)
@@ -282,16 +282,14 @@ arm_physmem_hardware_region(vm_paddr_t p
* pmap_extract() == 0 means failure.
*
* Also filter out the page at the end of the physical address space --
- * if addr is non-zero and addr+size is zero that means we wrapped to
- * the next byte beyond what vm_paddr_t can express. The calculations
- * in vm_page_startup() are going to have the same problem, so just work
- * around it by leaving the last page out.
+ * if addr is non-zero and addr+size is zero we wrapped to the next byte
+ * beyond what vm_paddr_t can express. That leads to a NULL pointer
+ * deref early in startup; work around it by leaving the last page out.
*
* XXX This just in: subtract out a whole megabyte, not just 1 page.
- * Reducing the size by anything less than 1MB results in a NULL pointer
- * deref in _vm_map_lock_read() very early in startup. Better to give
- * up a whole megabyte than leave some folks with an unusable system
- * while we investigate.
+ * Reducing the size by anything less than 1MB results in the NULL
+ * pointer deref in _vm_map_lock_read(). Better to give up a megabyte
+ * than leave some folks with an unusable system while we investigate.
*/
if (pa == 0) {
pa = PAGE_SIZE;
_______________________________________________
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"
