Author: jhibbits
Date: Fri Jun 9 20:26:42 2017
New Revision: 319759
URL: https://svnweb.freebsd.org/changeset/base/319759
Log:
Follow up r313841 on powerpc
Close a potential race in reading the CPU dtrace flags, where a thread can
start on one CPU, and partway through retrieving the flags be swapped out,
while another thread traps and sets the CPU_DTRACE_NOFAULT. This could
cause the first thread to return without handling the fault.
Discussed with: markj@
Modified:
head/sys/cddl/dev/dtrace/powerpc/dtrace_subr.c
Modified: head/sys/cddl/dev/dtrace/powerpc/dtrace_subr.c
==============================================================================
--- head/sys/cddl/dev/dtrace/powerpc/dtrace_subr.c Fri Jun 9 19:57:27
2017 (r319758)
+++ head/sys/cddl/dev/dtrace/powerpc/dtrace_subr.c Fri Jun 9 20:26:42
2017 (r319759)
@@ -267,6 +267,7 @@ dtrace_gethrestime(void)
int
dtrace_trap(struct trapframe *frame, u_int type)
{
+ uint16_t nofault;
/*
* A trap can occur while DTrace executes a probe. Before
@@ -277,7 +278,11 @@ dtrace_trap(struct trapframe *frame, u_int type)
*
* Check if DTrace has enabled 'no-fault' mode:
*/
- if ((cpu_core[curcpu].cpuc_dtrace_flags & CPU_DTRACE_NOFAULT) != 0) {
+ sched_pin();
+ nofault = cpu_core[curcpu].cpuc_dtrace_flags & CPU_DTRACE_NOFAULT;
+ sched_unpin();
+ if (nofault) {
+ KASSERT((frame->srr1 & PSL_EE) == 0, ("interrupts enabled"));
/*
* There are only a couple of trap types that are expected.
* All the rest will be handled in the usual way.
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