svn commit: r348742 - in head/sys: amd64/amd64 cddl/contrib/opensolaris/uts/common/dtrace i386/i386
Mark Johnston
markj at FreeBSD.org
Thu Jun 6 16:03:27 UTC 2019
Author: markj
Date: Thu Jun 6 16:03:25 2019
New Revision: 348742
URL: https://svnweb.freebsd.org/changeset/base/348742
Log:
Fix a race between fasttrap and the user breakpoint handler.
When disabling the last enabled userspace probe, fasttrap clears the
function pointers which hook in to the breakpoint handler. If a traced
thread hit a fasttrap breakpoint before it was removed, we must ensure
that it is able to call the hook; otherwise fasttrap will not consume
the trap and SIGTRAP will be delievered to the thread. Synchronize
with such threads by ensuring that they load the hook pointer with
interrupts disabled, and by completing an SMP rendezvous after removing
breakpoints and before clearing the pointers.
Reported by: Alexander Alexeev <Alexander.Alexeev at dell.com>
Tested by: Alexander Alexeev (earlier version)
Reviewed by: cem, kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D20526
Modified:
head/sys/amd64/amd64/trap.c
head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
head/sys/i386/i386/trap.c
Modified: head/sys/amd64/amd64/trap.c
==============================================================================
--- head/sys/amd64/amd64/trap.c Thu Jun 6 15:21:36 2019 (r348741)
+++ head/sys/amd64/amd64/trap.c Thu Jun 6 16:03:25 2019 (r348742)
@@ -113,6 +113,10 @@ void dblfault_handler(struct trapframe *frame);
static int trap_pfault(struct trapframe *, int);
static void trap_fatal(struct trapframe *, vm_offset_t);
+#ifdef KDTRACE_HOOKS
+static bool trap_user_dtrace(struct trapframe *,
+ int (**hook)(struct trapframe *));
+#endif
#define MAX_TRAP_MSG 32
static char *trap_msg[] = {
@@ -284,11 +288,11 @@ trap(struct trapframe *frame)
break;
case T_BPTFLT: /* bpt instruction fault */
- enable_intr();
#ifdef KDTRACE_HOOKS
- if (dtrace_pid_probe_ptr != NULL &&
- dtrace_pid_probe_ptr(frame) == 0)
+ if (trap_user_dtrace(frame, &dtrace_pid_probe_ptr))
return;
+#else
+ enable_intr();
#endif
signo = SIGTRAP;
ucode = TRAP_BRKPT;
@@ -425,9 +429,7 @@ trap(struct trapframe *frame)
break;
#ifdef KDTRACE_HOOKS
case T_DTRACE_RET:
- enable_intr();
- if (dtrace_return_probe_ptr != NULL)
- dtrace_return_probe_ptr(frame);
+ (void)trap_user_dtrace(frame, &dtrace_return_probe_ptr);
return;
#endif
}
@@ -947,6 +949,25 @@ trap_fatal(frame, eva)
else
panic("unknown/reserved trap");
}
+
+#ifdef KDTRACE_HOOKS
+/*
+ * Invoke a userspace DTrace hook. The hook pointer is cleared when no
+ * userspace probes are enabled, so we must synchronize with DTrace to ensure
+ * that a trapping thread is able to call the hook before it is cleared.
+ */
+static bool
+trap_user_dtrace(struct trapframe *frame, int (**hookp)(struct trapframe *))
+{
+ int (*hook)(struct trapframe *);
+
+ hook = (int (*)(struct trapframe *))atomic_load_ptr(hookp);
+ enable_intr();
+ if (hook != NULL)
+ return ((hook)(frame) == 0);
+ return (false);
+}
+#endif
/*
* Double fault handler. Called when a fault occurs while writing
Modified: head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c Thu Jun 6 15:21:36 2019 (r348741)
+++ head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c Thu Jun 6 16:03:25 2019 (r348742)
@@ -1125,31 +1125,17 @@ fasttrap_enable_callbacks(void)
static void
fasttrap_disable_callbacks(void)
{
-#ifdef illumos
- ASSERT(MUTEX_HELD(&cpu_lock));
-#endif
-
-
mutex_enter(&fasttrap_count_mtx);
ASSERT(fasttrap_pid_count > 0);
fasttrap_pid_count--;
if (fasttrap_pid_count == 0) {
-#ifdef illumos
- cpu_t *cur, *cpu = CPU;
-
- for (cur = cpu->cpu_next_onln; cur != cpu;
- cur = cur->cpu_next_onln) {
- rw_enter(&cur->cpu_ft_lock, RW_WRITER);
- }
-#endif
+ /*
+ * Synchronize with the breakpoint handler, which is careful to
+ * enable interrupts only after loading the hook pointer.
+ */
+ dtrace_sync();
dtrace_pid_probe_ptr = NULL;
dtrace_return_probe_ptr = NULL;
-#ifdef illumos
- for (cur = cpu->cpu_next_onln; cur != cpu;
- cur = cur->cpu_next_onln) {
- rw_exit(&cur->cpu_ft_lock);
- }
-#endif
}
mutex_exit(&fasttrap_count_mtx);
}
Modified: head/sys/i386/i386/trap.c
==============================================================================
--- head/sys/i386/i386/trap.c Thu Jun 6 15:21:36 2019 (r348741)
+++ head/sys/i386/i386/trap.c Thu Jun 6 16:03:25 2019 (r348742)
@@ -116,6 +116,10 @@ void syscall(struct trapframe *frame);
static int trap_pfault(struct trapframe *, int, vm_offset_t);
static void trap_fatal(struct trapframe *, vm_offset_t);
+#ifdef KDTRACE_HOOKS
+static bool trap_user_dtrace(struct trapframe *,
+ int (**hook)(struct trapframe *));
+#endif
void dblfault_handler(void);
extern inthand_t IDTVEC(bpt), IDTVEC(dbg), IDTVEC(int0x80_syscall);
@@ -322,11 +326,11 @@ trap(struct trapframe *frame)
break;
case T_BPTFLT: /* bpt instruction fault */
- enable_intr();
#ifdef KDTRACE_HOOKS
- if (dtrace_pid_probe_ptr != NULL &&
- dtrace_pid_probe_ptr(frame) == 0)
+ if (trap_user_dtrace(frame, &dtrace_pid_probe_ptr))
return;
+#else
+ enable_intr();
#endif
signo = SIGTRAP;
ucode = TRAP_BRKPT;
@@ -504,9 +508,7 @@ user_trctrap_out:
break;
#ifdef KDTRACE_HOOKS
case T_DTRACE_RET:
- enable_intr();
- if (dtrace_return_probe_ptr != NULL)
- dtrace_return_probe_ptr(frame);
+ (void)trap_user_dtrace(frame, &dtrace_return_probe_ptr);
return;
#endif
}
@@ -990,6 +992,25 @@ trap_fatal(frame, eva)
else
panic("unknown/reserved trap");
}
+
+#ifdef KDTRACE_HOOKS
+/*
+ * Invoke a userspace DTrace hook. The hook pointer is cleared when no
+ * userspace probes are enabled, so we must synchronize with DTrace to ensure
+ * that a trapping thread is able to call the hook before it is cleared.
+ */
+static bool
+trap_user_dtrace(struct trapframe *frame, int (**hookp)(struct trapframe *))
+{
+ int (*hook)(struct trapframe *);
+
+ hook = (int (*)(struct trapframe *))atomic_load_ptr(hookp);
+ enable_intr();
+ if (hook != NULL)
+ return ((hook)(frame) == 0);
+ return (false);
+}
+#endif
/*
* Double fault handler. Called when a fault occurs while writing
More information about the svn-src-head
mailing list