Author: mjg
Date: Fri Apr 27 15:16:34 2018
New Revision: 333064
URL: https://svnweb.freebsd.org/changeset/base/333064
Log:
systrace: track it like sdt probes
While here predict false.
Note the code is wrong (regardless of this change). Dereference of the
pointer can race with module unload. A fix would set the probe to a
nop stub instead of NULL.
Modified:
head/sys/cddl/dev/systrace/systrace.c
head/sys/kern/kern_dtrace.c
head/sys/kern/subr_syscall.c
head/sys/sys/sysent.h
Modified: head/sys/cddl/dev/systrace/systrace.c
==============================================================================
--- head/sys/cddl/dev/systrace/systrace.c Fri Apr 27 13:59:24 2018
(r333063)
+++ head/sys/cddl/dev/systrace/systrace.c Fri Apr 27 15:16:34 2018
(r333064)
@@ -135,6 +135,8 @@ extern const char *freebsd32_syscallnames[];
#error 1 << SYSTRACE_SHIFT must exceed number of system calls
#endif
+static int systrace_enabled_count;
+
static void systrace_load(void *);
static void systrace_unload(void *);
@@ -315,6 +317,9 @@ systrace_enable(void *arg, dtrace_id_t id, void *parg)
SYSENT[sysnum].sy_entry = id;
else
SYSENT[sysnum].sy_return = id;
+ systrace_enabled_count++;
+ if (systrace_enabled_count == 1)
+ systrace_enabled = true;
}
static void
@@ -324,6 +329,9 @@ systrace_disable(void *arg, dtrace_id_t id, void *parg
SYSENT[sysnum].sy_entry = 0;
SYSENT[sysnum].sy_return = 0;
+ systrace_enabled_count--;
+ if (systrace_enabled_count == 0)
+ systrace_enabled = false;
}
static void
Modified: head/sys/kern/kern_dtrace.c
==============================================================================
--- head/sys/kern/kern_dtrace.c Fri Apr 27 13:59:24 2018 (r333063)
+++ head/sys/kern/kern_dtrace.c Fri Apr 27 15:16:34 2018 (r333064)
@@ -56,7 +56,8 @@ dtrace_doubletrap_func_t dtrace_doubletrap_func;
dtrace_pid_probe_ptr_t dtrace_pid_probe_ptr;
dtrace_return_probe_ptr_t dtrace_return_probe_ptr;
-systrace_probe_func_t __read_frequently systrace_probe_func;
+bool __read_frequently systrace_enabled;
+systrace_probe_func_t systrace_probe_func;
/* Return the DTrace process data size compiled in the kernel hooks. */
size_t
Modified: head/sys/kern/subr_syscall.c
==============================================================================
--- head/sys/kern/subr_syscall.c Fri Apr 27 13:59:24 2018
(r333063)
+++ head/sys/kern/subr_syscall.c Fri Apr 27 15:16:34 2018
(r333064)
@@ -126,7 +126,8 @@ syscallenter(struct thread *td)
#ifdef KDTRACE_HOOKS
/* Give the syscall:::entry DTrace probe a chance to fire. */
- if (systrace_probe_func != NULL && sa->callp->sy_entry != 0)
+ if (__predict_false(systrace_enabled &&
+ sa->callp->sy_entry != 0))
(*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
#endif
@@ -140,7 +141,8 @@ syscallenter(struct thread *td)
#ifdef KDTRACE_HOOKS
/* Give the syscall:::return DTrace probe a chance to fire. */
- if (systrace_probe_func != NULL && sa->callp->sy_return != 0)
+ if (__predict_false(systrace_enabled &&
+ sa->callp->sy_return != 0))
(*systrace_probe_func)(sa, SYSTRACE_RETURN,
error ? -1 : td->td_retval[0]);
#endif
Modified: head/sys/sys/sysent.h
==============================================================================
--- head/sys/sys/sysent.h Fri Apr 27 13:59:24 2018 (r333063)
+++ head/sys/sys/sysent.h Fri Apr 27 15:16:34 2018 (r333064)
@@ -53,6 +53,7 @@ typedef void (*systrace_probe_func_t)(struct
syscall_a
enum systrace_probe_t, int);
typedef void (*systrace_args_func_t)(int, void *, uint64_t *, int *);
+extern bool systrace_enabled;
extern systrace_probe_func_t systrace_probe_func;
struct sysent { /* system call table */
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