PERFORCE change 143158 for review

[John Birrell]

http://perforce.freebsd.org/chv.cgi?CH=143158

Change 143158 by jb at freebsd3 on 2008/06/09 03:10:30

	Add the hooks for the syscall (systrace) provider.
	
	Note that this requires an ABI change, so a separate kernel option
	is required to make it work. BREAK_SYSENT_ABI should be obvious.

Affected files ...

.. //depot/projects/dtrace6/src/sys/i386/i386/trap.c#2 edit

Differences ...

==== //depot/projects/dtrace6/src/sys/i386/i386/trap.c#2 (text+ko) ====

@@ -49,6 +49,7 @@
 #include "opt_hwpmc_hooks.h"
 #include "opt_isa.h"
 #include "opt_kdb.h"
+#include "opt_kdtrace.h"
 #include "opt_ktrace.h"
 #include "opt_npx.h"
 #include "opt_trap.h"
@@ -109,6 +110,26 @@
 static void trap_fatal(struct trapframe *, vm_offset_t);
 void dblfault_handler(void);
 
+#ifdef KDTRACE_HOOKS
+#include <sys/dtrace_bsd.h>
+
+/*
+ * This is a hook which is initialised by the dtrace module
+ * to handle traps which might occur during DTrace probe
+ * execution.
+ */
+dtrace_trap_func_t	dtrace_trap_func;
+
+dtrace_doubletrap_func_t	dtrace_doubletrap_func;
+
+/*
+ * This is a hook which is initialised by the systrace module
+ * when it is loaded. This keeps the DTrace syscall provider
+ * implementation opaque. 
+ */
+systrace_probe_func_t	systrace_probe_func;
+#endif
+
 extern inthand_t IDTVEC(lcall_syscall);
 
 #define MAX_TRAP_MSG		30
@@ -215,6 +236,25 @@
 	    goto out;
 #endif
 
+#ifdef KDTRACE_HOOKS
+	/*
+	 * A trap can occur while DTrace executes a probe. Before
+	 * executing the probe, DTrace blocks re-scheduling and sets
+	 * a flag in it's per-cpu flags to indicate that it doesn't
+	 * want to fault. On returning from the the probe, the no-fault
+	 * flag is cleared and finally re-scheduling is enabled.
+	 *
+	 * If the DTrace kernel module has registered a trap handler,
+	 * call it and if it returns non-zero, assume that it has
+	 * handled the trap and modified the trap frame so that this
+	 * function can return normally.
+	 */
+	if ((type == T_PROTFLT || type == T_PAGEFLT) &&
+	    dtrace_trap_func != NULL)
+		if ((*dtrace_trap_func)(&frame, type))
+			goto out;
+#endif
+
 	if ((frame.tf_eflags & PSL_I) == 0) {
 		/*
 		 * Buggy application or kernel code has disabled
@@ -855,6 +895,10 @@
 void
 dblfault_handler()
 {
+#ifdef KDTRACE_HOOKS
+	if (dtrace_doubletrap_func != NULL)
+		(*dtrace_doubletrap_func)();
+#endif
 	printf("\nFatal double fault:\n");
 	printf("eip = 0x%x\n", PCPU_GET(common_tss.tss_eip));
 	printf("esp = 0x%x\n", PCPU_GET(common_tss.tss_esp));
@@ -980,9 +1024,34 @@
 
 		PTRACESTOP_SC(p, td, S_PT_SCE);
 
+#if defined(KDTRACE_HOOKS) && defined(BREAK_SYSENT_ABI)
+		/*
+		 * If the systrace module has registered it's probe
+		 * callback and if there is a probe active for the
+		 * syscall 'entry', process the probe.
+		 */
+		if (systrace_probe_func != NULL && callp->sy_entry != 0)
+			(*systrace_probe_func)(callp->sy_entry, code, callp,
+			    args);
+#endif
+
 		AUDIT_SYSCALL_ENTER(code, td);
 		error = (*callp->sy_call)(td, args);
 		AUDIT_SYSCALL_EXIT(error, td);
+
+		/* Save the latest error return value. */
+		td->td_errno = error;
+
+#if defined(KDTRACE_HOOKS) && defined(BREAK_SYSENT_ABI)
+		/*
+		 * If the systrace module has registered it's probe
+		 * callback and if there is a probe active for the
+		 * syscall 'return', process the probe.
+		 */
+		if (systrace_probe_func != NULL && callp->sy_return != 0)
+			(*systrace_probe_func)(callp->sy_return, code, callp,
+			    args);
+#endif
 	}
 
 	switch (error) {