tracing/syscalls: core infrastructure for syscalls tracing, enhancements

Impact: new feature

This adds the generic support for syscalls tracing. This is
currently exploited through a devoted tracer but other tracing
engines can use it. (They just have to play with
{start,stop}_ftrace_syscalls() and use the display callbacks
unless they want to override them.)

The syscalls prototypes definitions are abused here to steal
some metadata informations:

- syscall name, param types, param names, number of params

The syscall addr is not directly saved during this definition
because we don't know if its prototype is available in the
namespace. But we don't really need it. The arch has just to
build a function able to resolve the syscall number to its
metadata struct.

The current tracer prints the syscall names, parameters names
and values (and their types optionally). Currently the value is
a raw hex but higher level values diplaying is on my TODO list.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1236955332-10133-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 138 insertions, 8 deletions

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 66cf974..c72e599 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -1,6 +1,5 @@
-#include <linux/ftrace.h>
 #include <linux/kernel.h>
-
+#include <linux/ftrace.h>
 #include <asm/syscall.h>
 
 #include "trace_output.h"
@@ -8,6 +7,90 @@
 
 static atomic_t refcount;
 
+/* Our two options */
+enum {
+	TRACE_SYSCALLS_OPT_TYPES = 0x1,
+};
+
+static struct tracer_opt syscalls_opts[] = {
+	{ TRACER_OPT(syscall_arg_type, TRACE_SYSCALLS_OPT_TYPES) },
+	{ }
+};
+
+static struct tracer_flags syscalls_flags = {
+	.val = 0, /* By default: no args types */
+	.opts = syscalls_opts
+};
+
+enum print_line_t
+print_syscall_enter(struct trace_iterator *iter, int flags)
+{
+	struct trace_seq *s = &iter->seq;
+	struct trace_entry *ent = iter->ent;
+	struct syscall_trace_enter *trace;
+	struct syscall_metadata *entry;
+	int i, ret, syscall;
+
+	trace_assign_type(trace, ent);
+
+	syscall = trace->nr;
+
+	entry = syscall_nr_to_meta(syscall);
+	if (!entry)
+		goto end;
+
+	ret = trace_seq_printf(s, "%s(", entry->name);
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	for (i = 0; i < entry->nb_args; i++) {
+		/* parameter types */
+		if (syscalls_flags.val & TRACE_SYSCALLS_OPT_TYPES) {
+			ret = trace_seq_printf(s, "%s ", entry->types[i]);
+			if (!ret)
+				return TRACE_TYPE_PARTIAL_LINE;
+		}
+		/* parameter values */
+		ret = trace_seq_printf(s, "%s: %lx%s ", entry->args[i],
+				       trace->args[i],
+				       i == entry->nb_args - 1 ? ")" : ",");
+		if (!ret)
+			return TRACE_TYPE_PARTIAL_LINE;
+	}
+
+end:
+	trace_seq_printf(s, "\n");
+	return TRACE_TYPE_HANDLED;
+}
+
+enum print_line_t
+print_syscall_exit(struct trace_iterator *iter, int flags)
+{
+	struct trace_seq *s = &iter->seq;
+	struct trace_entry *ent = iter->ent;
+	struct syscall_trace_exit *trace;
+	int syscall;
+	struct syscall_metadata *entry;
+	int ret;
+
+	trace_assign_type(trace, ent);
+
+	syscall = trace->nr;
+
+	entry = syscall_nr_to_meta(syscall);
+	if (!entry) {
+		trace_seq_printf(s, "\n");
+		return TRACE_TYPE_HANDLED;
+	}
+
+	ret = trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
+				trace->ret);
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	return TRACE_TYPE_HANDLED;
+}
+
 void start_ftrace_syscalls(void)
 {
 	unsigned long flags;
@@ -16,6 +99,7 @@ void start_ftrace_syscalls(void)
 	if (atomic_inc_return(&refcount) != 1)
 		goto out;
 
+	arch_init_ftrace_syscalls();
 	read_lock_irqsave(&tasklist_lock, flags);
 
 	do_each_thread(g, t) {
@@ -48,20 +132,63 @@ out:
 
 void ftrace_syscall_enter(struct pt_regs *regs)
 {
+	struct syscall_trace_enter *entry;
+	struct syscall_metadata *sys_data;
+	struct ring_buffer_event *event;
+	int size;
 	int syscall_nr;
+	int cpu;
 
 	syscall_nr = syscall_get_nr(current, regs);
 
-	trace_printk("syscall %d enter\n", syscall_nr);
+	cpu = raw_smp_processor_id();
+
+	sys_data = syscall_nr_to_meta(syscall_nr);
+	if (!sys_data)
+		return;
+
+	size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
+
+	event = trace_current_buffer_lock_reserve(TRACE_SYSCALL_ENTER, size,
+							0, 0);
+	if (!event)
+		return;
+
+	entry = ring_buffer_event_data(event);
+	entry->nr = syscall_nr;
+	syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
+
+	trace_current_buffer_unlock_commit(event, 0, 0);
+	trace_wake_up();
 }
 
 void ftrace_syscall_exit(struct pt_regs *regs)
 {
+	struct syscall_trace_exit *entry;
+	struct syscall_metadata *sys_data;
+	struct ring_buffer_event *event;
 	int syscall_nr;
+	int cpu;
 
 	syscall_nr = syscall_get_nr(current, regs);
 
-	trace_printk("syscall %d exit\n", syscall_nr);
+	cpu = raw_smp_processor_id();
+
+	sys_data = syscall_nr_to_meta(syscall_nr);
+	if (!sys_data)
+		return;
+
+	event = trace_current_buffer_lock_reserve(TRACE_SYSCALL_EXIT,
+				sizeof(*entry), 0, 0);
+	if (!event)
+		return;
+
+	entry = ring_buffer_event_data(event);
+	entry->nr = syscall_nr;
+	entry->ret = syscall_get_return_value(current, regs);
+
+	trace_current_buffer_unlock_commit(event, 0, 0);
+	trace_wake_up();
 }
 
 static int init_syscall_tracer(struct trace_array *tr)
@@ -77,17 +204,20 @@ static void reset_syscall_tracer(struct trace_array *tr)
 }
 
 static struct trace_event syscall_enter_event = {
-	.type		= TRACE_SYSCALL_ENTER,
+	.type	 	= TRACE_SYSCALL_ENTER,
+	.trace		= print_syscall_enter,
 };
 
 static struct trace_event syscall_exit_event = {
-	.type		= TRACE_SYSCALL_EXIT,
+	.type	 	= TRACE_SYSCALL_EXIT,
+	.trace		= print_syscall_exit,
 };
 
 static struct tracer syscall_tracer __read_mostly = {
-	.name		= "syscall",
+	.name	     	= "syscall",
 	.init		= init_syscall_tracer,
-	.reset		= reset_syscall_tracer
+	.reset		= reset_syscall_tracer,
+	.flags		= &syscalls_flags,
 };
 
 __init int register_ftrace_syscalls(void)