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Subject[PATCH 15/16] tracing: Add fields format definition for syscall events
Date
Define the format of the syscall trace fields to parse the binary
values from a raw trace using the syscall events "format" file.

This is defined dynamically using the syscalls metadata.
It prepares the export of syscall event raw records to perf
counters.

Example:

$ cat /debug/tracing/events/syscalls/sys_enter_sched_getparam/format
name: sys_enter_sched_getparam
ID: 39
format:
field:unsigned short common_type; offset:0; size:2;
field:unsigned char common_flags; offset:2; size:1;
field:unsigned char common_preempt_count; offset:3; size:1;
field:int common_pid; offset:4; size:4;
field:int common_tgid; offset:8; size:4;

field:pid_t pid; offset:12; size:8;
field:struct sched_param * param; offset:20; size:8;

print fmt: "pid: 0x%08lx, param: 0x%08lx", ((unsigned long)(REC->pid)), ((unsigned long)(REC->param))

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>
---
include/linux/syscalls.h | 1 +
include/trace/syscall.h | 2 +
kernel/trace/trace_syscalls.c | 46 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 49 insertions(+), 0 deletions(-)
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 5541e75..87d06c1 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -189,6 +189,7 @@ static void prof_sysexit_disable_##sname(struct ftrace_event_call *event_call) \
.system = "syscalls", \
.event = &event_syscall_enter, \
.raw_init = init_enter_##sname, \
+ .show_format = ftrace_format_syscall, \
.regfunc = reg_event_syscall_enter, \
.unregfunc = unreg_event_syscall_enter, \
.data = "sys"#sname, \
diff --git a/include/trace/syscall.h b/include/trace/syscall.h
index 3ab6dd1..0cb0362 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -55,6 +55,8 @@ extern int reg_event_syscall_enter(void *ptr);
extern void unreg_event_syscall_enter(void *ptr);
extern int reg_event_syscall_exit(void *ptr);
extern void unreg_event_syscall_exit(void *ptr);
+extern int
+ftrace_format_syscall(struct ftrace_event_call *call, struct trace_seq *s);
enum print_line_t print_syscall_enter(struct trace_iterator *iter, int flags);
enum print_line_t print_syscall_exit(struct trace_iterator *iter, int flags);
#endif
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index f4eaec3..9ee6386 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -105,6 +105,52 @@ print_syscall_exit(struct trace_iterator *iter, int flags)
return TRACE_TYPE_HANDLED;
}

+int ftrace_format_syscall(struct ftrace_event_call *call, struct trace_seq *s)
+{
+ int i;
+ int nr;
+ int ret = 0;
+ struct syscall_metadata *entry;
+ int offset = sizeof(struct trace_entry);
+
+ nr = syscall_name_to_nr((char *)call->data);
+ entry = syscall_nr_to_meta(nr);
+
+ if (!entry)
+ return ret;
+
+ for (i = 0; i < entry->nb_args; i++) {
+ ret = trace_seq_printf(s, "\tfield:%s %s;", entry->types[i],
+ entry->args[i]);
+ if (!ret)
+ return 0;
+ ret = trace_seq_printf(s, "\toffset:%d;\tsize:%lu;\n", offset,
+ sizeof(unsigned long));
+ if (!ret)
+ return 0;
+ offset += sizeof(unsigned long);
+ }
+
+ trace_seq_printf(s, "\nprint fmt: \"");
+ for (i = 0; i < entry->nb_args; i++) {
+ ret = trace_seq_printf(s, "%s: 0x%%0%lulx%s", entry->args[i],
+ sizeof(unsigned long),
+ i == entry->nb_args - 1 ? "\", " : ", ");
+ if (!ret)
+ return 0;
+ }
+
+ for (i = 0; i < entry->nb_args; i++) {
+ ret = trace_seq_printf(s, "((unsigned long)(REC->%s))%s",
+ entry->args[i],
+ i == entry->nb_args - 1 ? "\n" : ", ");
+ if (!ret)
+ return 0;
+ }
+
+ return ret;
+}
+
void ftrace_syscall_enter(struct pt_regs *regs, long id)
{
struct syscall_trace_enter *entry;
--
1.6.2.3


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