[PATCH] Add support for userspace stacktraces in tracing/iter_ctrl

Török Edwin
2008-11-02T21:18:59Z

Usage example:
mount -t debugfs nodev /sys/kernel/debug
cd /sys/kernel/debug/tracing
echo userstacktrace >iter_ctrl
echo sched_switch >current_tracer
echo 1 >tracing_enabled
.... run application ...
echo 0 >tracing_enabled

Then read one of 'trace','latency_trace','trace_pipe'
It is recomended to compile your userspace programs with frame pointers
(at least glibc + the app you are tracing).

Signed-off-by: Török Edwin <edwintorok@gmail.com>
---
Documentation/ftrace.txt | 5 ++-
arch/x86/kernel/stacktrace.c | 57 +++++++++++++++++++++++++
include/linux/stacktrace.h | 8 ++++
kernel/trace/trace.c | 93 ++++++++++++++++++++++++++++++++++++++++++
kernel/trace/trace.h | 9 ++++
5 files changed, 171 insertions(+), 1 deletions(-)

diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt
index ea5a827..b81618e 100644
--- a/Documentation/ftrace.txt
+++ b/Documentation/ftrace.txt
@@ -330,7 +330,7 @@ output. To see what is available, simply cat the file:

cat /debug/tracing/iter_ctrl
print-parent nosym-offset nosym-addr noverbose noraw nohex nobin \
- noblock nostacktrace nosched-tree
+ noblock nostacktrace nosched-tree nouserstacktrace

To disable one of the options, echo in the option prepended with "no".

@@ -384,6 +384,9 @@ Here are the available options:
When a trace is recorded, so is the stack of functions.
This allows for back traces of trace sites.

+ userstacktrace - This option changes the trace.
+ It records a stacktrace of the current userspace thread.
+
sched-tree - TBD (any users??)

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index d1d850a..000a965 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -6,6 +6,7 @@
#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <linux/module.h>
+#include <linux/uaccess.h>
#include <asm/stacktrace.h>

static void save_stack_warning(void *data, char *msg)
@@ -90,3 +91,59 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
+
+struct stack_frame {
+ const void __user *next_fp;
+ unsigned long return_address;
+};
+
+static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
+{
+ int ret;
+
+ if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
+ return 0;
+
+ ret = 1;
+ pagefault_disable();
+ if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
+ ret = 0;
+ pagefault_enable();
+
+ return ret;
+}
+
+void save_stack_trace_user(struct stack_trace *trace)
+{
+ /*
+ * Trace user stack if we are not a kernel thread
+ */
+ if (current->mm) {
+ const struct pt_regs *regs = task_pt_regs(current);
+ const void __user *fp = (const void __user *)regs->bp;
+
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = regs->ip;
+
+ while (trace->nr_entries < trace->max_entries) {
+ struct stack_frame frame;
+ frame.next_fp = NULL;
+ frame.return_address = 0;
+ if (!copy_stack_frame(fp, &frame))
+ break;
+ if ((unsigned long)fp < regs->sp)
+ break;
+ if (frame.return_address)
+ trace->entries[trace->nr_entries++] =
+ frame.return_address;
+ if (fp == frame.next_fp)
+ break;
+ fp = frame.next_fp;
+ }
+ }
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+
diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 6b8e54a..46704a5 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -18,9 +18,17 @@ extern void save_stack_trace_tsk(struct task_struct *tsk,
struct stack_trace *trace);

extern void print_stack_trace(struct stack_trace *trace, int spaces);
+
+#ifdef CONFIG_X86
+extern void save_stack_trace_user(struct stack_trace *trace);
+#else
+# define save_stack_trace_user(trace) do { } while (0)
+#endif
+
#else
# define save_stack_trace(trace) do { } while (0)
# define save_stack_trace_tsk(tsk, trace) do { } while (0)
+# define save_stack_trace_user(trace) do { } while (0)
# define print_stack_trace(trace, spaces) do { } while (0)
#endif

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5b8c90d..bb965af 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -235,6 +235,7 @@ static const char *trace_options[] = {
"stacktrace",
"sched-tree",
"ftrace_printk",
+ "userstacktrace",
NULL
};

@@ -762,6 +763,44 @@ void __trace_stack(struct trace_array *tr,
ftrace_trace_stack(tr, data, flags, skip, preempt_count());
}

+static void ftrace_trace_userstack(struct trace_array *tr,
+ struct trace_array_cpu *data,
+ unsigned long flags, int pc)
+{
+ struct userstack_entry *entry;
+ struct stack_trace trace;
+ struct ring_buffer_event *event;
+ unsigned long irq_flags;
+
+ if (!(trace_flags & TRACE_ITER_USERSTACKTRACE))
+ return;
+
+ event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
+ &irq_flags);
+ if (!event)
+ return;
+ entry = ring_buffer_event_data(event);
+ tracing_generic_entry_update(&entry->ent, flags, pc);
+ entry->ent.type = TRACE_USER_STACK;
+
+ memset(&entry->caller, 0, sizeof(entry->caller));
+
+ trace.nr_entries = 0;
+ trace.max_entries = FTRACE_STACK_ENTRIES;
+ trace.skip = 0;
+ trace.entries = entry->caller;
+
+ save_stack_trace_user(&trace);
+ ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
+}
+
+void __trace_userstack(struct trace_array *tr,
+ struct trace_array_cpu *data,
+ unsigned long flags)
+{
+ ftrace_trace_userstack(tr, data, flags, preempt_count());
+}
+
static void
ftrace_trace_special(void *__tr, void *__data,
unsigned long arg1, unsigned long arg2, unsigned long arg3,
@@ -785,6 +824,7 @@ ftrace_trace_special(void *__tr, void *__data,
entry->arg3 = arg3;
ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
ftrace_trace_stack(tr, data, irq_flags, 4, pc);
+ ftrace_trace_userstack(tr, data, irq_flags, pc);

trace_wake_up();
}
@@ -823,6 +863,7 @@ tracing_sched_switch_trace(struct trace_array *tr,
entry->next_cpu = task_cpu(next);
ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
ftrace_trace_stack(tr, data, flags, 5, pc);
+ ftrace_trace_userstack(tr, data, flags, pc);
}

void
@@ -852,6 +893,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
entry->next_cpu = task_cpu(wakee);
ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
ftrace_trace_stack(tr, data, flags, 6, pc);
+ ftrace_trace_userstack(tr, data, flags, pc);

trace_wake_up();
}
@@ -1175,6 +1217,31 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
return ret;
}

+static int
+seq_print_userip_objs(const struct userstack_entry *entry, struct trace_seq *s,
+ unsigned long sym_flags)
+{
+ int ret = 1;
+ unsigned i;
+
+ for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
+ unsigned long ip = entry->caller[i];
+
+ if (ip == ULONG_MAX || !ret)
+ break;
+ if (i)
+ ret = trace_seq_puts(s, " <- ");
+ if (!ip) {
+ ret = trace_seq_puts(s, "??");
+ continue;
+ }
+ if (ret /*&& (sym_flags & TRACE_ITER_SYM_ADDR)*/)
+ ret = trace_seq_printf(s, " <" IP_FMT ">", ip);
+ }
+
+ return ret;
+}
+
static void print_lat_help_header(struct seq_file *m)
{
seq_puts(m, "# _------=> CPU# \n");
@@ -1462,6 +1529,16 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
trace_seq_print_cont(s, iter);
break;
}
+ case TRACE_USER_STACK: {
+ struct userstack_entry *field;
+
+ trace_assign_type(field, entry);
+
+ seq_print_userip_objs(field, s, sym_flags);
+ if (entry->flags & TRACE_FLAG_CONT)
+ trace_seq_print_cont(s, iter);
+ break;
+ }
default:
trace_seq_printf(s, "Unknown type %d\n", entry->type);
}
@@ -1598,6 +1675,19 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
trace_seq_print_cont(s, iter);
break;
}
+ case TRACE_USER_STACK: {
+ struct userstack_entry *field;
+
+ trace_assign_type(field, entry);
+
+ ret = seq_print_userip_objs(field, s, sym_flags);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+ ret = trace_seq_putc(s, '\n');
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+ break;
+ }
}
return TRACE_TYPE_HANDLED;
}
@@ -1657,6 +1747,7 @@ static enum print_line_t print_raw_fmt(struct trace_iterator *iter)
break;
}
case TRACE_SPECIAL:
+ case TRACE_USER_STACK:
case TRACE_STACK: {
struct special_entry *field;

@@ -1745,6 +1836,7 @@ static enum print_line_t print_hex_fmt(struct trace_iterator *iter)
break;
}
case TRACE_SPECIAL:
+ case TRACE_USER_STACK:
case TRACE_STACK: {
struct special_entry *field;

@@ -1799,6 +1891,7 @@ static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
break;
}
case TRACE_SPECIAL:
+ case TRACE_USER_STACK:
case TRACE_STACK: {
struct special_entry *field;

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8465ad0..4c81642 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -22,6 +22,7 @@ enum trace_type {
TRACE_MMIO_RW,
TRACE_MMIO_MAP,
TRACE_BOOT,
+ TRACE_USER_STACK,

__TRACE_LAST_TYPE
};
@@ -38,6 +39,7 @@ struct trace_entry {
unsigned char flags;
unsigned char preempt_count;
int pid;
+ int tgid;
};

/*
@@ -85,6 +87,11 @@ struct stack_entry {
unsigned long caller[FTRACE_STACK_ENTRIES];
};

+struct userstack_entry {
+ struct trace_entry ent;
+ unsigned long caller[FTRACE_STACK_ENTRIES];
+};
+
/*
* ftrace_printk entry:
*/
@@ -212,6 +219,7 @@ extern void __ftrace_bad_type(void);
IF_ASSIGN(var, ent, struct ctx_switch_entry, 0); \
IF_ASSIGN(var, ent, struct trace_field_cont, TRACE_CONT); \
IF_ASSIGN(var, ent, struct stack_entry, TRACE_STACK); \
+ IF_ASSIGN(var, ent, struct userstack_entry, TRACE_USER_STACK);\
IF_ASSIGN(var, ent, struct print_entry, TRACE_PRINT); \
IF_ASSIGN(var, ent, struct special_entry, 0); \
IF_ASSIGN(var, ent, struct trace_mmiotrace_rw, \
@@ -415,6 +423,7 @@ enum trace_iterator_flags {
TRACE_ITER_STACKTRACE = 0x100,
TRACE_ITER_SCHED_TREE = 0x200,
TRACE_ITER_PRINTK = 0x400,
+ TRACE_ITER_USERSTACKTRACE = 0x800
};

extern struct tracer nop_trace;
--
1.5.6.5