ftrace: add a buffer for output

Later patches will need to print the same things as the seq output
does. But those outputs will not use the seq utility. This patch
adds a buffer to the iterator, that can be used by either the
seq utility or other output.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 140 insertions, 68 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 777b859e1c2e..d39f4faec7c3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -169,6 +169,66 @@ void *head_page(struct trace_array_cpu *data)
         return page_address(page);
 }
 
+static notrace int
+trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
+{
+        int len = (PAGE_SIZE - 1) - s->len;
+        va_list ap;
+
+        if (!len)
+                return 0;
+
+        va_start(ap, fmt);
+        len = vsnprintf(s->buffer + s->len, len, fmt, ap);
+        va_end(ap);
+
+        s->len += len;
+
+        return len;
+}
+
+static notrace int
+trace_seq_puts(struct trace_seq *s, const char *str)
+{
+        int len = strlen(str);
+
+        if (len > ((PAGE_SIZE - 1) - s->len))
+                len = (PAGE_SIZE - 1) - s->len;
+
+        memcpy(s->buffer + s->len, str, len);
+        s->len += len;
+
+        return len;
+}
+
+static notrace int
+trace_seq_putc(struct trace_seq *s, unsigned char c)
+{
+        if (s->len >= (PAGE_SIZE - 1))
+                return 0;
+
+        s->buffer[s->len++] = c;
+
+        return 1;
+}
+
+static notrace void
+trace_seq_reset(struct trace_seq *s)
+{
+        s->len = 0;
+}
+
+static notrace void
+trace_print_seq(struct seq_file *m, struct trace_seq *s)
+{
+        int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
+
+        s->buffer[len] = 0;
+        seq_puts(m, s->buffer);
+
+        trace_seq_reset(s);
+}
+
 notrace static void
 flip_trace(struct trace_array_cpu *tr1, struct trace_array_cpu *tr2)
 {
@@ -756,25 +816,26 @@ static void s_stop(struct seq_file *m, void *p)
 }
 
 static void
-seq_print_sym_short(struct seq_file *m, const char *fmt, unsigned long address)
+seq_print_sym_short(struct trace_seq *s, const char *fmt, unsigned long address)
 {
 #ifdef CONFIG_KALLSYMS
         char str[KSYM_SYMBOL_LEN];
 
         kallsyms_lookup(address, NULL, NULL, NULL, str);
 
-        seq_printf(m, fmt, str);
+        trace_seq_printf(s, fmt, str);
 #endif
 }
 
 static void
-seq_print_sym_offset(struct seq_file *m, const char *fmt, unsigned long address)
+seq_print_sym_offset(struct trace_seq *s, const char *fmt,
+                     unsigned long address)
 {
 #ifdef CONFIG_KALLSYMS
         char str[KSYM_SYMBOL_LEN];
 
         sprint_symbol(str, address);
-        seq_printf(m, fmt, str);
+        trace_seq_printf(s, fmt, str);
 #endif
 }
 
@@ -785,20 +846,20 @@ seq_print_sym_offset(struct seq_file *m, const char *fmt, unsigned long address)
 #endif
 
 static notrace void
-seq_print_ip_sym(struct seq_file *m, unsigned long ip, unsigned long sym_flags)
+seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
 {
         if (!ip) {
-                seq_printf(m, "0");
+                trace_seq_printf(s, "0");
                 return;
         }
 
         if (sym_flags & TRACE_ITER_SYM_OFFSET)
-                seq_print_sym_offset(m, "%s", ip);
+                seq_print_sym_offset(s, "%s", ip);
         else
-                seq_print_sym_short(m, "%s", ip);
+                seq_print_sym_short(s, "%s", ip);
 
         if (sym_flags & TRACE_ITER_SYM_ADDR)
-                seq_printf(m, " <" IP_FMT ">", ip);
+                trace_seq_printf(s, " <" IP_FMT ">", ip);
 }
 
 static notrace void print_lat_help_header(struct seq_file *m)
@@ -881,9 +942,11 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 
         if (data->critical_start) {
                 seq_puts(m, " => started at: ");
-                seq_print_ip_sym(m, data->critical_start, sym_flags);
+                seq_print_ip_sym(&iter->seq, data->critical_start, sym_flags);
+                trace_print_seq(m, &iter->seq);
                 seq_puts(m, "\n => ended at:   ");
-                seq_print_ip_sym(m, data->critical_end, sym_flags);
+                seq_print_ip_sym(&iter->seq, data->critical_end, sym_flags);
+                trace_print_seq(m, &iter->seq);
                 seq_puts(m, "\n");
         }
 
@@ -891,61 +954,61 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 }
 
 static notrace void
-lat_print_generic(struct seq_file *m, struct trace_entry *entry, int cpu)
+lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
 {
         int hardirq, softirq;
         char *comm;
 
         comm = trace_find_cmdline(entry->pid);
 
-        seq_printf(m, "%8.8s-%-5d ", comm, entry->pid);
-        seq_printf(m, "%d", cpu);
-        seq_printf(m, "%c%c",
-                   (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : '.',
-                   ((entry->flags & TRACE_FLAG_NEED_RESCHED) ? 'N' : '.'));
+        trace_seq_printf(s, "%8.8s-%-5d ", comm, entry->pid);
+        trace_seq_printf(s, "%d", cpu);
+        trace_seq_printf(s, "%c%c",
+                        (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : '.',
+                        ((entry->flags & TRACE_FLAG_NEED_RESCHED) ? 'N' : '.'));
 
         hardirq = entry->flags & TRACE_FLAG_HARDIRQ;
         softirq = entry->flags & TRACE_FLAG_SOFTIRQ;
         if (hardirq && softirq)
-                seq_putc(m, 'H');
+                trace_seq_putc(s, 'H');
         else {
                 if (hardirq)
-                        seq_putc(m, 'h');
+                        trace_seq_putc(s, 'h');
                 else {
                         if (softirq)
-                                seq_putc(m, 's');
+                                trace_seq_putc(s, 's');
                         else
-                                seq_putc(m, '.');
+                                trace_seq_putc(s, '.');
                 }
         }
 
         if (entry->preempt_count)
-                seq_printf(m, "%x", entry->preempt_count);
+                trace_seq_printf(s, "%x", entry->preempt_count);
         else
-                seq_puts(m, ".");
+                trace_seq_puts(s, ".");
 }
 
 unsigned long preempt_mark_thresh = 100;
 
 static notrace void
-lat_print_timestamp(struct seq_file *m, unsigned long long abs_usecs,
+lat_print_timestamp(struct trace_seq *s, unsigned long long abs_usecs,
                     unsigned long rel_usecs)
 {
-        seq_printf(m, " %4lldus", abs_usecs);
+        trace_seq_printf(s, " %4lldus", abs_usecs);
         if (rel_usecs > preempt_mark_thresh)
-                seq_puts(m, "!: ");
+                trace_seq_puts(s, "!: ");
         else if (rel_usecs > 1)
-                seq_puts(m, "+: ");
+                trace_seq_puts(s, "+: ");
         else
-                seq_puts(m, " : ");
+                trace_seq_puts(s, " : ");
 }
 
 static const char state_to_char[] = TASK_STATE_TO_CHAR_STR;
 
 static notrace void
-print_lat_fmt(struct seq_file *m, struct trace_iterator *iter,
-              unsigned int trace_idx, int cpu)
+print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
 {
+        struct trace_seq *s = &iter->seq;
         unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
         struct trace_entry *next_entry = find_next_entry(iter, NULL);
         unsigned long verbose = (trace_flags & TRACE_ITER_VERBOSE);
@@ -962,39 +1025,40 @@ print_lat_fmt(struct seq_file *m, struct trace_iterator *iter,
 
         if (verbose) {
                 comm = trace_find_cmdline(entry->pid);
-                seq_printf(m, "%16s %5d %d %d %08x %08x [%08lx]"
-                           " %ld.%03ldms (+%ld.%03ldms): ",
-                           comm,
-                           entry->pid, cpu, entry->flags,
-                           entry->preempt_count, trace_idx,
-                           ns2usecs(entry->t),
-                           abs_usecs/1000,
-                           abs_usecs % 1000, rel_usecs/1000, rel_usecs % 1000);
+                trace_seq_printf(s, "%16s %5d %d %d %08x %08x [%08lx]"
+                                 " %ld.%03ldms (+%ld.%03ldms): ",
+                                 comm,
+                                 entry->pid, cpu, entry->flags,
+                                 entry->preempt_count, trace_idx,
+                                 ns2usecs(entry->t),
+                                 abs_usecs/1000,
+                                 abs_usecs % 1000, rel_usecs/1000,
+                                 rel_usecs % 1000);
         } else {
-                lat_print_generic(m, entry, cpu);
-                lat_print_timestamp(m, abs_usecs, rel_usecs);
+                lat_print_generic(s, entry, cpu);
+                lat_print_timestamp(s, abs_usecs, rel_usecs);
         }
         switch (entry->type) {
         case TRACE_FN:
-                seq_print_ip_sym(m, entry->fn.ip, sym_flags);
-                seq_puts(m, " (");
-                seq_print_ip_sym(m, entry->fn.parent_ip, sym_flags);
-                seq_puts(m, ")\n");
+                seq_print_ip_sym(s, entry->fn.ip, sym_flags);
+                trace_seq_puts(s, " (");
+                seq_print_ip_sym(s, entry->fn.parent_ip, sym_flags);
+                trace_seq_puts(s, ")\n");
                 break;
         case TRACE_CTX:
                 S = entry->ctx.prev_state < sizeof(state_to_char) ?
                         state_to_char[entry->ctx.prev_state] : 'X';
                 comm = trace_find_cmdline(entry->ctx.next_pid);
-                seq_printf(m, " %d:%d:%c --> %d:%d %s\n",
-                           entry->ctx.prev_pid,
-                           entry->ctx.prev_prio,
-                           S,
-                           entry->ctx.next_pid,
-                           entry->ctx.next_prio,
-                           comm);
+                trace_seq_printf(s, " %d:%d:%c --> %d:%d %s\n",
+                                 entry->ctx.prev_pid,
+                                 entry->ctx.prev_prio,
+                                 S,
+                                 entry->ctx.next_pid,
+                                 entry->ctx.next_prio,
+                                 comm);
                 break;
         default:
-                seq_printf(m, "Unknown type %d\n", entry->type);
+                trace_seq_printf(s, "Unknown type %d\n", entry->type);
         }
 }
 
@@ -1026,8 +1090,9 @@ static notrace void sync_time_offset(struct trace_iterator *iter)
 }
 
 static notrace void
-print_trace_fmt(struct seq_file *m, struct trace_iterator *iter)
+print_trace_fmt(struct trace_iterator *iter)
 {
+        struct trace_seq *s = &iter->seq;
         unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
         struct trace_entry *entry;
         unsigned long usec_rem;
@@ -1045,29 +1110,29 @@ print_trace_fmt(struct seq_file *m, struct trace_iterator *iter)
         usec_rem = do_div(t, 1000000ULL);
         secs = (unsigned long)t;
 
-        seq_printf(m, "%16s-%-5d ", comm, entry->pid);
-        seq_printf(m, "[%02d] ", iter->cpu);
-        seq_printf(m, "%5lu.%06lu: ", secs, usec_rem);
+        trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
+        trace_seq_printf(s, "[%02d] ", iter->cpu);
+        trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
 
         switch (entry->type) {
         case TRACE_FN:
-                seq_print_ip_sym(m, entry->fn.ip, sym_flags);
+                seq_print_ip_sym(s, entry->fn.ip, sym_flags);
                 if ((sym_flags & TRACE_ITER_PRINT_PARENT) &&
                                                 entry->fn.parent_ip) {
-                        seq_printf(m, " <-");
-                        seq_print_ip_sym(m, entry->fn.parent_ip, sym_flags);
+                        trace_seq_printf(s, " <-");
+                        seq_print_ip_sym(s, entry->fn.parent_ip, sym_flags);
                 }
-                seq_printf(m, "\n");
+                trace_seq_printf(s, "\n");
                 break;
         case TRACE_CTX:
                 S = entry->ctx.prev_state < sizeof(state_to_char) ?
                         state_to_char[entry->ctx.prev_state] : 'X';
-                seq_printf(m, " %d:%d:%c ==> %d:%d\n",
-                           entry->ctx.prev_pid,
-                           entry->ctx.prev_prio,
-                           S,
-                           entry->ctx.next_pid,
-                           entry->ctx.next_prio);
+                trace_seq_printf(s, " %d:%d:%c ==> %d:%d\n",
+                                 entry->ctx.prev_pid,
+                                 entry->ctx.prev_prio,
+                                 S,
+                                 entry->ctx.next_pid,
+                                 entry->ctx.next_prio);
                 break;
         }
 }
@@ -1108,9 +1173,10 @@ static int s_show(struct seq_file *m, void *v)
                 }
         } else {
                 if (iter->iter_flags & TRACE_FILE_LAT_FMT)
-                        print_lat_fmt(m, iter, iter->idx, iter->cpu);
+                        print_lat_fmt(iter, iter->idx, iter->cpu);
                 else
-                        print_trace_fmt(m, iter);
+                        print_trace_fmt(iter);
+                trace_print_seq(m, &iter->seq);
         }
 
         return 0;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 0ce127455b4b..f5b32ca0b457 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -111,11 +111,17 @@ struct tracer {
         int                     print_max;
 };
 
+struct trace_seq {
+        unsigned char           buffer[PAGE_SIZE];
+        unsigned int            len;
+};
+
 /*
  * Trace iterator - used by printout routines who present trace
  * results to users and which routines might sleep, etc:
  */
 struct trace_iterator {
+        struct trace_seq        seq;
         struct trace_array      *tr;
         struct tracer           *trace;