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tracing: Allow trace_printk() to go to other instance buffers

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Currently, trace_printk() just goes to the top level ring buffer. But
there may be times that it should go to one of the instances created by
the kernel command line.

Add a new trace_instance flag: traceprintk (also can use "printk" or
"trace_printk" as people tend to forget the actual flag name).

  trace_instance=foo^traceprintk

Will assign the trace_printk to this buffer at boot up.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineeth Pillai <vineeth@bitbyteword.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ross Zwisler <zwisler@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Aring <aahringo@redhat.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Jonathan Corbet" <corbet@lwn.net>
Link: https://lore.kernel.org/20240823014019.226694946@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2024-08-22 21:39:04 -04:00 committed by Steven Rostedt (Google)
parent b6fc31b687
commit ddb8ea9e5a
2 changed files with 45 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
Documentation/admin-guide/kernel-parameters.txt
View File

@ -6744,11 +6744,17 @@
event, and all events under the "initcall" system.
Flags can be added to the instance to modify its behavior when it is
created. The flags are separated by '^'. Currently there's only one flag
defined, and that's "traceoff", to have the tracing instance tracing
disabled after it is created.
created. The flags are separated by '^'.
trace_instance=foo^traceoff,sched,irq
The available flags are:
traceoff - Have the tracing instance tracing disabled after it is created.
traceprintk - Have trace_printk() write into this trace instance
(note, "printk" and "trace_printk" can also be used)
Currently, traceprintk flag cannot be used for memory
mapped ring buffers as described below.
trace_instance=foo^traceoff^traceprintk,sched,irq
The flags must come before the defined events.

46
kernel/trace/trace.c
View File

@ -500,6 +500,8 @@ static struct trace_array global_trace = {
.trace_flags = TRACE_DEFAULT_FLAGS,
};
static struct trace_array *printk_trace = &global_trace;
void trace_set_ring_buffer_expanded(struct trace_array *tr)
{
if (!tr)
@ -1117,7 +1119,7 @@ EXPORT_SYMBOL_GPL(__trace_array_puts);
*/
int __trace_puts(unsigned long ip, const char *str, int size)
{
return __trace_array_puts(&global_trace, ip, str, size);
return __trace_array_puts(printk_trace, ip, str, size);
}
EXPORT_SYMBOL_GPL(__trace_puts);
@ -1128,6 +1130,7 @@ EXPORT_SYMBOL_GPL(__trace_puts);
*/
int __trace_bputs(unsigned long ip, const char *str)
{
struct trace_array *tr = printk_trace;
struct ring_buffer_event *event;
struct trace_buffer *buffer;
struct bputs_entry *entry;
@ -1135,14 +1138,14 @@ int __trace_bputs(unsigned long ip, const char *str)
int size = sizeof(struct bputs_entry);
int ret = 0;
if (!(global_trace.trace_flags & TRACE_ITER_PRINTK))
if (!(tr->trace_flags & TRACE_ITER_PRINTK))
return 0;
if (unlikely(tracing_selftest_running || tracing_disabled))
return 0;
trace_ctx = tracing_gen_ctx();
buffer = global_trace.array_buffer.buffer;
buffer = tr->array_buffer.buffer;
ring_buffer_nest_start(buffer);
event = __trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size,
@ -1155,7 +1158,7 @@ int __trace_bputs(unsigned long ip, const char *str)
entry->str = str;
__buffer_unlock_commit(buffer, event);
ftrace_trace_stack(&global_trace, buffer, trace_ctx, 4, NULL);
ftrace_trace_stack(tr, buffer, trace_ctx, 4, NULL);
ret = 1;
out:
@ -3025,7 +3028,7 @@ void trace_dump_stack(int skip)
/* Skip 1 to skip this function. */
skip++;
#endif
__ftrace_trace_stack(global_trace.array_buffer.buffer,
__ftrace_trace_stack(printk_trace->array_buffer.buffer,
tracing_gen_ctx(), skip, NULL);
}
EXPORT_SYMBOL_GPL(trace_dump_stack);
@ -3244,7 +3247,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
struct trace_event_call *call = &event_bprint;
struct ring_buffer_event *event;
struct trace_buffer *buffer;
struct trace_array *tr = &global_trace;
struct trace_array *tr = printk_trace;
struct bprint_entry *entry;
unsigned int trace_ctx;
char *tbuffer;
@ -3342,7 +3345,7 @@ __trace_array_vprintk(struct trace_buffer *buffer,
memcpy(&entry->buf, tbuffer, len + 1);
if (!call_filter_check_discard(call, entry, buffer, event)) {
__buffer_unlock_commit(buffer, event);
ftrace_trace_stack(&global_trace, buffer, trace_ctx, 6, NULL);
ftrace_trace_stack(printk_trace, buffer, trace_ctx, 6, NULL);
}
out:
@ -3438,7 +3441,7 @@ int trace_array_printk_buf(struct trace_buffer *buffer,
int ret;
va_list ap;
if (!(global_trace.trace_flags & TRACE_ITER_PRINTK))
if (!(printk_trace->trace_flags & TRACE_ITER_PRINTK))
return 0;
va_start(ap, fmt);
@ -3450,7 +3453,7 @@ int trace_array_printk_buf(struct trace_buffer *buffer,
__printf(2, 0)
int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
{
return trace_array_vprintk(&global_trace, ip, fmt, args);
return trace_array_vprintk(printk_trace, ip, fmt, args);
}
EXPORT_SYMBOL_GPL(trace_vprintk);
@ -9666,6 +9669,9 @@ static int __remove_instance(struct trace_array *tr)
set_tracer_flag(tr, 1 << i, 0);
}
if (printk_trace == tr)
printk_trace = &global_trace;
tracing_set_nop(tr);
clear_ftrace_function_probes(tr);
event_trace_del_tracer(tr);
@ -10468,6 +10474,7 @@ __init static void enable_instances(void)
phys_addr_t start = 0;
phys_addr_t size = 0;
unsigned long addr = 0;
bool traceprintk = false;
bool traceoff = false;
char *flag_delim;
char *addr_delim;
@ -10489,13 +10496,18 @@ __init static void enable_instances(void)
char *flag;
while ((flag = strsep(&flag_delim, "^"))) {
if (strcmp(flag, "traceoff") == 0)
if (strcmp(flag, "traceoff") == 0) {
traceoff = true;
else
} else if ((strcmp(flag, "printk") == 0) ||
(strcmp(flag, "traceprintk") == 0) ||
(strcmp(flag, "trace_printk") == 0)) {
traceprintk = true;
} else {
pr_info("Tracing: Invalid instance flag '%s' for %s\n",
flag, name);
}
}
}
tok = addr_delim;
if (tok && isdigit(*tok)) {
@ -10548,6 +10560,18 @@ __init static void enable_instances(void)
if (traceoff)
tracer_tracing_off(tr);
if (traceprintk) {
/*
* The binary format of traceprintk can cause a crash if used
* by a buffer from another boot. Do not allow it for the
* memory mapped ring buffers.
*/
if (start)
pr_warn("Tracing: WARNING: memory mapped ring buffers cannot be used for trace_printk\n");
else
printk_trace = tr;
}
/* Only allow non mapped buffers to be deleted */
if (!start)
trace_array_put(tr);