want more explanation of a feature in terms of common code, review the common
ftrace.txt file.
+Ideally, everyone who wishes to retain performance while supporting tracing in
+their kernel should make it all the way to dynamic ftrace support.
+
Prerequisites
-------------
exiting of a function. On exit, the value is compared and if it does not
match, then it will panic the kernel. This is largely a sanity check for bad
code generation with gcc. If gcc for your port sanely updates the frame
-pointer under different opitmization levels, then ignore this option.
+pointer under different optimization levels, then ignore this option.
However, adding support for it isn't terribly difficult. In your assembly code
that calls prepare_ftrace_return(), pass the frame pointer as the 3rd argument.
HAVE_SYSCALL_TRACEPOINTS
----------------------
+------------------------
You need very few things to get the syscalls tracing in an arch.
HAVE_FTRACE_MCOUNT_RECORD
-------------------------
-See scripts/recordmcount.pl for more info.
+See scripts/recordmcount.pl for more info. Just fill in the arch-specific
+details for how to locate the addresses of mcount call sites via objdump.
+This option doesn't make much sense without also implementing dynamic ftrace.
+
+HAVE_DYNAMIC_FTRACE
+-------------------
+
+You will first need HAVE_FTRACE_MCOUNT_RECORD and HAVE_FUNCTION_TRACER, so
+scroll your reader back up if you got over eager.
+
+Once those are out of the way, you will need to implement:
+ - asm/ftrace.h:
+ - MCOUNT_ADDR
+ - ftrace_call_adjust()
+ - struct dyn_arch_ftrace{}
+ - asm code:
+ - mcount() (new stub)
+ - ftrace_caller()
+ - ftrace_call()
+ - ftrace_stub()
+ - C code:
+ - ftrace_dyn_arch_init()
+ - ftrace_make_nop()
+ - ftrace_make_call()
+ - ftrace_update_ftrace_func()
+
+First you will need to fill out some arch details in your asm/ftrace.h.
+
+Define MCOUNT_ADDR as the address of your mcount symbol similar to:
+ #define MCOUNT_ADDR ((unsigned long)mcount)
+Since no one else will have a decl for that function, you will need to:
+ extern void mcount(void);
+
+You will also need the helper function ftrace_call_adjust(). Most people
+will be able to stub it out like so:
+ static inline unsigned long ftrace_call_adjust(unsigned long addr)
+ {
+ return addr;
+ }
<details to be filled>
+Lastly you will need the custom dyn_arch_ftrace structure. If you need
+some extra state when runtime patching arbitrary call sites, this is the
+place. For now though, create an empty struct:
+ struct dyn_arch_ftrace {
+ /* No extra data needed */
+ };
+
+With the header out of the way, we can fill out the assembly code. While we
+did already create a mcount() function earlier, dynamic ftrace only wants a
+stub function. This is because the mcount() will only be used during boot
+and then all references to it will be patched out never to return. Instead,
+the guts of the old mcount() will be used to create a new ftrace_caller()
+function. Because the two are hard to merge, it will most likely be a lot
+easier to have two separate definitions split up by #ifdefs. Same goes for
+the ftrace_stub() as that will now be inlined in ftrace_caller().
+
+Before we get confused anymore, let's check out some pseudo code so you can
+implement your own stuff in assembly:
-HAVE_DYNAMIC_FTRACE
----------------------
+void mcount(void)
+{
+ return;
+}
+
+void ftrace_caller(void)
+{
+ /* implement HAVE_FUNCTION_TRACE_MCOUNT_TEST if you desire */
+
+ /* save all state needed by the ABI (see paragraph above) */
+
+ unsigned long frompc = ...;
+ unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
+
+ftrace_call:
+ ftrace_stub(frompc, selfpc);
+
+ /* restore all state needed by the ABI */
+
+ftrace_stub:
+ return;
+}
+
+This might look a little odd at first, but keep in mind that we will be runtime
+patching multiple things. First, only functions that we actually want to trace
+will be patched to call ftrace_caller(). Second, since we only have one tracer
+active at a time, we will patch the ftrace_caller() function itself to call the
+specific tracer in question. That is the point of the ftrace_call label.
+
+With that in mind, let's move on to the C code that will actually be doing the
+runtime patching. You'll need a little knowledge of your arch's opcodes in
+order to make it through the next section.
+
+Every arch has an init callback function. If you need to do something early on
+to initialize some state, this is the time to do that. Otherwise, this simple
+function below should be sufficient for most people:
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+ /* return value is done indirectly via data */
+ *(unsigned long *)data = 0;
+
+ return 0;
+}
+
+There are two functions that are used to do runtime patching of arbitrary
+functions. The first is used to turn the mcount call site into a nop (which
+is what helps us retain runtime performance when not tracing). The second is
+used to turn the mcount call site into a call to an arbitrary location (but
+typically that is ftracer_caller()). See the general function definition in
+linux/ftrace.h for the functions:
+ ftrace_make_nop()
+ ftrace_make_call()
+The rec->ip value is the address of the mcount call site that was collected
+by the scripts/recordmcount.pl during build time.
+
+The last function is used to do runtime patching of the active tracer. This
+will be modifying the assembly code at the location of the ftrace_call symbol
+inside of the ftrace_caller() function. So you should have sufficient padding
+at that location to support the new function calls you'll be inserting. Some
+people will be using a "call" type instruction while others will be using a
+"branch" type instruction. Specifically, the function is:
+ ftrace_update_ftrace_func()
+
+
+HAVE_DYNAMIC_FTRACE + HAVE_FUNCTION_GRAPH_TRACER
+------------------------------------------------
+
+The function grapher needs a few tweaks in order to work with dynamic ftrace.
+Basically, you will need to:
+ - update:
+ - ftrace_caller()
+ - ftrace_graph_call()
+ - ftrace_graph_caller()
+ - implement:
+ - ftrace_enable_ftrace_graph_caller()
+ - ftrace_disable_ftrace_graph_caller()
<details to be filled>
+Quick notes:
+ - add a nop stub after the ftrace_call location named ftrace_graph_call;
+ stub needs to be large enough to support a call to ftrace_graph_caller()
+ - update ftrace_graph_caller() to work with being called by the new
+ ftrace_caller() since some semantics may have changed
+ - ftrace_enable_ftrace_graph_caller() will runtime patch the
+ ftrace_graph_call location with a call to ftrace_graph_caller()
+ - ftrace_disable_ftrace_graph_caller() will runtime patch the
+ ftrace_graph_call location with nops
+/*
+ * Ftrace header. For implementation details beyond the random comments
+ * scattered below, see: Documentation/trace/ftrace-design.txt
+ */
+
#ifndef _LINUX_FTRACE_H
#define _LINUX_FTRACE_H
struct tracer;
struct dentry;
-DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
-
struct trace_print_flags {
unsigned long mask;
const char *name;
struct ring_buffer_iter *buffer_iter[NR_CPUS];
unsigned long iter_flags;
+ /* trace_seq for __print_flags() and __print_symbolic() etc. */
+ struct trace_seq tmp_seq;
+
/* The below is zeroed out in pipe_read */
struct trace_seq seq;
struct trace_entry *ent;
enum {
TRACE_EVENT_FL_ENABLED_BIT,
TRACE_EVENT_FL_FILTERED_BIT,
+ TRACE_EVENT_FL_RECORDED_CMD_BIT,
};
enum {
- TRACE_EVENT_FL_ENABLED = (1 << TRACE_EVENT_FL_ENABLED_BIT),
- TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT),
+ TRACE_EVENT_FL_ENABLED = (1 << TRACE_EVENT_FL_ENABLED_BIT),
+ TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT),
+ TRACE_EVENT_FL_RECORDED_CMD = (1 << TRACE_EVENT_FL_RECORDED_CMD_BIT),
};
struct ftrace_event_call {
* 32 bit flags:
* bit 1: enabled
* bit 2: filter_active
+ * bit 3: enabled cmd record
*
* Changes to flags must hold the event_mutex.
*
* struct trace_seq *s = &iter->seq;
* struct ftrace_raw_<call> *field; <-- defined in stage 1
* struct trace_entry *entry;
- * struct trace_seq *p;
+ * struct trace_seq *p = &iter->tmp_seq;
* int ret;
*
* entry = iter->ent;
*
* field = (typeof(field))entry;
*
- * p = &get_cpu_var(ftrace_event_seq);
* trace_seq_init(p);
* ret = trace_seq_printf(s, "%s: ", <call>);
* if (ret)
* ret = trace_seq_printf(s, <TP_printk> "\n");
- * put_cpu();
* if (!ret)
* return TRACE_TYPE_PARTIAL_LINE;
*
struct trace_seq *s = &iter->seq; \
struct ftrace_raw_##call *field; \
struct trace_entry *entry; \
- struct trace_seq *p; \
+ struct trace_seq *p = &iter->tmp_seq; \
int ret; \
\
event = container_of(trace_event, struct ftrace_event_call, \
\
field = (typeof(field))entry; \
\
- p = &get_cpu_var(ftrace_event_seq); \
trace_seq_init(p); \
ret = trace_seq_printf(s, "%s: ", event->name); \
if (ret) \
ret = trace_seq_printf(s, print); \
- put_cpu(); \
if (!ret) \
return TRACE_TYPE_PARTIAL_LINE; \
\
struct trace_seq *s = &iter->seq; \
struct ftrace_raw_##template *field; \
struct trace_entry *entry; \
- struct trace_seq *p; \
+ struct trace_seq *p = &iter->tmp_seq; \
int ret; \
\
entry = iter->ent; \
\
field = (typeof(field))entry; \
\
- p = &get_cpu_var(ftrace_event_seq); \
trace_seq_init(p); \
ret = trace_seq_printf(s, "%s: ", #call); \
if (ret) \
ret = trace_seq_printf(s, print); \
- put_cpu(); \
if (!ret) \
return TRACE_TYPE_PARTIAL_LINE; \
\
*/
struct ring_buffer_per_cpu {
int cpu;
+ atomic_t record_disabled;
struct ring_buffer *buffer;
spinlock_t reader_lock; /* serialize readers */
arch_spinlock_t lock;
unsigned long read;
u64 write_stamp;
u64 read_stamp;
- atomic_t record_disabled;
};
struct ring_buffer {
/* trace_flags holds trace_options default values */
unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
- TRACE_ITER_GRAPH_TIME;
+ TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD;
static int trace_stop_count;
static DEFINE_SPINLOCK(tracing_start_lock);
"latency-format",
"sleep-time",
"graph-time",
+ "record-cmd",
NULL
};
return;
WARN_ON_ONCE(!irqs_disabled());
+ if (!current_trace->use_max_tr) {
+ WARN_ON_ONCE(1);
+ return;
+ }
arch_spin_lock(&ftrace_max_lock);
tr->buffer = max_tr.buffer;
return;
WARN_ON_ONCE(!irqs_disabled());
+ if (!current_trace->use_max_tr) {
+ WARN_ON_ONCE(1);
+ return;
+ }
+
arch_spin_lock(&ftrace_max_lock);
ftrace_disable_cpu();
return -1;
}
- if (strlen(type->name) > MAX_TRACER_SIZE) {
+ if (strlen(type->name) >= MAX_TRACER_SIZE) {
pr_info("Tracer has a name longer than %d\n", MAX_TRACER_SIZE);
return -1;
}
trace_flags |= mask;
else
trace_flags &= ~mask;
+
+ if (mask == TRACE_ITER_RECORD_CMD)
+ trace_event_enable_cmd_record(enabled);
}
static ssize_t
if (ret < 0)
return ret;
+ if (!current_trace->use_max_tr)
+ goto out;
+
ret = ring_buffer_resize(max_tr.buffer, size);
if (ret < 0) {
int r;
return ret;
}
+ max_tr.entries = size;
+ out:
global_trace.entries = size;
return ret;
}
+
/**
* tracing_update_buffers - used by tracing facility to expand ring buffers
*
trace_branch_disable();
if (current_trace && current_trace->reset)
current_trace->reset(tr);
-
+ if (current_trace && current_trace->use_max_tr) {
+ /*
+ * We don't free the ring buffer. instead, resize it because
+ * The max_tr ring buffer has some state (e.g. ring->clock) and
+ * we want preserve it.
+ */
+ ring_buffer_resize(max_tr.buffer, 1);
+ max_tr.entries = 1;
+ }
destroy_trace_option_files(topts);
current_trace = t;
topts = create_trace_option_files(current_trace);
+ if (current_trace->use_max_tr) {
+ ret = ring_buffer_resize(max_tr.buffer, global_trace.entries);
+ if (ret < 0)
+ goto out;
+ max_tr.entries = global_trace.entries;
+ }
if (t->init) {
ret = tracer_init(t, tr);
}
tracing_start();
- max_tr.entries = global_trace.entries;
mutex_unlock(&trace_types_lock);
return cnt;
#ifdef CONFIG_TRACER_MAX_TRACE
- max_tr.buffer = ring_buffer_alloc(ring_buf_size,
- TRACE_BUFFER_FLAGS);
+ max_tr.buffer = ring_buffer_alloc(1, TRACE_BUFFER_FLAGS);
if (!max_tr.buffer) {
printk(KERN_ERR "tracer: failed to allocate max ring buffer!\n");
WARN_ON(1);
ring_buffer_free(global_trace.buffer);
goto out_free_cpumask;
}
- max_tr.entries = ring_buffer_size(max_tr.buffer);
- WARN_ON(max_tr.entries != global_trace.entries);
+ max_tr.entries = 1;
#endif
/* Allocate the first page for all buffers */
struct tracer *next;
int print_max;
struct tracer_flags *flags;
+ int use_max_tr;
};
TRACE_ITER_LATENCY_FMT = 0x20000,
TRACE_ITER_SLEEP_TIME = 0x40000,
TRACE_ITER_GRAPH_TIME = 0x80000,
+ TRACE_ITER_RECORD_CMD = 0x100000,
};
/*
return 0;
}
+extern void trace_event_enable_cmd_record(bool enable);
+
extern struct mutex event_mutex;
extern struct list_head ftrace_events;
}
EXPORT_SYMBOL_GPL(ftrace_event_reg);
+void trace_event_enable_cmd_record(bool enable)
+{
+ struct ftrace_event_call *call;
+
+ mutex_lock(&event_mutex);
+ list_for_each_entry(call, &ftrace_events, list) {
+ if (!(call->flags & TRACE_EVENT_FL_ENABLED))
+ continue;
+
+ if (enable) {
+ tracing_start_cmdline_record();
+ call->flags |= TRACE_EVENT_FL_RECORDED_CMD;
+ } else {
+ tracing_stop_cmdline_record();
+ call->flags &= ~TRACE_EVENT_FL_RECORDED_CMD;
+ }
+ }
+ mutex_unlock(&event_mutex);
+}
+
static int ftrace_event_enable_disable(struct ftrace_event_call *call,
int enable)
{
case 0:
if (call->flags & TRACE_EVENT_FL_ENABLED) {
call->flags &= ~TRACE_EVENT_FL_ENABLED;
- tracing_stop_cmdline_record();
+ if (call->flags & TRACE_EVENT_FL_RECORDED_CMD) {
+ tracing_stop_cmdline_record();
+ call->flags &= ~TRACE_EVENT_FL_RECORDED_CMD;
+ }
call->class->reg(call, TRACE_REG_UNREGISTER);
}
break;
case 1:
if (!(call->flags & TRACE_EVENT_FL_ENABLED)) {
- tracing_start_cmdline_record();
+ if (trace_flags & TRACE_ITER_RECORD_CMD) {
+ tracing_start_cmdline_record();
+ call->flags |= TRACE_EVENT_FL_RECORDED_CMD;
+ }
ret = call->class->reg(call, TRACE_REG_REGISTER);
if (ret) {
tracing_stop_cmdline_record();
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
+ .use_max_tr = 1,
};
# define register_irqsoff(trace) register_tracer(&trace)
#else
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
+ .use_max_tr = 1,
};
# define register_preemptoff(trace) register_tracer(&trace)
#else
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
+ .use_max_tr = 1,
};
# define register_preemptirqsoff(trace) register_tracer(&trace)
DECLARE_RWSEM(trace_event_mutex);
-DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
-EXPORT_PER_CPU_SYMBOL(ftrace_event_seq);
-
static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;
static int next_event_type = __TRACE_LAST_TYPE + 1;
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
+ .use_max_tr = 1,
};
static struct tracer wakeup_rt_tracer __read_mostly =
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
+ .use_max_tr = 1,
};
__init static int init_wakeup_tracer(void)
# 14: R_MIPS_NONE *ABS*
# 18: 00020021 nop
if ($is_module eq "0") {
- $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
+ $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
} else {
$mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
}
projects / firefly-linux-kernel-4.4.55.git / commitdiff