path: root/kernel/trace/trace_snapshot.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/fsnotify.h>

#include <asm/setup.h> /* COMMAND_LINE_SIZE */

#include "trace.h"

/* Used if snapshot allocated at boot */
static bool allocate_snapshot;
static bool snapshot_at_boot;

static char boot_snapshot_info[COMMAND_LINE_SIZE] __initdata;
static int boot_snapshot_index;

static int __init boot_alloc_snapshot(char *str)
{
	char *slot = boot_snapshot_info + boot_snapshot_index;
	int left = sizeof(boot_snapshot_info) - boot_snapshot_index;
	int ret;

	if (str[0] == '=') {
		str++;
		if (strlen(str) >= left)
			return -1;

		ret = snprintf(slot, left, "%s\t", str);
		boot_snapshot_index += ret;
	} else {
		allocate_snapshot = true;
		/* We also need the main ring buffer expanded */
		trace_set_ring_buffer_expanded(NULL);
	}
	return 1;
}
__setup("alloc_snapshot", boot_alloc_snapshot);


static int __init boot_snapshot(char *str)
{
	snapshot_at_boot = true;
	boot_alloc_snapshot(str);
	return 1;
}
__setup("ftrace_boot_snapshot", boot_snapshot);
static void tracing_snapshot_instance_cond(struct trace_array *tr,
					   void *cond_data)
{
	unsigned long flags;

	if (in_nmi()) {
		trace_array_puts(tr, "*** SNAPSHOT CALLED FROM NMI CONTEXT ***\n");
		trace_array_puts(tr, "*** snapshot is being ignored        ***\n");
		return;
	}

	if (!tr->allocated_snapshot) {
		trace_array_puts(tr, "*** SNAPSHOT NOT ALLOCATED ***\n");
		trace_array_puts(tr, "*** stopping trace here!   ***\n");
		tracer_tracing_off(tr);
		return;
	}

	if (tr->mapped) {
		trace_array_puts(tr, "*** BUFFER MEMORY MAPPED ***\n");
		trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n");
		return;
	}

	/* Note, snapshot can not be used when the tracer uses it */
	if (tracer_uses_snapshot(tr->current_trace)) {
		trace_array_puts(tr, "*** LATENCY TRACER ACTIVE ***\n");
		trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n");
		return;
	}

	local_irq_save(flags);
	update_max_tr(tr, current, smp_processor_id(), cond_data);
	local_irq_restore(flags);
}

void tracing_snapshot_instance(struct trace_array *tr)
{
	tracing_snapshot_instance_cond(tr, NULL);
}

/**
 * tracing_snapshot_cond - conditionally take a snapshot of the current buffer.
 * @tr:		The tracing instance to snapshot
 * @cond_data:	The data to be tested conditionally, and possibly saved
 *
 * This is the same as tracing_snapshot() except that the snapshot is
 * conditional - the snapshot will only happen if the
 * cond_snapshot.update() implementation receiving the cond_data
 * returns true, which means that the trace array's cond_snapshot
 * update() operation used the cond_data to determine whether the
 * snapshot should be taken, and if it was, presumably saved it along
 * with the snapshot.
 */
void tracing_snapshot_cond(struct trace_array *tr, void *cond_data)
{
	tracing_snapshot_instance_cond(tr, cond_data);
}
EXPORT_SYMBOL_GPL(tracing_snapshot_cond);

/**
 * tracing_cond_snapshot_data - get the user data associated with a snapshot
 * @tr:		The tracing instance
 *
 * When the user enables a conditional snapshot using
 * tracing_snapshot_cond_enable(), the user-defined cond_data is saved
 * with the snapshot.  This accessor is used to retrieve it.
 *
 * Should not be called from cond_snapshot.update(), since it takes
 * the tr->max_lock lock, which the code calling
 * cond_snapshot.update() has already done.
 *
 * Returns the cond_data associated with the trace array's snapshot.
 */
void *tracing_cond_snapshot_data(struct trace_array *tr)
{
	void *cond_data = NULL;

	local_irq_disable();
	arch_spin_lock(&tr->max_lock);

	if (tr->cond_snapshot)
		cond_data = tr->cond_snapshot->cond_data;

	arch_spin_unlock(&tr->max_lock);
	local_irq_enable();

	return cond_data;
}
EXPORT_SYMBOL_GPL(tracing_cond_snapshot_data);

/* resize @tr's buffer to the size of @size_tr's entries */
int resize_buffer_duplicate_size(struct array_buffer *trace_buf,
				 struct array_buffer *size_buf, int cpu_id)
{
	int cpu, ret = 0;

	if (cpu_id == RING_BUFFER_ALL_CPUS) {
		for_each_tracing_cpu(cpu) {
			ret = ring_buffer_resize(trace_buf->buffer,
				 per_cpu_ptr(size_buf->data, cpu)->entries, cpu);
			if (ret