[lttng-modules.git] / lttng-context-callstack-legacy-impl.h

/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
 *
 * lttng-context-callstack-legacy-impl.h
 *
 * LTTng callstack event context, legacy implementation. Targets
 * kernels and architectures not yet using the stacktrace common
 * infrastructure introduced in the upstream Linux kernel by commit
 * 214d8ca6ee "stacktrace: Provide common infrastructure" (merged in
 * Linux 5.2, then gradually introduced within architectures).
 *
 * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com>
 */

#define MAX_ENTRIES 128

enum lttng_cs_ctx_modes {
	CALLSTACK_KERNEL = 0,
	CALLSTACK_USER = 1,
	NR_CALLSTACK_MODES,
};

struct lttng_cs_dispatch {
	struct stack_trace stack_trace;
	unsigned long entries[MAX_ENTRIES];
};

struct lttng_cs {
	struct lttng_cs_dispatch dispatch[RING_BUFFER_MAX_NESTING];
};

struct field_data {
	struct lttng_cs __percpu *cs_percpu;
	enum lttng_cs_ctx_modes mode;
};

struct lttng_cs_type {
	const char *name;
	const char *save_func_name;
	void (*save_func)(struct stack_trace *trace);
};

static struct lttng_cs_type cs_types[] = {
	{
		.name		= "callstack_kernel",
		.save_func_name	= "save_stack_trace",
		.save_func	= NULL,
	},
	{
		.name		= "callstack_user",
		.save_func_name	= "save_stack_trace_user",
		.save_func	= NULL,
	},
};

static
const char *lttng_cs_ctx_mode_name(enum lttng_cs_ctx_modes mode)
{
	return cs_types[mode].name;
}

static
int init_type(enum lttng_cs_ctx_modes mode)
{
	unsigned long func;

	if (cs_types[mode].save_func)
		return 0;
	func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name);
	if (!func) {
		printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
				cs_types[mode].save_func_name);
		return -EINVAL;
	}
	cs_types[mode].save_func = (void *) func;
	return 0;
}

static
void lttng_cs_set_init(struct lttng_cs __percpu *cs_set)
{
	int cpu, i;

	for_each_possible_cpu(cpu) {
		struct lttng_cs *cs;

		cs = per_cpu_ptr(cs_set, cpu);
		for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
			struct lttng_cs_dispatch *dispatch;

			dispatch = &cs->dispatch[i];
			dispatch->stack_trace.entries = dispatch->entries;
			dispatch->stack_trace.max_entries = MAX_ENTRIES;
		}
	}
}

/* Keep track of nesting inside userspace callstack context code */
DEFINE_PER_CPU(int, callstack_user_nesting);

static
struct stack_trace *stack_trace_context(struct lttng_ctx_field *field,
					struct lib_ring_buffer_ctx *ctx)
{
	int buffer_nesting, cs_user_nesting;
	struct lttng_cs *cs;
	struct field_data *fdata = field->priv;

	/*
	 * Do not gather the userspace callstack context when the event was
	 * triggered by the userspace callstack context saving mechanism.
	 */
	cs_user_nesting = per_cpu(callstack_user_nesting, ctx->cpu);

	if (fdata->mode == CALLSTACK_USER && cs_user_nesting >= 1)
		return NULL;

	/*
	 * get_cpu() is not required, preemption is already
	 * disabled while event is written.
	 *
	 * max nesting is checked in lib_ring_buffer_get_cpu().
	 * Check it again as a safety net.
	 */
	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
	buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
	if (buffer_nesting >= RING_BUFFER_MAX_NESTING)
		return NULL;

	return &cs->dispatch[buffer_nesting].stack_trace;
}

/*
 * In order to reserve the correct size, the callstack is computed. The
 * resulting callstack is saved to be accessed in the record step.
 */
static
size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field,
				struct lib_ring_buffer_ctx *ctx,
				struct lttng_channel *chan)
{
	struct stack_trace *trace;
	struct field_data *fdata = field->priv;
	size_t orig_offset = offset;

	/* do not write data if no space is available */
	trace = stack_trace_context(field, ctx);
	if (unlikely(!trace)) {
		offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
		offset += sizeof(unsigned int);
		offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
		return offset - orig_offset;
	}

	/* reset stack trace, no need to clear memory */
	trace->nr_entries = 0;

	if (fdata->mode == CALLSTACK_USER)
		++per_cpu(callstack_user_nesting, ctx->cpu);

	/* do the real work and reserve space */
	cs_types[fdata->mode].save_func(trace);

	if (fdata->mode == CALLSTACK_USER)
		per_cpu(callstack_user_nesting, ctx->cpu)--;

	/*
	 * Remove final ULONG_MAX delimiter. If we cannot find it, add
	 * our own marker to show that the stack is incomplete. This is
	 * more compact for a trace.
	 */
	if (trace->nr_entries > 0
			&& trace->entries[trace->nr_entries - 1] == ULONG_MAX) {
		trace->nr_entries--;
	}
	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	offset += sizeof(unsigned int);
	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	offset += sizeof(unsigned long) * trace->nr_entries;
	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	if (trace->nr_entries == trace->max_entries)
		offset += sizeof(unsigned long);
	return offset - orig_offset;
}

static
void lttng_callstack_record(struct lttng_ctx_field *field,
			struct lib_ring_buffer_ctx *ctx,
			struct lttng_channel *chan)
{
	struct stack_trace *trace = stack_trace_context(field, ctx);
	unsigned int nr_seq_entries;

	if (unlikely(!trace)) {
		nr_seq_entries = 0;
		lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
		chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
		lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
		return;
	}
	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
	nr_seq_entries = trace->nr_entries;
	if (trace->nr_entries == trace->max_entries)
		nr_seq_entries++;
	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
	chan->ops->event_write(ctx, trace->entries,
			sizeof(unsigned long) * trace->nr_entries);
	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	if (trace->nr_entries == trace->max_entries) {
		unsigned long delim = ULONG_MAX;

		chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
	}
}
Commit	Line	Data
b6ee48d2 MD	1	/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
	2	*
	3	* lttng-context-callstack-legacy-impl.h
	4	*
	5	* LTTng callstack event context, legacy implementation. Targets
	6	* kernels and architectures not yet using the stacktrace common
	7	* infrastructure introduced in the upstream Linux kernel by commit
	8	* 214d8ca6ee "stacktrace: Provide common infrastructure" (merged in
	9	* Linux 5.2, then gradually introduced within architectures).
	10	*
	11	* Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	12	* Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com>
	13	*/
	14
	15	#define MAX_ENTRIES 128
	16
	17	enum lttng_cs_ctx_modes {
	18	CALLSTACK_KERNEL = 0,
	19	CALLSTACK_USER = 1,
	20	NR_CALLSTACK_MODES,
	21	};
	22
	23	struct lttng_cs_dispatch {
	24	struct stack_trace stack_trace;
	25	unsigned long entries[MAX_ENTRIES];
	26	};
	27
	28	struct lttng_cs {
	29	struct lttng_cs_dispatch dispatch[RING_BUFFER_MAX_NESTING];
	30	};
	31
	32	struct field_data {
	33	struct lttng_cs __percpu *cs_percpu;
	34	enum lttng_cs_ctx_modes mode;
	35	};
	36
	37	struct lttng_cs_type {
	38	const char *name;
	39	const char *save_func_name;
	40	void (save_func)(struct stack_trace trace);
	41	};
	42
	43	static struct lttng_cs_type cs_types[] = {
	44	{
	45	.name = "callstack_kernel",
	46	.save_func_name = "save_stack_trace",
	47	.save_func = NULL,
	48	},
	49	{
	50	.name = "callstack_user",
	51	.save_func_name = "save_stack_trace_user",
	52	.save_func = NULL,
	53	},
	54	};
	55
b5a89a3f MD	56	static
	57	const char *lttng_cs_ctx_mode_name(enum lttng_cs_ctx_modes mode)
	58	{
	59	return cs_types[mode].name;
	60	}
	61
b6ee48d2 MD	62	static
	63	int init_type(enum lttng_cs_ctx_modes mode)
	64	{
	65	unsigned long func;
	66
	67	if (cs_types[mode].save_func)
	68	return 0;
	69	func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name);
	70	if (!func) {
	71	printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
	72	cs_types[mode].save_func_name);
	73	return -EINVAL;
	74	}
	75	cs_types[mode].save_func = (void *) func;
	76	return 0;
	77	}
	78
b5a89a3f MD	79	static
	80	void lttng_cs_set_init(struct lttng_cs __percpu *cs_set)
	81	{
	82	int cpu, i;
	83
	84	for_each_possible_cpu(cpu) {
	85	struct lttng_cs *cs;
	86
	87	cs = per_cpu_ptr(cs_set, cpu);
	88	for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
	89	struct lttng_cs_dispatch *dispatch;
	90
	91	dispatch = &cs->dispatch[i];
	92	dispatch->stack_trace.entries = dispatch->entries;
	93	dispatch->stack_trace.max_entries = MAX_ENTRIES;
	94	}
	95	}
	96	}
	97
b6ee48d2 MD	98	/* Keep track of nesting inside userspace callstack context code */
	99	DEFINE_PER_CPU(int, callstack_user_nesting);
	100
	101	static
	102	struct stack_trace stack_trace_context(struct lttng_ctx_field field,
	103	struct lib_ring_buffer_ctx *ctx)
	104	{
	105	int buffer_nesting, cs_user_nesting;
	106	struct lttng_cs *cs;
	107	struct field_data *fdata = field->priv;
	108
	109	/*
	110	* Do not gather the userspace callstack context when the event was
	111	* triggered by the userspace callstack context saving mechanism.
	112	*/
	113	cs_user_nesting = per_cpu(callstack_user_nesting, ctx->cpu);
	114
	115	if (fdata->mode == CALLSTACK_USER && cs_user_nesting >= 1)
	116	return NULL;
	117
	118	/*
	119	* get_cpu() is not required, preemption is already
	120	* disabled while event is written.
	121	*
	122	* max nesting is checked in lib_ring_buffer_get_cpu().
	123	* Check it again as a safety net.
	124	*/
	125	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
	126	buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
	127	if (buffer_nesting >= RING_BUFFER_MAX_NESTING)
	128	return NULL;
	129
	130	return &cs->dispatch[buffer_nesting].stack_trace;
	131	}
	132
	133	/*
	134	* In order to reserve the correct size, the callstack is computed. The
	135	* resulting callstack is saved to be accessed in the record step.
	136	*/
	137	static
	138	size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field,
	139	struct lib_ring_buffer_ctx *ctx,
	140	struct lttng_channel *chan)
	141	{
	142	struct stack_trace *trace;
	143	struct field_data *fdata = field->priv;
	144	size_t orig_offset = offset;
	145
	146	/* do not write data if no space is available */
	147	trace = stack_trace_context(field, ctx);
	148	if (unlikely(!trace)) {
	149	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	150	offset += sizeof(unsigned int);
	151	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	152	return offset - orig_offset;
	153	}
	154
	155	/* reset stack trace, no need to clear memory */
	156	trace->nr_entries = 0;
	157
	158	if (fdata->mode == CALLSTACK_USER)
	159	++per_cpu(callstack_user_nesting, ctx->cpu);
	160
	161	/* do the real work and reserve space */
162	cs_types[fdata->mode].save_func(trace);
163
164	if (fdata->mode == CALLSTACK_USER)
165	per_cpu(callstack_user_nesting, ctx->cpu)--;
166
167	/*
168	* Remove final ULONG_MAX delimiter. If we cannot find it, add
169	* our own marker to show that the stack is incomplete. This is
170	* more compact for a trace.
171	*/
172	if (trace->nr_entries > 0
173	&& trace->entries[trace->nr_entries - 1] == ULONG_MAX) {
174	trace->nr_entries--;
175	}
176	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
177	offset += sizeof(unsigned int);
178	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
179	offset += sizeof(unsigned long) * trace->nr_entries;
180	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
181	if (trace->nr_entries == trace->max_entries)
182	offset += sizeof(unsigned long);
183	return offset - orig_offset;
184	}
185
186	static
187	void lttng_callstack_record(struct lttng_ctx_field *field,
188	struct lib_ring_buffer_ctx *ctx,
189	struct lttng_channel *chan)
190	{
191	struct stack_trace *trace = stack_trace_context(field, ctx);
192	unsigned int nr_seq_entries;
193
194	if (unlikely(!trace)) {
195	nr_seq_entries = 0;
196	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
197	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
198	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
199	return;
200	}
201	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
202	nr_seq_entries = trace->nr_entries;
203	if (trace->nr_entries == trace->max_entries)
204	nr_seq_entries++;
205	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
206	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
207	chan->ops->event_write(ctx, trace->entries,
208	sizeof(unsigned long) * trace->nr_entries);
209	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
210	if (trace->nr_entries == trace->max_entries) {
211	unsigned long delim = ULONG_MAX;
212
213	chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
214	}
215	}