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

/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
 *
 * 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 *length_name;
	const char *save_func_name;
	void (*save_func)(struct stack_trace *trace);
};

static struct lttng_cs_type cs_types[] = {
	{
		.name		= "callstack_kernel",
		.length_name	= "_callstack_kernel_length",
		.save_func_name	= "save_stack_trace",
		.save_func	= NULL,
	},
	{
		.name		= "callstack_user",
		.length_name	= "_callstack_user_length",
		.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
const char *lttng_cs_ctx_mode_length_name(enum lttng_cs_ctx_modes mode)
{
	return cs_types[mode].length_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;
}

static
size_t lttng_callstack_length_get_size(size_t offset, struct lttng_ctx_field *field,
				struct lib_ring_buffer_ctx *ctx,
				struct lttng_channel *chan)
{
	size_t orig_offset = offset;

	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	offset += sizeof(unsigned int);
	return offset - orig_offset;
}

/*
 * 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_sequence_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 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 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_length_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;

	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
	if (unlikely(!trace)) {
		nr_seq_entries = 0;
	} else {
		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));
}
static
void lttng_callstack_sequence_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;

	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
	if (unlikely(!trace)) {
		return;
	}
	nr_seq_entries = trace->nr_entries;
	if (trace->nr_entries == trace->max_entries)
		nr_seq_entries++;
	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
b7cdc182	1	/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
b6ee48d2 MD	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;
ceabb767	39	const char *length_name;
b6ee48d2 MD	40	const char *save_func_name;
	41	void (save_func)(struct stack_trace trace);
	42	};
	43
	44	static struct lttng_cs_type cs_types[] = {
	45	{
	46	.name = "callstack_kernel",
ceabb767	47	.length_name = "_callstack_kernel_length",
b6ee48d2 MD	48	.save_func_name = "save_stack_trace",
	49	.save_func = NULL,
	50	},
	51	{
	52	.name = "callstack_user",
ceabb767	53	.length_name = "_callstack_user_length",
b6ee48d2 MD	54	.save_func_name = "save_stack_trace_user",
	55	.save_func = NULL,
	56	},
	57	};
	58
b5a89a3f MD	59	static
	60	const char *lttng_cs_ctx_mode_name(enum lttng_cs_ctx_modes mode)
	61	{
	62	return cs_types[mode].name;
	63	}
	64
ceabb767 MD	65	static
	66	const char *lttng_cs_ctx_mode_length_name(enum lttng_cs_ctx_modes mode)
	67	{
	68	return cs_types[mode].length_name;
	69	}
	70
b6ee48d2 MD	71	static
	72	int init_type(enum lttng_cs_ctx_modes mode)
	73	{
	74	unsigned long func;
	75
	76	if (cs_types[mode].save_func)
	77	return 0;
	78	func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name);
	79	if (!func) {
	80	printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
	81	cs_types[mode].save_func_name);
	82	return -EINVAL;
	83	}
	84	cs_types[mode].save_func = (void *) func;
	85	return 0;
	86	}
	87
b5a89a3f MD	88	static
	89	void lttng_cs_set_init(struct lttng_cs __percpu *cs_set)
	90	{
	91	int cpu, i;
	92
	93	for_each_possible_cpu(cpu) {
	94	struct lttng_cs *cs;
	95
	96	cs = per_cpu_ptr(cs_set, cpu);
	97	for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
	98	struct lttng_cs_dispatch *dispatch;
	99
	100	dispatch = &cs->dispatch[i];
	101	dispatch->stack_trace.entries = dispatch->entries;
	102	dispatch->stack_trace.max_entries = MAX_ENTRIES;
	103	}
	104	}
	105	}
	106
b6ee48d2 MD	107	/* Keep track of nesting inside userspace callstack context code */
	108	DEFINE_PER_CPU(int, callstack_user_nesting);
	109
	110	static
	111	struct stack_trace stack_trace_context(struct lttng_ctx_field field,
	112	struct lib_ring_buffer_ctx *ctx)
	113	{
	114	int buffer_nesting, cs_user_nesting;
	115	struct lttng_cs *cs;
	116	struct field_data *fdata = field->priv;
	117
	118	/*
	119	* Do not gather the userspace callstack context when the event was
	120	* triggered by the userspace callstack context saving mechanism.
	121	*/
	122	cs_user_nesting = per_cpu(callstack_user_nesting, ctx->cpu);
	123
	124	if (fdata->mode == CALLSTACK_USER && cs_user_nesting >= 1)
	125	return NULL;
	126
	127	/*
	128	* get_cpu() is not required, preemption is already
	129	* disabled while event is written.
	130	*
	131	* max nesting is checked in lib_ring_buffer_get_cpu().
	132	* Check it again as a safety net.
	133	*/
	134	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
	135	buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
	136	if (buffer_nesting >= RING_BUFFER_MAX_NESTING)
	137	return NULL;
	138
	139	return &cs->dispatch[buffer_nesting].stack_trace;
	140	}
	141
ceabb767 MD	142	static
	143	size_t lttng_callstack_length_get_size(size_t offset, struct lttng_ctx_field *field,
	144	struct lib_ring_buffer_ctx *ctx,
	145	struct lttng_channel *chan)
	146	{
	147	size_t orig_offset = offset;
	148
	149	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	150	offset += sizeof(unsigned int);
	151	return offset - orig_offset;
	152	}
	153
b6ee48d2 MD	154	/*
	155	* In order to reserve the correct size, the callstack is computed. The
	156	* resulting callstack is saved to be accessed in the record step.
	157	*/
	158	static
ceabb767 MD	159	size_t lttng_callstack_sequence_get_size(size_t offset, struct lttng_ctx_field *field,
	160	struct lib_ring_buffer_ctx *ctx,
	161	struct lttng_channel *chan)
b6ee48d2 MD	162	{
	163	struct stack_trace *trace;
	164	struct field_data *fdata = field->priv;
	165	size_t orig_offset = offset;
	166
	167	/* do not write data if no space is available */
	168	trace = stack_trace_context(field, ctx);
	169	if (unlikely(!trace)) {
b6ee48d2 MD	170	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	171	return offset - orig_offset;
	172	}
	173
	174	/* reset stack trace, no need to clear memory */
	175	trace->nr_entries = 0;
	176
	177	if (fdata->mode == CALLSTACK_USER)
	178	++per_cpu(callstack_user_nesting, ctx->cpu);
	179
	180	/* do the real work and reserve space */
	181	cs_types[fdata->mode].save_func(trace);
	182
	183	if (fdata->mode == CALLSTACK_USER)
	184	per_cpu(callstack_user_nesting, ctx->cpu)--;
	185
	186	/*
	187	* Remove final ULONG_MAX delimiter. If we cannot find it, add
	188	* our own marker to show that the stack is incomplete. This is
	189	* more compact for a trace.
	190	*/
	191	if (trace->nr_entries > 0
	192	&& trace->entries[trace->nr_entries - 1] == ULONG_MAX) {
	193	trace->nr_entries--;
	194	}
b6ee48d2 MD	195	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	196	offset += sizeof(unsigned long) * trace->nr_entries;
	197	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	198	if (trace->nr_entries == trace->max_entries)
	199	offset += sizeof(unsigned long);
	200	return offset - orig_offset;
	201	}
	202
	203	static
ceabb767	204	void lttng_callstack_length_record(struct lttng_ctx_field *field,
b6ee48d2 MD	205	struct lib_ring_buffer_ctx *ctx,
	206	struct lttng_channel *chan)
	207	{
	208	struct stack_trace *trace = stack_trace_context(field, ctx);
	209	unsigned int nr_seq_entries;
	210
ceabb767	211	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
b6ee48d2 MD	212	if (unlikely(!trace)) {
b6ee48d2 MD	213	nr_seq_entries = 0;
ceabb767 MD	214	} else {
	215	nr_seq_entries = trace->nr_entries;
	216	if (trace->nr_entries == trace->max_entries)
	217	nr_seq_entries++;
	218	}
	219	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
	220	}
	221	static
	222	void lttng_callstack_sequence_record(struct lttng_ctx_field *field,
	223	struct lib_ring_buffer_ctx *ctx,
	224	struct lttng_channel *chan)
	225	{
	226	struct stack_trace *trace = stack_trace_context(field, ctx);
	227	unsigned int nr_seq_entries;
	228
	229	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
	230	if (unlikely(!trace)) {
b6ee48d2 MD	231	return;
b6ee48d2 MD	232	}
b6ee48d2 MD	233	nr_seq_entries = trace->nr_entries;
	234	if (trace->nr_entries == trace->max_entries)
	235	nr_seq_entries++;
b6ee48d2 MD	236	chan->ops->event_write(ctx, trace->entries,
	237	sizeof(unsigned long) * trace->nr_entries);
	238	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	239	if (trace->nr_entries == trace->max_entries) {
	240	unsigned long delim = ULONG_MAX;
	241
	242	chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
	243	}
	244	}