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

/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
 *
 * lttng-context-callstack-stackwalk-impl.h
 *
 * LTTng callstack event context, stackwalk implementation. Targets
 * kernels and architectures 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) 2014-2019 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_stack_trace {
	unsigned long entries[MAX_ENTRIES];
	unsigned int nr_entries;
};

struct lttng_cs {
	struct lttng_stack_trace stack_trace[RING_BUFFER_MAX_NESTING];
};

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

static
unsigned int (*save_func_kernel)(unsigned long *store, unsigned int size,
				unsigned int skipnr);
static
unsigned int (*save_func_user)(unsigned long *store, unsigned int size);

static
const char *lttng_cs_ctx_mode_name(enum lttng_cs_ctx_modes mode)
{
	switch (mode) {
	case CALLSTACK_KERNEL:
		return "callstack_kernel";
	case CALLSTACK_USER:
		return "callstack_user";
	default:
		return NULL;
	}
}

static
const char *lttng_cs_ctx_mode_length_name(enum lttng_cs_ctx_modes mode)
{
	switch (mode) {
	case CALLSTACK_KERNEL:
		return "_callstack_kernel_length";
	case CALLSTACK_USER:
		return "_callstack_user_length";
	default:
		return NULL;
	}
}

static
int init_type_callstack_kernel(void)
{
	unsigned long func;
	const char *func_name = "stack_trace_save";

	if (save_func_kernel)
		return 0;
	func = kallsyms_lookup_funcptr(func_name);
	if (!func) {
		printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
				func_name);
		return -EINVAL;
	}
	save_func_kernel = (void *) func;
	return 0;
}

static
int init_type_callstack_user(void)
{
	unsigned long func;
	const char *func_name = "stack_trace_save_user";

	if (save_func_user)
		return 0;
	func = kallsyms_lookup_funcptr(func_name);
	if (!func) {
		printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
				func_name);
		return -EINVAL;
	}
	save_func_user = (void *) func;
	return 0;
}

static
int init_type(enum lttng_cs_ctx_modes mode)
{
	switch (mode) {
	case CALLSTACK_KERNEL:
		return init_type_callstack_kernel();
	case CALLSTACK_USER:
		return init_type_callstack_user();
	default:
		return -EINVAL;
	}
}

static
void lttng_cs_set_init(struct lttng_cs __percpu *cs_set)
{
}

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

static
struct lttng_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->stack_trace[buffer_nesting];
}

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 lttng_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;

	switch (fdata->mode) {
	case CALLSTACK_KERNEL:
		/* do the real work and reserve space */
		trace->nr_entries = save_func_kernel(trace->entries,
						MAX_ENTRIES, 0);
		break;
	case CALLSTACK_USER:
		++per_cpu(callstack_user_nesting, ctx->cpu);
		/* do the real work and reserve space */
		trace->nr_entries = save_func_user(trace->entries,
						MAX_ENTRIES);
		per_cpu(callstack_user_nesting, ctx->cpu)--;
		break;
	default:
		WARN_ON_ONCE(1);
	}

	/*
	 * If the array is filled, add our own marker to show that the
	 * stack is incomplete.
	 */
	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 == 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 lttng_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 == 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 lttng_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 == 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 == 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)
b29c6286 MD	2	*
	3	* lttng-context-callstack-stackwalk-impl.h
	4	*
	5	* LTTng callstack event context, stackwalk implementation. Targets
	6	* kernels and architectures using the stacktrace common infrastructure
	7	* introduced in the upstream Linux kernel by commit 214d8ca6ee
	8	* "stacktrace: Provide common infrastructure" (merged in Linux 5.2,
	9	* then gradually introduced within architectures).
	10	*
	11	* Copyright (C) 2014-2019 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_stack_trace {
	24	unsigned long entries[MAX_ENTRIES];
	25	unsigned int nr_entries;
	26	};
	27
	28	struct lttng_cs {
	29	struct lttng_stack_trace stack_trace[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	static
	38	unsigned int (save_func_kernel)(unsigned long store, unsigned int size,
	39	unsigned int skipnr);
	40	static
	41	unsigned int (save_func_user)(unsigned long store, unsigned int size);
	42
	43	static
	44	const char *lttng_cs_ctx_mode_name(enum lttng_cs_ctx_modes mode)
	45	{
	46	switch (mode) {
	47	case CALLSTACK_KERNEL:
	48	return "callstack_kernel";
	49	case CALLSTACK_USER:
	50	return "callstack_user";
	51	default:
	52	return NULL;
	53	}
	54	}
	55
ceabb767 MD	56	static
	57	const char *lttng_cs_ctx_mode_length_name(enum lttng_cs_ctx_modes mode)
	58	{
	59	switch (mode) {
	60	case CALLSTACK_KERNEL:
	61	return "_callstack_kernel_length";
	62	case CALLSTACK_USER:
	63	return "_callstack_user_length";
	64	default:
	65	return NULL;
	66	}
	67	}
	68
b29c6286 MD	69	static
	70	int init_type_callstack_kernel(void)
	71	{
	72	unsigned long func;
	73	const char *func_name = "stack_trace_save";
	74
	75	if (save_func_kernel)
	76	return 0;
	77	func = kallsyms_lookup_funcptr(func_name);
	78	if (!func) {
	79	printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
	80	func_name);
	81	return -EINVAL;
	82	}
	83	save_func_kernel = (void *) func;
	84	return 0;
	85	}
	86
	87	static
	88	int init_type_callstack_user(void)
	89	{
	90	unsigned long func;
	91	const char *func_name = "stack_trace_save_user";
	92
	93	if (save_func_user)
	94	return 0;
	95	func = kallsyms_lookup_funcptr(func_name);
	96	if (!func) {
	97	printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
	98	func_name);
	99	return -EINVAL;
	100	}
	101	save_func_user = (void *) func;
	102	return 0;
	103	}
	104
	105	static
	106	int init_type(enum lttng_cs_ctx_modes mode)
	107	{
	108	switch (mode) {
	109	case CALLSTACK_KERNEL:
	110	return init_type_callstack_kernel();
	111	case CALLSTACK_USER:
	112	return init_type_callstack_user();
	113	default:
	114	return -EINVAL;
	115	}
	116	}
	117
	118	static
	119	void lttng_cs_set_init(struct lttng_cs __percpu *cs_set)
	120	{
	121	}
	122
	123	/* Keep track of nesting inside userspace callstack context code */
	124	DEFINE_PER_CPU(int, callstack_user_nesting);
	125
	126	static
	127	struct lttng_stack_trace stack_trace_context(struct lttng_ctx_field field,
	128	struct lib_ring_buffer_ctx *ctx)
	129	{
	130	int buffer_nesting, cs_user_nesting;
	131	struct lttng_cs *cs;
	132	struct field_data *fdata = field->priv;
133
134	/*
135	* Do not gather the userspace callstack context when the event was
136	* triggered by the userspace callstack context saving mechanism.
137	*/
138	cs_user_nesting = per_cpu(callstack_user_nesting, ctx->cpu);
139
140	if (fdata->mode == CALLSTACK_USER && cs_user_nesting >= 1)
141	return NULL;
142
143	/*
144	* get_cpu() is not required, preemption is already
145	* disabled while event is written.
146	*
147	* max nesting is checked in lib_ring_buffer_get_cpu().
148	* Check it again as a safety net.
149	*/
150	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
151	buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
152	if (buffer_nesting >= RING_BUFFER_MAX_NESTING)
153	return NULL;
154
155	return &cs->stack_trace[buffer_nesting];
156	}
157
ceabb767 MD	158	static
	159	size_t lttng_callstack_length_get_size(size_t offset, struct lttng_ctx_field *field,
	160	struct lib_ring_buffer_ctx *ctx,
	161	struct lttng_channel *chan)
	162	{
	163	size_t orig_offset = offset;
	164
	165	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
	166	offset += sizeof(unsigned int);
	167	return offset - orig_offset;
	168	}
	169
b29c6286 MD	170	/*
	171	* In order to reserve the correct size, the callstack is computed. The
	172	* resulting callstack is saved to be accessed in the record step.
	173	*/
	174	static
ceabb767 MD	175	size_t lttng_callstack_sequence_get_size(size_t offset, struct lttng_ctx_field *field,
	176	struct lib_ring_buffer_ctx *ctx,
	177	struct lttng_channel *chan)
b29c6286 MD	178	{
	179	struct lttng_stack_trace *trace;
	180	struct field_data *fdata = field->priv;
	181	size_t orig_offset = offset;
	182
	183	/* do not write data if no space is available */
	184	trace = stack_trace_context(field, ctx);
	185	if (unlikely(!trace)) {
b29c6286 MD	186	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	187	return offset - orig_offset;
	188	}
	189
	190	/* reset stack trace, no need to clear memory */
	191	trace->nr_entries = 0;
	192
	193	switch (fdata->mode) {
	194	case CALLSTACK_KERNEL:
	195	/* do the real work and reserve space */
	196	trace->nr_entries = save_func_kernel(trace->entries,
	197	MAX_ENTRIES, 0);
	198	break;
	199	case CALLSTACK_USER:
	200	++per_cpu(callstack_user_nesting, ctx->cpu);
	201	/* do the real work and reserve space */
	202	trace->nr_entries = save_func_user(trace->entries,
	203	MAX_ENTRIES);
	204	per_cpu(callstack_user_nesting, ctx->cpu)--;
	205	break;
	206	default:
	207	WARN_ON_ONCE(1);
	208	}
	209
	210	/*
	211	* If the array is filled, add our own marker to show that the
	212	* stack is incomplete.
	213	*/
b29c6286 MD	214	offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
	215	offset += sizeof(unsigned long) * trace->nr_entries;
	216	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	217	if (trace->nr_entries == MAX_ENTRIES)
	218	offset += sizeof(unsigned long);
	219	return offset - orig_offset;
	220	}
	221
	222	static
ceabb767	223	void lttng_callstack_length_record(struct lttng_ctx_field *field,
b29c6286 MD	224	struct lib_ring_buffer_ctx *ctx,
	225	struct lttng_channel *chan)
	226	{
	227	struct lttng_stack_trace *trace = stack_trace_context(field, ctx);
	228	unsigned int nr_seq_entries;
	229
ceabb767	230	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
b29c6286 MD	231	if (unlikely(!trace)) {
b29c6286 MD	232	nr_seq_entries = 0;
ceabb767 MD	233	} else {
	234	nr_seq_entries = trace->nr_entries;
	235	if (trace->nr_entries == MAX_ENTRIES)
	236	nr_seq_entries++;
	237	}
	238	chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
	239	}
	240
	241	static
	242	void lttng_callstack_sequence_record(struct lttng_ctx_field *field,
	243	struct lib_ring_buffer_ctx *ctx,
	244	struct lttng_channel *chan)
	245	{
	246	struct lttng_stack_trace *trace = stack_trace_context(field, ctx);
	247	unsigned int nr_seq_entries;
	248
	249	lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
	250	if (unlikely(!trace)) {
b29c6286 MD	251	return;
b29c6286 MD	252	}
b29c6286 MD	253	nr_seq_entries = trace->nr_entries;
	254	if (trace->nr_entries == MAX_ENTRIES)
	255	nr_seq_entries++;
b29c6286 MD	256	chan->ops->event_write(ctx, trace->entries,
	257	sizeof(unsigned long) * trace->nr_entries);
	258	/* Add our own ULONG_MAX delimiter to show incomplete stack. */
	259	if (trace->nr_entries == MAX_ENTRIES) {
	260	unsigned long delim = ULONG_MAX;
	261
	262	chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
	263	}
	264	}