| 1 | /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) |
| 2 | * |
| 3 | * lttng-context-prio.c |
| 4 | * |
| 5 | * LTTng priority context. |
| 6 | * |
| 7 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 8 | */ |
| 9 | |
| 10 | #include <linux/module.h> |
| 11 | #include <linux/slab.h> |
| 12 | #include <linux/sched.h> |
| 13 | #include <lttng/events.h> |
| 14 | #include <lttng/events-internal.h> |
| 15 | #include <ringbuffer/frontend_types.h> |
| 16 | #include <wrapper/vmalloc.h> |
| 17 | #include <wrapper/kallsyms.h> |
| 18 | #include <lttng/tracer.h> |
| 19 | |
| 20 | static |
| 21 | int (*wrapper_task_prio_sym)(struct task_struct *t); |
| 22 | |
| 23 | int wrapper_task_prio_init(void) |
| 24 | { |
| 25 | wrapper_task_prio_sym = (void *) kallsyms_lookup_funcptr("task_prio"); |
| 26 | if (!wrapper_task_prio_sym) { |
| 27 | printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n"); |
| 28 | return -EINVAL; |
| 29 | } |
| 30 | return 0; |
| 31 | } |
| 32 | |
| 33 | /* |
| 34 | * Canary function to check for 'task_prio()' at compile time. |
| 35 | * |
| 36 | * From 'include/linux/sched.h': |
| 37 | * |
| 38 | * extern int task_prio(const struct task_struct *p); |
| 39 | */ |
| 40 | __attribute__((unused)) static |
| 41 | int __canary__task_prio(const struct task_struct *p) |
| 42 | { |
| 43 | return task_prio(p); |
| 44 | } |
| 45 | |
| 46 | static |
| 47 | size_t prio_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset) |
| 48 | { |
| 49 | size_t size = 0; |
| 50 | |
| 51 | size += lib_ring_buffer_align(offset, lttng_alignof(int)); |
| 52 | size += sizeof(int); |
| 53 | return size; |
| 54 | } |
| 55 | |
| 56 | static |
| 57 | void prio_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, |
| 58 | struct lttng_kernel_ring_buffer_ctx *ctx, |
| 59 | struct lttng_channel *chan) |
| 60 | { |
| 61 | int prio; |
| 62 | |
| 63 | prio = wrapper_task_prio_sym(current); |
| 64 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(prio)); |
| 65 | chan->ops->event_write(ctx, &prio, sizeof(prio)); |
| 66 | } |
| 67 | |
| 68 | static |
| 69 | void prio_get_value(void *priv, |
| 70 | struct lttng_kernel_probe_ctx *lttng_probe_ctx, |
| 71 | struct lttng_ctx_value *value) |
| 72 | { |
| 73 | value->u.s64 = wrapper_task_prio_sym(current); |
| 74 | } |
| 75 | |
| 76 | static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field( |
| 77 | lttng_kernel_static_event_field("prio", |
| 78 | lttng_kernel_static_type_integer_from_type(int, __BYTE_ORDER, 10), |
| 79 | false, false, false), |
| 80 | prio_get_size, |
| 81 | prio_record, |
| 82 | prio_get_value, |
| 83 | NULL, NULL); |
| 84 | |
| 85 | int lttng_add_prio_to_ctx(struct lttng_kernel_ctx **ctx) |
| 86 | { |
| 87 | int ret; |
| 88 | |
| 89 | if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name)) |
| 90 | return -EEXIST; |
| 91 | ret = lttng_kernel_context_append(ctx, ctx_field); |
| 92 | wrapper_vmalloc_sync_mappings(); |
| 93 | return ret; |
| 94 | } |
| 95 | EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx); |