X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Flttng-context-callstack-legacy-impl.h;fp=src%2Flttng-context-callstack-legacy-impl.h;h=8d78fb95700891b0a2f2dc622b6c36b2b5f3fce6;hb=cfa6cc1d0f01c2cfcc1a679abf3a6572d411c309;hp=0000000000000000000000000000000000000000;hpb=cd4486798c2b046ea93b89439cd705e93c40b349;p=lttng-modules.git diff --git a/src/lttng-context-callstack-legacy-impl.h b/src/lttng-context-callstack-legacy-impl.h new file mode 100644 index 00000000..8d78fb95 --- /dev/null +++ b/src/lttng-context-callstack-legacy-impl.h @@ -0,0 +1,244 @@ +/* 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 + * Copyright (C) 2014 Francis Giraldeau + */ + +#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)); + } +}