--- /dev/null
+/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
+ *
+ * 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
+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];
+}
+
+/*
+ * 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 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 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;
+
+ 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 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 == 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 lttng_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 == 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 == MAX_ENTRIES) {
+ unsigned long delim = ULONG_MAX;
+
+ chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
+ }
+}
projects / lttng-modules.git / commitdiff
