+
+/* Callchain handling code. */
+static inline void
+callchain_store(struct perf_callchain_entry *entry,
+ u64 ip)
+{
+ if (entry->nr < PERF_MAX_STACK_DEPTH)
+ entry->ip[entry->nr++] = ip;
+}
+
+/*
+ * Leave userspace callchain empty for now. When we find a way to trace
+ * the user stack callchains, we add here.
+ */
+static void
+perf_callchain_user(struct pt_regs *regs,
+ struct perf_callchain_entry *entry)
+{
+}
+
+static void save_raw_perf_callchain(struct perf_callchain_entry *entry,
+ unsigned long reg29)
+{
+ unsigned long *sp = (unsigned long *)reg29;
+ unsigned long addr;
+
+ while (!kstack_end(sp)) {
+ addr = *sp++;
+ if (__kernel_text_address(addr)) {
+ callchain_store(entry, addr);
+ if (entry->nr >= PERF_MAX_STACK_DEPTH)
+ break;
+ }
+ }
+}
+
+static void
+perf_callchain_kernel(struct pt_regs *regs,
+ struct perf_callchain_entry *entry)
+{
+ unsigned long sp = regs->regs[29];
+#ifdef CONFIG_KALLSYMS
+ unsigned long ra = regs->regs[31];
+ unsigned long pc = regs->cp0_epc;
+
+ callchain_store(entry, PERF_CONTEXT_KERNEL);
+ if (raw_show_trace || !__kernel_text_address(pc)) {
+ unsigned long stack_page =
+ (unsigned long)task_stack_page(current);
+ if (stack_page && sp >= stack_page &&
+ sp <= stack_page + THREAD_SIZE - 32)
+ save_raw_perf_callchain(entry, sp);
+ return;
+ }
+ do {
+ callchain_store(entry, pc);
+ if (entry->nr >= PERF_MAX_STACK_DEPTH)
+ break;
+ pc = unwind_stack(current, &sp, pc, &ra);
+ } while (pc);
+#else
+ callchain_store(entry, PERF_CONTEXT_KERNEL);
+ save_raw_perf_callchain(entry, sp);
+#endif
+}
+
+static void
+perf_do_callchain(struct pt_regs *regs,
+ struct perf_callchain_entry *entry)
+{
+ int is_user;
+
+ if (!regs)
+ return;
+
+ is_user = user_mode(regs);
+
+ if (!current || !current->pid)
+ return;
+
+ if (is_user && current->state != TASK_RUNNING)
+ return;
+
+ if (!is_user) {
+ perf_callchain_kernel(regs, entry);
+ if (current->mm)
+ regs = task_pt_regs(current);
+ else
+ regs = NULL;
+ }
+ if (regs)
+ perf_callchain_user(regs, entry);
+}
+
+static DEFINE_PER_CPU(struct perf_callchain_entry, pmc_irq_entry);
+
+struct perf_callchain_entry *
+perf_callchain(struct pt_regs *regs)
+{
+ struct perf_callchain_entry *entry = &__get_cpu_var(pmc_irq_entry);
+
+ entry->nr = 0;
+ perf_do_callchain(regs, entry);
+ return entry;
+}