[PATCH v5 05/12] MIPS/Perf-events: add callchain support

[Deng-Cheng Zhu <dengcheng.zhu@xxxxxxxxx>]

This patch adds callchain support for MIPS Perf-events. For more info on
this feature, please refer to tools/perf/Documentation/perf-report.txt
and tools/perf/design.txt.

Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@xxxxxxxxx>
---
 arch/mips/kernel/perf_event.c |   98 ++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 97 insertions(+), 1 deletions(-)

diff --git a/arch/mips/kernel/perf_event.c b/arch/mips/kernel/perf_event.c
index 788815f..63ea0e9 100644
--- a/arch/mips/kernel/perf_event.c
+++ b/arch/mips/kernel/perf_event.c
@@ -5,7 +5,8 @@
  *
  * This code is based on the implementation for ARM, which is in turn
  * based on the sparc64 perf event code and the x86 code. Performance
- * counter access is based on the MIPS Oprofile code.
+ * counter access is based on the MIPS Oprofile code. And the callchain
+ * support references the code of MIPS traps.c.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -501,3 +502,98 @@ handle_associated_event(struct cpu_hw_events *cpuc,
 		mipspmu->disable_event(idx);
 }
 
+/*
+ * 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;
+}
+
+static void
+perf_callchain_user(struct pt_regs *regs,
+		    struct perf_callchain_entry *entry)
+{
+	unsigned long *sp;
+	unsigned long addr;
+
+	callchain_store(entry, PERF_CONTEXT_USER);
+
+	if (!user_mode(regs))
+		regs = task_pt_regs(current);
+
+	sp = (unsigned long *)(regs->regs[29] & ~3);
+
+	while (!kstack_end(sp)) {
+		unsigned long __user *p =
+			(unsigned long __user *)(unsigned long)sp++;
+		if (__get_user(addr, p)) {
+			pr_warning("Performance counter callchain "
+				"suppport: Bad stack address.\n");
+			break;
+		}
+		callchain_store(entry, addr);
+	}
+}
+
+static void
+perf_callchain_kernel(struct pt_regs *regs,
+		      struct perf_callchain_entry *entry)
+{
+	unsigned long sp = regs->regs[29];
+	unsigned long ra = regs->regs[31];
+	unsigned long pc = regs->cp0_epc;
+
+	if (unlikely(!__kernel_text_address(pc))) {
+		pr_warning("Performance counter callchain support "
+			"error.\n");
+		return;
+	}
+
+	callchain_store(entry, PERF_CONTEXT_KERNEL);
+
+	do {
+		callchain_store(entry, pc);
+		pc = unwind_stack(current, &sp, pc, &ra);
+	} while (pc);
+}
+
+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)
+		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;
+}
+
-- 
1.6.3.3