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Subject[PATCH 14/15] perf_counter: x86: callchain support
Provide the x86 perf_callchain() implementation.

Code based on the sysprof code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
arch/x86/kernel/cpu/perf_counter.c | 154 +++++++++++++++++++++++++++++++++++++
1 file changed, 154 insertions(+)

Index: linux-2.6/arch/x86/kernel/cpu/perf_counter.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_counter.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_counter.c
@@ -16,8 +16,10 @@
#include <linux/module.h>
#include <linux/kdebug.h>
#include <linux/sched.h>
+#include <linux/uaccess.h>

#include <asm/apic.h>
+#include <asm/stacktrace.h>

static bool perf_counters_initialized __read_mostly;

@@ -958,3 +960,155 @@ hw_perf_counter_init(struct perf_counter

return &x86_perf_counter_ops;
}
+
+/*
+ * callchain support
+ */
+
+static inline
+void callchain_store(struct perf_callchain_entry *entry, unsigned long ip)
+{
+ if (entry->nr < MAX_STACK_DEPTH)
+ entry->ip[entry->nr++] = ip;
+}
+
+static DEFINE_PER_CPU(struct perf_callchain_entry, irq_entry);
+static DEFINE_PER_CPU(struct perf_callchain_entry, nmi_entry);
+
+
+static void
+backtrace_warning_symbol(void *data, char *msg, unsigned long symbol)
+{
+ /* Ignore warnings */
+}
+
+static void backtrace_warning(void *data, char *msg)
+{
+ /* Ignore warnings */
+}
+
+static int backtrace_stack(void *data, char *name)
+{
+ /* Don't bother with IRQ stacks for now */
+ return -1;
+}
+
+static void backtrace_address(void *data, unsigned long addr, int reliable)
+{
+ struct perf_callchain_entry *entry = data;
+
+ if (reliable)
+ callchain_store(entry, addr);
+}
+
+static const struct stacktrace_ops backtrace_ops = {
+ .warning = backtrace_warning,
+ .warning_symbol = backtrace_warning_symbol,
+ .stack = backtrace_stack,
+ .address = backtrace_address,
+};
+
+static void
+perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry)
+{
+ unsigned long bp;
+ char *stack;
+
+ callchain_store(entry, instruction_pointer(regs));
+
+ stack = ((char *)regs + sizeof(struct pt_regs));
+#ifdef CONFIG_FRAME_POINTER
+ bp = frame_pointer(regs);
+#else
+ bp = 0;
+#endif
+
+ dump_trace(NULL, regs, (void *)stack, bp, &backtrace_ops, entry);
+}
+
+
+struct stack_frame {
+ const void __user *next_fp;
+ unsigned long return_address;
+};
+
+static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
+{
+ int ret;
+
+ if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
+ return 0;
+
+ ret = 1;
+ pagefault_disable();
+ if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
+ ret = 0;
+ pagefault_enable();
+
+ return ret;
+}
+
+static void
+perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry)
+{
+ struct stack_frame frame;
+ const void __user *fp;
+
+ regs = (struct pt_regs *)current->thread.sp0 - 1;
+ fp = (void __user *)regs->bp;
+
+ callchain_store(entry, regs->ip);
+
+ while (entry->nr < MAX_STACK_DEPTH) {
+ frame.next_fp = NULL;
+ frame.return_address = 0;
+
+ if (!copy_stack_frame(fp, &frame))
+ break;
+
+ if ((unsigned long)fp < user_stack_pointer(regs))
+ break;
+
+ callchain_store(entry, frame.return_address);
+ fp = frame.next_fp;
+ }
+}
+
+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 == 0)
+ 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);
+}
+
+struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
+{
+ struct perf_callchain_entry *entry;
+
+ if (in_nmi())
+ entry = &__get_cpu_var(nmi_entry);
+ else
+ entry = &__get_cpu_var(irq_entry);
+
+ entry->nr = 0;
+
+ perf_do_callchain(regs, entry);
+
+ return entry;
+}
--



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