perf_event.c

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/*
 * Linux performance counter support for MIPS.
 *
 * Copyright (C) 2010 MIPS Technologies, Inc.
 * Author: Deng-Cheng Zhu
 *
 * 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. And the callchain
 * support references the code of MIPS stacktrace.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
 * published by the Free Software Foundation.
 */

#include <linux/perf_event.h>

#include <asm/stacktrace.h>

/* Callchain handling code. */

/*
 * Leave userspace callchain empty for now. When we find a way to trace
 * the user stack callchains, we will add it here.
 */

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)) {
            perf_callchain_store(entry, addr);
            if (entry->nr >= PERF_MAX_STACK_DEPTH)
                break;
        }
    }
}

void perf_callchain_kernel(struct perf_callchain_entry *entry,
              struct pt_regs *regs)
{
    unsigned long sp = regs->regs[29];
#ifdef CONFIG_KALLSYMS
    unsigned long ra = regs->regs[31];
    unsigned long pc = regs->cp0_epc;

    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 {
        perf_callchain_store(entry, pc);
        if (entry->nr >= PERF_MAX_STACK_DEPTH)
            break;
        pc = unwind_stack(current, &sp, pc, &ra);
    } while (pc);
#else
    save_raw_perf_callchain(entry, sp);
#endif
}