/*
 * thread-stack.c: Synthesize a thread's stack using call / return events
 * Copyright (c) 2014, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 */

#include <linux/rbtree.h>
#include <linux/list.h>
#include "thread.h"
#include "event.h"
#include "machine.h"
#include "util.h"
#include "debug.h"
#include "symbol.h"
#include "comm.h"
#include "call-path.h"
#include "thread-stack.h"

#define STACK_GROWTH 2048

/**
 * struct thread_stack_entry - thread stack entry.
 * @ret_addr: return address
 * @timestamp: timestamp (if known)
 * @ref: external reference (e.g. db_id of sample)
 * @branch_count: the branch count when the entry was created
 * @cp: call path
 * @no_call: a 'call' was not seen
 */
struct thread_stack_entry {
        u64 ret_addr;
        u64 timestamp;
        u64 ref;
        u64 branch_count;
        struct call_path *cp;
        bool no_call;
};

/**
 * struct thread_stack - thread stack constructed from 'call' and 'return'
 *                       branch samples.
 * @stack: array that holds the stack
 * @cnt: number of entries in the stack
 * @sz: current maximum stack size
 * @trace_nr: current trace number
 * @branch_count: running branch count
 * @kernel_start: kernel start address
 * @last_time: last timestamp
 * @crp: call/return processor
 * @comm: current comm
 */
struct thread_stack {
        struct thread_stack_entry *stack;
        size_t cnt;
        size_t sz;
        u64 trace_nr;
        u64 branch_count;
        u64 kernel_start;
        u64 last_time;
        struct call_return_processor *crp;
        struct comm *comm;
};

static int thread_stack__grow(struct thread_stack *ts)
{
        struct thread_stack_entry *new_stack;
        size_t sz, new_sz;

        new_sz = ts->sz + STACK_GROWTH;
        sz = new_sz * sizeof(struct thread_stack_entry);

        new_stack = realloc(ts->stack, sz);
        if (!new_stack)
                return -ENOMEM;

        ts->stack = new_stack;
        ts->sz = new_sz;

        return 0;
}

static struct thread_stack *thread_stack__new(struct thread *thread,
                                              struct call_return_processor *crp)
{
        struct thread_stack *ts;

        ts = zalloc(sizeof(struct thread_stack));
        if (!ts)
                return NULL;

        if (thread_stack__grow(ts)) {
                free(ts);
                return NULL;
        }

        if (thread->mg && thread->mg->machine)
                ts->kernel_start = machine__kernel_start(thread->mg->machine);
        else
                ts->kernel_start = 1ULL << 63;
        ts->crp = crp;

        return ts;
}

static int thread_stack__push(struct thread_stack *ts, u64 ret_addr)
{
        int err = 0;

        if (ts->cnt == ts->sz) {
                err = thread_stack__grow(ts);
                if (err) {
                        pr_warning("Out of memory: discarding thread stack\n");
                        ts->cnt = 0;
                }
        }

        ts->stack[ts->cnt++].ret_addr = ret_addr;

        return err;
}

static void thread_stack__pop(struct thread_stack *ts, u64 ret_addr)
{
        size_t i;

        /*
         * In some cases there may be functions which are not seen to return.
         * For example when setjmp / longjmp has been used.  Or the perf context
         * switch in the kernel which doesn't stop and start tracing in exactly
         * the same code path.  When that happens the return address will be
         * further down the stack.  If the return address is not found at all,
         * we assume the opposite (i.e. this is a return for a call that wasn't
         * seen for some reason) and leave the stack alone.
         */
        for (i = ts->cnt; i; ) {
                if (ts->stack[--i].ret_addr == ret_addr) {
                        ts->cnt = i;
                        return;
                }
        }
}

static bool thread_stack__in_kernel(struct thread_stack *ts)
{
        if (!ts->cnt)
                return false;

        return ts->stack[ts->cnt - 1].cp->in_kernel;
}

static int thread_stack__call_return(struct thread *thread,
                                     struct thread_stack *ts, size_t idx,
                                     u64 timestamp, u64 ref, bool no_return)
{
        struct call_return_processor *crp = ts->crp;
        struct thread_stack_entry *tse;
        struct call_return cr = {
                .thread = thread,
                .comm = ts->comm,
                .db_id = 0,
        };

        tse = &ts->stack[idx];
        cr.cp = tse->cp;
        cr.call_time = tse->timestamp;
        cr.return_time = timestamp;
        cr.branch_count = ts->branch_count - tse->branch_count;
        cr.call_ref = tse->ref;
        cr.return_ref = ref;
        if (tse->no_call)
                cr.flags |= CALL_RETURN_NO_CALL;
        if (no_return)
                cr.flags |= CALL_RETURN_NO_RETURN;

        return crp->process(&cr, crp->data);
}

static int __thread_stack__flush(struct thread *thread, struct thread_stack *ts)
{
        struct call_return_processor *crp = ts->crp;
        int err;

        if (!crp) {
                ts->cnt = 0;
                return 0;
        }

        while (ts->cnt) {
                err = thread_stack__call_return(thread, ts, --ts->cnt,
                                                ts->last_time, 0, true);
                if (err) {
                        pr_err("Error flushing thread stack!\n");
                        ts->cnt = 0;
                        return err;
                }
        }

        return 0;
}

int thread_stack__flush(struct thread *thread)
{
        if (thread->ts)
                return __thread_stack__flush(thread, thread->ts);

        return 0;
}

int thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,
                        u64 to_ip, u16 insn_len, u64 trace_nr)
{
        if (!thread)
                return -EINVAL;

        if (!thread->ts) {
                thread->ts = thread_stack__new(thread, NULL);
                if (!thread->ts) {
                        pr_warning("Out of memory: no thread stack\n");
                        return -ENOMEM;
                }
                thread->ts->trace_nr = trace_nr;
        }

        /*
         * When the trace is discontinuous, the trace_nr changes.  In that case
         * the stack might be completely invalid.  Better to report nothing than
         * to report something misleading, so flush the stack.
         */
        if (trace_nr != thread->ts->trace_nr) {
                if (thread->ts->trace_nr)
                        __thread_stack__flush(thread, thread->ts);
                thread->ts->trace_nr = trace_nr;
        }

        /* Stop here if thread_stack__process() is in use */
        if (thread->ts->crp)
                return 0;

        if (flags & PERF_IP_FLAG_CALL) {
                u64 ret_addr;

                if (!to_ip)
                        return 0;
                ret_addr = from_ip + insn_len;
                if (ret_addr == to_ip)
                        return 0; /* Zero-length calls are excluded */
                return thread_stack__push(thread->ts, ret_addr);
        } else if (flags & PERF_IP_FLAG_RETURN) {
                if (!from_ip)
                        return 0;
                thread_stack__pop(thread->ts, to_ip);
        }

        return 0;
}

void thread_stack__set_trace_nr(struct thread *thread, u64 trace_nr)
{
        if (!thread || !thread->ts)
                return;

        if (trace_nr != thread->ts->trace_nr) {
                if (thread->ts->trace_nr)
                        __thread_stack__flush(thread, thread->ts);
                thread->ts->trace_nr = trace_nr;
        }
}

void thread_stack__free(struct thread *thread)
{
        if (thread->ts) {
                __thread_stack__flush(thread, thread->ts);
                zfree(&thread->ts->stack);
                zfree(&thread->ts);
        }
}

void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
                          size_t sz, u64 ip)
{
        size_t i;

        if (!thread || !thread->ts)
                chain->nr = 1;
        else
                chain->nr = min(sz, thread->ts->cnt + 1);

        chain->ips[0] = ip;

        for (i = 1; i < chain->nr; i++)
                chain->ips[i] = thread->ts->stack[thread->ts->cnt - i].ret_addr;
}

struct call_return_processor *
call_return_processor__new(int (*process)(struct call_return *cr, void *data),
                           void *data)
{
        struct call_return_processor *crp;

        crp = zalloc(sizeof(struct call_return_processor));
        if (!crp)
                return NULL;
        crp->cpr = call_path_root__new();
        if (!crp->cpr)
                goto out_free;
        crp->process = process;
        crp->data = data;
        return crp;

out_free:
        free(crp);
        return NULL;
}

void call_return_processor__free(struct call_return_processor *crp)
{
        if (crp) {
                call_path_root__free(crp->cpr);
                free(crp);
        }
}

static int thread_stack__push_cp(struct thread_stack *ts, u64 ret_addr,
                                 u64 timestamp, u64 ref, struct call_path *cp,
                                 bool no_call)
{
        struct thread_stack_entry *tse;
        int err;

        if (ts->cnt == ts->sz) {
                err = thread_stack__grow(ts);
                if (err)
                        return err;
        }

        tse = &ts->stack[ts->cnt++];
        tse->ret_addr = ret_addr;
        tse->timestamp = timestamp;
        tse->ref = ref;
        tse->branch_count = ts->branch_count;
        tse->cp = cp;
        tse->no_call = no_call;

        return 0;
}

static int thread_stack__pop_cp(struct thread *thread, struct thread_stack *ts,
                                u64 ret_addr, u64 timestamp, u64 ref,
                                struct symbol *sym)
{
        int err;

        if (!ts->cnt)
                return 1;

        if (ts->cnt == 1) {
                struct thread_stack_entry *tse = &ts->stack[0];

                if (tse->cp->sym == sym)
                        return thread_stack__call_return(thread, ts, --ts->cnt,
                                                         timestamp, ref, false);
        }

        if (ts->stack[ts->cnt - 1].ret_addr == ret_addr) {
                return thread_stack__call_return(thread, ts, --ts->cnt,
                                                 timestamp, ref, false);
        } else {
                size_t i = ts->cnt - 1;

                while (i--) {
                        if (ts->stack[i].ret_addr != ret_addr)
                                continue;
                        i += 1;
                        while (ts->cnt > i) {
                                err = thread_stack__call_return(thread, ts,
                                                                --ts->cnt,
                                                                timestamp, ref,
                                                                true);
                                if (err)
                                        return err;
                        }
                        return thread_stack__call_return(thread, ts, --ts->cnt,
                                                         timestamp, ref, false);
                }
        }

        return 1;
}

static int thread_stack__bottom(struct thread *thread, struct thread_stack *ts,
                                struct perf_sample *sample,
                                struct addr_location *from_al,
                                struct addr_location *to_al, u64 ref)
{
        struct call_path_root *cpr = ts->crp->cpr;
        struct call_path *cp;
        struct symbol *sym;
        u64 ip;

        if (sample->ip) {
                ip = sample->ip;
                sym = from_al->sym;
        } else if (sample->addr) {
                ip = sample->addr;
                sym = to_al->sym;
        } else {
                return 0;
        }

        cp = call_path__findnew(cpr, &cpr->call_path, sym, ip,
                                ts->kernel_start);
        if (!cp)
                return -ENOMEM;

        return thread_stack__push_cp(thread->ts, ip, sample->time, ref, cp,
                                     true);
}

static int thread_stack__no_call_return(struct thread *thread,
                                        struct thread_stack *ts,
                                        struct perf_sample *sample,
                                        struct addr_location *from_al,
                                        struct addr_location *to_al, u64 ref)
{
        struct call_path_root *cpr = ts->crp->cpr;
        struct call_path *cp, *parent;
        u64 ks = ts->kernel_start;
        int err;

        if (sample->ip >= ks && sample->addr < ks) {
                /* Return to userspace, so pop all kernel addresses */
                while (thread_stack__in_kernel(ts)) {
                        err = thread_stack__call_return(thread, ts, --ts->cnt,
                                                        sample->time, ref,
                                                        true);
                        if (err)
                                return err;
                }

                /* If the stack is empty, push the userspace address */
                if (!ts->cnt) {
                        cp = call_path__findnew(cpr, &cpr->call_path,
                                                to_al->sym, sample->addr,
                                                ts->kernel_start);
                        if (!cp)
                                return -ENOMEM;
                        return thread_stack__push_cp(ts, 0, sample->time, ref,
                                                     cp, true);
                }
        } else if (thread_stack__in_kernel(ts) && sample->ip < ks) {
                /* Return to userspace, so pop all kernel addresses */
                while (thread_stack__in_kernel(ts)) {
                        err = thread_stack__call_return(thread, ts, --ts->cnt,
                                                        sample->time, ref,
                                                        true);
                        if (err)
                                return err;
                }
        }

        if (ts->cnt)
                parent = ts->stack[ts->cnt - 1].cp;
        else
                parent = &cpr->call_path;

        /* This 'return' had no 'call', so push and pop top of stack */
        cp = call_path__findnew(cpr, parent, from_al->sym, sample->ip,
                                ts->kernel_start);
        if (!cp)
                return -ENOMEM;

        err = thread_stack__push_cp(ts, sample->addr, sample->time, ref, cp,
                                    true);
        if (err)
                return err;

        return thread_stack__pop_cp(thread, ts, sample->addr, sample->time, ref,
                                    to_al->sym);
}

static int thread_stack__trace_begin(struct thread *thread,
                                     struct thread_stack *ts, u64 timestamp,
                                     u64 ref)
{
        struct thread_stack_entry *tse;
        int err;

        if (!ts->cnt)
                return 0;

        /* Pop trace end */
        tse = &ts->stack[ts->cnt - 1];
        if (tse->cp->sym == NULL && tse->cp->ip == 0) {
                err = thread_stack__call_return(thread, ts, --ts->cnt,
                                                timestamp, ref, false);
                if (err)
                        return err;
        }

        return 0;
}

static int thread_stack__trace_end(struct thread_stack *ts,
                                   struct perf_sample *sample, u64 ref)
{
        struct call_path_root *cpr = ts->crp->cpr;
        struct call_path *cp;
        u64 ret_addr;

        /* No point having 'trace end' on the bottom of the stack */
        if (!ts->cnt || (ts->cnt == 1 && ts->stack[0].ref == ref))
                return 0;

        cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp, NULL, 0,
                                ts->kernel_start);
        if (!cp)
                return -ENOMEM;

        ret_addr = sample->ip + sample->insn_len;

        return thread_stack__push_cp(ts, ret_addr, sample->time, ref, cp,
                                     false);
}

int thread_stack__process(struct thread *thread, struct comm *comm,
                          struct perf_sample *sample,
                          struct addr_location *from_al,
                          struct addr_location *to_al, u64 ref,
                          struct call_return_processor *crp)
{
        struct thread_stack *ts = thread->ts;
        int err = 0;

        if (ts) {
                if (!ts->crp) {
                        /* Supersede thread_stack__event() */
                        thread_stack__free(thread);
                        thread->ts = thread_stack__new(thread, crp);
                        if (!thread->ts)
                                return -ENOMEM;
                        ts = thread->ts;
                        ts->comm = comm;
                }
        } else {
                thread->ts = thread_stack__new(thread, crp);
                if (!thread->ts)
                        return -ENOMEM;
                ts = thread->ts;
                ts->comm = comm;
        }

        /* Flush stack on exec */
        if (ts->comm != comm && thread->pid_ == thread->tid) {
                err = __thread_stack__flush(thread, ts);
                if (err)
                        return err;
                ts->comm = comm;
        }

        /* If the stack is empty, put the current symbol on the stack */
        if (!ts->cnt) {
                err = thread_stack__bottom(thread, ts, sample, from_al, to_al,
                                           ref);
                if (err)
                        return err;
        }

        ts->branch_count += 1;
        ts->last_time = sample->time;

        if (sample->flags & PERF_IP_FLAG_CALL) {
                struct call_path_root *cpr = ts->crp->cpr;
                struct call_path *cp;
                u64 ret_addr;

                if (!sample->ip || !sample->addr)
                        return 0;

                ret_addr = sample->ip + sample->insn_len;
                if (ret_addr == sample->addr)
                        return 0; /* Zero-length calls are excluded */

                cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp,
                                        to_al->sym, sample->addr,
                                        ts->kernel_start);
                if (!cp)
                        return -ENOMEM;
                err = thread_stack__push_cp(ts, ret_addr, sample->time, ref,
                                            cp, false);
        } else if (sample->flags & PERF_IP_FLAG_RETURN) {
                if (!sample->ip || !sample->addr)
                        return 0;

                err = thread_stack__pop_cp(thread, ts, sample->addr,
                                           sample->time, ref, from_al->sym);
                if (err) {
                        if (err < 0)
                                return err;
                        err = thread_stack__no_call_return(thread, ts, sample,
                                                           from_al, to_al, ref);
                }
        } else if (sample->flags & PERF_IP_FLAG_TRACE_BEGIN) {
                err = thread_stack__trace_begin(thread, ts, sample->time, ref);
        } else if (sample->flags & PERF_IP_FLAG_TRACE_END) {
                err = thread_stack__trace_end(ts, sample, ref);
        }

        return err;
}

size_t thread_stack__depth(struct thread *thread)
{
        if (!thread->ts)
                return 0;
        return thread->ts->cnt;
}