// SPDX-License-Identifier: GPL-2.0-only
/*
* thread-stack.c: Synthesize a thread's stack using call / return events
* Copyright (c) 2014, Intel Corporation.
*/
#include <linux/rbtree.h>
#include <linux/list.h>
#include <linux/log2.h>
#include <linux/zalloc.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "thread.h"
#include "event.h"
#include "machine.h"
#include "env.h"
#include "debug.h"
#include "symbol.h"
#include "comm.h"
#include "call-path.h"
#include "thread-stack.h"
#define STACK_GROWTH 2048
/*
* State of retpoline detection.
*
* RETPOLINE_NONE: no retpoline detection
* X86_RETPOLINE_POSSIBLE: x86 retpoline possible
* X86_RETPOLINE_DETECTED: x86 retpoline detected
*/
enum retpoline_state_t {
RETPOLINE_NONE,
X86_RETPOLINE_POSSIBLE,
X86_RETPOLINE_DETECTED,
};
/**
* 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
* @insn_count: the instruction count when the entry was created
* @cyc_count the cycle count when the entry was created
* @db_id: id used for db-export
* @cp: call path
* @no_call: a 'call' was not seen
* @trace_end: a 'call' but trace ended
* @non_call: a branch but not a 'call' to the start of a different symbol
*/
struct thread_stack_entry {
u64 ret_addr;
u64 timestamp;
u64 ref;
u64 branch_count;
u64 insn_count;
u64 cyc_count;
u64 db_id;
struct call_path *cp;
bool no_call;
bool trace_end;
bool non_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
* @insn_count: running instruction count
* @cyc_count running cycle count
* @kernel_start: kernel start address
* @last_time: last timestamp
* @crp: call/return processor
* @comm: current comm
* @arr_sz: size of array if this is the first element of an array
* @rstate: used to detect retpolines
* @br_stack_rb: branch stack (ring buffer)
* @br_stack_sz: maximum branch stack size
* @br_stack_pos: current position in @br_stack_rb
* @mispred_all: mark all branches as mispredicted
*/
struct thread_stack {
struct thread_stack_entry *stack;
size_t cnt;
size_t sz;
u64 trace_nr;
u64 branch_count;
u64 insn_count;
u64 cyc_count;
u64 kernel_start;
u64 last_time;
struct call_return_processor *crp;
struct comm *comm;
unsigned int arr_sz;
enum retpoline_state_t rstate;
struct branch_stack *br_stack_rb;
unsigned int br_stack_sz;
unsigned int br_stack_pos;
bool mispred_all;
};
/*
* Assume pid == tid == 0 identifies the idle task as defined by
* perf_session__register_idle_thread(). The idle task is really 1 task per cpu,
* and therefore requires a stack for each cpu.
*/
static inline bool thread_stack__per_cpu(struct thread *thread)
{
return !(thread__tid(thread) || thread__pid(thread));
}
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 int thread_stack__init(struct thread_stack *ts, struct thread *thread,
struct call_return_processor *crp,
bool callstack, unsigned int br_stack_sz)
{
int err;
if (callstack) {
err = thread_stack__grow(ts);
if (err)
return err;
}
if (br_stack_sz) {
size_t sz = sizeof(struct branch_stack);
sz += br_stack_sz * sizeof(struct branch_entry);
ts->br_stack_rb = zalloc(sz);
if (!ts->br_stack_rb)
return -ENOMEM;
ts->br_stack_sz = br_stack_sz;
}
if (thread__maps(thread) && maps__machine(thread__maps(thread))) {
struct machine *machine = maps__machine(thread__maps(thread));
const char *arch = perf_env__arch(machine->env);
ts->kernel_start = machine__kernel_start(machine);
if (!strcmp(arch, "x86"))
ts->rstate = X86_RETPOLINE_POSSIBLE;
} else {
ts->kernel_start = 1ULL << 63;
}
ts->crp = crp;
return 0;
}
static struct thread_stack *thread_stack__new(struct thread *thread, int cpu,
struct call_return_processor *crp,
bool callstack,
unsigned int br_stack_sz)
{
struct thread_stack *ts = thread__ts(thread), *new_ts;
unsigned int old_sz = ts ? ts->arr_sz : 0;
unsigned int new_sz = 1;
if (thread_stack__per_cpu(thread) && cpu > 0)
new_sz = roundup_pow_of_two(cpu + 1);
if (!ts || new_sz > old_sz) {
new_ts = calloc(new_sz, sizeof(*ts));
if (!new_ts)
return NULL;
if (ts)
memcpy(new_ts, ts, old_sz * sizeof(*ts));
new_ts->arr_sz = new_sz;
free(thread__ts(thread));
thread__set_ts(thread, new_ts);
ts = new_ts;
}
if (thread_stack__per_cpu(thread) && cpu > 0 &&
(unsigned int)cpu < ts->arr_sz)
ts += cpu;
if (!ts->stack &&
thread_stack__init(ts, thread, crp, callstack, br_stack_sz))
return NULL;
return ts;
}
static struct thread_stack *thread__cpu_stack(struct thread *thread, int cpu)
{
struct thread_stack *ts = thread__ts(thread);
if (cpu < 0)
cpu = 0;
if (!ts || (unsigned int)cpu >= ts->arr_sz)
return NULL;
ts += cpu;
if (!ts->stack)
return NULL;
return ts;
}
static inline struct thread_stack *thread__stack(struct thread *thread,
int cpu)
{
if (!thread)
return NULL;
if (thread_stack__per_cpu(thread))
return thread__cpu_stack(thread, cpu);
return thread__ts(thread);
}
static int thread_stack__push(struct thread_stack *ts, u64 ret_addr,
bool trace_end)
{
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].trace_end = trace_end;
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 void thread_stack__pop_trace_end(struct thread_stack *ts)
{
size_t i;
for (i = ts->cnt; i; ) {
if (ts->stack[--i].trace_end)
ts->cnt = i;
else
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,
};
u64 *parent_db_id;
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.insn_count = ts->insn_count - tse->insn_count;
cr.cyc_count = ts->cyc_count - tse->cyc_count;
cr.db_id = tse->db_id;
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;
if (tse->non_call)
cr.flags |= CALL_RETURN_NON_CALL;
/*
* The parent db_id must be assigned before exporting the child. Note
* it is not possible to export the parent first because its information
* is not yet complete because its 'return' has not yet been processed.
*/
parent_db_id = idx ? &(tse - 1)->db_id : NULL;
return crp->process(&cr, parent_db_id, 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;
ts->br_stack_pos = 0;
if (ts->br_stack_rb)
ts->br_stack_rb->nr = 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)
{
struct thread_stack *ts = thread__ts(thread);
unsigned int pos;
int err = 0;
if (ts) {
for (pos = 0; pos < ts->arr_sz; pos++) {
int ret = __thread_stack__flush(thread, ts + pos);
if (ret)
err = ret;
}
}
return err;
}
static void thread_stack__update_br_stack(struct thread_stack *ts, u32 flags,
u64 from_ip, u64 to_ip)
{
struct branch_stack *bs = ts->br_stack_rb;
struct branch_entry *be;
if (!ts->br_stack_pos)
ts->br_stack_pos = ts->br_stack_sz;
ts->br_stack_pos -= 1;
be = &bs->entries[ts->br_stack_pos];
be->from = from_ip;
be->to = to_ip;
be->flags.value = 0;
be->flags.abort = !!(flags & PERF_IP_FLAG_TX_ABORT);
be->flags.in_tx = !!(flags & PERF_IP_FLAG_IN_TX);
/* No support for mispredict */
be->flags.mispred = ts->mispred_all;
if (bs->nr < ts->br_stack_sz)
bs->nr += 1;
}
int thread_stack__event(struct thread *thread, int cpu, u32 flags, u64 from_ip,
u64 to_ip, u16 insn_len, u64 trace_nr, bool callstack,
unsigned int br_stack_sz, bool mispred_all)
{
struct thread_stack *ts = thread__stack(thread, cpu);
if (!thread)
return -EINVAL;
if (!ts) {
ts = thread_stack__new(thread, cpu, NULL, callstack, br_stack_sz);
if (!ts) {
pr_warning("Out of memory: no thread stack\n");
return -ENOMEM;
}
ts->trace_nr = trace_nr;
ts->mispred_all = mispred_all;
}
/*
* 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 != ts->trace_nr) {
if (ts->trace_nr)
__thread_stack__flush(thread, ts);
ts->trace_nr = trace_nr;
}
if (br_stack_sz)
thread_stack__update_br_stack(ts, flags, from_ip, to_ip);
/*
* Stop here if thread_stack__process() is in use, or not recording call
* stack.
*/
if (ts->crp || !callstack)
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(ts, ret_addr,
flags & PERF_IP_FLAG_TRACE_END);
} else if (flags & PERF_IP_FLAG_TRACE_BEGIN) {
/*
* If the caller did not change the trace number (which would
* have flushed the stack) then try to make sense of the stack.
* Possibly, tracing began after returning to the current
* address, so try to pop that. Also, do not expect a call made
* when the trace ended, to return, so pop that.
*/
thread_stack__pop(ts, to_ip);
thread_stack__pop_trace_end(ts);
} else if ((flags & PERF_IP_FLAG_RETURN) && from_ip) {
thread_stack__pop(ts, to_ip);
}
return 0;
}
void thread_stack__set_trace_nr(struct thread *thread, int cpu, u64 trace_nr)
{
struct thread_stack *ts = thread__stack(thread, cpu);
if (!ts)
return;
if (trace_nr != ts->trace_nr) {
if (ts->trace_nr)
__thread_stack__flush(thread, ts);
ts->trace_nr = trace_nr;
}
}
static void __thread_stack__free(struct thread *thread, struct thread_stack *ts)
{
__thread_stack__flush(thread, ts);
zfree(&ts->stack);
zfree(&ts->br_stack_rb);
}
static void thread_stack__reset(struct thread *thread, struct thread_stack *ts)
{
unsigned int arr_sz = ts->arr_sz;
__thread_stack__free(thread, ts);
memset(ts, 0, sizeof(*ts));
ts->arr_sz = arr_sz;
}
void thread_stack__free(struct thread *thread)
{
struct thread_stack *ts = thread__ts(thread);
unsigned int pos;
if (ts) {
for (pos = 0; pos < ts->arr_sz; pos++)
__thread_stack__free(thread, ts + pos);
free(thread__ts(thread));
thread__set_ts(thread, NULL);
}
}
static inline u64 callchain_context(u64 ip, u64 kernel_start)
{
return ip < kernel_start ? PERF_CONTEXT_USER : PERF_CONTEXT_KERNEL;
}
void thread_stack__sample(struct thread *thread, int cpu,
struct ip_callchain *chain,
size_t sz, u64 ip, u64 kernel_start)
{
struct thread_stack *ts = thread__stack(thread, cpu);
u64 context = callchain_context(ip, kernel_start);
u64 last_context;
size_t i, j;
if (sz < 2) {
chain->nr = 0;
return;
}
chain->ips[0] = context;
chain->ips[1] = ip;
if (!ts) {
chain->nr = 2;
return;
}
last_context = context;
for (i = 2, j = 1; i < sz && j <= ts->cnt; i++, j++) {
ip = ts->stack[ts->cnt - j].ret_addr;
context = callchain_context(ip, kernel_start);
if (context != last_context) {
if (i >= sz - 1)
break;
chain->ips[i++] = context;
last_context = context;
}
chain->ips[i] = ip;
}
chain->nr = i;
}
/*
* Hardware sample records, created some time after the event occurred, need to
* have subsequent addresses removed from the call chain.
*/
void thread_stack__sample_late(struct thread *thread, int cpu,
struct ip_callchain *chain, size_t sz,
u64 sample_ip, u64 kernel_start)
{
struct thread_stack *ts = thread__stack(thread, cpu);
u64 sample_context = callchain_context(sample_ip, kernel_start);
u64 last_context, context, ip;
size_t nr = 0, j;
if (sz < 2) {
chain->nr = 0;
return;
}
if (!ts)
goto out;
/*
* When tracing kernel space, kernel addresses occur at the top of the
* call chain after the event occurred but before tracing stopped.
* Skip them.
*/
for (j = 1; j <= ts->cnt; j++) {
ip = ts->stack[ts->cnt - j].ret_addr;
context = callchain_context(ip, kernel_start);
if (context == PERF_CONTEXT_USER ||
(context == sample_context && ip == sample_ip))
break;
}
last_context = sample_ip; /* Use sample_ip as an invalid context */
for (; nr < sz && j <= ts->cnt; nr++, j++) {
ip = ts->stack[ts->cnt - j].ret_addr;
context = callchain_context(ip, kernel_start);
if (context != last_context) {
if (nr >= sz - 1)
break;
chain->ips[nr++] = context;
last_context = context;
}
chain->ips[nr] = ip;
}
out:
if (nr) {
chain->nr = nr;
} else {
chain->ips[0] = sample_context;
chain->ips[1] = sample_ip;
chain->nr = 2;
}
}
void thread_stack__br_sample(struct thread *thread, int cpu,
struct branch_stack *dst, unsigned int sz)
{
struct thread_stack *ts = thread__stack(thread, cpu);
const size_t bsz = sizeof(struct branch_entry);
struct branch_stack *src;
struct branch_entry *be;
unsigned int nr;
dst->nr = 0;
if (!ts)
return;
src = ts->br_stack_rb;
if (!src->nr)
return;
dst->nr = min((unsigned int)src->nr, sz);
be = &dst->entries[0];
nr = min(ts->br_stack_sz - ts->br_stack_pos, (unsigned int)dst->nr);
memcpy(be, &src->entries[ts->br_stack_pos], bsz * nr);
if (src->nr >= ts->br_stack_sz) {
sz -= nr;
be = &dst->entries[nr];
nr = min(ts->br_stack_pos, sz);
memcpy(be, &src->entries[0], bsz * ts->br_stack_pos);
}
}
/* Start of user space branch entries */
static bool us_start(struct branch_entry *be, u64 kernel_start, bool *start)
{
if (!*start)
*start = be->to && be->to < kernel_start;
return *start;
}
/*
* Start of branch entries after the ip fell in between 2 branches, or user
* space branch entries.
*/
static bool ks_start(struct branch_entry *be, u64 sample_ip, u64 kernel_start,
bool *start, struct branch_entry *nb)
{
if (!*start) {
*start = (nb && sample_ip >= be->to && sample_ip <= nb->from) ||
be->from < kernel_start ||
(be->to && be->to < kernel_start);
}
return *start;
}
/*
* Hardware sample records, created some time after the event occurred, need to
* have subsequent addresses removed from the branch stack.
*/
void thread_stack__br_sample_late(struct thread *thread, int cpu,
struct branch_stack *dst, unsigned int sz,
u64 ip, u64 kernel_start)
{
struct thread_stack *ts = thread__stack(thread, cpu);
struct branch_entry *d, *s, *spos, *ssz;
struct branch_stack *src;
unsigned int nr = 0;
bool start = false;
dst->nr = 0;
if (!ts)
return;
src = ts->br_stack_rb;
if (!src->nr)
return;
spos = &src->entries[ts->br_stack_pos];
ssz = &src->entries[ts->br_stack_sz];
d = &dst->entries[0];
s = spos;
if (ip < kernel_start) {
/*
* User space sample: start copying branch entries when the
* branch is in user space.
*/
for (s = spos; s < ssz && nr < sz; s++) {
if (us_start(s, kernel_start, &start)) {
*d++ = *s;
nr += 1;
}
}
if (src->nr >= ts->br_stack_sz) {
for (s = &src->entries[0]; s < spos && nr < sz; s++) {
if (us_start(s, kernel_start, &start)) {
*d++ = *s;
nr += 1;
}
}
}
} else {
struct branch_entry *nb = NULL;
/*
* Kernel space sample: start copying branch entries when the ip
* falls in between 2 branches (or the branch is in user space
* because then the start must have been missed).
*/
for (s = spos; s < ssz && nr < sz; s++) {
if (ks_start(s, ip, kernel_start, &start, nb)) {
*d++ = *s;
nr += 1;
}
nb = s;
}
if (src->nr >= ts->br_stack_sz) {
for (s = &src->entries[0]; s < spos && nr < sz; s++) {
if (ks_start(s, ip, kernel_start, &start, nb)) {
*d++ = *s;
nr += 1;
}
nb = s;
}
}
}
dst->nr = nr;
}
struct call_return_processor *
call_return_processor__new(int (*process)(struct call_return *cr, u64 *parent_db_id, 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, bool trace_end)
{
struct thread_stack_entry *tse;
int err;
if (!cp)
return -ENOMEM;
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->insn_count = ts->insn_count;
tse->cyc_count = ts->cyc_count;
tse->cp = cp;
tse->no_call = no_call;
tse->trace_end = trace_end;
tse->non_call = false;
tse->db_id = 0;
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 &&
!ts->stack[ts->cnt - 1].non_call) {
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 ||
ts->stack[i].non_call)
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_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);
return thread_stack__push_cp(ts, ip, sample->time, ref, cp,
true, false);
}
static int thread_stack__pop_ks(struct thread *thread, struct thread_stack *ts,
struct perf_sample *sample, u64 ref)
{
u64 tm = sample->time;
int err;
/* Return to userspace, so pop all kernel addresses */
while (thread_stack__in_kernel(ts)) {
err = thread_stack__call_return(thread, ts, --ts->cnt,
tm, ref, true);
if (err)
return err;
}
return 0;
}
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 *root = &cpr->call_path;
struct symbol *fsym = from_al->sym;
struct symbol *tsym = to_al->sym;
struct call_path *cp, *parent;
u64 ks = ts->kernel_start;
u64 addr = sample->addr;
u64 tm = sample->time;
u64 ip = sample->ip;
int err;
if (ip >= ks && addr < ks) {
/* Return to userspace, so pop all kernel addresses */
err = thread_stack__pop_ks(thread, ts, sample, ref);
if (err)
return err;
/* If the stack is empty, push the userspace address */
if (!ts->cnt) {
cp = call_path__findnew(cpr, root, tsym, addr, ks);
return thread_stack__push_cp(ts, 0, tm, ref, cp, true,
false);
}
} else if (thread_stack__in_kernel(ts) && ip < ks) {
/* Return to userspace, so pop all kernel addresses */
err = thread_stack__pop_ks(thread, ts, sample, ref);
if (err)
return err;
}
if (ts->cnt)
parent = ts->stack[ts->cnt - 1].cp;
else
parent = root;
if (parent->sym == from_al->sym) {
/*
* At the bottom of the stack, assume the missing 'call' was
* before the trace started. So, pop the current symbol and push
* the 'to' symbol.
*/
if (ts->cnt == 1) {
err = thread_stack__call_return(thread, ts, --ts->cnt,
tm, ref, false);
if (err)
return err;
}
if (!ts->cnt) {
cp = call_path__findnew(cpr, root, tsym, addr, ks);
return thread_stack__push_cp(ts, addr, tm, ref, cp,
true, false);
}
/*
* Otherwise assume the 'return' is being used as a jump (e.g.
* retpoline) and just push the 'to' symbol.
*/
cp = call_path__findnew(cpr, parent, tsym, addr, ks);
err = thread_stack__push_cp(ts, 0, tm, ref, cp, true, false);
if (!err)
ts->stack[ts->cnt - 1].non_call = true;
return err;
}
/*
* Assume 'parent' has not yet returned, so push 'to', and then push and
* pop 'from'.
*/
cp = call_path__findnew(cpr, parent, tsym, addr, ks);
err = thread_stack__push_cp(ts, addr, tm, ref, cp, true, false);
if (err)
return err;
cp = call_path__findnew(cpr, cp, fsym, ip, ks);
err = thread_stack__push_cp(ts, ip, tm, ref, cp, true, false);
if (err)
return err;
return thread_stack__call_return(thread, ts, --ts->cnt, tm, ref, false);
}
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->trace_end) {
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);
ret_addr = sample->ip + sample->insn_len;
return thread_stack__push_cp(ts, ret_addr, sample->time, ref, cp,
false, true);
}
static bool is_x86_retpoline(const char *name)
{
return strstr(name, "__x86_indirect_thunk_") == name;
}
/*
* x86 retpoline functions pollute the call graph. This function removes them.
* This does not handle function return thunks, nor is there any improvement
* for the handling of inline thunks or extern thunks.
*/
static int thread_stack__x86_retpoline(struct thread_stack *ts,
struct perf_sample *sample,
struct addr_location *to_al)
{
struct thread_stack_entry *tse = &ts->stack[ts->cnt - 1];
struct call_path_root *cpr = ts->crp->cpr;
struct symbol *sym = tse->cp->sym;
struct symbol *tsym = to_al->sym;
struct call_path *cp;
if (sym && is_x86_retpoline(sym->name)) {
/*
* This is a x86 retpoline fn. It pollutes the call graph by
* showing up everywhere there is an indirect branch, but does
* not itself mean anything. Here the top-of-stack is removed,
* by decrementing the stack count, and then further down, the
* resulting top-of-stack is replaced with the actual target.
* The result is that the retpoline functions will no longer
* appear in the call graph. Note this only affects the call
* graph, since all the original branches are left unchanged.
*/
ts->cnt -= 1;
sym = ts->stack[ts->cnt - 2].cp->sym;
if (sym && sym == tsym && to_al->addr != tsym->start) {
/*
* Target is back to the middle of the symbol we came
* from so assume it is an indirect jmp and forget it
* altogether.
*/
ts->cnt -= 1;
return 0;
}
} else if (sym && sym == tsym) {
/*
* Target is back to the symbol we came from so assume it is an
* indirect jmp and forget it altogether.
*/
ts->cnt -= 1;
return 0;
}
cp = call_path__findnew(cpr, ts->stack[ts->cnt - 2].cp, tsym,
sample->addr, ts->kernel_start);
if (!cp)
return -ENOMEM;
/* Replace the top-of-stack with the actual target */
ts->stack[ts->cnt - 1].cp = cp;
return 0;
}
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__stack(thread, sample->cpu);
enum retpoline_state_t rstate;
int err = 0;
if (ts && !ts->crp) {
/* Supersede thread_stack__event() */
thread_stack__reset(thread, ts);
ts = NULL;
}
if (!ts) {
ts = thread_stack__new(thread, sample->cpu, crp, true, 0);
if (!ts)
return -ENOMEM;
ts->comm = comm;
}
rstate = ts->rstate;
if (rstate == X86_RETPOLINE_DETECTED)
ts->rstate = X86_RETPOLINE_POSSIBLE;
/* Flush stack on exec */
if (ts->comm != comm && thread__pid(thread) == thread__tid(thread)) {
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(ts, sample, from_al, to_al, ref);
if (err)
return err;
}
ts->branch_count += 1;
ts->insn_count += sample->insn_cnt;
ts->cyc_count += sample->cyc_cnt;
ts->last_time = sample->time;
if (sample->flags & PERF_IP_FLAG_CALL) {
bool trace_end = sample->flags & PERF_IP_FLAG_TRACE_END;
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);
err = thread_stack__push_cp(ts, ret_addr, sample->time, ref,
cp, false, trace_end);
/*
* A call to the same symbol but not the start of the symbol,
* may be the start of a x86 retpoline.
*/
if (!err && rstate == X86_RETPOLINE_POSSIBLE && to_al->sym &&
from_al->sym == to_al->sym &&
to_al->addr != to_al->sym->start)
ts->rstate = X86_RETPOLINE_DETECTED;
} else if (sample->flags & PERF_IP_FLAG_RETURN) {
if (!sample->addr) {
u32 return_from_kernel = PERF_IP_FLAG_SYSCALLRET |
PERF_IP_FLAG_INTERRUPT;
if (!(sample->flags & return_from_kernel))
return 0;
/* Pop kernel stack */
return thread_stack__pop_ks(thread, ts, sample, ref);
}
if (!sample->ip)
return 0;
/* x86 retpoline 'return' doesn't match the stack */
if (rstate == X86_RETPOLINE_DETECTED && ts->cnt > 2 &&
ts->stack[ts->cnt - 1].ret_addr != sample->addr)
return thread_stack__x86_retpoline(ts, sample, to_al);
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);
} else if (sample->flags & PERF_IP_FLAG_BRANCH &&
from_al->sym != to_al->sym && to_al->sym &&
to_al->addr == to_al->sym->start) {
struct call_path_root *cpr = ts->crp->cpr;
struct call_path *cp;
/*
* The compiler might optimize a call/ret combination by making
* it a jmp. Make that visible by recording on the stack a
* branch to the start of a different symbol. Note, that means
* when a ret pops the stack, all jmps must be popped off first.
*/
cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp,
to_al->sym, sample->addr,
ts->kernel_start);
err = thread_stack__push_cp(ts, 0, sample->time, ref, cp, false,
false);
if (!err)
ts->stack[ts->cnt - 1].non_call = true;
}
return err;
}
size_t thread_stack__depth(struct thread *thread, int cpu)
{
struct thread_stack *ts = thread__stack(thread, cpu);
if (!ts)
return 0;
return ts->cnt;
}
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