![Steven Rostedt (VMware)](/assets/img/avatar_default.png)
In order to handle direct calls along side of function graph tracer, a check
is made to see if the address being traced by the function graph tracer is a
direct call or not. To get the address used by direct callers, the return
address is subtracted by MCOUNT_INSN_SIZE.
For some archs with certain configurations, MCOUNT_INSN_SIZE is undefined
here. But these should not be using direct calls anyway. Just define
MCOUNT_INSN_SIZE to zero in this case.
Link: https://lore.kernel.org/r/202001020219.zvE3vsty%lkp@intel.com
Reported-by: kbuild test robot <lkp@intel.com>
Fixes: ff205766db
("ftrace: Fix function_graph tracer interaction with BPF trampoline")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
655 lines
17 KiB
C
655 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Infrastructure to took into function calls and returns.
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* Copyright (c) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
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* Mostly borrowed from function tracer which
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* is Copyright (c) Steven Rostedt <srostedt@redhat.com>
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*
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* Highly modified by Steven Rostedt (VMware).
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*/
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#include <linux/suspend.h>
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#include <linux/ftrace.h>
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#include <linux/slab.h>
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#include <trace/events/sched.h>
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#include "ftrace_internal.h"
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#ifdef CONFIG_DYNAMIC_FTRACE
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#define ASSIGN_OPS_HASH(opsname, val) \
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.func_hash = val, \
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.local_hash.regex_lock = __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
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#else
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#define ASSIGN_OPS_HASH(opsname, val)
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#endif
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static bool kill_ftrace_graph;
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int ftrace_graph_active;
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/* Both enabled by default (can be cleared by function_graph tracer flags */
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static bool fgraph_sleep_time = true;
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/**
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* ftrace_graph_is_dead - returns true if ftrace_graph_stop() was called
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*
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* ftrace_graph_stop() is called when a severe error is detected in
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* the function graph tracing. This function is called by the critical
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* paths of function graph to keep those paths from doing any more harm.
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*/
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bool ftrace_graph_is_dead(void)
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{
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return kill_ftrace_graph;
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}
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/**
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* ftrace_graph_stop - set to permanently disable function graph tracincg
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*
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* In case of an error int function graph tracing, this is called
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* to try to keep function graph tracing from causing any more harm.
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* Usually this is pretty severe and this is called to try to at least
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* get a warning out to the user.
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*/
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void ftrace_graph_stop(void)
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{
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kill_ftrace_graph = true;
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}
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/* Add a function return address to the trace stack on thread info.*/
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static int
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ftrace_push_return_trace(unsigned long ret, unsigned long func,
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unsigned long frame_pointer, unsigned long *retp)
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{
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unsigned long long calltime;
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int index;
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if (unlikely(ftrace_graph_is_dead()))
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return -EBUSY;
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if (!current->ret_stack)
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return -EBUSY;
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/*
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* We must make sure the ret_stack is tested before we read
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* anything else.
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*/
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smp_rmb();
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/* The return trace stack is full */
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if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
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atomic_inc(¤t->trace_overrun);
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return -EBUSY;
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}
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calltime = trace_clock_local();
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index = ++current->curr_ret_stack;
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barrier();
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current->ret_stack[index].ret = ret;
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current->ret_stack[index].func = func;
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current->ret_stack[index].calltime = calltime;
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#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
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current->ret_stack[index].fp = frame_pointer;
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#endif
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#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
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current->ret_stack[index].retp = retp;
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#endif
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return 0;
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}
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/*
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* Not all archs define MCOUNT_INSN_SIZE which is used to look for direct
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* functions. But those archs currently don't support direct functions
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* anyway, and ftrace_find_rec_direct() is just a stub for them.
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* Define MCOUNT_INSN_SIZE to keep those archs compiling.
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*/
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#ifndef MCOUNT_INSN_SIZE
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/* Make sure this only works without direct calls */
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# ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
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# error MCOUNT_INSN_SIZE not defined with direct calls enabled
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# endif
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# define MCOUNT_INSN_SIZE 0
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#endif
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int function_graph_enter(unsigned long ret, unsigned long func,
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unsigned long frame_pointer, unsigned long *retp)
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{
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struct ftrace_graph_ent trace;
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/*
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* Skip graph tracing if the return location is served by direct trampoline,
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* since call sequence and return addresses is unpredicatable anymore.
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* Ex: BPF trampoline may call original function and may skip frame
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* depending on type of BPF programs attached.
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*/
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if (ftrace_direct_func_count &&
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ftrace_find_rec_direct(ret - MCOUNT_INSN_SIZE))
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return -EBUSY;
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trace.func = func;
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trace.depth = ++current->curr_ret_depth;
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if (ftrace_push_return_trace(ret, func, frame_pointer, retp))
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goto out;
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/* Only trace if the calling function expects to */
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if (!ftrace_graph_entry(&trace))
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goto out_ret;
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return 0;
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out_ret:
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current->curr_ret_stack--;
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out:
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current->curr_ret_depth--;
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return -EBUSY;
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}
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/* Retrieve a function return address to the trace stack on thread info.*/
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static void
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ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
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unsigned long frame_pointer)
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{
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int index;
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index = current->curr_ret_stack;
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if (unlikely(index < 0 || index >= FTRACE_RETFUNC_DEPTH)) {
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ftrace_graph_stop();
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WARN_ON(1);
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/* Might as well panic, otherwise we have no where to go */
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*ret = (unsigned long)panic;
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return;
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}
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#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
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/*
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* The arch may choose to record the frame pointer used
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* and check it here to make sure that it is what we expect it
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* to be. If gcc does not set the place holder of the return
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* address in the frame pointer, and does a copy instead, then
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* the function graph trace will fail. This test detects this
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* case.
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*
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* Currently, x86_32 with optimize for size (-Os) makes the latest
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* gcc do the above.
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*
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* Note, -mfentry does not use frame pointers, and this test
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* is not needed if CC_USING_FENTRY is set.
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*/
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if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
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ftrace_graph_stop();
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WARN(1, "Bad frame pointer: expected %lx, received %lx\n"
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" from func %ps return to %lx\n",
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current->ret_stack[index].fp,
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frame_pointer,
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(void *)current->ret_stack[index].func,
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current->ret_stack[index].ret);
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*ret = (unsigned long)panic;
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return;
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}
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#endif
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*ret = current->ret_stack[index].ret;
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trace->func = current->ret_stack[index].func;
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trace->calltime = current->ret_stack[index].calltime;
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trace->overrun = atomic_read(¤t->trace_overrun);
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trace->depth = current->curr_ret_depth--;
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/*
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* We still want to trace interrupts coming in if
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* max_depth is set to 1. Make sure the decrement is
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* seen before ftrace_graph_return.
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*/
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barrier();
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}
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/*
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* Hibernation protection.
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* The state of the current task is too much unstable during
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* suspend/restore to disk. We want to protect against that.
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*/
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static int
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ftrace_suspend_notifier_call(struct notifier_block *bl, unsigned long state,
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void *unused)
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{
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switch (state) {
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case PM_HIBERNATION_PREPARE:
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pause_graph_tracing();
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break;
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case PM_POST_HIBERNATION:
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unpause_graph_tracing();
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break;
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}
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return NOTIFY_DONE;
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}
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static struct notifier_block ftrace_suspend_notifier = {
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.notifier_call = ftrace_suspend_notifier_call,
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};
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/*
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* Send the trace to the ring-buffer.
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* @return the original return address.
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*/
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unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
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{
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struct ftrace_graph_ret trace;
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unsigned long ret;
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ftrace_pop_return_trace(&trace, &ret, frame_pointer);
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trace.rettime = trace_clock_local();
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ftrace_graph_return(&trace);
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/*
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* The ftrace_graph_return() may still access the current
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* ret_stack structure, we need to make sure the update of
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* curr_ret_stack is after that.
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*/
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barrier();
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current->curr_ret_stack--;
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if (unlikely(!ret)) {
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ftrace_graph_stop();
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WARN_ON(1);
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/* Might as well panic. What else to do? */
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ret = (unsigned long)panic;
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}
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return ret;
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}
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/**
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* ftrace_graph_get_ret_stack - return the entry of the shadow stack
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* @task: The task to read the shadow stack from
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* @idx: Index down the shadow stack
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*
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* Return the ret_struct on the shadow stack of the @task at the
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* call graph at @idx starting with zero. If @idx is zero, it
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* will return the last saved ret_stack entry. If it is greater than
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* zero, it will return the corresponding ret_stack for the depth
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* of saved return addresses.
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*/
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struct ftrace_ret_stack *
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ftrace_graph_get_ret_stack(struct task_struct *task, int idx)
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{
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idx = task->curr_ret_stack - idx;
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if (idx >= 0 && idx <= task->curr_ret_stack)
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return &task->ret_stack[idx];
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return NULL;
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}
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/**
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* ftrace_graph_ret_addr - convert a potentially modified stack return address
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* to its original value
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*
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* This function can be called by stack unwinding code to convert a found stack
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* return address ('ret') to its original value, in case the function graph
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* tracer has modified it to be 'return_to_handler'. If the address hasn't
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* been modified, the unchanged value of 'ret' is returned.
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*
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* 'idx' is a state variable which should be initialized by the caller to zero
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* before the first call.
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*
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* 'retp' is a pointer to the return address on the stack. It's ignored if
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* the arch doesn't have HAVE_FUNCTION_GRAPH_RET_ADDR_PTR defined.
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*/
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#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
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unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
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unsigned long ret, unsigned long *retp)
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{
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int index = task->curr_ret_stack;
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int i;
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if (ret != (unsigned long)dereference_kernel_function_descriptor(return_to_handler))
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return ret;
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if (index < 0)
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return ret;
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for (i = 0; i <= index; i++)
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if (task->ret_stack[i].retp == retp)
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return task->ret_stack[i].ret;
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return ret;
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}
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#else /* !HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
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unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
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unsigned long ret, unsigned long *retp)
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{
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int task_idx;
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if (ret != (unsigned long)dereference_kernel_function_descriptor(return_to_handler))
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return ret;
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task_idx = task->curr_ret_stack;
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if (!task->ret_stack || task_idx < *idx)
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return ret;
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task_idx -= *idx;
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(*idx)++;
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return task->ret_stack[task_idx].ret;
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}
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#endif /* HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
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static struct ftrace_ops graph_ops = {
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.func = ftrace_stub,
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.flags = FTRACE_OPS_FL_RECURSION_SAFE |
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FTRACE_OPS_FL_INITIALIZED |
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FTRACE_OPS_FL_PID |
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FTRACE_OPS_FL_STUB,
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#ifdef FTRACE_GRAPH_TRAMP_ADDR
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.trampoline = FTRACE_GRAPH_TRAMP_ADDR,
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/* trampoline_size is only needed for dynamically allocated tramps */
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#endif
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ASSIGN_OPS_HASH(graph_ops, &global_ops.local_hash)
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};
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void ftrace_graph_sleep_time_control(bool enable)
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{
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fgraph_sleep_time = enable;
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}
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int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace)
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{
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return 0;
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}
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/*
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* Simply points to ftrace_stub, but with the proper protocol.
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* Defined by the linker script in linux/vmlinux.lds.h
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*/
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extern void ftrace_stub_graph(struct ftrace_graph_ret *);
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/* The callbacks that hook a function */
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trace_func_graph_ret_t ftrace_graph_return = ftrace_stub_graph;
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trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub;
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static trace_func_graph_ent_t __ftrace_graph_entry = ftrace_graph_entry_stub;
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/* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */
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static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
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{
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int i;
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int ret = 0;
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int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE;
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struct task_struct *g, *t;
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for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) {
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ret_stack_list[i] =
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kmalloc_array(FTRACE_RETFUNC_DEPTH,
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sizeof(struct ftrace_ret_stack),
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GFP_KERNEL);
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if (!ret_stack_list[i]) {
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start = 0;
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end = i;
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ret = -ENOMEM;
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goto free;
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}
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}
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read_lock(&tasklist_lock);
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do_each_thread(g, t) {
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if (start == end) {
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ret = -EAGAIN;
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goto unlock;
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}
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if (t->ret_stack == NULL) {
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atomic_set(&t->tracing_graph_pause, 0);
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atomic_set(&t->trace_overrun, 0);
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t->curr_ret_stack = -1;
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t->curr_ret_depth = -1;
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/* Make sure the tasks see the -1 first: */
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smp_wmb();
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t->ret_stack = ret_stack_list[start++];
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}
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} while_each_thread(g, t);
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unlock:
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read_unlock(&tasklist_lock);
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free:
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for (i = start; i < end; i++)
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kfree(ret_stack_list[i]);
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return ret;
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}
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static void
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ftrace_graph_probe_sched_switch(void *ignore, bool preempt,
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struct task_struct *prev, struct task_struct *next)
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{
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unsigned long long timestamp;
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int index;
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/*
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* Does the user want to count the time a function was asleep.
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* If so, do not update the time stamps.
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*/
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if (fgraph_sleep_time)
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return;
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timestamp = trace_clock_local();
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prev->ftrace_timestamp = timestamp;
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/* only process tasks that we timestamped */
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if (!next->ftrace_timestamp)
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return;
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/*
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* Update all the counters in next to make up for the
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* time next was sleeping.
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*/
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timestamp -= next->ftrace_timestamp;
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for (index = next->curr_ret_stack; index >= 0; index--)
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next->ret_stack[index].calltime += timestamp;
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}
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static int ftrace_graph_entry_test(struct ftrace_graph_ent *trace)
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{
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if (!ftrace_ops_test(&global_ops, trace->func, NULL))
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return 0;
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return __ftrace_graph_entry(trace);
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}
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/*
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* The function graph tracer should only trace the functions defined
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* by set_ftrace_filter and set_ftrace_notrace. If another function
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* tracer ops is registered, the graph tracer requires testing the
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* function against the global ops, and not just trace any function
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* that any ftrace_ops registered.
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*/
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void update_function_graph_func(void)
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{
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struct ftrace_ops *op;
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bool do_test = false;
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/*
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* The graph and global ops share the same set of functions
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* to test. If any other ops is on the list, then
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* the graph tracing needs to test if its the function
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* it should call.
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*/
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do_for_each_ftrace_op(op, ftrace_ops_list) {
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if (op != &global_ops && op != &graph_ops &&
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op != &ftrace_list_end) {
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do_test = true;
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/* in double loop, break out with goto */
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goto out;
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}
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} while_for_each_ftrace_op(op);
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out:
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if (do_test)
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ftrace_graph_entry = ftrace_graph_entry_test;
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else
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ftrace_graph_entry = __ftrace_graph_entry;
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}
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static DEFINE_PER_CPU(struct ftrace_ret_stack *, idle_ret_stack);
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static void
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graph_init_task(struct task_struct *t, struct ftrace_ret_stack *ret_stack)
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{
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atomic_set(&t->tracing_graph_pause, 0);
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atomic_set(&t->trace_overrun, 0);
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t->ftrace_timestamp = 0;
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/* make curr_ret_stack visible before we add the ret_stack */
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smp_wmb();
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t->ret_stack = ret_stack;
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}
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/*
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* Allocate a return stack for the idle task. May be the first
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* time through, or it may be done by CPU hotplug online.
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*/
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void ftrace_graph_init_idle_task(struct task_struct *t, int cpu)
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{
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t->curr_ret_stack = -1;
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t->curr_ret_depth = -1;
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/*
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* The idle task has no parent, it either has its own
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* stack or no stack at all.
|
|
*/
|
|
if (t->ret_stack)
|
|
WARN_ON(t->ret_stack != per_cpu(idle_ret_stack, cpu));
|
|
|
|
if (ftrace_graph_active) {
|
|
struct ftrace_ret_stack *ret_stack;
|
|
|
|
ret_stack = per_cpu(idle_ret_stack, cpu);
|
|
if (!ret_stack) {
|
|
ret_stack =
|
|
kmalloc_array(FTRACE_RETFUNC_DEPTH,
|
|
sizeof(struct ftrace_ret_stack),
|
|
GFP_KERNEL);
|
|
if (!ret_stack)
|
|
return;
|
|
per_cpu(idle_ret_stack, cpu) = ret_stack;
|
|
}
|
|
graph_init_task(t, ret_stack);
|
|
}
|
|
}
|
|
|
|
/* Allocate a return stack for newly created task */
|
|
void ftrace_graph_init_task(struct task_struct *t)
|
|
{
|
|
/* Make sure we do not use the parent ret_stack */
|
|
t->ret_stack = NULL;
|
|
t->curr_ret_stack = -1;
|
|
t->curr_ret_depth = -1;
|
|
|
|
if (ftrace_graph_active) {
|
|
struct ftrace_ret_stack *ret_stack;
|
|
|
|
ret_stack = kmalloc_array(FTRACE_RETFUNC_DEPTH,
|
|
sizeof(struct ftrace_ret_stack),
|
|
GFP_KERNEL);
|
|
if (!ret_stack)
|
|
return;
|
|
graph_init_task(t, ret_stack);
|
|
}
|
|
}
|
|
|
|
void ftrace_graph_exit_task(struct task_struct *t)
|
|
{
|
|
struct ftrace_ret_stack *ret_stack = t->ret_stack;
|
|
|
|
t->ret_stack = NULL;
|
|
/* NULL must become visible to IRQs before we free it: */
|
|
barrier();
|
|
|
|
kfree(ret_stack);
|
|
}
|
|
|
|
/* Allocate a return stack for each task */
|
|
static int start_graph_tracing(void)
|
|
{
|
|
struct ftrace_ret_stack **ret_stack_list;
|
|
int ret, cpu;
|
|
|
|
ret_stack_list = kmalloc_array(FTRACE_RETSTACK_ALLOC_SIZE,
|
|
sizeof(struct ftrace_ret_stack *),
|
|
GFP_KERNEL);
|
|
|
|
if (!ret_stack_list)
|
|
return -ENOMEM;
|
|
|
|
/* The cpu_boot init_task->ret_stack will never be freed */
|
|
for_each_online_cpu(cpu) {
|
|
if (!idle_task(cpu)->ret_stack)
|
|
ftrace_graph_init_idle_task(idle_task(cpu), cpu);
|
|
}
|
|
|
|
do {
|
|
ret = alloc_retstack_tasklist(ret_stack_list);
|
|
} while (ret == -EAGAIN);
|
|
|
|
if (!ret) {
|
|
ret = register_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
|
|
if (ret)
|
|
pr_info("ftrace_graph: Couldn't activate tracepoint"
|
|
" probe to kernel_sched_switch\n");
|
|
}
|
|
|
|
kfree(ret_stack_list);
|
|
return ret;
|
|
}
|
|
|
|
int register_ftrace_graph(struct fgraph_ops *gops)
|
|
{
|
|
int ret = 0;
|
|
|
|
mutex_lock(&ftrace_lock);
|
|
|
|
/* we currently allow only one tracer registered at a time */
|
|
if (ftrace_graph_active) {
|
|
ret = -EBUSY;
|
|
goto out;
|
|
}
|
|
|
|
register_pm_notifier(&ftrace_suspend_notifier);
|
|
|
|
ftrace_graph_active++;
|
|
ret = start_graph_tracing();
|
|
if (ret) {
|
|
ftrace_graph_active--;
|
|
goto out;
|
|
}
|
|
|
|
ftrace_graph_return = gops->retfunc;
|
|
|
|
/*
|
|
* Update the indirect function to the entryfunc, and the
|
|
* function that gets called to the entry_test first. Then
|
|
* call the update fgraph entry function to determine if
|
|
* the entryfunc should be called directly or not.
|
|
*/
|
|
__ftrace_graph_entry = gops->entryfunc;
|
|
ftrace_graph_entry = ftrace_graph_entry_test;
|
|
update_function_graph_func();
|
|
|
|
ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET);
|
|
out:
|
|
mutex_unlock(&ftrace_lock);
|
|
return ret;
|
|
}
|
|
|
|
void unregister_ftrace_graph(struct fgraph_ops *gops)
|
|
{
|
|
mutex_lock(&ftrace_lock);
|
|
|
|
if (unlikely(!ftrace_graph_active))
|
|
goto out;
|
|
|
|
ftrace_graph_active--;
|
|
ftrace_graph_return = ftrace_stub_graph;
|
|
ftrace_graph_entry = ftrace_graph_entry_stub;
|
|
__ftrace_graph_entry = ftrace_graph_entry_stub;
|
|
ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET);
|
|
unregister_pm_notifier(&ftrace_suspend_notifier);
|
|
unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
|
|
|
|
out:
|
|
mutex_unlock(&ftrace_lock);
|
|
}
|