android-kvm / linux / 0a30896fc5025e71c350449760b240fba5581b42 / . / include / linux / trace_recursion.h

/* SPDX-License-Identifier: GPL-2.0 */ | |

#ifndef _LINUX_TRACE_RECURSION_H | |

#define _LINUX_TRACE_RECURSION_H | |

#include <linux/interrupt.h> | |

#include <linux/sched.h> | |

#ifdef CONFIG_TRACING | |

/* Only current can touch trace_recursion */ | |

/* | |

* For function tracing recursion: | |

* The order of these bits are important. | |

* | |

* When function tracing occurs, the following steps are made: | |

* If arch does not support a ftrace feature: | |

* call internal function (uses INTERNAL bits) which calls... | |

* If callback is registered to the "global" list, the list | |

* function is called and recursion checks the GLOBAL bits. | |

* then this function calls... | |

* The function callback, which can use the FTRACE bits to | |

* check for recursion. | |

* | |

* Now if the arch does not support a feature, and it calls | |

* the global list function which calls the ftrace callback | |

* all three of these steps will do a recursion protection. | |

* There's no reason to do one if the previous caller already | |

* did. The recursion that we are protecting against will | |

* go through the same steps again. | |

* | |

* To prevent the multiple recursion checks, if a recursion | |

* bit is set that is higher than the MAX bit of the current | |

* check, then we know that the check was made by the previous | |

* caller, and we can skip the current check. | |

*/ | |

enum { | |

/* Function recursion bits */ | |

TRACE_FTRACE_BIT, | |

TRACE_FTRACE_NMI_BIT, | |

TRACE_FTRACE_IRQ_BIT, | |

TRACE_FTRACE_SIRQ_BIT, | |

/* INTERNAL_BITs must be greater than FTRACE_BITs */ | |

TRACE_INTERNAL_BIT, | |

TRACE_INTERNAL_NMI_BIT, | |

TRACE_INTERNAL_IRQ_BIT, | |

TRACE_INTERNAL_SIRQ_BIT, | |

TRACE_BRANCH_BIT, | |

/* | |

* Abuse of the trace_recursion. | |

* As we need a way to maintain state if we are tracing the function | |

* graph in irq because we want to trace a particular function that | |

* was called in irq context but we have irq tracing off. Since this | |

* can only be modified by current, we can reuse trace_recursion. | |

*/ | |

TRACE_IRQ_BIT, | |

/* Set if the function is in the set_graph_function file */ | |

TRACE_GRAPH_BIT, | |

/* | |

* In the very unlikely case that an interrupt came in | |

* at a start of graph tracing, and we want to trace | |

* the function in that interrupt, the depth can be greater | |

* than zero, because of the preempted start of a previous | |

* trace. In an even more unlikely case, depth could be 2 | |

* if a softirq interrupted the start of graph tracing, | |

* followed by an interrupt preempting a start of graph | |

* tracing in the softirq, and depth can even be 3 | |

* if an NMI came in at the start of an interrupt function | |

* that preempted a softirq start of a function that | |

* preempted normal context!!!! Luckily, it can't be | |

* greater than 3, so the next two bits are a mask | |

* of what the depth is when we set TRACE_GRAPH_BIT | |

*/ | |

TRACE_GRAPH_DEPTH_START_BIT, | |

TRACE_GRAPH_DEPTH_END_BIT, | |

/* | |

* To implement set_graph_notrace, if this bit is set, we ignore | |

* function graph tracing of called functions, until the return | |

* function is called to clear it. | |

*/ | |

TRACE_GRAPH_NOTRACE_BIT, | |

/* | |

* When transitioning between context, the preempt_count() may | |

* not be correct. Allow for a single recursion to cover this case. | |

*/ | |

TRACE_TRANSITION_BIT, | |

/* Used to prevent recursion recording from recursing. */ | |

TRACE_RECORD_RECURSION_BIT, | |

}; | |

#define trace_recursion_set(bit) do { (current)->trace_recursion |= (1<<(bit)); } while (0) | |

#define trace_recursion_clear(bit) do { (current)->trace_recursion &= ~(1<<(bit)); } while (0) | |

#define trace_recursion_test(bit) ((current)->trace_recursion & (1<<(bit))) | |

#define trace_recursion_depth() \ | |

(((current)->trace_recursion >> TRACE_GRAPH_DEPTH_START_BIT) & 3) | |

#define trace_recursion_set_depth(depth) \ | |

do { \ | |

current->trace_recursion &= \ | |

~(3 << TRACE_GRAPH_DEPTH_START_BIT); \ | |

current->trace_recursion |= \ | |

((depth) & 3) << TRACE_GRAPH_DEPTH_START_BIT; \ | |

} while (0) | |

#define TRACE_CONTEXT_BITS 4 | |

#define TRACE_FTRACE_START TRACE_FTRACE_BIT | |

#define TRACE_FTRACE_MAX ((1 << (TRACE_FTRACE_START + TRACE_CONTEXT_BITS)) - 1) | |

#define TRACE_LIST_START TRACE_INTERNAL_BIT | |

#define TRACE_LIST_MAX ((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1) | |

#define TRACE_CONTEXT_MASK TRACE_LIST_MAX | |

/* | |

* Used for setting context | |

* NMI = 0 | |

* IRQ = 1 | |

* SOFTIRQ = 2 | |

* NORMAL = 3 | |

*/ | |

enum { | |

TRACE_CTX_NMI, | |

TRACE_CTX_IRQ, | |

TRACE_CTX_SOFTIRQ, | |

TRACE_CTX_NORMAL, | |

}; | |

static __always_inline int trace_get_context_bit(void) | |

{ | |

unsigned long pc = preempt_count(); | |

if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) | |

return TRACE_CTX_NORMAL; | |

else | |

return pc & NMI_MASK ? TRACE_CTX_NMI : | |

pc & HARDIRQ_MASK ? TRACE_CTX_IRQ : TRACE_CTX_SOFTIRQ; | |

} | |

#ifdef CONFIG_FTRACE_RECORD_RECURSION | |

extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip); | |

# define do_ftrace_record_recursion(ip, pip) \ | |

do { \ | |

if (!trace_recursion_test(TRACE_RECORD_RECURSION_BIT)) { \ | |

trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \ | |

ftrace_record_recursion(ip, pip); \ | |

trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \ | |

} \ | |

} while (0) | |

#else | |

# define do_ftrace_record_recursion(ip, pip) do { } while (0) | |

#endif | |

static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip, | |

int start, int max) | |

{ | |

unsigned int val = READ_ONCE(current->trace_recursion); | |

int bit; | |

/* A previous recursion check was made */ | |

if ((val & TRACE_CONTEXT_MASK) > max) | |

return 0; | |

bit = trace_get_context_bit() + start; | |

if (unlikely(val & (1 << bit))) { | |

/* | |

* It could be that preempt_count has not been updated during | |

* a switch between contexts. Allow for a single recursion. | |

*/ | |

bit = TRACE_TRANSITION_BIT; | |

if (val & (1 << bit)) { | |

do_ftrace_record_recursion(ip, pip); | |

return -1; | |

} | |

} else { | |

/* Normal check passed, clear the transition to allow it again */ | |

val &= ~(1 << TRACE_TRANSITION_BIT); | |

} | |

val |= 1 << bit; | |

current->trace_recursion = val; | |

barrier(); | |

return bit + 1; | |

} | |

static __always_inline void trace_clear_recursion(int bit) | |

{ | |

if (!bit) | |

return; | |

barrier(); | |

bit--; | |

trace_recursion_clear(bit); | |

} | |

/** | |

* ftrace_test_recursion_trylock - tests for recursion in same context | |

* | |

* Use this for ftrace callbacks. This will detect if the function | |

* tracing recursed in the same context (normal vs interrupt), | |

* | |

* Returns: -1 if a recursion happened. | |

* >= 0 if no recursion | |

*/ | |

static __always_inline int ftrace_test_recursion_trylock(unsigned long ip, | |

unsigned long parent_ip) | |

{ | |

return trace_test_and_set_recursion(ip, parent_ip, TRACE_FTRACE_START, TRACE_FTRACE_MAX); | |

} | |

/** | |

* ftrace_test_recursion_unlock - called when function callback is complete | |

* @bit: The return of a successful ftrace_test_recursion_trylock() | |

* | |

* This is used at the end of a ftrace callback. | |

*/ | |

static __always_inline void ftrace_test_recursion_unlock(int bit) | |

{ | |

trace_clear_recursion(bit); | |

} | |

#endif /* CONFIG_TRACING */ | |

#endif /* _LINUX_TRACE_RECURSION_H */ |