forked from mirrors/linux
1dcaa3b462
Context tracking's __ct_state() function can be invoked from noinstr state where RCU is not watching. This means that its use of atomic_read() causes KASAN to invoke the non-noinstr __kasan_check_read() function from the noinstr function __ct_state(). This is problematic because someone tracing the __kasan_check_read() function could get a nasty surprise because of RCU not watching. This commit therefore replaces the __ct_state() function's use of atomic_read() with arch_atomic_read(), which KASAN does not attempt to add instrumention to. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Marco Elver <elver@google.com> Reviewed-by: Marco Elver <elver@google.com>
146 lines
3.8 KiB
C
146 lines
3.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_CONTEXT_TRACKING_STATE_H
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#define _LINUX_CONTEXT_TRACKING_STATE_H
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#include <linux/percpu.h>
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#include <linux/static_key.h>
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#include <linux/context_tracking_irq.h>
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/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
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#define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
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enum ctx_state {
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CONTEXT_DISABLED = -1, /* returned by ct_state() if unknown */
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CONTEXT_KERNEL = 0,
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CONTEXT_IDLE = 1,
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CONTEXT_USER = 2,
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CONTEXT_GUEST = 3,
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CONTEXT_MAX = 4,
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};
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/* Even value for idle, else odd. */
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#define RCU_DYNTICKS_IDX CONTEXT_MAX
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#define CT_STATE_MASK (CONTEXT_MAX - 1)
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#define CT_DYNTICKS_MASK (~CT_STATE_MASK)
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struct context_tracking {
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#ifdef CONFIG_CONTEXT_TRACKING_USER
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/*
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* When active is false, probes are unset in order
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* to minimize overhead: TIF flags are cleared
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* and calls to user_enter/exit are ignored. This
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* may be further optimized using static keys.
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*/
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bool active;
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int recursion;
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#endif
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#ifdef CONFIG_CONTEXT_TRACKING
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atomic_t state;
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#endif
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#ifdef CONFIG_CONTEXT_TRACKING_IDLE
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long dynticks_nesting; /* Track process nesting level. */
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long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
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#endif
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};
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#ifdef CONFIG_CONTEXT_TRACKING
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DECLARE_PER_CPU(struct context_tracking, context_tracking);
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static __always_inline int __ct_state(void)
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{
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return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
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}
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#endif
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#ifdef CONFIG_CONTEXT_TRACKING_IDLE
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static __always_inline int ct_dynticks(void)
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{
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return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_DYNTICKS_MASK;
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}
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static __always_inline int ct_dynticks_cpu(int cpu)
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{
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struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
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return atomic_read(&ct->state) & CT_DYNTICKS_MASK;
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}
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static __always_inline int ct_dynticks_cpu_acquire(int cpu)
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{
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struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
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return atomic_read_acquire(&ct->state) & CT_DYNTICKS_MASK;
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}
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static __always_inline long ct_dynticks_nesting(void)
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{
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return __this_cpu_read(context_tracking.dynticks_nesting);
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}
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static __always_inline long ct_dynticks_nesting_cpu(int cpu)
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{
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struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
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return ct->dynticks_nesting;
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}
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static __always_inline long ct_dynticks_nmi_nesting(void)
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{
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return __this_cpu_read(context_tracking.dynticks_nmi_nesting);
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}
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static __always_inline long ct_dynticks_nmi_nesting_cpu(int cpu)
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{
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struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
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return ct->dynticks_nmi_nesting;
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}
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#endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
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#ifdef CONFIG_CONTEXT_TRACKING_USER
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extern struct static_key_false context_tracking_key;
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static __always_inline bool context_tracking_enabled(void)
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{
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return static_branch_unlikely(&context_tracking_key);
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}
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static __always_inline bool context_tracking_enabled_cpu(int cpu)
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{
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return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
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}
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static inline bool context_tracking_enabled_this_cpu(void)
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{
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return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
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}
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/**
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* ct_state() - return the current context tracking state if known
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*
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* Returns the current cpu's context tracking state if context tracking
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* is enabled. If context tracking is disabled, returns
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* CONTEXT_DISABLED. This should be used primarily for debugging.
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*/
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static __always_inline int ct_state(void)
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{
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int ret;
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if (!context_tracking_enabled())
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return CONTEXT_DISABLED;
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preempt_disable();
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ret = __ct_state();
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preempt_enable();
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return ret;
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}
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#else
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static __always_inline bool context_tracking_enabled(void) { return false; }
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static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; }
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static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; }
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#endif /* CONFIG_CONTEXT_TRACKING_USER */
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#endif
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