cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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preempt.h (4189B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2#ifndef __ASM_PREEMPT_H
      3#define __ASM_PREEMPT_H
      4
      5#include <asm/rmwcc.h>
      6#include <asm/percpu.h>
      7#include <linux/thread_info.h>
      8#include <linux/static_call_types.h>
      9
     10DECLARE_PER_CPU(int, __preempt_count);
     11
     12/* We use the MSB mostly because its available */
     13#define PREEMPT_NEED_RESCHED	0x80000000
     14
     15/*
     16 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
     17 * that a decrement hitting 0 means we can and should reschedule.
     18 */
     19#define PREEMPT_ENABLED	(0 + PREEMPT_NEED_RESCHED)
     20
     21/*
     22 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
     23 * that think a non-zero value indicates we cannot preempt.
     24 */
     25static __always_inline int preempt_count(void)
     26{
     27	return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
     28}
     29
     30static __always_inline void preempt_count_set(int pc)
     31{
     32	int old, new;
     33
     34	do {
     35		old = raw_cpu_read_4(__preempt_count);
     36		new = (old & PREEMPT_NEED_RESCHED) |
     37			(pc & ~PREEMPT_NEED_RESCHED);
     38	} while (raw_cpu_cmpxchg_4(__preempt_count, old, new) != old);
     39}
     40
     41/*
     42 * must be macros to avoid header recursion hell
     43 */
     44#define init_task_preempt_count(p) do { } while (0)
     45
     46#define init_idle_preempt_count(p, cpu) do { \
     47	per_cpu(__preempt_count, (cpu)) = PREEMPT_DISABLED; \
     48} while (0)
     49
     50/*
     51 * We fold the NEED_RESCHED bit into the preempt count such that
     52 * preempt_enable() can decrement and test for needing to reschedule with a
     53 * single instruction.
     54 *
     55 * We invert the actual bit, so that when the decrement hits 0 we know we both
     56 * need to resched (the bit is cleared) and can resched (no preempt count).
     57 */
     58
     59static __always_inline void set_preempt_need_resched(void)
     60{
     61	raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
     62}
     63
     64static __always_inline void clear_preempt_need_resched(void)
     65{
     66	raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
     67}
     68
     69static __always_inline bool test_preempt_need_resched(void)
     70{
     71	return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
     72}
     73
     74/*
     75 * The various preempt_count add/sub methods
     76 */
     77
     78static __always_inline void __preempt_count_add(int val)
     79{
     80	raw_cpu_add_4(__preempt_count, val);
     81}
     82
     83static __always_inline void __preempt_count_sub(int val)
     84{
     85	raw_cpu_add_4(__preempt_count, -val);
     86}
     87
     88/*
     89 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
     90 * a decrement which hits zero means we have no preempt_count and should
     91 * reschedule.
     92 */
     93static __always_inline bool __preempt_count_dec_and_test(void)
     94{
     95	return GEN_UNARY_RMWcc("decl", __preempt_count, e, __percpu_arg([var]));
     96}
     97
     98/*
     99 * Returns true when we need to resched and can (barring IRQ state).
    100 */
    101static __always_inline bool should_resched(int preempt_offset)
    102{
    103	return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
    104}
    105
    106#ifdef CONFIG_PREEMPTION
    107
    108extern asmlinkage void preempt_schedule(void);
    109extern asmlinkage void preempt_schedule_thunk(void);
    110
    111#define preempt_schedule_dynamic_enabled	preempt_schedule_thunk
    112#define preempt_schedule_dynamic_disabled	NULL
    113
    114extern asmlinkage void preempt_schedule_notrace(void);
    115extern asmlinkage void preempt_schedule_notrace_thunk(void);
    116
    117#define preempt_schedule_notrace_dynamic_enabled	preempt_schedule_notrace_thunk
    118#define preempt_schedule_notrace_dynamic_disabled	NULL
    119
    120#ifdef CONFIG_PREEMPT_DYNAMIC
    121
    122DECLARE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled);
    123
    124#define __preempt_schedule() \
    125do { \
    126	__STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule); \
    127	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
    128} while (0)
    129
    130DECLARE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled);
    131
    132#define __preempt_schedule_notrace() \
    133do { \
    134	__STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule_notrace); \
    135	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
    136} while (0)
    137
    138#else /* PREEMPT_DYNAMIC */
    139
    140#define __preempt_schedule() \
    141	asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT);
    142
    143#define __preempt_schedule_notrace() \
    144	asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT);
    145
    146#endif /* PREEMPT_DYNAMIC */
    147
    148#endif /* PREEMPTION */
    149
    150#endif /* __ASM_PREEMPT_H */