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linux-stable/include/linux/thread_info.h
Mark Rutland 7ad639840a thread_info: Add helpers to snapshot thread flags 
In <linux/thread_info.h> there are helpers to manipulate individual thread
flags, but where code wants to check several flags at once, it must open
code reading current_thread_info()->flags and operating on a snapshot.

As some flags can be set remotely it's necessary to use READ_ONCE() to get
a consistent snapshot even when IRQs are disabled, but some code forgets to
do this. Generally this is unlike to cause a problem in practice, but it is
somewhat unsound, and KCSAN will legitimately warn that there is a data
race.

To make it easier to do the right thing, and to highlight that concurrent
modification is possible, add new helpers to snapshot the flags, which
should be used in preference to plain reads. Subsequent patches will move
existing code to use the new helpers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marco Elver <elver@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20211129130653.2037928-2-mark.rutland@arm.com
2021-12-01 00:06:43 +01:00

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/* SPDX-License-Identifier: GPL-2.0 */
/* thread_info.h: common low-level thread information accessors
*
* Copyright (C) 2002 David Howells (dhowells@redhat.com)
* - Incorporating suggestions made by Linus Torvalds
*/
#ifndef _LINUX_THREAD_INFO_H
#define _LINUX_THREAD_INFO_H
#include <linux/types.h>
#include <linux/limits.h>
#include <linux/bug.h>
#include <linux/restart_block.h>
#include <linux/errno.h>
#ifdef CONFIG_THREAD_INFO_IN_TASK
/*
* For CONFIG_THREAD_INFO_IN_TASK kernels we need <asm/current.h> for the
* definition of current, but for !CONFIG_THREAD_INFO_IN_TASK kernels,
* including <asm/current.h> can cause a circular dependency on some platforms.
*/
#include <asm/current.h>
#define current_thread_info() ((struct thread_info *)current)
#endif
#include <linux/bitops.h>
/*
* For per-arch arch_within_stack_frames() implementations, defined in
* asm/thread_info.h.
*/
enum {
BAD_STACK = -1,
NOT_STACK = 0,
GOOD_FRAME,
GOOD_STACK,
};
#ifdef CONFIG_GENERIC_ENTRY
enum syscall_work_bit {
SYSCALL_WORK_BIT_SECCOMP,
SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT,
SYSCALL_WORK_BIT_SYSCALL_TRACE,
SYSCALL_WORK_BIT_SYSCALL_EMU,
SYSCALL_WORK_BIT_SYSCALL_AUDIT,
SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH,
SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP,
};
#define SYSCALL_WORK_SECCOMP BIT(SYSCALL_WORK_BIT_SECCOMP)
#define SYSCALL_WORK_SYSCALL_TRACEPOINT BIT(SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT)
#define SYSCALL_WORK_SYSCALL_TRACE BIT(SYSCALL_WORK_BIT_SYSCALL_TRACE)
#define SYSCALL_WORK_SYSCALL_EMU BIT(SYSCALL_WORK_BIT_SYSCALL_EMU)
#define SYSCALL_WORK_SYSCALL_AUDIT BIT(SYSCALL_WORK_BIT_SYSCALL_AUDIT)
#define SYSCALL_WORK_SYSCALL_USER_DISPATCH BIT(SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH)
#define SYSCALL_WORK_SYSCALL_EXIT_TRAP BIT(SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP)
#endif
#include <asm/thread_info.h>
#ifdef __KERNEL__
#ifndef arch_set_restart_data
#define arch_set_restart_data(restart) do { } while (0)
#endif
static inline long set_restart_fn(struct restart_block *restart,
long (*fn)(struct restart_block *))
{
restart->fn = fn;
arch_set_restart_data(restart);
return -ERESTART_RESTARTBLOCK;
}
#ifndef THREAD_ALIGN
#define THREAD_ALIGN THREAD_SIZE
#endif
#define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO)
/*
* flag set/clear/test wrappers
* - pass TIF_xxxx constants to these functions
*/
static inline void set_ti_thread_flag(struct thread_info *ti, int flag)
{
set_bit(flag, (unsigned long *)&ti->flags);
}
static inline void clear_ti_thread_flag(struct thread_info *ti, int flag)
{
clear_bit(flag, (unsigned long *)&ti->flags);
}
static inline void update_ti_thread_flag(struct thread_info *ti, int flag,
bool value)
{
if (value)
set_ti_thread_flag(ti, flag);
else
clear_ti_thread_flag(ti, flag);
}
static inline int test_and_set_ti_thread_flag(struct thread_info *ti, int flag)
{
return test_and_set_bit(flag, (unsigned long *)&ti->flags);
}
static inline int test_and_clear_ti_thread_flag(struct thread_info *ti, int flag)
{
return test_and_clear_bit(flag, (unsigned long *)&ti->flags);
}
static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
{
return test_bit(flag, (unsigned long *)&ti->flags);
}
/*
* This may be used in noinstr code, and needs to be __always_inline to prevent
* inadvertent instrumentation.
*/
static __always_inline unsigned long read_ti_thread_flags(struct thread_info *ti)
{
return READ_ONCE(ti->flags);
}
#define set_thread_flag(flag) \
set_ti_thread_flag(current_thread_info(), flag)
#define clear_thread_flag(flag) \
clear_ti_thread_flag(current_thread_info(), flag)
#define update_thread_flag(flag, value) \
update_ti_thread_flag(current_thread_info(), flag, value)
#define test_and_set_thread_flag(flag) \
test_and_set_ti_thread_flag(current_thread_info(), flag)
#define test_and_clear_thread_flag(flag) \
test_and_clear_ti_thread_flag(current_thread_info(), flag)
#define test_thread_flag(flag) \
test_ti_thread_flag(current_thread_info(), flag)
#define read_thread_flags() \
read_ti_thread_flags(current_thread_info())
#define read_task_thread_flags(t) \
read_ti_thread_flags(task_thread_info(t))
#ifdef CONFIG_GENERIC_ENTRY
#define set_syscall_work(fl) \
set_bit(SYSCALL_WORK_BIT_##fl, &current_thread_info()->syscall_work)
#define test_syscall_work(fl) \
test_bit(SYSCALL_WORK_BIT_##fl, &current_thread_info()->syscall_work)
#define clear_syscall_work(fl) \
clear_bit(SYSCALL_WORK_BIT_##fl, &current_thread_info()->syscall_work)
#define set_task_syscall_work(t, fl) \
set_bit(SYSCALL_WORK_BIT_##fl, &task_thread_info(t)->syscall_work)
#define test_task_syscall_work(t, fl) \
test_bit(SYSCALL_WORK_BIT_##fl, &task_thread_info(t)->syscall_work)
#define clear_task_syscall_work(t, fl) \
clear_bit(SYSCALL_WORK_BIT_##fl, &task_thread_info(t)->syscall_work)
#else /* CONFIG_GENERIC_ENTRY */
#define set_syscall_work(fl) \
set_ti_thread_flag(current_thread_info(), TIF_##fl)
#define test_syscall_work(fl) \
test_ti_thread_flag(current_thread_info(), TIF_##fl)
#define clear_syscall_work(fl) \
clear_ti_thread_flag(current_thread_info(), TIF_##fl)
#define set_task_syscall_work(t, fl) \
set_ti_thread_flag(task_thread_info(t), TIF_##fl)
#define test_task_syscall_work(t, fl) \
test_ti_thread_flag(task_thread_info(t), TIF_##fl)
#define clear_task_syscall_work(t, fl) \
clear_ti_thread_flag(task_thread_info(t), TIF_##fl)
#endif /* !CONFIG_GENERIC_ENTRY */
#define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED)
#ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES
static inline int arch_within_stack_frames(const void * const stack,
const void * const stackend,
const void *obj, unsigned long len)
{
return 0;
}
#endif
#ifdef CONFIG_HARDENED_USERCOPY
extern void __check_object_size(const void *ptr, unsigned long n,
bool to_user);
static __always_inline void check_object_size(const void *ptr, unsigned long n,
bool to_user)
{
if (!__builtin_constant_p(n))
__check_object_size(ptr, n, to_user);
}
#else
static inline void check_object_size(const void *ptr, unsigned long n,
bool to_user)
{ }
#endif /* CONFIG_HARDENED_USERCOPY */
extern void __compiletime_error("copy source size is too small")
__bad_copy_from(void);
extern void __compiletime_error("copy destination size is too small")
__bad_copy_to(void);
static inline void copy_overflow(int size, unsigned long count)
{
WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
}
static __always_inline __must_check bool
check_copy_size(const void *addr, size_t bytes, bool is_source)
{
int sz = __builtin_object_size(addr, 0);
if (unlikely(sz >= 0 && sz < bytes)) {
if (!__builtin_constant_p(bytes))
copy_overflow(sz, bytes);
else if (is_source)
__bad_copy_from();
else
__bad_copy_to();
return false;
}
if (WARN_ON_ONCE(bytes > INT_MAX))
return false;
check_object_size(addr, bytes, is_source);
return true;
}
#ifndef arch_setup_new_exec
static inline void arch_setup_new_exec(void) { }
#endif
#endif /* __KERNEL__ */
#endif /* _LINUX_THREAD_INFO_H */
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