![Marco Elver](/assets/img/avatar_default.png)
The volatile accesses no longer need to be wrapped in data_race() because compilers that emit instrumentation distinguishing volatile accesses are required for KCSAN. Consequently, the explicit kcsan_check_atomic*() are no longer required either since the compiler emits instrumentation distinguishing the volatile accesses. Finally, simplify __READ_ONCE_SCALAR() and remove __WRITE_ONCE_SCALAR(). [ bp: Convert commit message to passive voice. ] Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lkml.kernel.org/r/20200521142047.169334-9-elver@google.com
447 lines
13 KiB
C
447 lines
13 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef __LINUX_COMPILER_H
|
|
#define __LINUX_COMPILER_H
|
|
|
|
#include <linux/compiler_types.h>
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
#ifdef __KERNEL__
|
|
|
|
/*
|
|
* Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
|
|
* to disable branch tracing on a per file basis.
|
|
*/
|
|
#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
|
|
&& !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
|
|
void ftrace_likely_update(struct ftrace_likely_data *f, int val,
|
|
int expect, int is_constant);
|
|
|
|
#define likely_notrace(x) __builtin_expect(!!(x), 1)
|
|
#define unlikely_notrace(x) __builtin_expect(!!(x), 0)
|
|
|
|
#define __branch_check__(x, expect, is_constant) ({ \
|
|
long ______r; \
|
|
static struct ftrace_likely_data \
|
|
__aligned(4) \
|
|
__section(_ftrace_annotated_branch) \
|
|
______f = { \
|
|
.data.func = __func__, \
|
|
.data.file = __FILE__, \
|
|
.data.line = __LINE__, \
|
|
}; \
|
|
______r = __builtin_expect(!!(x), expect); \
|
|
ftrace_likely_update(&______f, ______r, \
|
|
expect, is_constant); \
|
|
______r; \
|
|
})
|
|
|
|
/*
|
|
* Using __builtin_constant_p(x) to ignore cases where the return
|
|
* value is always the same. This idea is taken from a similar patch
|
|
* written by Daniel Walker.
|
|
*/
|
|
# ifndef likely
|
|
# define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
|
|
# endif
|
|
# ifndef unlikely
|
|
# define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
|
|
# endif
|
|
|
|
#ifdef CONFIG_PROFILE_ALL_BRANCHES
|
|
/*
|
|
* "Define 'is'", Bill Clinton
|
|
* "Define 'if'", Steven Rostedt
|
|
*/
|
|
#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
|
|
|
|
#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
|
|
|
|
#define __trace_if_value(cond) ({ \
|
|
static struct ftrace_branch_data \
|
|
__aligned(4) \
|
|
__section(_ftrace_branch) \
|
|
__if_trace = { \
|
|
.func = __func__, \
|
|
.file = __FILE__, \
|
|
.line = __LINE__, \
|
|
}; \
|
|
(cond) ? \
|
|
(__if_trace.miss_hit[1]++,1) : \
|
|
(__if_trace.miss_hit[0]++,0); \
|
|
})
|
|
|
|
#endif /* CONFIG_PROFILE_ALL_BRANCHES */
|
|
|
|
#else
|
|
# define likely(x) __builtin_expect(!!(x), 1)
|
|
# define unlikely(x) __builtin_expect(!!(x), 0)
|
|
#endif
|
|
|
|
/* Optimization barrier */
|
|
#ifndef barrier
|
|
# define barrier() __memory_barrier()
|
|
#endif
|
|
|
|
#ifndef barrier_data
|
|
# define barrier_data(ptr) barrier()
|
|
#endif
|
|
|
|
/* workaround for GCC PR82365 if needed */
|
|
#ifndef barrier_before_unreachable
|
|
# define barrier_before_unreachable() do { } while (0)
|
|
#endif
|
|
|
|
/* Unreachable code */
|
|
#ifdef CONFIG_STACK_VALIDATION
|
|
/*
|
|
* These macros help objtool understand GCC code flow for unreachable code.
|
|
* The __COUNTER__ based labels are a hack to make each instance of the macros
|
|
* unique, to convince GCC not to merge duplicate inline asm statements.
|
|
*/
|
|
#define annotate_reachable() ({ \
|
|
asm volatile("%c0:\n\t" \
|
|
".pushsection .discard.reachable\n\t" \
|
|
".long %c0b - .\n\t" \
|
|
".popsection\n\t" : : "i" (__COUNTER__)); \
|
|
})
|
|
#define annotate_unreachable() ({ \
|
|
asm volatile("%c0:\n\t" \
|
|
".pushsection .discard.unreachable\n\t" \
|
|
".long %c0b - .\n\t" \
|
|
".popsection\n\t" : : "i" (__COUNTER__)); \
|
|
})
|
|
#define ASM_UNREACHABLE \
|
|
"999:\n\t" \
|
|
".pushsection .discard.unreachable\n\t" \
|
|
".long 999b - .\n\t" \
|
|
".popsection\n\t"
|
|
|
|
/* Annotate a C jump table to allow objtool to follow the code flow */
|
|
#define __annotate_jump_table __section(.rodata..c_jump_table)
|
|
|
|
#ifdef CONFIG_DEBUG_ENTRY
|
|
/* Begin/end of an instrumentation safe region */
|
|
#define instrumentation_begin() ({ \
|
|
asm volatile("%c0:\n\t" \
|
|
".pushsection .discard.instr_begin\n\t" \
|
|
".long %c0b - .\n\t" \
|
|
".popsection\n\t" : : "i" (__COUNTER__)); \
|
|
})
|
|
|
|
/*
|
|
* Because instrumentation_{begin,end}() can nest, objtool validation considers
|
|
* _begin() a +1 and _end() a -1 and computes a sum over the instructions.
|
|
* When the value is greater than 0, we consider instrumentation allowed.
|
|
*
|
|
* There is a problem with code like:
|
|
*
|
|
* noinstr void foo()
|
|
* {
|
|
* instrumentation_begin();
|
|
* ...
|
|
* if (cond) {
|
|
* instrumentation_begin();
|
|
* ...
|
|
* instrumentation_end();
|
|
* }
|
|
* bar();
|
|
* instrumentation_end();
|
|
* }
|
|
*
|
|
* If instrumentation_end() would be an empty label, like all the other
|
|
* annotations, the inner _end(), which is at the end of a conditional block,
|
|
* would land on the instruction after the block.
|
|
*
|
|
* If we then consider the sum of the !cond path, we'll see that the call to
|
|
* bar() is with a 0-value, even though, we meant it to happen with a positive
|
|
* value.
|
|
*
|
|
* To avoid this, have _end() be a NOP instruction, this ensures it will be
|
|
* part of the condition block and does not escape.
|
|
*/
|
|
#define instrumentation_end() ({ \
|
|
asm volatile("%c0: nop\n\t" \
|
|
".pushsection .discard.instr_end\n\t" \
|
|
".long %c0b - .\n\t" \
|
|
".popsection\n\t" : : "i" (__COUNTER__)); \
|
|
})
|
|
#endif /* CONFIG_DEBUG_ENTRY */
|
|
|
|
#else
|
|
#define annotate_reachable()
|
|
#define annotate_unreachable()
|
|
#define __annotate_jump_table
|
|
#endif
|
|
|
|
#ifndef instrumentation_begin
|
|
#define instrumentation_begin() do { } while(0)
|
|
#define instrumentation_end() do { } while(0)
|
|
#endif
|
|
|
|
#ifndef ASM_UNREACHABLE
|
|
# define ASM_UNREACHABLE
|
|
#endif
|
|
#ifndef unreachable
|
|
# define unreachable() do { \
|
|
annotate_unreachable(); \
|
|
__builtin_unreachable(); \
|
|
} while (0)
|
|
#endif
|
|
|
|
/*
|
|
* KENTRY - kernel entry point
|
|
* This can be used to annotate symbols (functions or data) that are used
|
|
* without their linker symbol being referenced explicitly. For example,
|
|
* interrupt vector handlers, or functions in the kernel image that are found
|
|
* programatically.
|
|
*
|
|
* Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
|
|
* are handled in their own way (with KEEP() in linker scripts).
|
|
*
|
|
* KENTRY can be avoided if the symbols in question are marked as KEEP() in the
|
|
* linker script. For example an architecture could KEEP() its entire
|
|
* boot/exception vector code rather than annotate each function and data.
|
|
*/
|
|
#ifndef KENTRY
|
|
# define KENTRY(sym) \
|
|
extern typeof(sym) sym; \
|
|
static const unsigned long __kentry_##sym \
|
|
__used \
|
|
__section("___kentry" "+" #sym ) \
|
|
= (unsigned long)&sym;
|
|
#endif
|
|
|
|
#ifndef RELOC_HIDE
|
|
# define RELOC_HIDE(ptr, off) \
|
|
({ unsigned long __ptr; \
|
|
__ptr = (unsigned long) (ptr); \
|
|
(typeof(ptr)) (__ptr + (off)); })
|
|
#endif
|
|
|
|
#ifndef OPTIMIZER_HIDE_VAR
|
|
/* Make the optimizer believe the variable can be manipulated arbitrarily. */
|
|
#define OPTIMIZER_HIDE_VAR(var) \
|
|
__asm__ ("" : "=r" (var) : "0" (var))
|
|
#endif
|
|
|
|
/* Not-quite-unique ID. */
|
|
#ifndef __UNIQUE_ID
|
|
# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
|
|
#endif
|
|
|
|
/*
|
|
* Prevent the compiler from merging or refetching reads or writes. The
|
|
* compiler is also forbidden from reordering successive instances of
|
|
* READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
|
|
* particular ordering. One way to make the compiler aware of ordering is to
|
|
* put the two invocations of READ_ONCE or WRITE_ONCE in different C
|
|
* statements.
|
|
*
|
|
* These two macros will also work on aggregate data types like structs or
|
|
* unions.
|
|
*
|
|
* Their two major use cases are: (1) Mediating communication between
|
|
* process-level code and irq/NMI handlers, all running on the same CPU,
|
|
* and (2) Ensuring that the compiler does not fold, spindle, or otherwise
|
|
* mutilate accesses that either do not require ordering or that interact
|
|
* with an explicit memory barrier or atomic instruction that provides the
|
|
* required ordering.
|
|
*/
|
|
#include <asm/barrier.h>
|
|
#include <linux/kasan-checks.h>
|
|
#include <linux/kcsan-checks.h>
|
|
|
|
/**
|
|
* data_race - mark an expression as containing intentional data races
|
|
*
|
|
* This data_race() macro is useful for situations in which data races
|
|
* should be forgiven. One example is diagnostic code that accesses
|
|
* shared variables but is not a part of the core synchronization design.
|
|
*
|
|
* This macro *does not* affect normal code generation, but is a hint
|
|
* to tooling that data races here are to be ignored.
|
|
*/
|
|
#define data_race(expr) \
|
|
({ \
|
|
__kcsan_disable_current(); \
|
|
({ \
|
|
__unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \
|
|
__kcsan_enable_current(); \
|
|
__v; \
|
|
}); \
|
|
})
|
|
|
|
/*
|
|
* Use __READ_ONCE() instead of READ_ONCE() if you do not require any
|
|
* atomicity or dependency ordering guarantees. Note that this may result
|
|
* in tears!
|
|
*/
|
|
#define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
|
|
|
|
#define __READ_ONCE_SCALAR(x) \
|
|
({ \
|
|
__unqual_scalar_typeof(x) __x = __READ_ONCE(x); \
|
|
smp_read_barrier_depends(); \
|
|
(typeof(x))__x; \
|
|
})
|
|
|
|
#define READ_ONCE(x) \
|
|
({ \
|
|
compiletime_assert_rwonce_type(x); \
|
|
__READ_ONCE_SCALAR(x); \
|
|
})
|
|
|
|
#define __WRITE_ONCE(x, val) \
|
|
do { \
|
|
*(volatile typeof(x) *)&(x) = (val); \
|
|
} while (0)
|
|
|
|
#define WRITE_ONCE(x, val) \
|
|
do { \
|
|
compiletime_assert_rwonce_type(x); \
|
|
__WRITE_ONCE(x, val); \
|
|
} while (0)
|
|
|
|
#ifdef CONFIG_KASAN
|
|
/*
|
|
* We can't declare function 'inline' because __no_sanitize_address conflicts
|
|
* with inlining. Attempt to inline it may cause a build failure.
|
|
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
|
|
* '__maybe_unused' allows us to avoid defined-but-not-used warnings.
|
|
*/
|
|
# define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
|
|
# define __no_sanitize_or_inline __no_kasan_or_inline
|
|
#else
|
|
# define __no_kasan_or_inline __always_inline
|
|
#endif
|
|
|
|
#define __no_kcsan __no_sanitize_thread
|
|
#ifdef __SANITIZE_THREAD__
|
|
/*
|
|
* Rely on __SANITIZE_THREAD__ instead of CONFIG_KCSAN, to avoid not inlining in
|
|
* compilation units where instrumentation is disabled.
|
|
*/
|
|
# define __no_kcsan_or_inline __no_kcsan notrace __maybe_unused
|
|
# define __no_sanitize_or_inline __no_kcsan_or_inline
|
|
#else
|
|
# define __no_kcsan_or_inline __always_inline
|
|
#endif
|
|
|
|
#ifndef __no_sanitize_or_inline
|
|
#define __no_sanitize_or_inline __always_inline
|
|
#endif
|
|
|
|
static __no_sanitize_or_inline
|
|
unsigned long __read_once_word_nocheck(const void *addr)
|
|
{
|
|
return __READ_ONCE(*(unsigned long *)addr);
|
|
}
|
|
|
|
/*
|
|
* Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need to load a
|
|
* word from memory atomically but without telling KASAN/KCSAN. This is
|
|
* usually used by unwinding code when walking the stack of a running process.
|
|
*/
|
|
#define READ_ONCE_NOCHECK(x) \
|
|
({ \
|
|
unsigned long __x; \
|
|
compiletime_assert(sizeof(x) == sizeof(__x), \
|
|
"Unsupported access size for READ_ONCE_NOCHECK()."); \
|
|
__x = __read_once_word_nocheck(&(x)); \
|
|
smp_read_barrier_depends(); \
|
|
(typeof(x))__x; \
|
|
})
|
|
|
|
static __no_kasan_or_inline
|
|
unsigned long read_word_at_a_time(const void *addr)
|
|
{
|
|
kasan_check_read(addr, 1);
|
|
return *(unsigned long *)addr;
|
|
}
|
|
|
|
#endif /* __KERNEL__ */
|
|
|
|
/*
|
|
* Force the compiler to emit 'sym' as a symbol, so that we can reference
|
|
* it from inline assembler. Necessary in case 'sym' could be inlined
|
|
* otherwise, or eliminated entirely due to lack of references that are
|
|
* visible to the compiler.
|
|
*/
|
|
#define __ADDRESSABLE(sym) \
|
|
static void * __section(.discard.addressable) __used \
|
|
__PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
|
|
|
|
/**
|
|
* offset_to_ptr - convert a relative memory offset to an absolute pointer
|
|
* @off: the address of the 32-bit offset value
|
|
*/
|
|
static inline void *offset_to_ptr(const int *off)
|
|
{
|
|
return (void *)((unsigned long)off + *off);
|
|
}
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
|
|
/* Compile time object size, -1 for unknown */
|
|
#ifndef __compiletime_object_size
|
|
# define __compiletime_object_size(obj) -1
|
|
#endif
|
|
#ifndef __compiletime_warning
|
|
# define __compiletime_warning(message)
|
|
#endif
|
|
#ifndef __compiletime_error
|
|
# define __compiletime_error(message)
|
|
#endif
|
|
|
|
#ifdef __OPTIMIZE__
|
|
# define __compiletime_assert(condition, msg, prefix, suffix) \
|
|
do { \
|
|
extern void prefix ## suffix(void) __compiletime_error(msg); \
|
|
if (!(condition)) \
|
|
prefix ## suffix(); \
|
|
} while (0)
|
|
#else
|
|
# define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
|
|
#endif
|
|
|
|
#define _compiletime_assert(condition, msg, prefix, suffix) \
|
|
__compiletime_assert(condition, msg, prefix, suffix)
|
|
|
|
/**
|
|
* compiletime_assert - break build and emit msg if condition is false
|
|
* @condition: a compile-time constant condition to check
|
|
* @msg: a message to emit if condition is false
|
|
*
|
|
* In tradition of POSIX assert, this macro will break the build if the
|
|
* supplied condition is *false*, emitting the supplied error message if the
|
|
* compiler has support to do so.
|
|
*/
|
|
#define compiletime_assert(condition, msg) \
|
|
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
|
|
|
|
#define compiletime_assert_atomic_type(t) \
|
|
compiletime_assert(__native_word(t), \
|
|
"Need native word sized stores/loads for atomicity.")
|
|
|
|
/*
|
|
* Yes, this permits 64-bit accesses on 32-bit architectures. These will
|
|
* actually be atomic in some cases (namely Armv7 + LPAE), but for others we
|
|
* rely on the access being split into 2x32-bit accesses for a 32-bit quantity
|
|
* (e.g. a virtual address) and a strong prevailing wind.
|
|
*/
|
|
#define compiletime_assert_rwonce_type(t) \
|
|
compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
|
|
"Unsupported access size for {READ,WRITE}_ONCE().")
|
|
|
|
/* &a[0] degrades to a pointer: a different type from an array */
|
|
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
|
|
|
|
/*
|
|
* This is needed in functions which generate the stack canary, see
|
|
* arch/x86/kernel/smpboot.c::start_secondary() for an example.
|
|
*/
|
|
#define prevent_tail_call_optimization() mb()
|
|
|
|
#endif /* __LINUX_COMPILER_H */
|