| 1 | /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1) |
| 2 | * |
| 3 | * wrapper/compiler.h |
| 4 | * |
| 5 | * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 6 | */ |
| 7 | |
| 8 | #ifndef _LTTNG_WRAPPER_COMPILER_H |
| 9 | #define _LTTNG_WRAPPER_COMPILER_H |
| 10 | |
| 11 | #include <linux/compiler.h> |
| 12 | #include <linux/version.h> |
| 13 | |
| 14 | /* |
| 15 | * Don't allow compiling with buggy compiler. |
| 16 | */ |
| 17 | |
| 18 | #ifdef GCC_VERSION |
| 19 | |
| 20 | /* |
| 21 | * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58854 |
| 22 | */ |
| 23 | # ifdef __ARMEL__ |
| 24 | # if GCC_VERSION >= 40800 && GCC_VERSION <= 40802 |
| 25 | # error Your gcc version produces clobbered frame accesses |
| 26 | # endif |
| 27 | # endif |
| 28 | #endif |
| 29 | |
| 30 | /* |
| 31 | * READ/WRITE_ONCE were introduced in kernel 3.19 and ACCESS_ONCE |
| 32 | * was removed in 4.15. Prefer READ/WRITE but fallback to ACCESS |
| 33 | * when they are not available. |
| 34 | */ |
| 35 | #ifndef READ_ONCE |
| 36 | # define READ_ONCE(x) ACCESS_ONCE(x) |
| 37 | #endif |
| 38 | |
| 39 | #ifndef WRITE_ONCE |
| 40 | # define WRITE_ONCE(x, val) ({ ACCESS_ONCE(x) = val; }) |
| 41 | #endif |
| 42 | |
| 43 | /* |
| 44 | * In v4.15 a smp read barrier was added to READ_ONCE to replace |
| 45 | * lockless_dereference(), replicate this behavior on prior kernels |
| 46 | * and remove calls to smp_read_barrier_depends which was dropped |
| 47 | * in v5.9. |
| 48 | */ |
| 49 | #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,15,0)) |
| 50 | #define LTTNG_READ_ONCE(x) READ_ONCE(x) |
| 51 | #else |
| 52 | #define LTTNG_READ_ONCE(x) \ |
| 53 | ({ \ |
| 54 | typeof(x) __val = READ_ONCE(x); \ |
| 55 | smp_read_barrier_depends(); \ |
| 56 | __val; \ |
| 57 | }) |
| 58 | #endif |
| 59 | |
| 60 | #endif /* _LTTNG_WRAPPER_COMPILER_H */ |