diff options
Diffstat (limited to 'tools/lib/bpf/bpf_helpers.h')
| -rw-r--r-- | tools/lib/bpf/bpf_helpers.h | 29 |
1 files changed, 24 insertions, 5 deletions
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 5de3eb267125..fb04eaf367f1 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -76,6 +76,30 @@ #endif /* + * Compiler (optimization) barrier. + */ +#ifndef barrier +#define barrier() asm volatile("" ::: "memory") +#endif + +/* Variable-specific compiler (optimization) barrier. It's a no-op which makes + * compiler believe that there is some black box modification of a given + * variable and thus prevents compiler from making extra assumption about its + * value and potential simplifications and optimizations on this variable. + * + * E.g., compiler might often delay or even omit 32-bit to 64-bit casting of + * a variable, making some code patterns unverifiable. Putting barrier_var() + * in place will ensure that cast is performed before the barrier_var() + * invocation, because compiler has to pessimistically assume that embedded + * asm section might perform some extra operations on that variable. + * + * This is a variable-specific variant of more global barrier(). + */ +#ifndef barrier_var +#define barrier_var(var) asm volatile("" : "=r"(var) : "0"(var)) +#endif + +/* * Helper macro to throw a compilation error if __bpf_unreachable() gets * built into the resulting code. This works given BPF back end does not * implement __builtin_trap(). This is useful to assert that certain paths @@ -149,13 +173,8 @@ enum libbpf_tristate { #define __kconfig __attribute__((section(".kconfig"))) #define __ksym __attribute__((section(".ksyms"))) -#if __has_attribute(btf_type_tag) #define __kptr __attribute__((btf_type_tag("kptr"))) #define __kptr_ref __attribute__((btf_type_tag("kptr_ref"))) -#else -#define __kptr -#define __kptr_ref -#endif #ifndef ___bpf_concat #define ___bpf_concat(a, b) a ## b |