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Diffstat (limited to 'src/basic/dlfcn-util.h')
| -rw-r--r-- | src/basic/dlfcn-util.h | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/src/basic/dlfcn-util.h b/src/basic/dlfcn-util.h new file mode 100644 index 0000000..83ab320 --- /dev/null +++ b/src/basic/dlfcn-util.h @@ -0,0 +1,82 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +#pragma once + +#include <dlfcn.h> + +#include "macro.h" + +static inline void* safe_dlclose(void *dl) { + if (!dl) + return NULL; + + assert_se(dlclose(dl) == 0); + return NULL; +} + +static inline void dlclosep(void **dlp) { + safe_dlclose(*dlp); +} + +int dlsym_many_or_warn_sentinel(void *dl, int log_level, ...) _sentinel_; +int dlopen_many_sym_or_warn_sentinel(void **dlp, const char *filename, int log_level, ...) _sentinel_; + +#define dlsym_many_or_warn(dl, log_level, ...) \ + dlsym_many_or_warn_sentinel(dl, log_level, __VA_ARGS__, NULL) +#define dlopen_many_sym_or_warn(dlp, filename, log_level, ...) \ + dlopen_many_sym_or_warn_sentinel(dlp, filename, log_level, __VA_ARGS__, NULL) + +#define DLSYM_PROTOTYPE(symbol) \ + extern typeof(symbol)* sym_##symbol +#define DLSYM_FUNCTION(symbol) \ + typeof(symbol)* sym_##symbol = NULL + +/* Macro useful for putting together variable/symbol name pairs when calling dlsym_many_or_warn(). Assumes + * that each library symbol to resolve will be placed in a variable with the "sym_" prefix, i.e. a symbol + * "foobar" is loaded into a variable "sym_foobar". */ +#define DLSYM_ARG(arg) \ + ({ assert_cc(__builtin_types_compatible_p(typeof(sym_##arg), typeof(&arg))); &sym_##arg; }), STRINGIFY(arg) + +/* libbpf is a bit confused about type-safety and API compatibility. Provide a macro that can tape over that mess. Sad. */ +#define DLSYM_ARG_FORCE(arg) \ + &sym_##arg, STRINGIFY(arg) + +#define ELF_NOTE_DLOPEN_VENDOR "FDO" +#define ELF_NOTE_DLOPEN_TYPE UINT32_C(0x407c0c0a) +#define ELF_NOTE_DLOPEN_PRIORITY_REQUIRED "required" +#define ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED "recommended" +#define ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED "suggested" + +/* Add an ".note.dlopen" ELF note to our binary that declares our weak dlopen() dependency. This + * information can be read from an ELF file via "readelf -p .note.dlopen" or an equivalent command. */ +#define _ELF_NOTE_DLOPEN(json, variable_name) \ + __attribute__((used, section(".note.dlopen"))) _Alignas(sizeof(uint32_t)) static const struct { \ + struct { \ + uint32_t n_namesz, n_descsz, n_type; \ + } nhdr; \ + char name[sizeof(ELF_NOTE_DLOPEN_VENDOR)]; \ + _Alignas(sizeof(uint32_t)) char dlopen_json[sizeof(json)]; \ + } variable_name = { \ + .nhdr = { \ + .n_namesz = sizeof(ELF_NOTE_DLOPEN_VENDOR), \ + .n_descsz = sizeof(json), \ + .n_type = ELF_NOTE_DLOPEN_TYPE, \ + }, \ + .name = ELF_NOTE_DLOPEN_VENDOR, \ + .dlopen_json = json, \ + } + +#define _SONAME_ARRAY1(a) "[\""a"\"]" +#define _SONAME_ARRAY2(a, b) "[\""a"\",\""b"\"]" +#define _SONAME_ARRAY3(a, b, c) "[\""a"\",\""b"\",\""c"\"]" +#define _SONAME_ARRAY4(a, b, c, d) "[\""a"\",\""b"\",\""c"\"",\""d"\"]" +#define _SONAME_ARRAY5(a, b, c, d, e) "[\""a"\",\""b"\",\""c"\"",\""d"\",\""e"\"]" +#define _SONAME_ARRAY_GET(_1,_2,_3,_4,_5,NAME,...) NAME +#define _SONAME_ARRAY(...) _SONAME_ARRAY_GET(__VA_ARGS__, _SONAME_ARRAY5, _SONAME_ARRAY4, _SONAME_ARRAY3, _SONAME_ARRAY2, _SONAME_ARRAY1)(__VA_ARGS__) + +/* The 'priority' must be one of 'required', 'recommended' or 'suggested' as per specification, use the + * macro defined above to specify it. + * Multiple sonames can be passed and they will be automatically constructed into a json array (but note that + * due to preprocessor language limitations if more than the limit defined above is used, a new + * _SONAME_ARRAY<X+1> will need to be added). */ +#define ELF_NOTE_DLOPEN(feature, description, priority, ...) \ + _ELF_NOTE_DLOPEN("[{\"feature\":\"" feature "\",\"description\":\"" description "\",\"priority\":\"" priority "\",\"soname\":" _SONAME_ARRAY(__VA_ARGS__) "}]", UNIQ_T(s, UNIQ)) |