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libbpf: Fix build with latest gcc/binutils with LTO

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After updating to binutils 2.35, the build began to fail with an
assembler error. A bug was opened on the Red Hat Bugzilla a few days
later for the same issue.

Work around the problem by using the new `symver` attribute (introduced
in GCC 10) as needed instead of assembler directives.

This addresses Red Hat ([0]) and OpenSUSE ([1]) bug reports, as well as libbpf
issue ([2]).

  [0]: https://bugzilla.redhat.com/show_bug.cgi?id=1863059
  [1]: https://bugzilla.opensuse.org/show_bug.cgi?id=1188749
  [2]: Closes: https://github.com/libbpf/libbpf/issues/338

Co-developed-by: Patrick McCarty <patrick.mccarty@intel.com>
Co-developed-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Patrick McCarty <patrick.mccarty@intel.com>
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210907221023.2660953-1-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
2021-09-07 15:10:23 -07:00
committed by Alexei Starovoitov
parent d6be5947ef
commit 006a5099fc
2 changed files with 21 additions and 8 deletions
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25
tools/lib/bpf/libbpf_internal.h
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@@ -90,17 +90,30 @@
/* Symbol versioning is different between static and shared library.
* Properly versioned symbols are needed for shared library, but
* only the symbol of the new version is needed for static library.
* Starting with GNU C 10, use symver attribute instead of .symver assembler
* directive, which works better with GCC LTO builds.
*/
#ifdef SHARED
# define COMPAT_VERSION(internal_name, api_name, version) \
#if defined(SHARED) && defined(__GNUC__) && __GNUC__ >= 10
#define DEFAULT_VERSION(internal_name, api_name, version) \
__attribute__((symver(#api_name "@@" #version)))
#define COMPAT_VERSION(internal_name, api_name, version) \
__attribute__((symver(#api_name "@" #version)))
#elif defined(SHARED)
#define COMPAT_VERSION(internal_name, api_name, version) \
asm(".symver " #internal_name "," #api_name "@" #version);
# define DEFAULT_VERSION(internal_name, api_name, version) \
#define DEFAULT_VERSION(internal_name, api_name, version) \
asm(".symver " #internal_name "," #api_name "@@" #version);
#else
# define COMPAT_VERSION(internal_name, api_name, version)
# define DEFAULT_VERSION(internal_name, api_name, version) \
#else /* !SHARED */
#define COMPAT_VERSION(internal_name, api_name, version)
#define DEFAULT_VERSION(internal_name, api_name, version) \
extern typeof(internal_name) api_name \
__attribute__((alias(#internal_name)));
#endif
extern void libbpf_print(enum libbpf_print_level level,