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Andrii Nakryiko f3f9ee4228 libbpf: Handle GCC noreturn-turned-volatile quirk

[ Upstream commit 32022fd97e ]

Handle a GCC quirk of emitting extra volatile modifier in DWARF (and
subsequently preserved in BTF by pahole) for function pointers marked as
__attribute__((noreturn)). This was the way to mark such functions before GCC
2.5 added noreturn attribute. Drop such func_proto modifiers, similarly to how
it's done for array (also to handle GCC quirk/bug).

Such volatile attribute is emitted by GCC only, so existing selftests can't
express such test. Simple repro is like this (compiled with GCC + BTF
generated by pahole):

  struct my_struct {
      void __attribute__((noreturn)) (*fn)(int);
  };
  struct my_struct a;

Without this fix, output will be:

struct my_struct {
    voidvolatile  (*fn)(int);
};

With the fix:

struct my_struct {
    void (*fn)(int);
};

Fixes: 351131b51c ("libbpf: add btf_dump API for BTF-to-C conversion")
Reported-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/bpf/20200610052335.2862559-1-andriin@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

2020-06-24 17:50:43 +02:00

api

tools api fs: Make xxx__mountpoint() more scalable

2020-06-22 09:30:58 +02:00

bpf

libbpf: Handle GCC noreturn-turned-volatile quirk

2020-06-24 17:50:43 +02:00

lockdep

lockdep/lib/tests: Test dynamic key registration

2019-02-28 07:55:48 +01:00

subcmd

libsubcmd: Use -O0 with DEBUG=1