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libbpf: preserve errno across pr_warn/pr_info/pr_debug

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As suggested in [0], make sure that libbpf_print saves and restored
errno and as such guaranteed that no matter what actual print callback
user installs, macros like pr_warn/pr_info/pr_debug are completely
transparent as far as errno goes.

While libbpf code is pretty careful about not clobbering important errno
values accidentally with pr_warn(), it's a trivial change to make sure
that pr_warn can be used anywhere without a risk of clobbering errno.

No functional changes, just future proofing.

  [0] https://github.com/libbpf/libbpf/pull/536

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Daniel Müller <deso@posteo.net>
Link: https://lore.kernel.org/r/20220810183425.1998735-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2022-08-10 11:34:25 -07:00 committed by Alexei Starovoitov
parent 43caeec90d
commit d7c5802faf
1 changed files with 5 additions and 0 deletions
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5
tools/lib/bpf/libbpf.c
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@ -223,13 +223,18 @@ __printf(2, 3)
void libbpf_print(enum libbpf_print_level level, const char *format, ...)
{
va_list args;
int old_errno;
if (!__libbpf_pr)
return;
old_errno = errno;
va_start(args, format);
__libbpf_pr(level, format, args);
va_end(args);
errno = old_errno;
}
static void pr_perm_msg(int err)