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bpftool: Print newline before '}' for struct with padding only fields

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[ Upstream commit 44a726c3f23cf762ef4ce3c1709aefbcbe97f62c ]

btf_dump_emit_struct_def attempts to print empty structures at a
single line, e.g. `struct empty {}`. However, it has to account for a
case when there are no regular but some padding fields in the struct.
In such case `vlen` would be zero, but size would be non-zero.

E.g. here is struct bpf_timer from vmlinux.h before this patch:

 struct bpf_timer {
 	long: 64;
	long: 64;};

And after this patch:

 struct bpf_dynptr {
 	long: 64;
	long: 64;
 };

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221001104425.415768-1-eddyz87@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eduard Zingerman 2022-10-01 13:44:24 +03:00 committed by Greg Kroah-Hartman
parent 1c87a6f82a
commit 77e41187a3
1 changed files with 5 additions and 1 deletions
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6
tools/lib/bpf/btf_dump.c
View File

@ -1011,7 +1011,11 @@ static void btf_dump_emit_struct_def(struct btf_dump *d,
if (is_struct)
btf_dump_emit_bit_padding(d, off, t->size * 8, align, false, lvl + 1);
if (vlen)
/*
* Keep `struct empty {}` on a single line,
* only print newline when there are regular or padding fields.
*/
if (vlen || t->size)
btf_dump_printf(d, "\n");
btf_dump_printf(d, "%s}", pfx(lvl));
if (packed)