From c9e982b879465ca74e3593ce82808aa259265a71 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Wed, 13 Oct 2021 18:09:00 +0200 Subject: [PATCH] libbpf: Fix dumping big-endian bitfields On big-endian arches not only bytes, but also bits are numbered in reverse order (see e.g. S/390 ELF ABI Supplement, but this is also true for other big-endian arches as well). Signed-off-by: Ilya Leoshkevich Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20211013160902.428340-3-iii@linux.ibm.com --- tools/lib/bpf/btf_dump.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index 5ef42f0abed12..679bf34e3f47f 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -1562,29 +1562,28 @@ static int btf_dump_get_bitfield_value(struct btf_dump *d, __u64 *value) { __u16 left_shift_bits, right_shift_bits; - __u8 nr_copy_bits, nr_copy_bytes; const __u8 *bytes = data; - int sz = t->size; + __u8 nr_copy_bits; __u64 num = 0; int i; /* Maximum supported bitfield size is 64 bits */ - if (sz > 8) { - pr_warn("unexpected bitfield size %d\n", sz); + if (t->size > 8) { + pr_warn("unexpected bitfield size %d\n", t->size); return -EINVAL; } /* Bitfield value retrieval is done in two steps; first relevant bytes are * stored in num, then we left/right shift num to eliminate irrelevant bits. */ - nr_copy_bits = bit_sz + bits_offset; - nr_copy_bytes = t->size; #if __BYTE_ORDER == __LITTLE_ENDIAN - for (i = nr_copy_bytes - 1; i >= 0; i--) + for (i = t->size - 1; i >= 0; i--) num = num * 256 + bytes[i]; + nr_copy_bits = bit_sz + bits_offset; #elif __BYTE_ORDER == __BIG_ENDIAN - for (i = 0; i < nr_copy_bytes; i++) + for (i = 0; i < t->size; i++) num = num * 256 + bytes[i]; + nr_copy_bits = t->size * 8 - bits_offset; #else # error "Unrecognized __BYTE_ORDER__" #endif -- 2.30.2