From: Andrii Nakryiko <andriin@xxxxxx>
This patch fixes a bug in class__find_holes() with determining byte hole
as a bit hole in case where previous member is not bitfield, but current
one is aligned bitfield. See example below, notice hole classification
hw_stopped field..
$ cat test/bit_test.c
struct s {
long unused: 62;
/* 2 bit hole */
int hw_stopped;
/* 4 byte hole */
long unused2: 55;
/* 9 bit padding */
};
int main() {
static struct s s;
return 0;
}
$ clang -g test/bit_test.c -o test/bit_test
$ pahole -JV test/bit_test
File test/bit_test:
[1] STRUCT s kind_flag=1 size=24 vlen=3
unused type_id=2 bitfield_size=62 bits_offset=0
hw_stopped type_id=3 bitfield_size=0 bits_offset=64
unused2 type_id=2 bitfield_size=55 bits_offset=128
[2] INT long int size=8 bit_offset=0 nr_bits=64 encoding=SIGNED
[3] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
BEFORE:
$ pahole -F btf test/bit_test
struct s {
long int unused:62; /* 0: 0 8 */
/* XXX 2 bits hole, try to pack */
int hw_stopped; /* 8 4 */
/* XXX 32 bits hole, try to pack */
long int unused2:55; /* 16: 0 8 */
/* size: 24, cachelines: 1, members: 3 */
/* sum members: 4 */
/* sum bitfield members: 117 bits, bit holes: 2, sum bit holes: 34 bits */
/* bit_padding: 9 bits */
/* last cacheline: 24 bytes */
};
AFTER:
$ pahole -F btf test/bit_test
struct s {
long int unused:62; /* 0: 0 8 */
/* XXX 2 bits hole, try to pack */
int hw_stopped; /* 8 4 */
/* XXX 4 bytes hole, try to pack */
long int unused2:55; /* 16: 0 8 */
/* size: 24, cachelines: 1, members: 3 */
/* sum members: 4, holes: 1, sum holes: 4 */
/* sum bitfield members: 117 bits, bit holes: 1, sum bit holes: 2 bits */
/* bit_padding: 9 bits */
/* last cacheline: 24 bytes */
};
Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
---
dwarves.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/dwarves.c b/dwarves.c
index efa58a9..5be50b0 100644
--- a/dwarves.c
+++ b/dwarves.c
@@ -1223,9 +1223,9 @@ void class__find_holes(struct class *class)
if (pos->bitfield_size) {
int aligned_start = pos->byte_offset * 8;
/* we can have some alignment byte padding left,
- * but we need to be carful about bitfield spanning
+ * but we need to be careful about bitfield spanning
* multiple aligned boundaries */
- if (last_seen_bit < aligned_start && aligned_start < bit_start) {
+ if (last_seen_bit < aligned_start && aligned_start <= bit_start) {
byte_holes = pos->byte_offset - last_seen_bit / 8;
last_seen_bit = aligned_start;
}
--
2.17.1
