Hi Baruch,
On Fri, May 3, 2019 at 6:06 AM Baruch Siach <baruch@xxxxxxxxxx> wrote:
strace 5.0 fails to build for m86k/5208 with the Buildroot generated
toolchain:
In file included from bpf_attr_check.c:6:0:
static_assert.h:20:25: error: static assertion failed: "bpf_prog_info_struct.nr_jited_ksyms offset mismatch"
# define static_assert _Static_assert
^
bpf_attr_check.c:913:2: note: in expansion of macro ‘static_assert’
static_assert(offsetof(struct bpf_prog_info_struct, nr_jited_ksyms) == offsetof(struct bpf_prog_info, nr_jited_ksyms),
^~~~~~~~~~~~~
The direct cause is a difference in the hole after the gpl_compatible
field. Here is pahole output for the kernel struct (from v4.19):
struct bpf_prog_info {
...
__u32 ifindex; /* 80 4 */
__u32 gpl_compatible:1; /* 84: 0 4 */
/* XXX 15 bits hole, try to pack */
/* Bitfield combined with next fields */
__u64 netns_dev; /* 86 8 */
I guess that should be "__aligned_u64 netns_dev;", to not rely on
implicit alignment.
And this is for the strace struct:
struct bpf_prog_info_struct {
...
uint32_t ifindex; /* 80 4 */
uint32_t gpl_compatible:1; /* 84: 0 4 */
/* XXX 31 bits hole, try to pack */
How come the uint64_t below is 8-byte aligned, not 2-byte aligned?
Does strace use a special definition of uint64_t?
uint64_t netns_dev; /* 88 8 */
How should this be fixed?
IMHO all "__u64" in structs tagged "__attribute__((aligned(8)))" should
be replaced by "__aligned_u64", which is what the (whitespace-damaged)
diff below does.
Note that changing __bpf_md_ptr() may have a visible effect, as it is
used with struct bpf_sock, which has a size that is not a multiple of
8 bytes. So depending on architecture, a hole may appear.
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -362,7 +362,7 @@ union bpf_attr {
__aligned_u64 value;
__aligned_u64 next_key;
};
- __u64 flags;
+ __aligned_u64 flags;
};
struct { /* anonymous struct used by BPF_PROG_LOAD command */
@@ -452,7 +452,7 @@ union bpf_attr {
} query;
struct {
- __u64 name;
+ __aligned_u64 name;
__u32 prog_fd;
} raw_tracepoint;
@@ -476,8 +476,8 @@ union bpf_attr {
*/
__u32 prog_id; /* output: prod_id */
__u32 fd_type; /* output: BPF_FD_TYPE_* */
- __u64 probe_offset; /* output: probe_offset */
- __u64 probe_addr; /* output: probe_addr */
+ __aligned_u64 probe_offset; /* output: probe_offset */
+ __aligned_u64 probe_addr; /* output: probe_addr */
} task_fd_query;
} __attribute__((aligned(8)));
@@ -2878,7 +2878,7 @@ enum bpf_lwt_encap_mode {
#define __bpf_md_ptr(type, name) \
union { \
type name; \
- __u64 :64; \
+ __aligned_u64 :64; \
} __attribute__((aligned(8)))
/* user accessible mirror of in-kernel sk_buff.
@@ -3129,15 +3129,15 @@ struct bpf_prog_info {
__u32 xlated_prog_len;
__aligned_u64 jited_prog_insns;
__aligned_u64 xlated_prog_insns;
- __u64 load_time; /* ns since boottime */
+ __aligned_u64 load_time; /* ns since boottime */
__u32 created_by_uid;
__u32 nr_map_ids;
__aligned_u64 map_ids;
char name[BPF_OBJ_NAME_LEN];
__u32 ifindex;
__u32 gpl_compatible:1;
- __u64 netns_dev;
- __u64 netns_ino;
+ __aligned_u64 netns_dev;
+ __aligned_u64 netns_ino;
__u32 nr_jited_ksyms;
__u32 nr_jited_func_lens;
__aligned_u64 jited_ksyms;
@@ -3154,8 +3154,8 @@ struct bpf_prog_info {
__u32 jited_line_info_rec_size;
__u32 nr_prog_tags;
__aligned_u64 prog_tags;
- __u64 run_time_ns;
- __u64 run_cnt;
+ __aligned_u64 run_time_ns;
+ __aligned_u64 run_cnt;
} __attribute__((aligned(8)));
struct bpf_map_info {
@@ -3168,8 +3168,8 @@ struct bpf_map_info {
char name[BPF_OBJ_NAME_LEN];
__u32 ifindex;
__u32 :32;
- __u64 netns_dev;
- __u64 netns_ino;
+ __aligned_u64 netns_dev;
+ __aligned_u64 netns_ino;
__u32 btf_id;
__u32 btf_key_type_id;
__u32 btf_value_type_id;
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
