bpf: enforce usage of __aligned_u64 in the UAPI header

Use __aligned_u64 instead of __u64 everywhere in the UAPI header, similarly to v4.17-rc1~94^2~58^2 "RDMA: Change all uapi headers to use __aligned_u64 instead of __u64".

This commit doesn't change structure layouts, but imposes additional alignment requirements on struct bpf_stack_build_id, struct bpf_sock_ops, struct bpf_perf_event_value, and struct bpf_raw_tracepoint_args; of them only struct bpf_sock_ops and struct bpf_perf_event_value have 64-bit fields that were present in a released kernel without this additional alignment requirement (bytes_received and bytes_acked were added to struct bpf_sock_ops in commit v4.16-rc1~123^2~33^2~5^2~4, struct bpf_perf_event_value was added in commit v4.15-rc1~84^2~532^2~3).

Signed-off-by Eugene Syromiatnikov <[email protected]>

---
 include/uapi/linux/bpf.h       | 22 +++++++++++-----------
 tools/include/uapi/linux/bpf.h | 22 +++++++++++-----------
 2 files changed, 22 insertions(+), 22 deletions(-)

include/uapi/linux/bpf.h +11 -11

index 903010a..174e99a 100644
@@ -259,8 +259,8 @@ struct bpf_stack_build_id {
        __s32           status;
        unsigned char   build_id[BPF_BUILD_ID_SIZE];
        union {
-               __u64   offset;
-               __u64   ip;
+               __aligned_u64   offset;
+               __aligned_u64   ip;
        };
 };
 

@@ -288,7 +288,7 @@ union bpf_attr {
                        __aligned_u64 value;
                        __aligned_u64 next_key;
                };
-               __u64           flags;
+               __aligned_u64   flags;
        };
 
        struct { /* anonymous struct used by BPF_PROG_LOAD command */

@@ -360,7 +360,7 @@ union bpf_attr {
        } query;
 
        struct {
-               __u64 name;
+               __aligned_u64 name;
                __u32 prog_fd;
        } raw_tracepoint;
 } __attribute__((aligned(8)));

@@ -1011,7 +1011,7 @@ 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;

@@ -1101,8 +1101,8 @@ struct bpf_sock_ops {
        __u32 lost_out;
        __u32 sacked_out;
        __u32 sk_txhash;
-       __u64 bytes_received;
-       __u64 bytes_acked;
+       __aligned_u64 bytes_received;
+       __aligned_u64 bytes_acked;
 };
 
 /* Definitions for bpf_sock_ops_cb_flags */

@@ -1189,9 +1189,9 @@ enum {
 #define TCP_BPF_SNDCWND_CLAMP  1002    /* Set sndcwnd_clamp */
 
 struct bpf_perf_event_value {
-       __u64 counter;
-       __u64 enabled;
-       __u64 running;
+       __aligned_u64 counter;
+       __aligned_u64 enabled;
+       __aligned_u64 running;
 };
 
 #define BPF_DEVCG_ACC_MKNOD    (1ULL << 0)

@@ -1209,7 +1209,7 @@ struct bpf_cgroup_dev_ctx {
 };
 
 struct bpf_raw_tracepoint_args {
-       __u64 args[0];
+       __aligned_u64 args[0];
 };
 
 #endif /* _UAPI__LINUX_BPF_H__ */

tools/include/uapi/linux/bpf.h +11 -12

index 903010a..174e99a 100644
@@ -259,8 +259,8 @@ struct bpf_stack_build_id {
        __s32           status;
        unsigned char   build_id[BPF_BUILD_ID_SIZE];
        union {
-               __u64   offset;
-               __u64   ip;
+               __aligned_u64   offset;
+               __aligned_u64   ip;
        };
 };
 

@@ -288,7 +288,7 @@ union bpf_attr {
                        __aligned_u64 value;
                        __aligned_u64 next_key;
                };
-               __u64           flags;
+               __aligned_u64   flags;
        };
 
        struct { /* anonymous struct used by BPF_PROG_LOAD command */

@@ -360,7 +360,7 @@ union bpf_attr {
        } query;
 
        struct {
-               __u64 name;
+               __aligned_u64 name;
                __u32 prog_fd;
        } raw_tracepoint;
 } __attribute__((aligned(8)));

@@ -1011,7 +1011,7 @@ 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;

@@ -1101,8 +1101,8 @@ struct bpf_sock_ops {
        __u32 lost_out;
        __u32 sacked_out;
        __u32 sk_txhash;
-       __u64 bytes_received;
-       __u64 bytes_acked;
+       __aligned_u64 bytes_received;
+       __aligned_u64 bytes_acked;
 };
 
 /* Definitions for bpf_sock_ops_cb_flags */

@@ -1189,9 +1189,9 @@ enum {
 #define TCP_BPF_SNDCWND_CLAMP  1002    /* Set sndcwnd_clamp */
 
 struct bpf_perf_event_value {
-       __u64 counter;
-       __u64 enabled;
-       __u64 running;
+       __aligned_u64 counter;
+       __aligned_u64 enabled;
+       __aligned_u64 running;
 };
 
 #define BPF_DEVCG_ACC_MKNOD    (1ULL << 0)

@@ -1209,7 +1209,7 @@ struct bpf_cgroup_dev_ctx {
 };
 
 struct bpf_raw_tracepoint_args {
-       __u64 args[0];
+       __aligned_u64 args[0];
 };
 
 #endif /* _UAPI__LINUX_BPF_H__ */
--

2.1.4

I think these changes are not necessary. Is it a general guidance to only use 64-bit aligned
variables in UAPI headers?