This patch makes 2 changes regarding alignment padding
for the "map_extra" field.
1) In the kernel header, "map_extra" and "btf_value_type_id"
are rearranged to consolidate the hole.
Before:
struct bpf_map {
...
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
/* XXX 4 bytes hole, try to pack */
u64 map_extra; /* 48 8 */
int spin_lock_off; /* 56 4 */
int timer_off; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
u32 id; /* 64 4 */
int numa_node; /* 68 4 */
...
bool frozen; /* 117 1 */
/* XXX 10 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
...
struct work_struct work; /* 144 72 */
/* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */
struct mutex freeze_mutex; /* 216 144 */
/* --- cacheline 5 boundary (320 bytes) was 40 bytes ago --- */
u64 writecnt; /* 360 8 */
/* size: 384, cachelines: 6, members: 26 */
/* sum members: 354, holes: 2, sum holes: 14 */
/* padding: 16 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 10 */
} __attribute__((__aligned__(64)));
After:
struct bpf_map {
...
u32 max_entries; /* 36 4 */
u64 map_extra; /* 40 8 */
u32 map_flags; /* 48 4 */
int spin_lock_off; /* 52 4 */
int timer_off; /* 56 4 */
u32 id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
int numa_node; /* 64 4 */
...
bool frozen /* 113 1 */
/* XXX 14 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
...
struct work_struct work; /* 144 72 */
/* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */
struct mutex freeze_mutex; /* 216 144 */
/* --- cacheline 5 boundary (320 bytes) was 40 bytes ago --- */
u64 writecnt; /* 360 8 */
/* size: 384, cachelines: 6, members: 26 */
/* sum members: 354, holes: 1, sum holes: 14 */
/* padding: 16 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 14 */
} __attribute__((__aligned__(64)));
2) Add alignment padding to the bpf_map_info struct
More details can be found in commit 36f9814a494a ("bpf: fix uapi hole
for 32 bit compat applications")
Signed-off-by: Joanne Koong <joannekoong@xxxxxx>
---
include/linux/bpf.h | 6 +++---
include/uapi/linux/bpf.h | 1 +
tools/include/uapi/linux/bpf.h | 1 +
3 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6deebf8bf78f..d695b2ef67d5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -168,23 +168,23 @@ struct bpf_map {
u32 key_size;
u32 value_size;
u32 max_entries;
- u32 map_flags;
u64 map_extra; /* any per-map-type extra fields */
+ u32 map_flags;
int spin_lock_off; /* >=0 valid offset, <0 error */
int timer_off; /* >=0 valid offset, <0 error */
u32 id;
int numa_node;
u32 btf_key_type_id;
u32 btf_value_type_id;
+ u32 btf_vmlinux_value_type_id;
struct btf *btf;
#ifdef CONFIG_MEMCG_KMEM
struct mem_cgroup *memcg;
#endif
char name[BPF_OBJ_NAME_LEN];
- u32 btf_vmlinux_value_type_id;
bool bypass_spec_v1;
bool frozen; /* write-once; write-protected by freeze_mutex */
- /* 22 bytes hole */
+ /* 14 bytes hole */
/* The 3rd and 4th cacheline with misc members to avoid false sharing
* particularly with refcounting.
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index bd0c9f0487f6..ba5af15e25f5 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5662,6 +5662,7 @@ struct bpf_map_info {
__u32 btf_id;
__u32 btf_key_type_id;
__u32 btf_value_type_id;
+ __u32 :32; /* alignment pad */
__u64 map_extra;
} __attribute__((aligned(8)));
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index bd0c9f0487f6..ba5af15e25f5 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5662,6 +5662,7 @@ struct bpf_map_info {
__u32 btf_id;
__u32 btf_key_type_id;
__u32 btf_value_type_id;
+ __u32 :32; /* alignment pad */
__u64 map_extra;
} __attribute__((aligned(8)));
--
2.30.2
