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bpf: support for mmapable bpf map array (5.10+)

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automatically fall back for older kernels

Test: TreeHugger
Flag: EXEMPT mainline
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ice377331442f71fa69f086a3be8a8c10cbc6575f
This commit is contained in:
Maciej Żenczykowski 2025-08-07 14:41:49 -07:00
commit ede2d5fe39
2 changed files with 12 additions and 4 deletions
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13
bpf/loader/NetBpfLoad.cpp
View file

@ -419,6 +419,11 @@ int readCodeSections(ElfObject& elfObj, vector<codeSection>& cs) {
return 0;
}
static unsigned int sanitizeMapFlags(unsigned int map_flags) {
if (!isAtLeastKernelVersion(5, 10, 0)) map_flags &= ~BPF_F_MMAPABLE;
return map_flags;
}
static bool mapMatchesExpectations(const unique_fd& fd,
const struct bpf_map_def& mapDef, const enum bpf_map_type type) {
// bpfGetFd... family of functions require at minimum a 4.14 kernel,
@ -441,7 +446,7 @@ static bool mapMatchesExpectations(const unique_fd& fd,
// DEVMAPs are readonly from the bpf program side's point of view, as such
// the kernel in kernel/bpf/devmap.c dev_map_init_map() will set the flag
int desired_map_flags = (int)mapDef.map_flags;
unsigned int desired_map_flags = sanitizeMapFlags(mapDef.map_flags);
if (type == BPF_MAP_TYPE_DEVMAP || type == BPF_MAP_TYPE_DEVMAP_HASH)
desired_map_flags |= BPF_F_RDONLY_PROG;
@ -464,7 +469,7 @@ static bool mapMatchesExpectations(const unique_fd& fd,
(fd_key_size == (int)mapDef.key_size) &&
(fd_value_size == (int)mapDef.value_size) &&
(fd_max_entries == (int)desired_max_entries) &&
(fd_map_flags == desired_map_flags)) {
(fd_map_flags == (int)desired_map_flags)) {
return true;
}
@ -869,7 +874,7 @@ static int createMaps(ElfObject& elfObj, vector<struct bpf_map_def>& md, vector<
.key_size = md[i].key_size,
.value_size = md[i].value_size,
.max_entries = max_entries,
.map_flags = md[i].map_flags,
.map_flags = sanitizeMapFlags(md[i].map_flags),
};
if (isAtLeastKernelVersion(4, 15, 0))
strlcpy(req.map_name, md[i].name(), sizeof(req.map_name));
@ -1169,7 +1174,7 @@ static int prepareLoadMaps(const struct bpf_object* obj, const vector<struct bpf
}
bpf_map__set_type(m, sanitizeMapType(md[i].type));
bpf_map__set_map_flags(m, md[i].map_flags);
bpf_map__set_map_flags(m, sanitizeMapFlags(md[i].map_flags));
}
return 0;
}

3
bpf/progs/include/bpf_helpers.h
View file

@ -236,10 +236,13 @@ static long (*bpf_sk_storage_delete_unsafe) (const void* sk_storage,
#define ABSOLUTE(x) ((x) < 0 ? -(x) : (x))
#define BPF_MAP_TYPE_MMAPABLE_ARRAY BPF_MAP_TYPE_ARRAY
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_ARRAY 0
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_DEVMAP_HASH 0
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_HASH 0
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_LPM_TRIE BPF_F_NO_PREALLOC
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_MMAPABLE_ARRAY BPF_F_MMAPABLE
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_PERCPU_ARRAY 0
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_RINGBUF 0
#define DEFAULT_FLAGS_FOR_BPF_MAP_TYPE_SK_STORAGE BPF_F_NO_PREALLOC