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Message-ID: <20251125145857.98134-3-leon.hwang@linux.dev>
Date: Tue, 25 Nov 2025 22:58:51 +0800
From: Leon Hwang <leon.hwang@...ux.dev>
To: bpf@...r.kernel.org
Cc: ast@...nel.org,
andrii@...nel.org,
daniel@...earbox.net,
jolsa@...nel.org,
yonghong.song@...ux.dev,
song@...nel.org,
eddyz87@...il.com,
dxu@...uu.xyz,
deso@...teo.net,
martin.lau@...ux.dev,
john.fastabend@...il.com,
kpsingh@...nel.org,
sdf@...ichev.me,
haoluo@...gle.com,
shuah@...nel.org,
kerneljasonxing@...il.com,
chen.dylane@...ux.dev,
willemb@...gle.com,
paul.chaignon@...il.com,
a.s.protopopov@...il.com,
memxor@...il.com,
yatsenko@...a.com,
tklauser@...tanz.ch,
leon.hwang@...ux.dev,
kernel-patches-bot@...com,
linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: [PATCH bpf-next v11 2/8] bpf: Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags
Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags and check them for
following APIs:
* 'map_lookup_elem()'
* 'map_update_elem()'
* 'generic_map_lookup_batch()'
* 'generic_map_update_batch()'
And, get the correct value size for these APIs.
Acked-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Leon Hwang <leon.hwang@...ux.dev>
---
v10 -> v11:
- Use '(BPF_F_ALL_CPUS << 1) - 1' as allowed_flags in map_update_elem().
- Add BPF_EXIST to allowed_flags in generic_map_update_batch().
---
include/linux/bpf.h | 23 +++++++++++++++++++++-
include/uapi/linux/bpf.h | 2 ++
kernel/bpf/syscall.c | 36 ++++++++++++++++++++--------------
tools/include/uapi/linux/bpf.h | 2 ++
4 files changed, 47 insertions(+), 16 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6498be4c44f8..d84af3719b59 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3829,14 +3829,35 @@ bpf_prog_update_insn_ptrs(struct bpf_prog *prog, u32 *offsets, void *image)
}
#endif
+static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type)
+{
+ return false;
+}
+
static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 allowed_flags)
{
- if (flags & ~allowed_flags)
+ u32 cpu;
+
+ if ((u32)flags & ~allowed_flags)
return -EINVAL;
if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
return -EINVAL;
+ if (!(flags & BPF_F_CPU) && flags >> 32)
+ return -EINVAL;
+
+ if (flags & (BPF_F_CPU | BPF_F_ALL_CPUS)) {
+ if (!bpf_map_supports_cpu_flags(map->map_type))
+ return -EINVAL;
+ if ((flags & BPF_F_CPU) && (flags & BPF_F_ALL_CPUS))
+ return -EINVAL;
+
+ cpu = flags >> 32;
+ if ((flags & BPF_F_CPU) && cpu >= num_possible_cpus())
+ return -ERANGE;
+ }
+
return 0;
}
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f5713f59ac10..8b6279ca6e66 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1373,6 +1373,8 @@ enum {
BPF_NOEXIST = 1, /* create new element if it didn't exist */
BPF_EXIST = 2, /* update existing element */
BPF_F_LOCK = 4, /* spin_lock-ed map_lookup/map_update */
+ BPF_F_CPU = 8, /* cpu flag for percpu maps, upper 32-bit of flags is a cpu number */
+ BPF_F_ALL_CPUS = 16, /* update value across all CPUs for percpu maps */
};
/* flags for BPF_MAP_CREATE command */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index cef8963d69f9..3c3e3b4095b9 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -133,12 +133,14 @@ bool bpf_map_write_active(const struct bpf_map *map)
return atomic64_read(&map->writecnt) != 0;
}
-static u32 bpf_map_value_size(const struct bpf_map *map)
-{
- if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
- map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
- map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY ||
- map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
+static u32 bpf_map_value_size(const struct bpf_map *map, u64 flags)
+{
+ if (flags & (BPF_F_CPU | BPF_F_ALL_CPUS))
+ return map->value_size;
+ else if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
+ map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
+ map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY ||
+ map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
return round_up(map->value_size, 8) * num_possible_cpus();
else if (IS_FD_MAP(map))
return sizeof(u32);
@@ -1732,7 +1734,7 @@ static int map_lookup_elem(union bpf_attr *attr)
if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
return -EPERM;
- err = bpf_map_check_op_flags(map, attr->flags, BPF_F_LOCK);
+ err = bpf_map_check_op_flags(map, attr->flags, BPF_F_LOCK | BPF_F_CPU);
if (err)
return err;
@@ -1740,7 +1742,7 @@ static int map_lookup_elem(union bpf_attr *attr)
if (IS_ERR(key))
return PTR_ERR(key);
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, attr->flags);
err = -ENOMEM;
value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);
@@ -1781,6 +1783,7 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
bpfptr_t uvalue = make_bpfptr(attr->value, uattr.is_kernel);
struct bpf_map *map;
void *key, *value;
+ u64 allowed_flags;
u32 value_size;
int err;
@@ -1797,7 +1800,8 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
goto err_put;
}
- err = bpf_map_check_op_flags(map, attr->flags, ~0);
+ allowed_flags = (BPF_F_ALL_CPUS << 1) - 1;
+ err = bpf_map_check_op_flags(map, attr->flags, allowed_flags);
if (err)
goto err_put;
@@ -1807,7 +1811,7 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
goto err_put;
}
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, attr->flags);
value = kvmemdup_bpfptr(uvalue, value_size);
if (IS_ERR(value)) {
err = PTR_ERR(value);
@@ -2001,13 +2005,15 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
void __user *keys = u64_to_user_ptr(attr->batch.keys);
u32 value_size, cp, max_count;
void *key, *value;
+ u64 allowed_flags;
int err = 0;
- err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK);
+ allowed_flags = BPF_EXIST | BPF_F_LOCK | BPF_F_CPU | BPF_F_ALL_CPUS;
+ err = bpf_map_check_op_flags(map, attr->batch.elem_flags, allowed_flags);
if (err)
return err;
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, attr->batch.elem_flags);
max_count = attr->batch.count;
if (!max_count)
@@ -2062,11 +2068,11 @@ int generic_map_lookup_batch(struct bpf_map *map,
u32 value_size, cp, max_count;
int err;
- err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK);
+ err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK | BPF_F_CPU);
if (err)
return err;
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, attr->batch.elem_flags);
max_count = attr->batch.count;
if (!max_count)
@@ -2188,7 +2194,7 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
goto err_put;
}
- value_size = bpf_map_value_size(map);
+ value_size = bpf_map_value_size(map, 0);
err = -ENOMEM;
value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index f5713f59ac10..8b6279ca6e66 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1373,6 +1373,8 @@ enum {
BPF_NOEXIST = 1, /* create new element if it didn't exist */
BPF_EXIST = 2, /* update existing element */
BPF_F_LOCK = 4, /* spin_lock-ed map_lookup/map_update */
+ BPF_F_CPU = 8, /* cpu flag for percpu maps, upper 32-bit of flags is a cpu number */
+ BPF_F_ALL_CPUS = 16, /* update value across all CPUs for percpu maps */
};
/* flags for BPF_MAP_CREATE command */
--
2.51.2
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