Commit d7ba4cc9 authored by JP Kobryn's avatar JP Kobryn Committed by Alexei Starovoitov
Browse files

bpf: return long from bpf_map_ops funcs 



This patch changes the return types of bpf_map_ops functions to long, where
previously int was returned. Using long allows for bpf programs to maintain
the sign bit in the absence of sign extension during situations where
inlined bpf helper funcs make calls to the bpf_map_ops funcs and a negative
error is returned.

The definitions of the helper funcs are generated from comments in the bpf
uapi header at `include/uapi/linux/bpf.h`. The return type of these
helpers was previously changed from int to long in commit bdb7b79b. For
any case where one of the map helpers call the bpf_map_ops funcs that are
still returning 32-bit int, a compiler might not include sign extension
instructions to properly convert the 32-bit negative value a 64-bit
negative value.

For example:
bpf assembly excerpt of an inlined helper calling a kernel function and
checking for a specific error:

; err = bpf_map_update_elem(&mymap, &key, &val, BPF_NOEXIST);
  ...
  46:	call   0xffffffffe103291c	; htab_map_update_elem
; if (err && err != -EEXIST) {
  4b:	cmp    $0xffffffffffffffef,%rax ; cmp -EEXIST,%rax

kernel function assembly excerpt of return value from
`htab_map_update_elem` returning 32-bit int:

movl $0xffffffef, %r9d
...
movl %r9d, %eax

...results in the comparison:
cmp $0xffffffffffffffef, $0x00000000ffffffef

Fixes: bdb7b79b ("bpf: Switch most helper return values from 32-bit int to 64-bit long")
Tested-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarJP Kobryn <inwardvessel@gmail.com>
Link: https://lore.kernel.org/r/20230322194754.185781-3-inwardvessel@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 830154cd

include/linux/bpf.h

+7 −7
Original line number Diff line number Diff line
@@ -96,11 +96,11 @@ struct bpf_map_ops { 


	/* funcs callable from userspace and from eBPF programs */

	void *(*map_lookup_elem)(struct bpf_map *map, void *key);

	int (*map_update_elem)(struct bpf_map *map, void *key, void *value, u64 flags);

	int (*map_delete_elem)(struct bpf_map *map, void *key);

	int (*map_push_elem)(struct bpf_map *map, void *value, u64 flags);

	int (*map_pop_elem)(struct bpf_map *map, void *value);

	int (*map_peek_elem)(struct bpf_map *map, void *value);

	long (*map_update_elem)(struct bpf_map *map, void *key, void *value, u64 flags);

	long (*map_delete_elem)(struct bpf_map *map, void *key);

	long (*map_push_elem)(struct bpf_map *map, void *value, u64 flags);

	long (*map_pop_elem)(struct bpf_map *map, void *value);

	long (*map_peek_elem)(struct bpf_map *map, void *value);

	void *(*map_lookup_percpu_elem)(struct bpf_map *map, void *key, u32 cpu);



	/* funcs called by prog_array and perf_event_array map */
@@ -139,7 +139,7 @@ struct bpf_map_ops { 
	struct bpf_local_storage __rcu ** (*map_owner_storage_ptr)(void *owner);



	/* Misc helpers.*/

	int (*map_redirect)(struct bpf_map *map, u64 key, u64 flags);

	long (*map_redirect)(struct bpf_map *map, u64 key, u64 flags);



	/* map_meta_equal must be implemented for maps that can be

	 * used as an inner map.  It is a runtime check to ensure
@@ -157,7 +157,7 @@ struct bpf_map_ops { 
	int (*map_set_for_each_callback_args)(struct bpf_verifier_env *env,

					      struct bpf_func_state *caller,

					      struct bpf_func_state *callee);

	int (*map_for_each_callback)(struct bpf_map *map,

	long (*map_for_each_callback)(struct bpf_map *map,

				     bpf_callback_t callback_fn,

				     void *callback_ctx, u64 flags);

include/linux/filter.h

+3 −3
Original line number Diff line number Diff line
@@ -1504,7 +1504,7 @@ static inline bool bpf_sk_lookup_run_v6(struct net *net, int protocol, 
}

#endif /* IS_ENABLED(CONFIG_IPV6) */



static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u64 index,

static __always_inline long __bpf_xdp_redirect_map(struct bpf_map *map, u64 index,

						   u64 flags, const u64 flag_mask,

						   void *lookup_elem(struct bpf_map *map, u32 key))

{

kernel/bpf/arraymap.c

+6 −6
Original line number Diff line number Diff line
@@ -307,7 +307,7 @@ static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key 
}



/* Called from syscall or from eBPF program */

static int array_map_update_elem(struct bpf_map *map, void *key, void *value,

static long array_map_update_elem(struct bpf_map *map, void *key, void *value,

				  u64 map_flags)

{

	struct bpf_array *array = container_of(map, struct bpf_array, map);
@@ -386,7 +386,7 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value, 
}



/* Called from syscall or from eBPF program */

static int array_map_delete_elem(struct bpf_map *map, void *key)

static long array_map_delete_elem(struct bpf_map *map, void *key)

{

	return -EINVAL;

}
@@ -686,7 +686,7 @@ static const struct bpf_iter_seq_info iter_seq_info = { 
	.seq_priv_size		= sizeof(struct bpf_iter_seq_array_map_info),

};



static int bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback_fn,

static long bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback_fn,

				    void *callback_ctx, u64 flags)

{

	u32 i, key, num_elems = 0;
@@ -871,7 +871,7 @@ int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file, 
	return 0;

}



static int fd_array_map_delete_elem(struct bpf_map *map, void *key)

static long fd_array_map_delete_elem(struct bpf_map *map, void *key)

{

	struct bpf_array *array = container_of(map, struct bpf_array, map);

	void *old_ptr;

kernel/bpf/bloom_filter.c

+6 −6
Original line number Diff line number Diff line
@@ -41,7 +41,7 @@ static u32 hash(struct bpf_bloom_filter *bloom, void *value, 
	return h & bloom->bitset_mask;

}



static int bloom_map_peek_elem(struct bpf_map *map, void *value)

static long bloom_map_peek_elem(struct bpf_map *map, void *value)

{

	struct bpf_bloom_filter *bloom =

		container_of(map, struct bpf_bloom_filter, map);
@@ -56,7 +56,7 @@ static int bloom_map_peek_elem(struct bpf_map *map, void *value) 
	return 0;

}



static int bloom_map_push_elem(struct bpf_map *map, void *value, u64 flags)

static long bloom_map_push_elem(struct bpf_map *map, void *value, u64 flags)

{

	struct bpf_bloom_filter *bloom =

		container_of(map, struct bpf_bloom_filter, map);
@@ -73,12 +73,12 @@ static int bloom_map_push_elem(struct bpf_map *map, void *value, u64 flags) 
	return 0;

}



static int bloom_map_pop_elem(struct bpf_map *map, void *value)

static long bloom_map_pop_elem(struct bpf_map *map, void *value)

{

	return -EOPNOTSUPP;

}



static int bloom_map_delete_elem(struct bpf_map *map, void *value)

static long bloom_map_delete_elem(struct bpf_map *map, void *value)

{

	return -EOPNOTSUPP;

}
@@ -177,7 +177,7 @@ static void *bloom_map_lookup_elem(struct bpf_map *map, void *key) 
	return ERR_PTR(-EINVAL);

}



static int bloom_map_update_elem(struct bpf_map *map, void *key,

static long bloom_map_update_elem(struct bpf_map *map, void *key,

				  void *value, u64 flags)

{

	/* The eBPF program should use map_push_elem instead */

kernel/bpf/bpf_cgrp_storage.c

+3 −3
Original line number Diff line number Diff line
@@ -93,7 +93,7 @@ static void *bpf_cgrp_storage_lookup_elem(struct bpf_map *map, void *key) 
	return sdata ? sdata->data : NULL;

}



static int bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key,

static long bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key,

					 void *value, u64 map_flags)

{

	struct bpf_local_storage_data *sdata;
@@ -125,7 +125,7 @@ static int cgroup_storage_delete(struct cgroup *cgroup, struct bpf_map *map) 
	return 0;

}



static int bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)

static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)

{

	struct cgroup *cgroup;

	int err, fd;