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Merge branch 'libbpf: add bpf_core_cast() helper'

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Andrii Nakryiko says:

====================
Add bpf_core_cast(<ptr>, <type>) macro wrapper around bpf_rdonly_cast() kfunc
to make it easier to use this functionality in BPF code. See patch #2 for
BPF selftests conversions demonstrating improvements in code succinctness.
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Martin KaFai Lau 2024-01-30 15:55:50 -08:00
commit e400925057
10 changed files with 27 additions and 24 deletions
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13
tools/lib/bpf/bpf_core_read.h
View File

@ -2,6 +2,8 @@
#ifndef __BPF_CORE_READ_H__
#define __BPF_CORE_READ_H__
#include <bpf/bpf_helpers.h>
/*
* enum bpf_field_info_kind is passed as a second argument into
* __builtin_preserve_field_info() built-in to get a specific aspect of
@ -292,6 +294,17 @@ enum bpf_enum_value_kind {
#define bpf_core_read_user_str(dst, sz, src) \
bpf_probe_read_user_str(dst, sz, (const void *)__builtin_preserve_access_index(src))
extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
/*
* Cast provided pointer *ptr* into a pointer to a specified *type* in such
* a way that BPF verifier will become aware of associated kernel-side BTF
* type. This allows to access members of kernel types directly without the
* need to use BPF_CORE_READ() macros.
*/
#define bpf_core_cast(ptr, type) \
((typeof(type) *)bpf_rdonly_cast((ptr), bpf_core_type_id_kernel(type)))
#define ___concat(a, b) a ## b
#define ___apply(fn, n) ___concat(fn, n)
#define ___nth(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, __11, N, ...) N

2
tools/testing/selftests/bpf/bpf_kfuncs.h
View File

@ -63,7 +63,7 @@ extern int bpf_sk_assign_tcp_reqsk(struct __sk_buff *skb, struct sock *sk,
void *bpf_cast_to_kern_ctx(void *) __ksym;
void *bpf_rdonly_cast(void *obj, __u32 btf_id) __ksym;
extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
extern int bpf_get_file_xattr(struct file *file, const char *name,
struct bpf_dynptr *value_ptr) __ksym;

3
tools/testing/selftests/bpf/progs/connect_unix_prog.c
View File

@ -28,8 +28,7 @@ int connect_unix_prog(struct bpf_sock_addr *ctx)
if (sa_kern->uaddrlen != unaddrlen)
return 0;
sa_kern_unaddr = bpf_rdonly_cast(sa_kern->uaddr,
bpf_core_type_id_kernel(struct sockaddr_un));
sa_kern_unaddr = bpf_core_cast(sa_kern->uaddr, struct sockaddr_un);
if (memcmp(sa_kern_unaddr->sun_path, SERVUN_REWRITE_ADDRESS,
sizeof(SERVUN_REWRITE_ADDRESS) - 1) != 0)
return 0;

3
tools/testing/selftests/bpf/progs/getpeername_unix_prog.c
View File

@ -27,8 +27,7 @@ int getpeername_unix_prog(struct bpf_sock_addr *ctx)
if (sa_kern->uaddrlen != unaddrlen)
return 1;
sa_kern_unaddr = bpf_rdonly_cast(sa_kern->uaddr,
bpf_core_type_id_kernel(struct sockaddr_un));
sa_kern_unaddr = bpf_core_cast(sa_kern->uaddr, struct sockaddr_un);
if (memcmp(sa_kern_unaddr->sun_path, SERVUN_REWRITE_ADDRESS,
sizeof(SERVUN_REWRITE_ADDRESS) - 1) != 0)
return 1;

3
tools/testing/selftests/bpf/progs/getsockname_unix_prog.c
View File

@ -27,8 +27,7 @@ int getsockname_unix_prog(struct bpf_sock_addr *ctx)
if (sa_kern->uaddrlen != unaddrlen)
return 1;
sa_kern_unaddr = bpf_rdonly_cast(sa_kern->uaddr,
bpf_core_type_id_kernel(struct sockaddr_un));
sa_kern_unaddr = bpf_core_cast(sa_kern->uaddr, struct sockaddr_un);
if (memcmp(sa_kern_unaddr->sun_path, SERVUN_REWRITE_ADDRESS,
sizeof(SERVUN_REWRITE_ADDRESS) - 1) != 0)
return 1;

3
tools/testing/selftests/bpf/progs/recvmsg_unix_prog.c
View File

@ -27,8 +27,7 @@ int recvmsg_unix_prog(struct bpf_sock_addr *ctx)
if (sa_kern->uaddrlen != unaddrlen)
return 1;
sa_kern_unaddr = bpf_rdonly_cast(sa_kern->uaddr,
bpf_core_type_id_kernel(struct sockaddr_un));
sa_kern_unaddr = bpf_core_cast(sa_kern->uaddr, struct sockaddr_un);
if (memcmp(sa_kern_unaddr->sun_path, SERVUN_ADDRESS,
sizeof(SERVUN_ADDRESS) - 1) != 0)
return 1;

3
tools/testing/selftests/bpf/progs/sendmsg_unix_prog.c
View File

@ -28,8 +28,7 @@ int sendmsg_unix_prog(struct bpf_sock_addr *ctx)
if (sa_kern->uaddrlen != unaddrlen)
return 0;
sa_kern_unaddr = bpf_rdonly_cast(sa_kern->uaddr,
bpf_core_type_id_kernel(struct sockaddr_un));
sa_kern_unaddr = bpf_core_cast(sa_kern->uaddr, struct sockaddr_un);
if (memcmp(sa_kern_unaddr->sun_path, SERVUN_REWRITE_ADDRESS,
sizeof(SERVUN_REWRITE_ADDRESS) - 1) != 0)
return 0;

4
tools/testing/selftests/bpf/progs/sk_storage_omem_uncharge.c
View File

@ -12,8 +12,6 @@ int cookie_found = 0;
__u64 cookie = 0;
__u32 omem = 0;
void *bpf_rdonly_cast(void *, __u32) __ksym;
struct {
__uint(type, BPF_MAP_TYPE_SK_STORAGE);
__uint(map_flags, BPF_F_NO_PREALLOC);
@ -29,7 +27,7 @@ int BPF_PROG(bpf_local_storage_destroy, struct bpf_local_storage *local_storage)
if (local_storage_ptr != local_storage)
return 0;
sk = bpf_rdonly_cast(sk_ptr, bpf_core_type_id_kernel(struct sock));
sk = bpf_core_cast(sk_ptr, struct sock);
if (sk->sk_cookie.counter != cookie)
return 0;

4
tools/testing/selftests/bpf/progs/sock_iter_batch.c
View File

@ -32,7 +32,7 @@ int iter_tcp_soreuse(struct bpf_iter__tcp *ctx)
if (!sk)
return 0;
sk = bpf_rdonly_cast(sk, bpf_core_type_id_kernel(struct sock));
sk = bpf_core_cast(sk, struct sock);
if (sk->sk_family != AF_INET6 ||
sk->sk_state != TCP_LISTEN ||
!ipv6_addr_loopback(&sk->sk_v6_rcv_saddr))
@ -68,7 +68,7 @@ int iter_udp_soreuse(struct bpf_iter__udp *ctx)
if (!sk)
return 0;
sk = bpf_rdonly_cast(sk, bpf_core_type_id_kernel(struct sock));
sk = bpf_core_cast(sk, struct sock);
if (sk->sk_family != AF_INET6 ||
!ipv6_addr_loopback(&sk->sk_v6_rcv_saddr))
return 0;

13
tools/testing/selftests/bpf/progs/type_cast.c
View File

@ -4,6 +4,7 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
#include "bpf_kfuncs.h"
struct {
__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
@ -19,9 +20,6 @@ char name[IFNAMSIZ];
unsigned int inum;
unsigned int meta_len, frag0_len, kskb_len, kskb2_len;
void *bpf_cast_to_kern_ctx(void *) __ksym;
void *bpf_rdonly_cast(void *, __u32) __ksym;
SEC("?xdp")
int md_xdp(struct xdp_md *ctx)
{
@ -48,13 +46,12 @@ int md_skb(struct __sk_buff *skb)
/* Simulate the following kernel macro:
* #define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
*/
shared_info = bpf_rdonly_cast(kskb->head + kskb->end,
bpf_core_type_id_kernel(struct skb_shared_info));
shared_info = bpf_core_cast(kskb->head + kskb->end, struct skb_shared_info);
meta_len = shared_info->meta_len;
frag0_len = shared_info->frag_list->len;
/* kskb2 should be equal to kskb */
kskb2 = bpf_rdonly_cast(kskb, bpf_core_type_id_kernel(struct sk_buff));
kskb2 = bpf_core_cast(kskb, typeof(*kskb2));
kskb2_len = kskb2->len;
return 0;
}
@ -65,7 +62,7 @@ int BPF_PROG(untrusted_ptr, struct pt_regs *regs, long id)
struct task_struct *task, *task_dup;
task = bpf_get_current_task_btf();
task_dup = bpf_rdonly_cast(task, bpf_core_type_id_kernel(struct task_struct));
task_dup = bpf_core_cast(task, struct task_struct);
(void)bpf_task_storage_get(&enter_id, task_dup, 0, 0);
return 0;
}
@ -73,7 +70,7 @@ int BPF_PROG(untrusted_ptr, struct pt_regs *regs, long id)
SEC("?tracepoint/syscalls/sys_enter_nanosleep")
int kctx_u64(void *ctx)
{
u64 *kctx = bpf_rdonly_cast(ctx, bpf_core_type_id_kernel(u64));
u64 *kctx = bpf_core_cast(ctx, u64);
(void)kctx;
return 0;