From f56a653c1fd13a197076dec4461c656fd2adec73 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Wed, 18 Apr 2018 15:56:01 -0700 Subject: [PATCH] bpf: btf: Add BPF_BTF_LOAD command This patch adds a BPF_BTF_LOAD command which 1) loads and verifies the BTF (implemented in earlier patches) 2) returns a BTF fd to userspace. In the next patch, the BTF fd can be specified during BPF_MAP_CREATE. It currently limits to CAP_SYS_ADMIN. Signed-off-by: Martin KaFai Lau Acked-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann --- include/linux/btf.h | 4 +++ include/uapi/linux/bpf.h | 9 ++++++ kernel/bpf/btf.c | 67 ++++++++++++++++++++++++++++++++++++++++ kernel/bpf/syscall.c | 17 ++++++++++ 4 files changed, 97 insertions(+) diff --git a/include/linux/btf.h b/include/linux/btf.h index d8bdab0280ba..a7c7072535ea 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -8,7 +8,11 @@ struct btf; struct btf_type; +union bpf_attr; +void btf_put(struct btf *btf); +int btf_new_fd(const union bpf_attr *attr); +struct btf *btf_get_by_fd(int fd); /* Figure out the size of a type_id. If type_id is a modifier * (e.g. const), it will be resolved to find out the type with size. * diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 9a2d1a04eb24..795bcd577750 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -95,6 +95,7 @@ enum bpf_cmd { BPF_OBJ_GET_INFO_BY_FD, BPF_PROG_QUERY, BPF_RAW_TRACEPOINT_OPEN, + BPF_BTF_LOAD, }; enum bpf_map_type { @@ -363,6 +364,14 @@ union bpf_attr { __u64 name; __u32 prog_fd; } raw_tracepoint; + + struct { /* anonymous struct for BPF_BTF_LOAD */ + __aligned_u64 btf; + __aligned_u64 btf_log_buf; + __u32 btf_size; + __u32 btf_log_size; + __u32 btf_log_level; + }; } __attribute__((aligned(8))); /* BPF helper function descriptions: diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 10ee41589da2..2322340694cf 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -7,6 +7,8 @@ #include #include #include +#include +#include #include #include #include @@ -190,6 +192,7 @@ struct btf { u32 nr_types; u32 types_size; u32 data_size; + refcount_t refcnt; }; enum verifier_phase { @@ -604,6 +607,17 @@ static void btf_free(struct btf *btf) kfree(btf); } +static void btf_get(struct btf *btf) +{ + refcount_inc(&btf->refcnt); +} + +void btf_put(struct btf *btf) +{ + if (btf && refcount_dec_and_test(&btf->refcnt)) + btf_free(btf); +} + static int env_resolve_init(struct btf_verifier_env *env) { struct btf *btf = env->btf; @@ -1963,6 +1977,7 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size, if (!err) { btf_verifier_env_free(env); + btf_get(btf); return btf; } @@ -1980,3 +1995,55 @@ void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj, btf_type_ops(t)->seq_show(btf, t, type_id, obj, 0, m); } + +static int btf_release(struct inode *inode, struct file *filp) +{ + btf_put(filp->private_data); + return 0; +} + +static const struct file_operations btf_fops = { + .release = btf_release, +}; + +int btf_new_fd(const union bpf_attr *attr) +{ + struct btf *btf; + int fd; + + btf = btf_parse(u64_to_user_ptr(attr->btf), + attr->btf_size, attr->btf_log_level, + u64_to_user_ptr(attr->btf_log_buf), + attr->btf_log_size); + if (IS_ERR(btf)) + return PTR_ERR(btf); + + fd = anon_inode_getfd("btf", &btf_fops, btf, + O_RDONLY | O_CLOEXEC); + if (fd < 0) + btf_put(btf); + + return fd; +} + +struct btf *btf_get_by_fd(int fd) +{ + struct btf *btf; + struct fd f; + + f = fdget(fd); + + if (!f.file) + return ERR_PTR(-EBADF); + + if (f.file->f_op != &btf_fops) { + fdput(f); + return ERR_PTR(-EINVAL); + } + + btf = f.file->private_data; + btf_get(btf); + fdput(f); + + return btf; +} diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 4ca46df19c9a..cd8ebadc66eb 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -11,6 +11,7 @@ */ #include #include +#include #include #include #include @@ -2023,6 +2024,19 @@ static int bpf_obj_get_info_by_fd(const union bpf_attr *attr, return err; } +#define BPF_BTF_LOAD_LAST_FIELD btf_log_level + +static int bpf_btf_load(const union bpf_attr *attr) +{ + if (CHECK_ATTR(BPF_BTF_LOAD)) + return -EINVAL; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + return btf_new_fd(attr); +} + SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size) { union bpf_attr attr = {}; @@ -2103,6 +2117,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz case BPF_RAW_TRACEPOINT_OPEN: err = bpf_raw_tracepoint_open(&attr); break; + case BPF_BTF_LOAD: + err = bpf_btf_load(&attr); + break; default: err = -EINVAL; break;