Adding bpf_functions object to gather and carry functions
based on their BTF id. It will be used in following patch
to attach multiple functions to bpf ftrace probe program.
With bpf_functions object we can do such attachment at one
single moment, so it will speed up tools that need this.
New struct is added to union bpf_attr, that is used for
new command BPF_FUNCTIONS_ADD:
struct { /* BPF_FUNCTIONS_ADD */
__u32 fd;
__u32 btf_id;
} functions_add;
When fd == -1 new bpf_functions object is created with one
function (specified by btf_id) and its fd is returned.
For fd >= 0 the function (specified by btf_id) is added
to the existing object for the given fd.
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 5 ++
kernel/bpf/syscall.c | 137 +++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 5 ++
3 files changed, 147 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index e1ee1be7e49b..5d616735fe1b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -862,6 +862,7 @@ enum bpf_cmd {
BPF_ITER_CREATE,
BPF_LINK_DETACH,
BPF_PROG_BIND_MAP,
+ BPF_FUNCTIONS_ADD,
};
enum bpf_map_type {
@@ -1458,6 +1459,10 @@ union bpf_attr {
__u32 flags; /* extra flags */
} prog_bind_map;
+ struct { /* BPF_FUNCTIONS_ADD */
+ __u32 fd;
+ __u32 btf_id;
+ } functions_add;
} __attribute__((aligned(8)));
/* The description below is an attempt at providing documentation to eBPF
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 90cd58520bd4..b240a500cae5 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2265,6 +2265,140 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
return err;
}
+#define BPF_FUNCTIONS_ALLOC 100
+#define BPF_FUNCTIONS_MAX (BPF_FUNCTIONS_ALLOC*10)
+
+struct bpf_functions {
+ struct mutex mutex;
+ unsigned long *addrs;
+ int cnt;
+ int alloc;
+};
+
+static int bpf_functions_release(struct inode *inode, struct file *file)
+{
+ struct bpf_functions *funcs = file->private_data;
+
+ kfree(funcs->addrs);
+ kfree(funcs);
+ return 0;
+}
+
+static const struct file_operations bpf_functions_fops = {
+ .release = bpf_functions_release,
+};
+
+static struct bpf_functions *bpf_functions_get_from_fd(u32 ufd, struct fd *p)
+{
+ struct fd f = fdget(ufd);
+
+ if (!f.file)
+ return ERR_PTR(-EBADF);
+ if (f.file->f_op != &bpf_functions_fops) {
+ fdput(f);
+ return ERR_PTR(-EINVAL);
+ }
+ *p = f;
+ return f.file->private_data;
+}
+
+static unsigned long bpf_get_kernel_func_addr(u32 btf_id, struct btf *btf)
+{
+ const struct btf_type *t;
+ const char *tname;
+
+ t = btf_type_by_id(btf, btf_id);
+ if (!t)
+ return 0;
+ tname = btf_name_by_offset(btf, t->name_off);
+ if (!tname)
+ return 0;
+ if (!btf_type_is_func(t))
+ return 0;
+ t = btf_type_by_id(btf, t->type);
+ if (!btf_type_is_func_proto(t))
+ return 0;
+
+ return kallsyms_lookup_name(tname);
+}
+
+#define BPF_FUNCTIONS_ADD_LAST_FIELD functions_add.btf_id
+
+static int bpf_functions_add(union bpf_attr *attr)
+{
+ struct bpf_functions *funcs;
+ unsigned long addr, *p;
+ struct fd orig = { };
+ int ret = 0, fd;
+ struct btf *btf;
+
+ if (CHECK_ATTR(BPF_FUNCTIONS_ADD))
+ return -EINVAL;
+
+ if (!attr->functions_add.btf_id)
+ return -EINVAL;
+
+ /* fd >= 0 use existing bpf_functions object
+ * fd == -1 create new bpf_functions object
+ */
+ fd = attr->functions_add.fd;
+ if (fd < -1)
+ return -EINVAL;
+
+ btf = bpf_get_btf_vmlinux();
+ if (!btf)
+ return -EINVAL;
+
+ addr = bpf_get_kernel_func_addr(attr->functions_add.btf_id, btf);
+ if (!addr)
+ return -EINVAL;
+
+ if (!ftrace_location(addr))
+ return -EINVAL;
+
+ if (fd >= 0) {
+ funcs = bpf_functions_get_from_fd(fd, &orig);
+ if (IS_ERR(funcs))
+ return PTR_ERR(funcs);
+ } else {
+ funcs = kzalloc(sizeof(*funcs), GFP_USER);
+ if (!funcs)
+ return -ENOMEM;
+
+ mutex_init(&funcs->mutex);
+ fd = anon_inode_getfd("bpf-functions", &bpf_functions_fops,
+ funcs, O_CLOEXEC);
+ if (fd < 0) {
+ kfree(funcs);
+ return fd;
+ }
+ ret = fd;
+ }
+
+ mutex_lock(&funcs->mutex);
+
+ if (funcs->cnt == BPF_FUNCTIONS_MAX) {
+ ret = -EINVAL;
+ goto out_put;
+ }
+ if (funcs->cnt == funcs->alloc) {
+ funcs->alloc += BPF_FUNCTIONS_ALLOC;
+ p = krealloc(funcs->addrs, funcs->alloc * sizeof(p[0]), GFP_USER);
+ if (!p) {
+ ret = -ENOMEM;
+ goto out_put;
+ }
+ funcs->addrs = p;
+ }
+
+ funcs->addrs[funcs->cnt++] = addr;
+
+out_put:
+ mutex_unlock(&funcs->mutex);
+ fdput(orig);
+ return ret;
+}
+
#define BPF_OBJ_LAST_FIELD file_flags
static int bpf_obj_pin(const union bpf_attr *attr)
@@ -4487,6 +4621,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_PROG_BIND_MAP:
err = bpf_prog_bind_map(&attr);
break;
+ case BPF_FUNCTIONS_ADD:
+ err = bpf_functions_add(&attr);
+ break;
default:
err = -EINVAL;
break;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index e1ee1be7e49b..5d616735fe1b 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -862,6 +862,7 @@ enum bpf_cmd {
BPF_ITER_CREATE,
BPF_LINK_DETACH,
BPF_PROG_BIND_MAP,
+ BPF_FUNCTIONS_ADD,
};
enum bpf_map_type {
@@ -1458,6 +1459,10 @@ union bpf_attr {
__u32 flags; /* extra flags */
} prog_bind_map;
+ struct { /* BPF_FUNCTIONS_ADD */
+ __u32 fd;
+ __u32 btf_id;
+ } functions_add;
} __attribute__((aligned(8)));
/* The description below is an attempt at providing documentation to eBPF
--
2.30.2
