Re: [PATCHv5 bpf-next 03/28] bpf: Add multi uprobe link

Yafang Shao
2023-07-31T03:28:19Z

On Sun, Jul 30, 2023 at 9:43 PM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding new multi uprobe link that allows to attach bpf program
> to multiple uprobes.
>
> Uprobes to attach are specified via new link_create uprobe_multi
> union:
>
> struct {
> __aligned_u64 path;
> __aligned_u64 offsets;
> __aligned_u64 ref_ctr_offsets;
> __u32 cnt;
> __u32 flags;
> } uprobe_multi;
>
> Uprobes are defined for single binary specified in path and multiple
> calling sites specified in offsets array with optional reference
> counters specified in ref_ctr_offsets array. All specified arrays
> have length of 'cnt'.
>
> The 'flags' supports single bit for now that marks the uprobe as
> return probe.
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>

LGTM!
Acked-by: Yafang Shao <laoar.shao@gmail.com>

> ---
> include/linux/trace_events.h | 6 +
> include/uapi/linux/bpf.h | 16 +++
> kernel/bpf/syscall.c | 14 +-
> kernel/trace/bpf_trace.c | 237 +++++++++++++++++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 16 +++
> 5 files changed, 286 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index e66d04dbe56a..5b85cf18c350 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -752,6 +752,7 @@ int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
> u32 *fd_type, const char **buf,
> u64 *probe_offset, u64 *probe_addr);
> int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
> +int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
> #else
> static inline unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
> {
> @@ -798,6 +799,11 @@ bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> {
> return -EOPNOTSUPP;
> }
> +static inline int
> +bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> +{
> + return -EOPNOTSUPP;
> +}
> #endif
>
> enum {
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 7abb382dc6c1..f112a0b948f3 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -1039,6 +1039,7 @@ enum bpf_attach_type {
> BPF_NETFILTER,
> BPF_TCX_INGRESS,
> BPF_TCX_EGRESS,
> + BPF_TRACE_UPROBE_MULTI,
> __MAX_BPF_ATTACH_TYPE
> };
>
> @@ -1057,6 +1058,7 @@ enum bpf_link_type {
> BPF_LINK_TYPE_STRUCT_OPS = 9,
> BPF_LINK_TYPE_NETFILTER = 10,
> BPF_LINK_TYPE_TCX = 11,
> + BPF_LINK_TYPE_UPROBE_MULTI = 12,
> MAX_BPF_LINK_TYPE,
> };
>
> @@ -1190,6 +1192,13 @@ enum {
> BPF_F_KPROBE_MULTI_RETURN = (1U << 0)
> };
>
> +/* link_create.uprobe_multi.flags used in LINK_CREATE command for
> + * BPF_TRACE_UPROBE_MULTI attach type to create return probe.
> + */
> +enum {
> + BPF_F_UPROBE_MULTI_RETURN = (1U << 0)
> +};
> +
> /* link_create.netfilter.flags used in LINK_CREATE command for
> * BPF_PROG_TYPE_NETFILTER to enable IP packet defragmentation.
> */
> @@ -1626,6 +1635,13 @@ union bpf_attr {
> };
> __u64 expected_revision;
> } tcx;
> + struct {
> + __aligned_u64 path;
> + __aligned_u64 offsets;
> + __aligned_u64 ref_ctr_offsets;
> + __u32 cnt;
> + __u32 flags;
> + } uprobe_multi;
> };
> } link_create;
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 7c01186d4078..75c83300339e 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2815,10 +2815,12 @@ static void bpf_link_free_id(int id)
>
> /* Clean up bpf_link and corresponding anon_inode file and FD. After
> * anon_inode is created, bpf_link can't be just kfree()'d due to deferred
> - * anon_inode's release() call. This helper marksbpf_link as
> + * anon_inode's release() call. This helper marks bpf_link as
> * defunct, releases anon_inode file and puts reserved FD. bpf_prog's refcnt
> * is not decremented, it's the responsibility of a calling code that failed
> * to complete bpf_link initialization.
> + * This helper eventually calls link's dealloc callback, but does not call
> + * link's release callback.
> */
> void bpf_link_cleanup(struct bpf_link_primer *primer)
> {
> @@ -3757,8 +3759,12 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,
> if (prog->expected_attach_type == BPF_TRACE_KPROBE_MULTI &&
> attach_type != BPF_TRACE_KPROBE_MULTI)
> return -EINVAL;
> + if (prog->expected_attach_type == BPF_TRACE_UPROBE_MULTI &&
> + attach_type != BPF_TRACE_UPROBE_MULTI)
> + return -EINVAL;
> if (attach_type != BPF_PERF_EVENT &&
> - attach_type != BPF_TRACE_KPROBE_MULTI)
> + attach_type != BPF_TRACE_KPROBE_MULTI &&
> + attach_type != BPF_TRACE_UPROBE_MULTI)
> return -EINVAL;
> return 0;
> case BPF_PROG_TYPE_SCHED_CLS:
> @@ -4954,8 +4960,10 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
> case BPF_PROG_TYPE_KPROBE:
> if (attr->link_create.attach_type == BPF_PERF_EVENT)
> ret = bpf_perf_link_attach(attr, prog);
> - else
> + else if (attr->link_create.attach_type == BPF_TRACE_KPROBE_MULTI)
> ret = bpf_kprobe_multi_link_attach(attr, prog);
> + else if (attr->link_create.attach_type == BPF_TRACE_UPROBE_MULTI)
> + ret = bpf_uprobe_multi_link_attach(attr, prog);
> break;
> default:
> ret = -EINVAL;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index c92eb8c6ff08..10284fd46f98 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -23,6 +23,7 @@
> #include <linux/sort.h>
> #include <linux/key.h>
> #include <linux/verification.h>
> +#include <linux/namei.h>
>
> #include <net/bpf_sk_storage.h>
>
> @@ -2965,3 +2966,239 @@ static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
> return 0;
> }
> #endif
> +
> +#ifdef CONFIG_UPROBES
> +struct bpf_uprobe_multi_link;
> +
> +struct bpf_uprobe {
> + struct bpf_uprobe_multi_link *link;
> + loff_t offset;
> + struct uprobe_consumer consumer;
> +};
> +
> +struct bpf_uprobe_multi_link {
> + struct path path;
> + struct bpf_link link;
> + u32 cnt;
> + struct bpf_uprobe *uprobes;
> +};
> +
> +struct bpf_uprobe_multi_run_ctx {
> + struct bpf_run_ctx run_ctx;
> + unsigned long entry_ip;
> +};
> +
> +static void bpf_uprobe_unregister(struct path *path, struct bpf_uprobe *uprobes,
> + u32 cnt)
> +{
> + u32 i;
> +
> + for (i = 0; i < cnt; i++) {
> + uprobe_unregister(d_real_inode(path->dentry), uprobes[i].offset,
> + &uprobes[i].consumer);
> + }
> +}
> +
> +static void bpf_uprobe_multi_link_release(struct bpf_link *link)
> +{
> + struct bpf_uprobe_multi_link *umulti_link;
> +
> + umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
> + bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt);
> +}
> +
> +static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
> +{
> + struct bpf_uprobe_multi_link *umulti_link;
> +
> + umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
> + path_put(&umulti_link->path);
> + kvfree(umulti_link->uprobes);
> + kfree(umulti_link);
> +}
> +
> +static const struct bpf_link_ops bpf_uprobe_multi_link_lops = {
> + .release = bpf_uprobe_multi_link_release,
> + .dealloc = bpf_uprobe_multi_link_dealloc,
> +};
> +
> +static int uprobe_prog_run(struct bpf_uprobe *uprobe,
> + unsigned long entry_ip,
> + struct pt_regs *regs)
> +{
> + struct bpf_uprobe_multi_link *link = uprobe->link;
> + struct bpf_uprobe_multi_run_ctx run_ctx = {
> + .entry_ip = entry_ip,
> + };
> + struct bpf_prog *prog = link->link.prog;
> + bool sleepable = prog->aux->sleepable;
> + struct bpf_run_ctx *old_run_ctx;
> + int err = 0;
> +
> + might_fault();
> +
> + migrate_disable();
> +
> + if (sleepable)
> + rcu_read_lock_trace();
> + else
> + rcu_read_lock();
> +
> + old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> + err = bpf_prog_run(link->link.prog, regs);
> + bpf_reset_run_ctx(old_run_ctx);
> +
> + if (sleepable)
> + rcu_read_unlock_trace();
> + else
> + rcu_read_unlock();
> +
> + migrate_enable();
> + return err;
> +}
> +
> +static int
> +uprobe_multi_link_handler(struct uprobe_consumer *con, struct pt_regs *regs)
> +{
> + struct bpf_uprobe *uprobe;
> +
> + uprobe = container_of(con, struct bpf_uprobe, consumer);
> + return uprobe_prog_run(uprobe, instruction_pointer(regs), regs);
> +}
> +
> +static int
> +uprobe_multi_link_ret_handler(struct uprobe_consumer *con, unsigned long func, struct pt_regs *regs)
> +{
> + struct bpf_uprobe *uprobe;
> +
> + uprobe = container_of(con, struct bpf_uprobe, consumer);
> + return uprobe_prog_run(uprobe, func, regs);
> +}
> +
> +int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> +{
> + struct bpf_uprobe_multi_link *link = NULL;
> + unsigned long __user *uref_ctr_offsets;
> + unsigned long *ref_ctr_offsets = NULL;
> + struct bpf_link_primer link_primer;
> + struct bpf_uprobe *uprobes = NULL;
> + unsigned long __user *uoffsets;
> + void __user *upath;
> + u32 flags, cnt, i;
> + struct path path;
> + char *name;
> + int err;
> +
> + /* no support for 32bit archs yet */
> + if (sizeof(u64) != sizeof(void *))
> + return -EOPNOTSUPP;
> +
> + if (prog->expected_attach_type != BPF_TRACE_UPROBE_MULTI)
> + return -EINVAL;
> +
> + flags = attr->link_create.uprobe_multi.flags;
> + if (flags & ~BPF_F_UPROBE_MULTI_RETURN)
> + return -EINVAL;
> +
> + /*
> + * path, offsets and cnt are mandatory,
> + * ref_ctr_offsets is optional
> + */
> + upath = u64_to_user_ptr(attr->link_create.uprobe_multi.path);
> + uoffsets = u64_to_user_ptr(attr->link_create.uprobe_multi.offsets);
> + cnt = attr->link_create.uprobe_multi.cnt;
> +
> + if (!upath || !uoffsets || !cnt)
> + return -EINVAL;
> +
> + uref_ctr_offsets = u64_to_user_ptr(attr->link_create.uprobe_multi.ref_ctr_offsets);
> +
> + name = strndup_user(upath, PATH_MAX);
> + if (IS_ERR(name)) {
> + err = PTR_ERR(name);
> + return err;
> + }
> +
> + err = kern_path(name, LOOKUP_FOLLOW, &path);
> + kfree(name);
> + if (err)
> + return err;
> +
> + if (!d_is_reg(path.dentry)) {
> + err = -EBADF;
> + goto error_path_put;
> + }
> +
> + err = -ENOMEM;
> +
> + link = kzalloc(sizeof(*link), GFP_KERNEL);
> + uprobes = kvcalloc(cnt, sizeof(*uprobes), GFP_KERNEL);
> +
> + if (!uprobes || !link)
> + goto error_free;
> +
> + if (uref_ctr_offsets) {
> + ref_ctr_offsets = kvcalloc(cnt, sizeof(*ref_ctr_offsets), GFP_KERNEL);
> + if (!ref_ctr_offsets)
> + goto error_free;
> + }
> +
> + for (i = 0; i < cnt; i++) {
> + if (uref_ctr_offsets && __get_user(ref_ctr_offsets[i], uref_ctr_offsets + i)) {
> + err = -EFAULT;
> + goto error_free;
> + }
> + if (__get_user(uprobes[i].offset, uoffsets + i)) {
> + err = -EFAULT;
> + goto error_free;
> + }
> +
> + uprobes[i].link = link;
> +
> + if (flags & BPF_F_UPROBE_MULTI_RETURN)
> + uprobes[i].consumer.ret_handler = uprobe_multi_link_ret_handler;
> + else
> + uprobes[i].consumer.handler = uprobe_multi_link_handler;
> + }
> +
> + link->cnt = cnt;
> + link->uprobes = uprobes;
> + link->path = path;
> +
> + bpf_link_init(&link->link, BPF_LINK_TYPE_UPROBE_MULTI,
> + &bpf_uprobe_multi_link_lops, prog);
> +
> + err = bpf_link_prime(&link->link, &link_primer);
> + if (err)
> + goto error_free;
> +
> + for (i = 0; i < cnt; i++) {
> + err = uprobe_register_refctr(d_real_inode(link->path.dentry),
> + uprobes[i].offset,
> + ref_ctr_offsets ? ref_ctr_offsets[i] : 0,
> + &uprobes[i].consumer);
> + if (err) {
> + bpf_uprobe_unregister(&path, uprobes, i);
> + bpf_link_cleanup(&link_primer);
> + kvfree(ref_ctr_offsets);
> + return err;
> + }
> + }
> +
> + kvfree(ref_ctr_offsets);
> + return bpf_link_settle(&link_primer);
> +
> +error_free:
> + kvfree(ref_ctr_offsets);
> + kvfree(uprobes);
> + kfree(link);
> +error_path_put:
> + path_put(&path);
> + return err;
> +}
> +#else /* !CONFIG_UPROBES */
> +int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> +{
> + return -EOPNOTSUPP;
> +}
> +#endif /* CONFIG_UPROBES */
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 7abb382dc6c1..f112a0b948f3 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -1039,6 +1039,7 @@ enum bpf_attach_type {
> BPF_NETFILTER,
> BPF_TCX_INGRESS,
> BPF_TCX_EGRESS,
> + BPF_TRACE_UPROBE_MULTI,
> __MAX_BPF_ATTACH_TYPE
> };
>
> @@ -1057,6 +1058,7 @@ enum bpf_link_type {
> BPF_LINK_TYPE_STRUCT_OPS = 9,
> BPF_LINK_TYPE_NETFILTER = 10,
> BPF_LINK_TYPE_TCX = 11,
> + BPF_LINK_TYPE_UPROBE_MULTI = 12,
> MAX_BPF_LINK_TYPE,
> };
>
> @@ -1190,6 +1192,13 @@ enum {
> BPF_F_KPROBE_MULTI_RETURN = (1U << 0)
> };
>
> +/* link_create.uprobe_multi.flags used in LINK_CREATE command for
> + * BPF_TRACE_UPROBE_MULTI attach type to create return probe.
> + */
> +enum {
> + BPF_F_UPROBE_MULTI_RETURN = (1U << 0)
> +};
> +
> /* link_create.netfilter.flags used in LINK_CREATE command for
> * BPF_PROG_TYPE_NETFILTER to enable IP packet defragmentation.
> */
> @@ -1626,6 +1635,13 @@ union bpf_attr {
> };
> __u64 expected_revision;
> } tcx;
> + struct {
> + __aligned_u64 path;
> + __aligned_u64 offsets;
> + __aligned_u64 ref_ctr_offsets;
> + __u32 cnt;
> + __u32 flags;
> + } uprobe_multi;
> };
> } link_create;
>
> --
> 2.41.0
>

--
Regards
Yafang