From: Yonghong Song <yonghong.song@linux.dev>
To: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: Yafang Shao <laoar.shao@gmail.com>,
bpf@vger.kernel.org, Martin KaFai Lau <kafai@fb.com>,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>
Subject: Re: [PATCHv6 bpf-next 03/28] bpf: Add multi uprobe link
Date: Fri, 4 Aug 2023 14:55:29 -0700 [thread overview]
Message-ID: <8f678d1a-d2c2-c979-f37e-db0f4bf6e933@linux.dev> (raw)
In-Reply-To: <20230803073420.1558613-4-jolsa@kernel.org>
On 8/3/23 12:33 AM, Jiri Olsa 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>
> Acked-by: Yafang Shao <laoar.shao@gmail.com>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> 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(-)
>
[...]
> +
> +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();
Could you explain what you try to protect here
with might_fault()?
In my opinion, might_fault() is unnecessary here
since the calling context is process context and
there is no mmap_lock held, so might_fault()
won't capture anything.
might_fault() is used in iter.c and trampoline.c
since their calling context is more complex
than here and might_fault() may actually capture
issues.
> +
> + migrate_disable();
> +
> + if (sleepable)
> + rcu_read_lock_trace();
> + else
> + rcu_read_lock();
Looking at trampoline.c and iter.c, typical
usage is
rcu_read_lock_trace()/rcu_read_lock()
migrate_disable()
Your above sequenence could be correct too. But it
is great if we can keep consistency here.
> +
> + 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);
Is it possible we may miss some of below 'error_free' cleanups?
In my opinion, we should replace
kvfree(ref_ctr_offsets);
return err;
with
goto error_free;
Could you double check?
> + 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 */
[...]
next prev parent reply other threads:[~2023-08-04 21:55 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-03 7:33 [PATCHv6 bpf-next 00/28] bpf: Add multi uprobe link Jiri Olsa
2023-08-03 7:33 ` [PATCHv6 bpf-next 01/28] bpf: Switch BPF_F_KPROBE_MULTI_RETURN macro to enum Jiri Olsa
2023-08-03 7:33 ` [PATCHv6 bpf-next 02/28] bpf: Add attach_type checks under bpf_prog_attach_check_attach_type Jiri Olsa
2023-08-03 7:33 ` [PATCHv6 bpf-next 03/28] bpf: Add multi uprobe link Jiri Olsa
2023-08-04 21:55 ` Yonghong Song [this message]
2023-08-05 21:11 ` Jiri Olsa
2023-08-03 7:33 ` [PATCHv6 bpf-next 04/28] bpf: Add cookies support for uprobe_multi link Jiri Olsa
2023-08-03 7:33 ` [PATCHv6 bpf-next 05/28] bpf: Add pid filter " Jiri Olsa
2023-08-03 7:33 ` [PATCHv6 bpf-next 06/28] bpf: Add bpf_get_func_ip helper support for uprobe link Jiri Olsa
2023-08-03 7:33 ` [PATCHv6 bpf-next 07/28] libbpf: Add uprobe_multi attach type and link names Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 08/28] libbpf: Move elf_find_func_offset* functions to elf object Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 09/28] libbpf: Add elf_open/elf_close functions Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 10/28] libbpf: Add elf symbol iterator Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 11/28] libbpf: Add elf_resolve_syms_offsets function Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 12/28] libbpf: Add elf_resolve_pattern_offsets function Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 13/28] libbpf: Add bpf_link_create support for multi uprobes Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 14/28] libbpf: Add bpf_program__attach_uprobe_multi function Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 15/28] libbpf: Add support for u[ret]probe.multi[.s] program sections Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 16/28] libbpf: Add uprobe multi link detection Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 17/28] libbpf: Add uprobe multi link support to bpf_program__attach_usdt Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 18/28] selftests/bpf: Move get_time_ns to testing_helpers.h Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 19/28] selftests/bpf: Add uprobe_multi skel test Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 20/28] selftests/bpf: Add uprobe_multi api test Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 21/28] selftests/bpf: Add uprobe_multi link test Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 22/28] selftests/bpf: Add uprobe_multi test program Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 23/28] selftests/bpf: Add uprobe_multi bench test Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 24/28] selftests/bpf: Add uprobe_multi usdt test code Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 25/28] selftests/bpf: Add uprobe_multi usdt bench test Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 26/28] selftests/bpf: Add uprobe_multi cookie test Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 27/28] selftests/bpf: Add uprobe_multi pid filter tests Jiri Olsa
2023-08-03 7:34 ` [PATCHv6 bpf-next 28/28] selftests/bpf: Add extra link to uprobe_multi tests Jiri Olsa
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