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libbpf: Add support to set kprobe/uprobe attach mode

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By default, libbpf will attach the kprobe/uprobe BPF program in the
latest mode that supported by kernel. In this patch, we add the support
to let users manually attach kprobe/uprobe in legacy or perf mode.

There are 3 mode that supported by the kernel to attach kprobe/uprobe:

  LEGACY: create perf event in legacy way and don't use bpf_link
  PERF: create perf event with perf_event_open() and don't use bpf_link

Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Biao Jiang <benbjiang@tencent.com>
Link: create perf event with perf_event_open() and use bpf_link
Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/
Link: https://lore.kernel.org/bpf/20230306064833.7932-2-imagedong@tencent.com

Users now can manually choose the mode with
bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
This commit is contained in:
Menglong Dong 2023-03-06 14:48:31 +08:00 committed by Andrii Nakryiko
parent fd4cb29f2a
commit f8b299bc6a
2 changed files with 84 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
tools/lib/bpf/libbpf.c
View File

@ -9724,6 +9724,7 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
char errmsg[STRERR_BUFSIZE];
struct bpf_link_perf *link;
int prog_fd, link_fd = -1, err;
bool force_ioctl_attach;
if (!OPTS_VALID(opts, bpf_perf_event_opts))
return libbpf_err_ptr(-EINVAL);
@ -9747,7 +9748,8 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
link->link.dealloc = &bpf_link_perf_dealloc;
link->perf_event_fd = pfd;
if (kernel_supports(prog->obj, FEAT_PERF_LINK)) {
force_ioctl_attach = OPTS_GET(opts, force_ioctl_attach, false);
if (kernel_supports(prog->obj, FEAT_PERF_LINK) && !force_ioctl_attach) {
DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
.perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
@ -10106,6 +10108,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
const struct bpf_kprobe_opts *opts)
{
DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
enum probe_attach_mode attach_mode;
char errmsg[STRERR_BUFSIZE];
char *legacy_probe = NULL;
struct bpf_link *link;
@ -10116,11 +10119,32 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
if (!OPTS_VALID(opts, bpf_kprobe_opts))
return libbpf_err_ptr(-EINVAL);
attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
retprobe = OPTS_GET(opts, retprobe, false);
offset = OPTS_GET(opts, offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
legacy = determine_kprobe_perf_type() < 0;
switch (attach_mode) {
case PROBE_ATTACH_MODE_LEGACY:
legacy = true;
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_PERF:
if (legacy)
return libbpf_err_ptr(-ENOTSUP);
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_LINK:
if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
return libbpf_err_ptr(-ENOTSUP);
break;
case PROBE_ATTACH_MODE_DEFAULT:
break;
default:
return libbpf_err_ptr(-EINVAL);
}
if (!legacy) {
pfd = perf_event_open_probe(false /* uprobe */, retprobe,
func_name, offset,
@ -10852,6 +10876,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
const char *archive_path = NULL, *archive_sep = NULL;
char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
enum probe_attach_mode attach_mode;
char full_path[PATH_MAX];
struct bpf_link *link;
size_t ref_ctr_off;
@ -10862,6 +10887,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
if (!OPTS_VALID(opts, bpf_uprobe_opts))
return libbpf_err_ptr(-EINVAL);
attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
retprobe = OPTS_GET(opts, retprobe, false);
ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
@ -10903,6 +10929,26 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
}
legacy = determine_uprobe_perf_type() < 0;
switch (attach_mode) {
case PROBE_ATTACH_MODE_LEGACY:
legacy = true;
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_PERF:
if (legacy)
return libbpf_err_ptr(-ENOTSUP);
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_LINK:
if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
return libbpf_err_ptr(-ENOTSUP);
break;
case PROBE_ATTACH_MODE_DEFAULT:
break;
default:
return libbpf_err_ptr(-EINVAL);
}
if (!legacy) {
pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
func_offset, pid, ref_ctr_off);

50
tools/lib/bpf/libbpf.h
View File

@ -447,12 +447,15 @@ LIBBPF_API struct bpf_link *
bpf_program__attach(const struct bpf_program *prog);
struct bpf_perf_event_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
/* custom user-provided value fetchable through bpf_get_attach_cookie() */
__u64 bpf_cookie;
/* don't use BPF link when attach BPF program */
bool force_ioctl_attach;
size_t :0;
};
#define bpf_perf_event_opts__last_field bpf_cookie
#define bpf_perf_event_opts__last_field force_ioctl_attach
LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd);
@ -461,8 +464,25 @@ LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event_opts(const struct bpf_program *prog, int pfd,
const struct bpf_perf_event_opts *opts);
/**
* enum probe_attach_mode - the mode to attach kprobe/uprobe
*
* force libbpf to attach kprobe/uprobe in specific mode, -ENOTSUP will
* be returned if it is not supported by the kernel.
*/
enum probe_attach_mode {
/* attach probe in latest supported mode by kernel */
PROBE_ATTACH_MODE_DEFAULT = 0,
/* attach probe in legacy mode, using debugfs/tracefs */
PROBE_ATTACH_MODE_LEGACY,
/* create perf event with perf_event_open() syscall */
PROBE_ATTACH_MODE_PERF,
/* attach probe with BPF link */
PROBE_ATTACH_MODE_LINK,
};
struct bpf_kprobe_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
/* custom user-provided value fetchable through bpf_get_attach_cookie() */
__u64 bpf_cookie;
@ -470,9 +490,11 @@ struct bpf_kprobe_opts {
size_t offset;
/* kprobe is return probe */
bool retprobe;
/* kprobe attach mode */
enum probe_attach_mode attach_mode;
size_t :0;
};
#define bpf_kprobe_opts__last_field retprobe
#define bpf_kprobe_opts__last_field attach_mode
LIBBPF_API struct bpf_link *
bpf_program__attach_kprobe(const struct bpf_program *prog, bool retprobe,
@ -506,7 +528,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
const struct bpf_kprobe_multi_opts *opts);
struct bpf_ksyscall_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
/* custom user-provided value fetchable through bpf_get_attach_cookie() */
__u64 bpf_cookie;
@ -552,7 +574,7 @@ bpf_program__attach_ksyscall(const struct bpf_program *prog,
const struct bpf_ksyscall_opts *opts);
struct bpf_uprobe_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
/* offset of kernel reference counted USDT semaphore, added in
* a6ca88b241d5 ("trace_uprobe: support reference counter in fd-based uprobe")
@ -570,9 +592,11 @@ struct bpf_uprobe_opts {
* binary_path.
*/
const char *func_name;
/* uprobe attach mode */
enum probe_attach_mode attach_mode;
size_t :0;
};
#define bpf_uprobe_opts__last_field func_name
#define bpf_uprobe_opts__last_field attach_mode
/**
* @brief **bpf_program__attach_uprobe()** attaches a BPF program
@ -646,7 +670,7 @@ bpf_program__attach_usdt(const struct bpf_program *prog,
const struct bpf_usdt_opts *opts);
struct bpf_tracepoint_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
/* custom user-provided value fetchable through bpf_get_attach_cookie() */
__u64 bpf_cookie;
@ -1110,7 +1134,7 @@ struct user_ring_buffer;
typedef int (*ring_buffer_sample_fn)(void *ctx, void *data, size_t size);
struct ring_buffer_opts {
size_t sz; /* size of this struct, for forward/backward compatiblity */
size_t sz; /* size of this struct, for forward/backward compatibility */
};
#define ring_buffer_opts__last_field sz
@ -1475,7 +1499,7 @@ LIBBPF_API void
bpf_object__destroy_subskeleton(struct bpf_object_subskeleton *s);
struct gen_loader_opts {
size_t sz; /* size of this struct, for forward/backward compatiblity */
size_t sz; /* size of this struct, for forward/backward compatibility */
const char *data;
const char *insns;
__u32 data_sz;
@ -1493,13 +1517,13 @@ enum libbpf_tristate {
};
struct bpf_linker_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
};
#define bpf_linker_opts__last_field sz
struct bpf_linker_file_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
};
#define bpf_linker_file_opts__last_field sz
@ -1542,7 +1566,7 @@ typedef int (*libbpf_prog_attach_fn_t)(const struct bpf_program *prog, long cook
struct bpf_link **link);
struct libbpf_prog_handler_opts {
/* size of this struct, for forward/backward compatiblity */
/* size of this struct, for forward/backward compatibility */
size_t sz;
/* User-provided value that is passed to prog_setup_fn,
* prog_prepare_load_fn, and prog_attach_fn callbacks. Allows user to