Commit 2147c8d0 authored by Hengqi Chen's avatar Hengqi Chen Committed by Andrii Nakryiko
Browse files

libbpf: Allow Golang symbols in uprobe secdef 

Golang symbols in ELF files are different from C/C++
which contains special characters like '*', '(' and ')'.
With generics, things get more complicated, there are
symbols like:

  github.com/cilium/ebpf/internal.(*Deque[go.shape.interface { Format(fmt.State, int32); TypeName() string;github.com/cilium/ebpf/btf.copy() github.com/cilium/ebpf/btf.Type}]).Grow

Matching such symbols using `%m[^\n]` in sscanf, this
excludes newline which typically does not appear in ELF
symbols. This should work in most use-cases and also
work for unicode letters in identifiers. If newline do
show up in ELF symbols, users can still attach to such
symbol by specifying bpf_uprobe_opts::func_name.

A working example can be found at this repo ([0]).

  [0]: https://github.com/chenhengqi/libbpf-go-symbols



Suggested-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarHengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230929155954.92448-1-hengqi.chen@gmail.com
parent 9e09b750

tools/lib/bpf/libbpf.c

+16 −6
Original line number Diff line number Diff line
@@ -11114,7 +11114,7 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru 


	*link = NULL;



	n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%ms",

	n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[^\n]",

		   &probe_type, &binary_path, &func_name);

	switch (n) {

	case 1:
@@ -11624,14 +11624,14 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, 
static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)

{

	DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);

	char *probe_type = NULL, *binary_path = NULL, *func_name = NULL;

	int n, ret = -EINVAL;

	char *probe_type = NULL, *binary_path = NULL, *func_name = NULL, *func_off;

	int n, c, ret = -EINVAL;

	long offset = 0;



	*link = NULL;



	n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[a-zA-Z0-9_.@]+%li",

		   &probe_type, &binary_path, &func_name, &offset);

	n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[^\n]",

		   &probe_type, &binary_path, &func_name);

	switch (n) {

	case 1:

		/* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */
@@ -11642,7 +11642,17 @@ static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf 
			prog->name, prog->sec_name);

		break;

	case 3:

	case 4:

		/* check if user specifies `+offset`, if yes, this should be

		 * the last part of the string, make sure sscanf read to EOL

		 */

		func_off = strrchr(func_name, '+');

		if (func_off) {

			n = sscanf(func_off, "+%li%n", &offset, &c);

			if (n == 1 && *(func_off + c) == '\0')

				func_off[0] = '\0';

			else

				offset = 0;

		}

		opts.retprobe = strcmp(probe_type, "uretprobe") == 0 ||

				strcmp(probe_type, "uretprobe.s") == 0;

		if (opts.retprobe && offset != 0) {