Commit 90db26e6 authored by Alan Maguire's avatar Alan Maguire Committed by Andrii Nakryiko
Browse files

libbpf: Improve string parsing for uprobe auto-attach 



For uprobe auto-attach, the parsing can be simplified for the SEC()
name to a single sscanf(); the return value of the sscanf can then
be used to distinguish between sections that simply specify
"u[ret]probe" (and thus cannot auto-attach), those that specify
"u[ret]probe/binary_path:function+offset" etc.

Suggested-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1649245431-29956-3-git-send-email-alan.maguire@oracle.com
parent a1c9d61b

tools/lib/bpf/libbpf.c

+33 −48
Original line number Diff line number Diff line
@@ -10913,60 +10913,45 @@ 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 *func, *probe_name, *func_end;

	char *func_name, binary_path[512];

	unsigned long long raw_offset;

	size_t offset = 0;

	int n;

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

	int n, ret = -EINVAL;

	long offset = 0;



	*link = NULL;



	opts.retprobe = str_has_pfx(prog->sec_name, "uretprobe");

	if (opts.retprobe)

		probe_name = prog->sec_name + sizeof("uretprobe") - 1;

	else

		probe_name = prog->sec_name + sizeof("uprobe") - 1;

	if (probe_name[0] == '/')

		probe_name++;



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

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

	switch (n) {

	case 1:

		/* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */

	if (strlen(probe_name) == 0)

		return 0;



	snprintf(binary_path, sizeof(binary_path), "%s", probe_name);

	/* ':' should be prior to function+offset */

	func_name = strrchr(binary_path, ':');

	if (!func_name) {

		pr_warn("section '%s' missing ':function[+offset]' specification\n",

			prog->sec_name);

		return -EINVAL;

	}

	func_name[0] = '\0';

	func_name++;

	n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset);

	if (n < 1) {

		pr_warn("uprobe name '%s' is invalid\n", func_name);

		return -EINVAL;

	}

		ret = 0;

		break;

	case 2:

		pr_warn("prog '%s': section '%s' missing ':function[+offset]' specification\n",

			prog->name, prog->sec_name);

		break;

	case 3:

	case 4:

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

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

		free(func);

		pr_warn("uretprobes do not support offset specification\n");

		return -EINVAL;

			pr_warn("prog '%s': uretprobes do not support offset specification\n",

				prog->name);

			break;

		}



	/* Is func a raw address? */

	errno = 0;

	raw_offset = strtoull(func, &func_end, 0);

	if (!errno && !*func_end) {

		free(func);

		func = NULL;

		offset = (size_t)raw_offset;

		opts.func_name = func_name;

		*link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);

		ret = libbpf_get_error(*link);

		break;

	default:

		pr_warn("prog '%s': invalid format of section definition '%s'\n", prog->name,

			prog->sec_name);

		break;

	}

	opts.func_name = func;

	free(probe_type);

	free(binary_path);

	free(func_name);



	*link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);

	free(func);

	return libbpf_get_error(*link);

	return ret;

}



struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,