From: Alan Maguire <alan.maguire@oracle.com>
Date: Wed, 30 Mar 2022 16:26:36 +0100
Subject: libbpf: auto-resolve programs/libraries when necessary for uprobes
Patch-mainline: v5.19-rc1
Git-commit: 1ce3a60e3c287479f15147ffc61c35b2e436a0d5
References: jsc#PED-1377
bpf_program__attach_uprobe_opts() requires a binary_path argument
specifying binary to instrument. Supporting simply specifying
"libc.so.6" or "foo" should be possible too.
Library search checks LD_LIBRARY_PATH, then /usr/lib64, /usr/lib.
This allows users to run BPF programs prefixed with
LD_LIBRARY_PATH=/path2/lib while still searching standard locations.
Similarly for non .so files, we check PATH and /usr/bin, /usr/sbin.
Path determination will be useful for auto-attach of BPF uprobe programs
using SEC() definition.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1648654000-21758-2-git-send-email-alan.maguire@oracle.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/lib/bpf/libbpf.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 53 insertions(+), 1 deletion(-)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10517,6 +10517,46 @@ static int perf_event_uprobe_open_legacy
return pfd;
}
+/* Get full path to program/shared library. */
+static int resolve_full_path(const char *file, char *result, size_t result_sz)
+{
+ const char *search_paths[2];
+ int i;
+
+ if (strstr(file, ".so")) {
+ search_paths[0] = getenv("LD_LIBRARY_PATH");
+ search_paths[1] = "/usr/lib64:/usr/lib";
+ } else {
+ search_paths[0] = getenv("PATH");
+ search_paths[1] = "/usr/bin:/usr/sbin";
+ }
+
+ for (i = 0; i < ARRAY_SIZE(search_paths); i++) {
+ const char *s;
+
+ if (!search_paths[i])
+ continue;
+ for (s = search_paths[i]; s != NULL; s = strchr(s, ':')) {
+ char *next_path;
+ int seg_len;
+
+ if (s[0] == ':')
+ s++;
+ next_path = strchr(s, ':');
+ seg_len = next_path ? next_path - s : strlen(s);
+ if (!seg_len)
+ continue;
+ snprintf(result, result_sz, "%.*s/%s", seg_len, s, file);
+ /* ensure it is an executable file/link */
+ if (access(result, R_OK | X_OK) < 0)
+ continue;
+ pr_debug("resolved '%s' to '%s'\n", file, result);
+ return 0;
+ }
+ }
+ return -ENOENT;
+}
+
LIBBPF_API struct bpf_link *
bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
const char *binary_path, size_t func_offset,
@@ -10524,6 +10564,7 @@ bpf_program__attach_uprobe_opts(const st
{
DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
+ char full_binary_path[PATH_MAX];
struct bpf_link *link;
size_t ref_ctr_off;
int pfd, err;
@@ -10536,12 +10577,23 @@ bpf_program__attach_uprobe_opts(const st
ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
+ if (binary_path && !strchr(binary_path, '/')) {
+ err = resolve_full_path(binary_path, full_binary_path,
+ sizeof(full_binary_path));
+ if (err) {
+ pr_warn("prog '%s': failed to resolve full path for '%s'\n",
+ prog->name, binary_path);
+ return libbpf_err_ptr(err);
+ }
+ binary_path = full_binary_path;
+ }
+
legacy = determine_uprobe_perf_type() < 0;
if (!legacy) {
pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
func_offset, pid, ref_ctr_off);
} else {
- char probe_name[512];
+ char probe_name[PATH_MAX + 64];
if (ref_ctr_off)
return libbpf_err_ptr(-EINVAL);