netdev - [PATCH v2 bpf-next 1/3] libbpf: improve library identification for uprobe binary path resolution

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Message-Id: <1649245431-29956-2-git-send-email-alan.maguire@oracle.com>
Date:   Wed,  6 Apr 2022 12:43:49 +0100
From:   Alan Maguire <alan.maguire@...cle.com>
To:     andrii@...nel.org, ast@...nel.org, daniel@...earbox.net
Cc:     kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Alan Maguire <alan.maguire@...cle.com>
Subject: [PATCH v2 bpf-next 1/3] libbpf: improve library identification for uprobe binary path resolution

In the process of doing path resolution for uprobe attach, libraries are
identified by matching a ".so" substring in the binary_path.
This matches a lot of patterns that do not conform to library.so[.version]
format, so instead match a ".so" _suffix_, and if that fails match a
".so." substring for the versioned library case.

Suggested-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Alan Maguire <alan.maguire@...cle.com>
---
 tools/lib/bpf/libbpf.c          |  2 +-
 tools/lib/bpf/libbpf_internal.h | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1111e9d..c92226a 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10766,7 +10766,7 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)
 	const char *search_paths[3] = {};
 	int i;
 
-	if (strstr(file, ".so")) {
+	if (str_has_sfx(file, ".so") || strstr(file, ".so.")) {
 		search_paths[0] = getenv("LD_LIBRARY_PATH");
 		search_paths[1] = "/usr/lib64:/usr/lib";
 		search_paths[2] = arch_specific_lib_paths();
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index dd0d4cc..0802724 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -103,6 +103,17 @@
 #define str_has_pfx(str, pfx) \
 	(strncmp(str, pfx, __builtin_constant_p(pfx) ? sizeof(pfx) - 1 : strlen(pfx)) == 0)
 
+/* suffix check */
+static inline bool str_has_sfx(const char *str, const char *sfx)
+{
+	size_t str_len = strlen(str);
+	size_t sfx_len = strlen(sfx);
+
+	if (sfx_len <= str_len)
+		return strcmp(str + str_len - sfx_len, sfx);
+	return false;
+}
+
 /* Symbol versioning is different between static and shared library.
  * Properly versioned symbols are needed for shared library, but
  * only the symbol of the new version is needed for static library.
-- 
1.8.3.1