From: Lucas De Marchi <lucas.de.marchi@gmail.com>
Date: Sat, 30 Nov 2024 06:38:11 +0000 (-0600)
Subject: libkmod/zlib: Allow to load libz.so on demand
X-Git-Tag: v34~35
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b8f00f7bc527fa38a9ed6f652ec01a8eef85dc88;p=thirdparty%2Fkmod.git

libkmod/zlib: Allow to load libz.so on demand

Use dlfcn helpers to load libz once it's needed.

Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/262
---

diff --git a/libkmod/libkmod-file-zlib.c b/libkmod/libkmod-file-zlib.c
index a7e27b80..fd382939 100644
--- a/libkmod/libkmod-file-zlib.c
+++ b/libkmod/libkmod-file-zlib.c
@@ -3,6 +3,9 @@
  * Copyright © 2024 Intel Corporation
  */
 
+/* TODO: replace with build system define once supported */
+#define DLSYM_LOCALLY_ENABLED 0
+
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -20,6 +23,24 @@
 
 #define READ_STEP (4 * 1024 * 1024)
 
+#define DL_SYMBOL_TABLE(M) \
+	M(gzclose)         \
+	M(gzdopen)         \
+	M(gzerror)         \
+	M(gzread)
+
+DL_SYMBOL_TABLE(DECLARE_SYM)
+
+static int dlopen_zlib(void)
+{
+	static void *dl = NULL;
+
+	if (!DLSYM_LOCALLY_ENABLED)
+		return 0;
+
+	return dlsym_many(&dl, "libz.so.1", DL_SYMBOL_TABLE(DLSYM_ARG) NULL);
+}
+
 int kmod_file_load_zlib(struct kmod_file *file)
 {
 	_cleanup_free_ unsigned char *p = NULL;
@@ -28,12 +49,19 @@ int kmod_file_load_zlib(struct kmod_file *file)
 	gzFile gzf;
 	int gzfd;
 
+	ret = dlopen_zlib();
+	if (ret < 0) {
+		ERR(file->ctx, "zlib: can't load and resolve symbols (%s)",
+		    strerror(-ret));
+		return -EINVAL;
+	}
+
 	errno = 0;
 	gzfd = fcntl(file->fd, F_DUPFD_CLOEXEC, 3);
 	if (gzfd < 0)
 		return -errno;
 
-	gzf = gzdopen(gzfd, "rb"); /* takes ownership of the fd */
+	gzf = sym_gzdopen(gzfd, "rb"); /* takes ownership of the fd */
 	if (gzf == NULL) {
 		close(gzfd);
 		return -errno;
@@ -52,12 +80,12 @@ int kmod_file_load_zlib(struct kmod_file *file)
 			p = tmp;
 		}
 
-		r = gzread(gzf, p + did, total - did);
+		r = sym_gzread(gzf, p + did, total - did);
 		if (r == 0)
 			break;
 		else if (r < 0) {
 			int gzerr;
-			const char *gz_errmsg = gzerror(gzf, &gzerr);
+			const char *gz_errmsg = sym_gzerror(gzf, &gzerr);
 
 			ERR(file->ctx, "gzip: %s\n", gz_errmsg);
 
@@ -70,11 +98,11 @@ int kmod_file_load_zlib(struct kmod_file *file)
 
 	file->memory = TAKE_PTR(p);
 	file->size = did;
-	gzclose(gzf);
+	sym_gzclose(gzf);
 
 	return 0;
 
 error:
-	gzclose(gzf); /* closes the gzfd */
+	sym_gzclose(gzf);
 	return ret;
 }