libkmod/xz: Allow to load liblzma.so on demand

Use dlfcn helpers to load liblzma 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-xz.c b/libkmod/libkmod-file-xz.c
index 636ef707074686700e5cf1a6732ceb4965ac9d34..3f44b43dbcd509a31de0c7ac886ef87c9ae4adcf 100644 (file)
--- a/libkmod/libkmod-file-xz.c
+++ b/libkmod/libkmod-file-xz.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 <lzma.h>
 #include <stdio.h>
@@ -18,6 +21,23 @@
 #include "libkmod-internal.h"
 #include "libkmod-internal-file.h"
 
+#define DL_SYMBOL_TABLE(M)     \
+       M(lzma_stream_decoder) \
+       M(lzma_code)           \
+       M(lzma_end)
+
+DL_SYMBOL_TABLE(DECLARE_SYM)
+
+static int dlopen_lzma(void)
+{
+       static void *dl = NULL;
+
+       if (!DLSYM_LOCALLY_ENABLED)
+               return 0;
+
+       return dlsym_many(&dl, "liblzma.so.5", DL_SYMBOL_TABLE(DLSYM_ARG) NULL);
+}
+
 static void xz_uncompress_belch(struct kmod_file *file, lzma_ret ret)
 {
        switch (ret) {
@@ -66,7 +86,7 @@ static int xz_uncompress(lzma_stream *strm, struct kmod_file *file)
                        if (rdret == 0)
                                action = LZMA_FINISH;
                }
-               ret = lzma_code(strm, action);
+               ret = sym_lzma_code(strm, action);
                if (strm->avail_out == 0 || ret != LZMA_OK) {
                        size_t write_size = BUFSIZ - strm->avail_out;
                        char *tmp = realloc(p, total + write_size);
@@ -102,7 +122,13 @@ int kmod_file_load_xz(struct kmod_file *file)
        lzma_ret lzret;
        int ret;
 
-       lzret = lzma_stream_decoder(&strm, UINT64_MAX, LZMA_CONCATENATED);
+       ret = dlopen_lzma();
+       if (ret < 0) {
+               ERR(file->ctx, "xz: can't load and resolve symbols (%s)", strerror(-ret));
+               return -EINVAL;
+       }
+
+       lzret = sym_lzma_stream_decoder(&strm, UINT64_MAX, LZMA_CONCATENATED);
        if (lzret == LZMA_MEM_ERROR) {
                ERR(file->ctx, "xz: %s\n", strerror(ENOMEM));
                return -ENOMEM;
@@ -111,6 +137,6 @@ int kmod_file_load_xz(struct kmod_file *file)
                return -EINVAL;
        }
        ret = xz_uncompress(&strm, file);
-       lzma_end(&strm);
+       sym_lzma_end(&strm);
        return ret;
 }