[LTP] [PATCH v4 1/3] lib: Fix kernel module detection on BusyBox

[Petr Vorel]

BusyBox modprobe implementation does not support -n switch.

It does support -D, which could be used, *but* unless is busybox binary
configured with CONFIG_MODPROBE_SMALL=y (IMHO the default).

We could use modinfo and grep output for 'filename:', but we agreed on
ML that having our own implementation will be the best as it also
does not require modinfo as external dependency.

Implementation searches for for module presence in /lib/modules/$(uname
-r)/modules.{dep,builtin}. On Android expect files in /system/lib/modules
directory.

Also treat '-' and '_' in module name as the same (follow kmod implementation).

On Android still assume all drivers are available because modules.* files might
not be available. We could search modules in /system/lib/modules, but to
to determine built-in drivers we need modules.builtin (it's required
also by Busybox mod{info,probe} implementation).

This fixes many tests on BusyBox, e.g. *all* network tests (tests using
tst_net.sh) after 305a78e4c ("tst_net.sh: Require veth for netns").

Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
 lib/tst_kernel.c | 104 +++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 92 insertions(+), 12 deletions(-)

diff --git a/lib/tst_kernel.c b/lib/tst_kernel.c
index 57fa4b2be..b5caf7b20 100644
--- a/lib/tst_kernel.c
+++ b/lib/tst_kernel.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2017 Cyril Hrubis <chrubis@suse.cz>
+ * Copyright (c) 2020-2021 Petr Vorel <pvorel@suse.cz>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,8 +18,11 @@
 
 #include <sys/personality.h>
 #include <sys/utsname.h>
+#include <limits.h>
+
 #include "test.h"
 #include "tst_kernel.h"
+#include "old_safe_stdio.h"
 
 static int get_kernel_bits_from_uname(struct utsname *buf)
 {
@@ -81,20 +85,96 @@ int tst_kernel_bits(void)
 	return kernel_bits;
 }
 
-int tst_check_driver(const char *name)
+static int tst_search_driver(const char *driver, const char *file)
 {
-#ifndef __ANDROID__
-	const char * const argv[] = { "modprobe", "-n", name, NULL };
-	int res = tst_cmd_(NULL, argv, "/dev/null", "/dev/null",
-			       TST_CMD_PASS_RETVAL);
-
-	/* 255 - it looks like modprobe not available */
-	return (res == 255) ? 0 : res;
-#else
-	/* Android modprobe may not have '-n', or properly installed
-	 * module.*.bin files to determine built-in drivers. Assume
-	 * all drivers are available.
+	struct stat st;
+	char buf[PATH_MAX];
+	char *path = NULL, *search = NULL, *sep = NULL;
+	FILE *f;
+	int ret = -1;
+
+	struct utsname uts;
+
+	if (uname(&uts)) {
+		tst_brkm(TBROK | TERRNO, NULL, "uname() failed");
+		return -1;
+	}
+	SAFE_ASPRINTF(NULL, &path, "/lib/modules/%s/%s", uts.release, file);
+
+	if (stat(path, &st) || !(S_ISREG(st.st_mode) || S_ISLNK(st.st_mode))) {
+		tst_resm(TWARN, "expected file %s does not exist or not a file", path);
+		return -1;
+	}
+
+	if (access(path, R_OK)) {
+		tst_resm(TWARN, "file %s cannot be read", path);
+		return -1;
+	}
+
+	SAFE_ASPRINTF(NULL, &search, "/%s.ko", driver);
+
+	f = SAFE_FOPEN(NULL, path, "r");
+
+	while (fgets(buf, sizeof(buf), f)) {
+		/* Cut dependencies after : */
+		if ((sep = strchr(buf, ':')))
+			*sep = 0;
+
+		if (strstr(buf, search) != NULL) {
+			ret = 0;
+			break;
+		}
+	}
+
+	SAFE_FCLOSE(NULL, f);
+	free(search);
+	free(path);
+
+	return ret;
+}
+
+static int tst_check_driver_(const char *driver)
+{
+	if (!tst_search_driver(driver, "modules.dep") ||
+		!tst_search_driver(driver, "modules.builtin"))
+		return 0;
+
+	return 1;
+}
+
+int tst_check_driver(const char *driver)
+{
+#ifdef __ANDROID__
+	/*
+	 * Android may not have properly installed modules.* files. We could
+	 * search modules in /system/lib/modules, but to to determine built-in
+	 * drivers we need modules.builtin. Therefore assume all drivers are
+	 * available.
 	 */
 	return 0;
 #endif
+
+	if (!tst_check_driver_(driver))
+		return 0;
+
+	int ret = 1;
+
+	if (strrchr(driver, '-') || strrchr(driver, '_')) {
+		char *driver2 = strdup(driver);
+		char *ix = driver2;
+		char find = '-', replace = '_';
+
+		if (strrchr(driver, '_')) {
+			find = '_';
+			replace = '-';
+		}
+
+		while ((ix = strchr(ix, find)))
+			*ix++ = replace;
+
+		ret = tst_check_driver_(driver2);
+		free(driver2);
+	}
+
+	return ret;
 }
-- 
2.30.0