From: Christian Goeschel Ndjomouo <cgoesc2@wgu.edu>
Date: Mon, 25 May 2026 20:38:53 +0000 (-0400)
Subject: chmem: add helper function to sensibly detect the 'valid_zones' attribute
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3f53e5d2d5dae65538465210da8dbb0380ede62a;p=thirdparty%2Futil-linux.git

chmem: add helper function to sensibly detect the 'valid_zones' attribute

On some systems the first available memory blocks start at an index
greater than 0, and on such systems we fail to properly detect the
valid_zones attribute, because we naively checked for the presence
of the memory block directory 'memory0'. To sensibly and reliably
detect the first memory block, we can use the directory sysmem->dirs
that are sorted in numeric order, so we can assume that the first
entry is the first memory block, i.e. sysmem->dirs[0]->d_name is
the name of the first configurable memory block.

Signed-off-by: Christian Goeschel Ndjomouo <cgoesc2@wgu.edu>
---

diff --git a/sys-utils/chmem.c b/sys-utils/chmem.c
index 00a5f863b..8a70d85eb 100644
--- a/sys-utils/chmem.c
+++ b/sys-utils/chmem.c
@@ -84,6 +84,23 @@ static const char *const zone_names[] = {
 	[ZONE_DEVICE]	= "Device",
 };
 
+
+static int have_mem_blk_zones(struct path_cxt *pctx, const char *dirname)
+{
+	int rc = 0;
+	char *path = NULL;
+
+	if (!pctx || !dirname)
+		return -EINVAL;
+
+	path = ul_strconcat(dirname, "/valid_zones");
+	if (ul_path_access(pctx, F_OK, path) == 0)
+		rc = 1;
+
+	free(path);
+	return rc;
+}
+
 /*
  * name must be null-terminated
  */
@@ -667,7 +684,7 @@ int main(int argc, char **argv)
 		.memmap_on_memory = -1,
 	}, *desc = &_desc;
 	int cmd = CMD_NONE, zone_id = -1;
-	char *zone = NULL, *sysroot = NULL;
+	char *zone = NULL, *sysroot = NULL, *first_memblk_dirname = NULL;
 	int c, rc;
 
 	static const struct option longopts[] = {
@@ -758,14 +775,17 @@ int main(int argc, char **argv)
 		err(EXIT_FAILURE, _("failed to initialize %s handler"), _PATH_SYS_MEMCONFIG);
 	if (sysroot && ul_path_set_prefix(desc->sysmemconfig, sysroot) != 0)
 		err(EXIT_FAILURE, _("invalid argument to --sysroot"));
-	if (ul_path_access(desc->sysmemconfig, F_OK, "memory0") == 0)
-		desc->have_memconfig = 1;
 
 	read_info(desc);
 	parse_parameter(desc, argv[optind]);
 
+	first_memblk_dirname = desc->dirs[0]->d_name;
+
+	if (ul_path_access(desc->sysmemconfig, F_OK, first_memblk_dirname) == 0)
+		desc->have_memconfig = 1;
+
 	/* The valid_zones sysfs attribute was introduced with kernel 3.18 */
-	if (ul_path_access(desc->sysmem, F_OK, "memory0/valid_zones") == 0)
+	if (have_mem_blk_zones(desc->sysmem, first_memblk_dirname) > 0)
 		desc->have_zones = 1;
 	else if (zone)
 		warnx(_("zone ignored, no valid_zones sysfs attribute present"));