pc-bios/s390-ccw: Allow to select a different pxelinux.cfg entry via loadparm

Since we're linking the network booting code into the main firmware
binary nowadays, we can support the "loadparm" parameter now quite
easily for pxelinux.cfg config files that contain multiple entries.

Reviewed-by: Jared Rossi <jrossi@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20250709083443.41574-2-thuth@redhat.com>

1 files changed, 24 insertions, 8 deletions

diff --git a/pc-bios/s390-ccw/netmain.c b/pc-bios/s390-ccw/netmain.c
index 719a547..c0aafca 100644
--- a/pc-bios/s390-ccw/netmain.c
+++ b/pc-bios/s390-ccw/netmain.c
@@ -332,6 +332,27 @@ static int load_kernel_with_initrd(filename_ip_t *fn_ip,
     return rc;
 }
 
+static int net_select_and_load_kernel(filename_ip_t *fn_ip,
+                                      int num_ent, int selected,
+                                      struct pl_cfg_entry *entries)
+{
+    unsigned int loadparm = get_loadparm_index();
+
+    if (num_ent <= 0) {
+        return -1;
+    }
+
+    IPL_assert(loadparm <= num_ent,
+               "loadparm is set to an entry that is not available in the "
+               "pxelinux.cfg file!");
+
+    if (loadparm > 0) {
+        selected = loadparm - 1;
+    }
+
+    return load_kernel_with_initrd(fn_ip, &entries[selected]);
+}
+
 #define MAX_PXELINUX_ENTRIES 16
 
 static int net_try_pxelinux_cfg(filename_ip_t *fn_ip)
@@ -343,11 +364,8 @@ static int net_try_pxelinux_cfg(filename_ip_t *fn_ip)
                                       DEFAULT_TFTP_RETRIES,
                                       cfgbuf, sizeof(cfgbuf),
                                       entries, MAX_PXELINUX_ENTRIES, &def_ent);
-    if (num_ent > 0) {
-        return load_kernel_with_initrd(fn_ip, &entries[def_ent]);
-    }
 
-    return -1;
+    return net_select_and_load_kernel(fn_ip, num_ent, def_ent, entries);
 }
 
 /**
@@ -433,10 +451,8 @@ static int net_try_direct_tftp_load(filename_ip_t *fn_ip)
 
             num_ent = pxelinux_parse_cfg(cfgbuf, sizeof(cfgbuf), entries,
                                          MAX_PXELINUX_ENTRIES, &def_ent);
-            if (num_ent <= 0) {
-                return -1;
-            }
-            return load_kernel_with_initrd(fn_ip, &entries[def_ent]);
+            return net_select_and_load_kernel(fn_ip, num_ent, def_ent,
+                                              entries);
         }
     }