x86/loader: add -shim option

Add new -shim command line option, wire up for the x86 loader.
When specified load shim into the new "etc/boot/shim" fw_cfg file.

Needs OVMF changes too to be actually useful.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-ID: <20240905141211.1253307-6-kraxel@redhat.com>

hw/core/machine.c

@@ -305,6 +305,21 @@ static void machine_set_kernel(Object *obj, const char *value, Error **errp)
     ms->kernel_filename = g_strdup(value);
 }
 
+static char *machine_get_shim(Object *obj, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    return g_strdup(ms->shim_filename);
+}
+
+static void machine_set_shim(Object *obj, const char *value, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    g_free(ms->shim_filename);
+    ms->shim_filename = g_strdup(value);
+}
+
 static char *machine_get_initrd(Object *obj, Error **errp)
 {
     MachineState *ms = MACHINE(obj);
@@ -1082,6 +1097,11 @@ static void machine_class_init(ObjectClass *oc, void *data)
     object_class_property_set_description(oc, "kernel",
         "Linux kernel image file");
 
+    object_class_property_add_str(oc, "shim",
+        machine_get_shim, machine_set_shim);
+    object_class_property_set_description(oc, "shim",
+        "shim.efi file");
+
     object_class_property_add_str(oc, "initrd",
         machine_get_initrd, machine_set_initrd);
     object_class_property_set_description(oc, "initrd",

hw/i386/x86-common.c

@@ -965,6 +965,22 @@ void x86_load_linux(X86MachineState *x86ms,
     /* kernel without setup header patches */
     fw_cfg_add_file(fw_cfg, "etc/boot/kernel", kernel, kernel_size);
 
+    if (machine->shim_filename) {
+        GMappedFile *mapped_file;
+        GError *gerr = NULL;
+
+        mapped_file = g_mapped_file_new(machine->shim_filename, false, &gerr);
+        if (!mapped_file) {
+            fprintf(stderr, "qemu: error reading shim %s: %s\n",
+                    machine->shim_filename, gerr->message);
+            exit(1);
+        }
+
+        fw_cfg_add_file(fw_cfg, "etc/boot/shim",
+                        g_mapped_file_get_contents(mapped_file),
+                        g_mapped_file_get_length(mapped_file));
+    }
+
     if (sev_enabled()) {
         sev_add_kernel_loader_hashes(&sev_load_ctx, &error_fatal);
     }

include/hw/boards.h

@@ -431,6 +431,7 @@ struct MachineState {
     BootConfiguration boot_config;
     char *kernel_filename;
     char *kernel_cmdline;
+    char *shim_filename;
     char *initrd_filename;
     const char *cpu_type;
     AccelState *accelerator;

qemu-options.hx

@@ -4145,6 +4145,13 @@ SRST
     or in multiboot format.
 ERST
 
+DEF("shim", HAS_ARG, QEMU_OPTION_shim, \
+    "-shim shim.efi use 'shim.efi' to boot the kernel\n", QEMU_ARCH_ALL)
+SRST
+``-shim shim.efi``
+    Use 'shim.efi' to boot the kernel
+ERST
+
 DEF("append", HAS_ARG, QEMU_OPTION_append, \
     "-append cmdline use 'cmdline' as kernel command line\n", QEMU_ARCH_ALL)
 SRST

system/vl.c

@@ -2427,6 +2427,7 @@ static void configure_accelerators(const char *progname)
 static void qemu_validate_options(const QDict *machine_opts)
 {
     const char *kernel_filename = qdict_get_try_str(machine_opts, "kernel");
+    const char *shim_filename = qdict_get_try_str(machine_opts, "shim");
     const char *initrd_filename = qdict_get_try_str(machine_opts, "initrd");
     const char *kernel_cmdline = qdict_get_try_str(machine_opts, "append");
 
@@ -2436,6 +2437,11 @@ static void qemu_validate_options(const QDict *machine_opts)
             exit(1);
         }
 
+        if (shim_filename != NULL) {
+            error_report("-shim only allowed with -kernel option");
+            exit(1);
+        }
+
         if (initrd_filename != NULL) {
             error_report("-initrd only allowed with -kernel option");
             exit(1);
@@ -2912,6 +2918,9 @@ void qemu_init(int argc, char **argv)
             case QEMU_OPTION_kernel:
                 qdict_put_str(machine_opts_dict, "kernel", optarg);
                 break;
+            case QEMU_OPTION_shim:
+                qdict_put_str(machine_opts_dict, "shim", optarg);
+                break;
             case QEMU_OPTION_initrd:
                 qdict_put_str(machine_opts_dict, "initrd", optarg);
                 break;