core: split out smbios type 11 reader into src/shared/smbios11.[ch]

src/shared/meson.build

@@ -157,6 +157,7 @@ shared_sources = files(
         'service-util.c',
         'sleep-config.c',
         'smack-util.c',
+        'smbios11.c',
         'socket-label.c',
         'socket-netlink.c',
         'spawn-ask-password-agent.c',

src/shared/smbios11.c

@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "alloc-util.h"
+#include "fileio.h"
+#include "macro.h"
+#include "smbios11.h"
+#include "virt.h"
+
+int read_smbios11_field(unsigned i, size_t max_size, char **ret_data, size_t *ret_size) {
+        _cleanup_free_ char *p = NULL, *contents = NULL;
+        _cleanup_free_ void *data = NULL;
+        size_t size, contents_size;
+        int r;
+
+        assert(ret_data);
+        assert(ret_size);
+
+        /* Parses DMI OEM strings fields (SMBIOS type 11), as settable with qemu's -smbios type=11,value=… switch. */
+
+        if (detect_container() > 0) /* don't access /sys/ in a container */
+                return -ENOENT;
+
+        if (asprintf(&p, "/sys/firmware/dmi/entries/11-%u/raw", i) < 0)
+                return -ENOMEM;
+
+        struct dmi_field_header {
+                uint8_t type;
+                uint8_t length;
+                uint16_t handle;
+                uint8_t count;
+                char contents[];
+        } _packed_ *dmi_field_header;
+
+        assert_cc(offsetof(struct dmi_field_header, contents) == 5);
+
+        r = read_virtual_file(
+                        p,
+                        max_size >= SIZE_MAX - offsetof(struct dmi_field_header, contents) ? SIZE_MAX :
+                        sizeof(dmi_field_header) + max_size,
+                        (char**) &data, &size);
+        if (r < 0)
+                return r;
+
+        if (size < offsetof(struct dmi_field_header, contents))
+                return -EBADMSG;
+
+        dmi_field_header = data;
+        if (dmi_field_header->type != 11 ||
+            dmi_field_header->length != offsetof(struct dmi_field_header, contents))
+                return -EBADMSG;
+
+        contents_size = size - offsetof(struct dmi_field_header, contents);
+        contents = memdup_suffix0(dmi_field_header->contents, contents_size);
+        if (!contents)
+                return -ENOMEM;
+
+        *ret_data = TAKE_PTR(contents);
+        *ret_size = contents_size;
+
+        return r; /* NB! read_virtual_file() returns 0 on incomplete reads, and 1 in complete reads */
+}

src/shared/smbios11.h

@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <sys/types.h>
+
+int read_smbios11_field(unsigned i, size_t max_size, char **ret_data, size_t *ret_size);