qemu_firmware: Introduce qemuFirmwareFetchConfigs

Implementation for yet another part of firmware description
specification. This one covers selecting which files to parse.

There are three locations from which description files can be
loaded. In order of preference, from most generic to most
specific these are:

  /usr/share/qemu/firmware
  /etc/qemu/firmware
  $XDG_CONFIG_HOME/qemu/firmware

If a file is found in two or more locations then the most specific
one is used. Moreover, if file is empty then it means it is
overriding some generic description and disabling it.

Again, this is described in more details and with nice examples
in firmware.json specification (qemu commit 3a0adfc9bf).

However, there's one slight difference - for the root user the
home directory is not searched. This follows rules laid out by
similar look up processes, e.g. PKI x509 certs are not searched
in /root but they are looked for under /home.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

src/qemu/qemu_firmware.c

@@ -21,9 +21,11 @@
 #include <config.h>
 
 #include "qemu_firmware.h"
+#include "configmake.h"
 #include "qemu_capabilities.h"
 #include "virarch.h"
 #include "virfile.h"
+#include "virhash.h"
 #include "virjson.h"
 #include "virlog.h"
 #include "virstring.h"
@@ -899,3 +901,144 @@ qemuFirmwareFormat(qemuFirmwarePtr fw)
 
     return virJSONValueToString(doc, true);
 }
+
+
+static int
+qemuFirmwareBuildFileList(virHashTablePtr files, const char *dir)
+{
+    DIR *dirp;
+    struct dirent *ent = NULL;
+    int rc;
+    int ret = -1;
+
+    if ((rc = virDirOpenIfExists(&dirp, dir)) < 0)
+        return -1;
+
+    if (rc == 0)
+        return 0;
+
+    while ((rc = virDirRead(dirp, &ent, dir)) > 0) {
+        VIR_AUTOFREE(char *) filename = NULL;
+        VIR_AUTOFREE(char *) path = NULL;
+
+        if (ent->d_type != DT_REG && ent->d_type != DT_LNK)
+            continue;
+
+        if (STRPREFIX(ent->d_name, "."))
+            continue;
+
+        if (VIR_STRDUP(filename, ent->d_name) < 0)
+            goto cleanup;
+
+        if (virAsprintf(&path, "%s/%s", dir, filename) < 0)
+            goto cleanup;
+
+        if (virHashUpdateEntry(files, filename, path) < 0)
+            goto cleanup;
+
+        path = NULL;
+    }
+
+    if (rc < 0)
+        goto cleanup;
+
+    ret = 0;
+ cleanup:
+    virDirClose(&dirp);
+    return ret;
+}
+
+static int
+qemuFirmwareFilesSorter(const virHashKeyValuePair *a,
+                        const virHashKeyValuePair *b)
+{
+    return strcmp(a->key, b->key);
+}
+
+#define QEMU_FIRMWARE_SYSTEM_LOCATION PREFIX "/share/qemu/firmware"
+#define QEMU_FIRMWARE_ETC_LOCATION SYSCONFDIR "/qemu/firmware"
+
+int
+qemuFirmwareFetchConfigs(char ***firmwares,
+                         bool privileged)
+{
+    VIR_AUTOPTR(virHashTable) files = NULL;
+    VIR_AUTOFREE(char *) homeConfig = NULL;
+    VIR_AUTOFREE(char *) xdgConfig = NULL;
+    VIR_AUTOFREE(virHashKeyValuePairPtr) pairs = NULL;
+    virHashKeyValuePairPtr tmp = NULL;
+
+    *firmwares = NULL;
+
+    if (privileged) {
+        /* This is a slight divergence from the specification.
+         * Since the system daemon runs as root, it doesn't make
+         * much sense to parse files in root's home directory. It
+         * makes sense only for session daemon which runs under
+         * regular user. */
+        if (VIR_STRDUP(xdgConfig, virGetEnvBlockSUID("XDG_CONFIG_HOME")) < 0)
+            return -1;
+
+        if (!xdgConfig) {
+            VIR_AUTOFREE(char *) home = virGetUserDirectory();
+
+            if (!home)
+                return -1;
+
+            if (virAsprintf(&xdgConfig, "%s/.config", home) < 0)
+                return -1;
+        }
+
+        if (virAsprintf(&homeConfig, "%s/qemu/firmware", xdgConfig) < 0)
+            return -1;
+    }
+
+    if (!(files = virHashCreate(10, virHashValueFree)))
+        return -1;
+
+    if (qemuFirmwareBuildFileList(files, QEMU_FIRMWARE_SYSTEM_LOCATION) < 0)
+        return -1;
+
+    if (qemuFirmwareBuildFileList(files, QEMU_FIRMWARE_ETC_LOCATION) < 0)
+        return -1;
+
+    if (homeConfig &&
+        qemuFirmwareBuildFileList(files, homeConfig) < 0)
+        return -1;
+
+    /* At this point, the @files hash table contains unique set of filenames
+     * where each filename (as key) has the highest priority full pathname
+     * associated with it. */
+
+    if (virHashSize(files) == 0)
+        return 0;
+
+    if (!(pairs = virHashGetItems(files, qemuFirmwareFilesSorter)))
+        return -1;
+
+    for (tmp = pairs; tmp->key; tmp++) {
+        const char *path = tmp->value;
+        off_t len;
+
+        if ((len = virFileLength(path, -1)) < 0) {
+            virReportSystemError(errno,
+                                 _("unable to get size of '%s'"),
+                                 path);
+            return -1;
+        }
+
+        VIR_DEBUG("firmware description path '%s' len=%jd",
+                  path, (intmax_t) len);
+
+        if (len == 0) {
+            /* Empty files are used to mask less specific instances
+             * of the same file. */
+            continue;
+        }
+
+        if (virStringListAdd(firmwares, path) < 0)
+            return -1;
+    }
+
+    return 0;
+}

src/qemu/qemu_firmware.h

@@ -37,4 +37,8 @@ qemuFirmwareParse(const char *path);
 char *
 qemuFirmwareFormat(qemuFirmwarePtr fw);
 
+int
+qemuFirmwareFetchConfigs(char ***firmwares,
+                         bool privileged);
+
 #endif /* LIBVIRT_QEMU_FIRMWARE_H */