tools: Introduce a xc_xenver_buildid() wrapper

... which converts binary content to hex automatically.

Update libxl to match.  No API/ABI change.

This removes a latent libxl bug for cases when the buildid is longer than 4092
bytes.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>

tools/include/xenctrl.h

@@ -1581,6 +1581,7 @@ char *xc_xenver_extraversion(xc_interface *xch);
 char *xc_xenver_capabilities(xc_interface *xch);
 char *xc_xenver_changeset(xc_interface *xch);
 char *xc_xenver_commandline(xc_interface *xch);
+char *xc_xenver_buildid(xc_interface *xch);
 
 int xc_flask_op(xc_interface *xch, xen_flask_op_t *op);
 

tools/libs/ctrl/xc_version.c

@@ -171,3 +171,36 @@ char *xc_xenver_commandline(xc_interface *xch)
 {
     return varbuf_simple_string(xch, XENVER_commandline2);
 }
+
+static void str2hex(char *dst, const unsigned char *src, size_t n)
+{
+    static const unsigned char hex[] = "0123456789abcdef";
+
+    for ( ; n; n-- )
+    {
+        unsigned char c = *src++;
+
+        *dst++ = hex[c >> 4];
+        *dst++ = hex[c & 0xf];
+    }
+}
+
+char *xc_xenver_buildid(xc_interface *xch)
+{
+    xen_varbuf_t *hbuf = varbuf_op(xch, XENVER_build_id);
+    char *res;
+
+    if ( !hbuf )
+        return NULL;
+
+    res = malloc((hbuf->len * 2) + 1);
+    if ( res )
+    {
+        str2hex(res, hbuf->buf, hbuf->len);
+        res[hbuf->len * 2] = '\0';
+    }
+
+    xencall_free_buffer(xch->xcall, hbuf);
+
+    return res;
+}

tools/libs/light/libxl.c

@@ -546,38 +546,6 @@ libxl_numainfo *libxl_get_numainfo(libxl_ctx *ctx, int *nr)
     return ret;
 }
 
-static int libxl__xc_version_wrap(libxl__gc *gc, libxl_version_info *info,
-                                  xen_build_id_t *build)
-{
-    int r;
-
-    r = xc_version(CTX->xch, XENVER_build_id, build);
-    switch (r) {
-    case -EPERM:
-    case -ENODATA:
-    case 0:
-        info->build_id = libxl__strdup(NOGC, "");
-        break;
-
-    case -ENOBUFS:
-        break;
-
-    default:
-        if (r > 0) {
-            unsigned int i;
-
-            info->build_id = libxl__zalloc(NOGC, (r * 2) + 1);
-
-            for (i = 0; i < r ; i++)
-                snprintf(&info->build_id[i * 2], 3, "%02hhx", build->buf[i]);
-
-            r = 0;
-        }
-        break;
-    }
-    return r;
-}
-
 const libxl_version_info* libxl_get_version_info(libxl_ctx *ctx)
 {
     GC_INIT(ctx);
@@ -587,7 +555,6 @@ const libxl_version_info* libxl_get_version_info(libxl_ctx *ctx)
         xen_build_id_t build_id;
     } u;
     long xen_version;
-    int r;
     libxl_version_info *info = &ctx->version_info;
 
     if (info->xen_version_extra != NULL)
@@ -614,17 +581,8 @@ const libxl_version_info* libxl_get_version_info(libxl_ctx *ctx)
     info->pagesize = xc_version(ctx->xch, XENVER_pagesize, NULL);
 
     info->commandline = xc_xenver_commandline(ctx->xch);
+    info->build_id = xc_xenver_buildid(ctx->xch);
 
-    u.build_id.len = sizeof(u) - sizeof(u.build_id);
-    r = libxl__xc_version_wrap(gc, info, &u.build_id);
-    if (r == -ENOBUFS) {
-            xen_build_id_t *build_id;
-
-            build_id = libxl__zalloc(gc, info->pagesize);
-            build_id->len = info->pagesize - sizeof(*build_id);
-            r = libxl__xc_version_wrap(gc, info, build_id);
-            if (r) LOGEV(ERROR, r, "getting build_id");
-    }
  out:
     GC_FREE;
     return info;