EFI: add EFI_LOAD_OPTION support

When booting Xen via UEFI the Xen config file can contain multiple
sections each describing different boot options. It is currently only
possible to choose which section to boot with if the buffer contains a
string. UEFI provides a different standard to pass optional arguments
to an application, and in this patch we make Xen properly parse this
buffer, thus making it possible to have separate EFI boot options
present for the different config sections.

Signed-off-by: Tamas K Lengyel <tamas@tklengyel.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 64d12685d35747d3734c1ad8ac27634e83bcf7db..146452011a1aa6386a6aca4e4b838c2bed7f7173 100644 (file)
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -88,6 +88,14 @@ typedef struct _EFI_APPLE_PROPERTIES {
     EFI_APPLE_PROPERTIES_GETALL GetAll;
 } EFI_APPLE_PROPERTIES;
 
+typedef struct _EFI_LOAD_OPTION {
+    UINT32 Attributes;
+    UINT16 FilePathListLength;
+    CHAR16 Description[];
+} EFI_LOAD_OPTION;
+
+#define LOAD_OPTION_ACTIVE              0x00000001
+
 union string {
     CHAR16 *w;
     char *s;
@@ -275,6 +283,16 @@ static int __init wstrncmp(const CHAR16 *s1, const CHAR16 *s2, UINTN n)
     return n ? *s1 - *s2 : 0;
 }
 
+static const CHAR16 *__init wmemchr(const CHAR16 *s, CHAR16 c, UINTN n)
+{
+    while ( n && *s != c )
+    {
+        --n;
+        ++s;
+    }
+    return n ? s : NULL;
+}
+
 static CHAR16 *__init s2w(union string *str)
 {
     const char *s = str->s;
@@ -374,14 +392,59 @@ static void __init PrintErrMesg(const CHAR16 *mesg, EFI_STATUS ErrCode)
 }
 
 static unsigned int __init get_argv(unsigned int argc, CHAR16 **argv,
-                                    CHAR16 *cmdline, UINTN cmdsize,
+                                    VOID *data, UINTN size, UINTN *offset,
                                     CHAR16 **options)
 {
-    CHAR16 *ptr = (CHAR16 *)(argv + argc + 1), *prev = NULL;
+    CHAR16 *ptr = (CHAR16 *)(argv + argc + 1), *prev = NULL, *cmdline = NULL;
     bool prev_sep = true;
 
-    for ( ; cmdsize > sizeof(*cmdline) && *cmdline;
-            cmdsize -= sizeof(*cmdline), ++cmdline )
+    if ( argc )
+    {
+        cmdline = data + *offset;
+        /* EFI_LOAD_OPTION does not supply an image name as first component. */
+        if ( *offset )
+            *argv++ = NULL;
+    }
+    else if ( size > sizeof(*cmdline) && !(size % sizeof(*cmdline)) &&
+              (wmemchr(data, 0, size / sizeof(*cmdline)) ==
+               data + size - sizeof(*cmdline)) )
+    {
+        /* Plain command line, as usually passed by the EFI shell. */
+        *offset = 0;
+        cmdline = data;
+    }
+    else if ( size > sizeof(EFI_LOAD_OPTION) )
+    {
+        const EFI_LOAD_OPTION *elo = data;
+        /* The minimum size the buffer needs to be. */
+        size_t elo_min = offsetof(EFI_LOAD_OPTION, Description[1]) +
+                         elo->FilePathListLength;
+
+        if ( (elo->Attributes & LOAD_OPTION_ACTIVE) && size > elo_min &&
+             !((size - elo_min) % sizeof(*cmdline)) )
+        {
+            const CHAR16 *desc = elo->Description;
+            const CHAR16 *end = wmemchr(desc, 0,
+                                        (size - elo_min) / sizeof(*desc) + 1);
+
+            if ( end )
+            {
+                *offset = elo_min + (end - desc) * sizeof(*desc);
+                if ( (size -= *offset) > sizeof(*cmdline) )
+                {
+                    cmdline = data + *offset;
+                    /* Cater for the image name as first component. */
+                    ++argc;
+                }
+            }
+        }
+    }
+
+    if ( !cmdline )
+        return 0;
+
+    for ( ; size > sizeof(*cmdline) && *cmdline;
+            size -= sizeof(*cmdline), ++cmdline )
     {
         bool cur_sep = *cmdline == L' ' || *cmdline == L'\t';
 
@@ -1095,15 +1158,17 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
 
     if ( use_cfg_file )
     {
+        UINTN offset = 0;
+
         argc = get_argv(0, NULL, loaded_image->LoadOptions,
-                        loaded_image->LoadOptionsSize, NULL);
+                        loaded_image->LoadOptionsSize, &offset, NULL);
         if ( argc > 0 &&
              efi_bs->AllocatePool(EfiLoaderData,
                                   (argc + 1) * sizeof(*argv) +
                                       loaded_image->LoadOptionsSize,
                                   (void **)&argv) == EFI_SUCCESS )
             get_argv(argc, argv, loaded_image->LoadOptions,
-                     loaded_image->LoadOptionsSize, &options);
+                     loaded_image->LoadOptionsSize, &offset, &options);
         else
             argc = 0;
         for ( i = 1; i < argc; ++i )
@@ -1244,6 +1309,19 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
             efi_bs->FreePool(name.w);
         }
 
+        /*
+         * EFI_LOAD_OPTION does not supply an image name as first component:
+         * Make one up.
+         */
+        if ( argc && !*argv )
+        {
+            EFI_FILE_HANDLE handle = get_parent_handle(loaded_image,
+                                                       &file_name);
+
+            handle->Close(handle);
+            *argv = file_name;
+        }
+
         name.s = get_value(&cfg, section.s, "options");
         efi_arch_handle_cmdline(argc ? *argv : NULL, options, name.s);