A boot loader can load files from outside ESP.
In these cases device could be not provided or path could
be something not supported.
In these cases allows to boot anyway, all information
could be provided using UKI or using other boot loader
features.
Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com>
---
Changes since v1:
- set "leaf" to NULL instead of a buffer with an empty string;
- keep read_file fatal if cannot load file (except configuration).
---
xen/common/efi/boot.c | 34 +++++++++++++++++++++++++++++-----
1 file changed, 29 insertions(+), 5 deletions(-)
diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 1a9b4e7dae..b18af2f1f4 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -443,6 +443,18 @@ static EFI_FILE_HANDLE __init get_parent_handle(const EFI_LOADED_IMAGE *loaded_i
CHAR16 *pathend, *ptr;
EFI_STATUS ret;
+ /*
+ * In some cases the image could not come from a specific device.
+ * For instance this can happen if Xen was loaded using GRUB2 "linux"
+ * command.
+ */
+ *leaf = NULL;
+ if ( !loaded_image->DeviceHandle )
+ {
+ PrintStr(L"Xen image loaded without providing a device\r\n");
+ return NULL;
+ }
+
do {
EFI_FILE_IO_INTERFACE *fio;
@@ -466,7 +478,15 @@ static EFI_FILE_HANDLE __init get_parent_handle(const EFI_LOADED_IMAGE *loaded_i
if ( DevicePathType(dp) != MEDIA_DEVICE_PATH ||
DevicePathSubType(dp) != MEDIA_FILEPATH_DP )
- blexit(L"Unsupported device path component");
+ {
+ /*
+ * The image could come from an unsupported device.
+ * For instance this can happen if Xen was loaded using GRUB2
+ * "chainloader" command and the file was not from ESP.
+ */
+ PrintStr(L"Unsupported device path component\r\n");
+ return NULL;
+ }
if ( *buffer )
{
@@ -772,8 +792,11 @@ static bool __init read_file(EFI_FILE_HANDLE dir_handle, CHAR16 *name,
if ( !name )
PrintErrMesg(L"No filename", EFI_OUT_OF_RESOURCES);
- ret = dir_handle->Open(dir_handle, &FileHandle, name,
- EFI_FILE_MODE_READ, 0);
+ if ( dir_handle )
+ ret = dir_handle->Open(dir_handle, &FileHandle, name,
+ EFI_FILE_MODE_READ, 0);
+ else
+ ret = EFI_NOT_FOUND;
if ( file == &cfg && ret == EFI_NOT_FOUND )
return false;
if ( EFI_ERROR(ret) )
@@ -1404,7 +1427,7 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE ImageHandle,
/* Read and parse the config file. */
if ( read_section(loaded_image, L"config", &cfg, NULL) )
PrintStr(L"Using builtin config file\r\n");
- else if ( !cfg_file_name )
+ else if ( !cfg_file_name && file_name)
{
CHAR16 *tail;
@@ -1515,7 +1538,8 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE ImageHandle,
efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
cfg.addr = 0;
- dir_handle->Close(dir_handle);
+ if ( dir_handle )
+ dir_handle->Close(dir_handle);
if ( gop && !base_video )
{
--
2.43.0On Tue, Jun 24, 2025 at 03:27:08PM +0100, Frediano Ziglio wrote:
> A boot loader can load files from outside ESP.
> In these cases device could be not provided or path could
> be something not supported.
> In these cases allows to boot anyway, all information
> could be provided using UKI or using other boot loader
> features.
>
> Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> ---
> Changes since v1:
> - set "leaf" to NULL instead of a buffer with an empty string;
> - keep read_file fatal if cannot load file (except configuration).
> ---
> xen/common/efi/boot.c | 34 +++++++++++++++++++++++++++++-----
> 1 file changed, 29 insertions(+), 5 deletions(-)
>
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index 1a9b4e7dae..b18af2f1f4 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -443,6 +443,18 @@ static EFI_FILE_HANDLE __init get_parent_handle(const EFI_LOADED_IMAGE *loaded_i
> CHAR16 *pathend, *ptr;
> EFI_STATUS ret;
>
> + /*
> + * In some cases the image could not come from a specific device.
> + * For instance this can happen if Xen was loaded using GRUB2 "linux"
> + * command.
> + */
> + *leaf = NULL;
> + if ( !loaded_image->DeviceHandle )
> + {
> + PrintStr(L"Xen image loaded without providing a device\r\n");
> + return NULL;
> + }
> +
> do {
> EFI_FILE_IO_INTERFACE *fio;
>
> @@ -466,7 +478,15 @@ static EFI_FILE_HANDLE __init get_parent_handle(const EFI_LOADED_IMAGE *loaded_i
>
> if ( DevicePathType(dp) != MEDIA_DEVICE_PATH ||
> DevicePathSubType(dp) != MEDIA_FILEPATH_DP )
> - blexit(L"Unsupported device path component");
> + {
> + /*
> + * The image could come from an unsupported device.
> + * For instance this can happen if Xen was loaded using GRUB2
> + * "chainloader" command and the file was not from ESP.
> + */
> + PrintStr(L"Unsupported device path component\r\n");
> + return NULL;
> + }
>
> if ( *buffer )
> {
> @@ -772,8 +792,11 @@ static bool __init read_file(EFI_FILE_HANDLE dir_handle, CHAR16 *name,
>
> if ( !name )
> PrintErrMesg(L"No filename", EFI_OUT_OF_RESOURCES);
> - ret = dir_handle->Open(dir_handle, &FileHandle, name,
> - EFI_FILE_MODE_READ, 0);
> + if ( dir_handle )
> + ret = dir_handle->Open(dir_handle, &FileHandle, name,
> + EFI_FILE_MODE_READ, 0);
> + else
> + ret = EFI_NOT_FOUND;
> if ( file == &cfg && ret == EFI_NOT_FOUND )
> return false;
> if ( EFI_ERROR(ret) )
> @@ -1404,7 +1427,7 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE ImageHandle,
> /* Read and parse the config file. */
> if ( read_section(loaded_image, L"config", &cfg, NULL) )
> PrintStr(L"Using builtin config file\r\n");
> - else if ( !cfg_file_name )
> + else if ( !cfg_file_name && file_name)
> {
> CHAR16 *tail;
>
> @@ -1515,7 +1538,8 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE ImageHandle,
> efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
> cfg.addr = 0;
>
> - dir_handle->Close(dir_handle);
> + if ( dir_handle )
> + dir_handle->Close(dir_handle);
>
> if ( gop && !base_video )
> {
> --
> 2.43.0
>
--
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
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