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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH-4.16 v2] xen/efi: Fix Grub2 boot on arm64
On Thu, 4 Nov 2021, Luca Fancellu wrote:
> > On 4 Nov 2021, at 21:35, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> >
> > On Thu, 4 Nov 2021, Luca Fancellu wrote:
> >>> On 4 Nov 2021, at 20:56, Stefano Stabellini <sstabellini@xxxxxxxxxx>
> >>> wrote:
> >>>
> >>> On Thu, 4 Nov 2021, Jan Beulich wrote:
> >>>> On 04.11.2021 15:12, Luca Fancellu wrote:
> >>>>> --- a/xen/common/efi/boot.c
> >>>>> +++ b/xen/common/efi/boot.c
> >>>>> @@ -449,6 +449,15 @@ static EFI_FILE_HANDLE __init
> >>>>> get_parent_handle(EFI_LOADED_IMAGE *loaded_image,
> >>>>> CHAR16 *pathend, *ptr;
> >>>>> EFI_STATUS ret;
> >>>>>
> >>>>> + /*
> >>>>> + * Grub2 running on top of EDK2 has been observed to supply a NULL
> >>>>> + * DeviceHandle. We can't use that to gain access to the
> >>>>> filesystem.
> >>>>> + * However the system can still boot if it doesn’t require access
> >>>>> to the
> >>>>> + * filesystem.
> >>>>> + */
> >>>>> + if ( !loaded_image->DeviceHandle )
> >>>>> + return NULL;
> >>>>> +
> >>>>> do {
> >>>>> EFI_FILE_IO_INTERFACE *fio;
> >>>>>
> >>>>> @@ -581,6 +590,8 @@ static bool __init read_file(EFI_FILE_HANDLE
> >>>>> dir_handle, CHAR16 *name,
> >>>>> EFI_STATUS ret;
> >>>>> const CHAR16 *what = NULL;
> >>>>>
> >>>>> + if ( !dir_handle )
> >>>>> + blexit(L"Error: No access to the filesystem");
> >>>>> if ( !name )
> >>>>> PrintErrMesg(L"No filename", EFI_OUT_OF_RESOURCES);
> >>>>> ret = dir_handle->Open(dir_handle, &FileHandle, name,
> >>>>> @@ -1333,8 +1344,18 @@ efi_start(EFI_HANDLE ImageHandle,
> >>>>> EFI_SYSTEM_TABLE *SystemTable)
> >>>>> EFI_FILE_HANDLE handle = get_parent_handle(loaded_image,
> >>>>> &file_name);
> >>>>>
> >>>>> - handle->Close(handle);
> >>>>> - *argv = file_name;
> >>>>> + if ( !handle )
> >>>>> + {
> >>>>> + PrintErr(L"Error retrieving image name: no filesystem
> >>>>> access."
> >>>>> + L" Setting default to xen.efi");
> >>>>> + PrintErr(newline);
> >>>>> + *argv = L"xen.efi";
> >>>>> + }
> >>>>> + else
> >>>>> + {
> >>>>> + handle->Close(handle);
> >>>>> + *argv = file_name;
> >>>>> + }
> >>>>> }
> >>>>>
> >>>>> name.s = get_value(&cfg, section.s, "options");
> >>>>> @@ -1369,7 +1390,8 @@ efi_start(EFI_HANDLE ImageHandle,
> >>>>> EFI_SYSTEM_TABLE *SystemTable)
> >>>>> /* Get the number of boot modules specified on the DT or an error
> >>>>> (<0) */
> >>>>> dt_modules_found = efi_check_dt_boot(dir_handle);
> >>>>>
> >>>>> - dir_handle->Close(dir_handle);
> >>>>> + if ( dir_handle )
> >>>>> + dir_handle->Close(dir_handle);
> >>>>>
> >>>>> if ( dt_modules_found < 0 )
> >>>>> /* efi_check_dt_boot throws some error */
> >>>>>
> >>>>
> >>>> I'm sorry, but I think we need to take a step back here and revisit
> >>>> the earlier change. If that hadn't moved obtaining dir_handle out by
> >>>> one level of scope, nothing bad would have happened to the case that
> >>>> you're now trying to fix, I understand? So perhaps that part wants
> >>>> undoing, with efi_check_dt_boot() instead getting passed loaded_image.
> >>>> That way, down the call tree the needed handle can be obtained via
> >>>> another call to get_parent_handle(), and quite likely in the scenario
> >>>> you're trying to fix here execution wouldn't even make it there. This
> >>>> then wouldn't be much different to the image name retrieval calling
> >>>> get_parent_handle() a 2nd time, rather than trying to re-use
> >>>> dir_handle.
> >>>>
> >>>> Net effect being that I think get_parent_handle() would then again
> >>>> only be called when the returned handle is actually needed, and hence
> >>>> when failure of HandleProtocol() (for DeviceHandle being NULL just
> >>>> like for any other reason) is indeed an error that needs reporting.
> >>>
> >>> In my opinion the current version is good enough. Regardless, I looked
> >>> at your suggestion into details. As it took me some time to understand
> >>> it, I thought I would share the code changes that I think correspond to
> >>> what you wrote. Does everything check out?
> >>>
> >>> If so, I think it looks fine, maybe a bit better than the current
> >>> version. I'll leave that to you and Luca.
> >>>
> >>>
> >>> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> >>> index c3ae9751ab..9dcd8547cd 100644
> >>> --- a/xen/arch/arm/efi/efi-boot.h
> >>> +++ b/xen/arch/arm/efi/efi-boot.h
> >>> @@ -8,6 +8,8 @@
> >>> #include <asm/setup.h>
> >>> #include <asm/smp.h>
> >>>
> >>> +extern EFI_FILE_HANDLE __init get_parent_handle(EFI_LOADED_IMAGE
> >>> *loaded_image,
> >>> + CHAR16 **leaf);
> >>> typedef struct {
> >>> char *name;
> >>> unsigned int name_len;
> >>> @@ -54,7 +56,7 @@ static int handle_module_node(EFI_FILE_HANDLE
> >>> dir_handle,
> >>> bool is_domu_module);
> >>> static int handle_dom0less_domain_node(EFI_FILE_HANDLE dir_handle,
> >>> int domain_node);
> >>> -static int efi_check_dt_boot(EFI_FILE_HANDLE dir_handle);
> >>> +static int efi_check_dt_boot(EFI_LOADED_IMAGE *loaded_image);
> >>>
> >>> #define DEVICE_TREE_GUID \
> >>> {0xb1b621d5, 0xf19c, 0x41a5, {0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa,
> >>> 0xe0}}
> >>> @@ -851,10 +853,14 @@ static int __init
> >>> handle_dom0less_domain_node(EFI_FILE_HANDLE dir_handle,
> >>> * dom0 and domU guests to be loaded.
> >>> * Returns the number of multiboot modules found or a negative number for
> >>> error.
> >>> */
> >>> -static int __init efi_check_dt_boot(EFI_FILE_HANDLE dir_handle)
> >>> +static int __init efi_check_dt_boot(EFI_LOADED_IMAGE *loaded_image)
> >>> {
> >>> int chosen, node, addr_len, size_len;
> >>> unsigned int i = 0, modules_found = 0;
> >>> + EFI_FILE_HANDLE dir_handle;
> >>> + CHAR16 *file_name;
> >>> +
> >>> + dir_handle = get_parent_handle(loaded_image, &file_name);
> >>
> >> We can’t use get_parent_handle here because we will end up with the same
> >> problem,
> >> we would need to use the filesystem if and only if we need to use it,
> >
> > Understood, but it would work the same way as this version of the patch:
> > if we end up calling read_file with dir_handle == NULL, then read_file
> > would do:
> >
> > blexit(L"Error: No access to the filesystem");
> >
> > If we don't end up calling read_file, then everything works even if
> > dir_handle == NULL. Right?
>
> Oh yes sorry my bad Stefano! Having this version of the patch, it will work.
>
> My understanding was instead that the Jan suggestion is to revert the place
> of call of get_parent_handle (like in your code diff), but also to remove the
> changes to get_parent_handle and read_file.
> I guess Jan will specify his preference, but if he meant the last one, then
> the only way I see...
I think we should keep the changes to get_parent_handle and read_file,
otherwise it will make it awkward, and those changes are good in their
own right anyway.
> >> so the way I see
> >> is to pass loaded_image down to the stack until allocate_module_file(…),
> >> in this
> >> function we can use get_parent_handle(…) because the user wants us to do
> >> that.
> >> The downside is that we must close the handle there, so for each loaded
> >> file we will
> >> request and close the handle. Is this something we don’t bother too much?
> >
> > Yeah, that doesn't seem ideal.
>
> … is this one.
>
> >
> >
> >>>
> >>> /* Check for the chosen node in the current DTB */
> >>> chosen = setup_chosen_node(fdt, &addr_len, &size_len);
> >>> @@ -895,6 +901,8 @@ static int __init efi_check_dt_boot(EFI_FILE_HANDLE
> >>> dir_handle)
> >>> efi_bs->FreePool(modules[i].name);
> >>> }
> >>>
> >>> + dir_handle->Close(dir_handle);
> >>> +
> >>> return modules_found;
> >>> }
> >>>
> >>> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> >>> index 112b7e7571..2407671a7d 100644
> >>> --- a/xen/common/efi/boot.c
> >>> +++ b/xen/common/efi/boot.c
> >>> @@ -167,7 +167,7 @@ static void __init PrintErr(const CHAR16 *s)
> >>> }
> >>>
> >>> #ifndef CONFIG_HAS_DEVICE_TREE
> >>> -static int __init efi_check_dt_boot(EFI_FILE_HANDLE dir_handle)
> >>> +static int __init efi_check_dt_boot(EFI_LOADED_IMAGE *loaded_image)
> >>> {
> >>> return 0;
> >>> }
> >>> @@ -439,8 +439,8 @@ static unsigned int __init get_argv(unsigned int
> >>> argc, CHAR16 **argv,
> >>> return argc;
> >>> }
> >>>
> >>> -static EFI_FILE_HANDLE __init get_parent_handle(EFI_LOADED_IMAGE
> >>> *loaded_image,
> >>> - CHAR16 **leaf)
> >>> +EFI_FILE_HANDLE __init get_parent_handle(EFI_LOADED_IMAGE *loaded_image,
> >>> + CHAR16 **leaf)
> >>> {
> >>> static EFI_GUID __initdata fs_protocol = SIMPLE_FILE_SYSTEM_PROTOCOL;
> >>> static CHAR16 __initdata buffer[512];
> >>> @@ -1236,9 +1236,6 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE
> >>> *SystemTable)
> >>>
> >>> efi_arch_relocate_image(0);
> >>>
> >>> - /* Get the file system interface. */
> >>> - dir_handle = get_parent_handle(loaded_image, &file_name);
> >>> -
> >>> if ( use_cfg_file )
> >>> {
> >>> UINTN depth, cols, rows, size;
> >>> @@ -1251,6 +1248,9 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE
> >>> *SystemTable)
> >>>
> >>> gop = efi_get_gop();
> >>>
> >>> + /* Get the file system interface. */
> >>> + dir_handle = get_parent_handle(loaded_image, &file_name);
> >>> +
> >>> /* Read and parse the config file. */
> >>> if ( read_section(loaded_image, L"config", &cfg, NULL) )
> >>> PrintStr(L"Using builtin config file\r\n");
> >>> @@ -1344,18 +1344,8 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE
> >>> *SystemTable)
> >>> EFI_FILE_HANDLE handle = get_parent_handle(loaded_image,
> >>> &file_name);
> >>>
> >>> - if ( !handle )
> >>> - {
> >>> - PrintErr(L"Error retrieving image name: no filesystem
> >>> access."
> >>> - L" Setting default to xen.efi");
> >>> - PrintErr(newline);
> >>> - *argv = L"xen.efi";
> >>> - }
> >>> - else
> >>> - {
> >>> - handle->Close(handle);
> >>> - *argv = file_name;
> >>> - }
> >>> + handle->Close(handle);
> >>> + *argv = file_name;
> >>> }
> >>>
> >>> name.s = get_value(&cfg, section.s, "options");
> >>> @@ -1383,15 +1373,14 @@ efi_start(EFI_HANDLE ImageHandle,
> >>> EFI_SYSTEM_TABLE *SystemTable)
> >>> efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
> >>> cfg.addr = 0;
> >>>
> >>> + dir_handle->Close(dir_handle);
> >>> +
> >>> if ( gop && !base_video )
> >>> gop_mode = efi_find_gop_mode(gop, cols, rows, depth);
> >>> }
> >>>
> >>> /* Get the number of boot modules specified on the DT or an error (<0)
> >>> */
> >>> - dt_modules_found = efi_check_dt_boot(dir_handle);
> >>> -
> >>> - if ( dir_handle )
> >>> - dir_handle->Close(dir_handle);
> >>> + dt_modules_found = efi_check_dt_boot(loaded_image);
> >>>
> >>> if ( dt_modules_found < 0 )
> >>> /* efi_check_dt_boot throws some error */
>
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