There are currently two ways to specify the initrd to be passed to the
Linux kernel when booting via the EFI stub:
- it can be passed as a initrd= command line option when doing a pure PE
  boot (as opposed to the EFI handover protocol that exists for x86)
- otherwise, the bootloader or firmware can load the initrd into memory,
  and pass the address and size via the bootparams struct (x86) or
  device tree (ARM)

In the first case, we are limited to loading from the same file system
that the kernel was loaded from, and it is also problematic in a trusted
boot context, given that we cannot easily protect the command line from
tampering without either adding complicated white/blacklisting of boot
arguments or locking down the command line altogether.

In the second case, we force the bootloader to duplicate knowledge about
the boot protocol which is already encoded in the stub, and which may be
subject to change over time, e.g., bootparams struct definitions, memory
allocation/alignment requirements for the placement of the initrd etc etc.
In the ARM case, it also requires the bootloader to modify the hardware
description provided by the firmware, as it is passed in the same file.
On systems where the initrd is measured after loading, it creates a time
window where the initrd contents might be manipulated in memory before
handing over to the kernel.

Address these concerns by adding support for loading the initrd into
memory by invoking the EFI LoadFile2 protocol installed on a vendor
GUIDed device path that specifically designates a Linux initrd.
This addresses the above concerns, by putting the EFI stub in charge of
placement in memory and of passing the base and size to the kernel proper
(via whatever means it desires) while still leaving it up to the firmware
or bootloader to obtain the file contents, potentially from other file
systems than the one the kernel itself was loaded from. On platforms that
implement measured boot, it permits the firmware to take the measurement
right before the kernel actually consumes the contents.
Acked-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

In preparation of adding support for loading the initrd via a special
device path, add the struct definition of a vendor GUIDed device path
node to efi.h.

Since we will be producing these data structures rather than just
consumsing the ones instantiated by the firmware, refactor the various
device path node definitions so we can take the size of each node using
sizeof() rather than having to resort to opaque arithmetic in the static
initializers.

While at it, drop the #if IS_ENABLED() check for the declaration of
efi_get_device_by_path(), which is unnecessary, and constify its first
argument as well.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

When possible, IS_ENABLED() conditionals are preferred over #ifdefs,
given that the latter hide the code from the compiler entirely, which
reduces build test coverage when the option is not enabled.

So replace an instance in the x86 efi startup code.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Reindent the efi_memory_map_data initializer so that all the = signs
are aligned vertically, making the resulting code much easier to read.
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

In efi_capsule_write() the value 0 assigned to ret is never used.

Identified with cppcheck.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/20200223205435.114915-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Remove an unused variable in __init efi_esrt_init().
Simplify a logical constraint.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/20200223204557.114634-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

The memory for files is allocated not reallocated.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/20200221191829.18149-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Provide descriptions for the functions invoking the EFI_RNG_PROTOCOL.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://lore.kernel.org/r/20200221114716.4372-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Update the description of of efi_relocate_kernel() to match Sphinx style.

Update parameter references in the description of other memory functions
to use @param style.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20200220065317.9096-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Provide descriptions of:

* efi_get_memory_map()
* efi_low_alloc_above()
* efi_free()
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20200218063038.3436-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Do not check the value of status twice.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/20200216184050.3100-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Provide a Sphinx style function description for efi_allocate_pages().
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/20200216171340.6070-1-xypron.glpk@gmx.deSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Add the protocol definitions, GUIDs and mixed mode glue so that
the EFI loadfile protocol can be used from the stub. This will
be used in a future patch to load the initrd.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

We will be adding support for loading the initrd from a GUIDed
device path in a subsequent patch, so update the prototype of
the LocateDevicePath() boot service to make it callable from
our code.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

We currently parse the command non-destructively, to avoid having to
allocate memory for a copy before passing it to the standard parsing
routines that are used by the core kernel, and which modify the input
to delineate the parsed tokens with NUL characters.

Instead, we call strstr() and strncmp() to go over the input multiple
times, and match prefixes rather than tokens, which implies that we
would match, e.g., 'nokaslrfoo' in the stub and disable KASLR, while
the kernel would disregard the option and run with KASLR enabled.

In order to avoid having to reason about whether and how this behavior
may be abused, let's clean up the parsing routines, and rebuild them
on top of the existing helpers.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

On x86, the preferred load address of the initrd is still below 4 GB,
even though in some cases, we can cope with an initrd that is loaded
above that.

To simplify the code, and to make it more straightforward to introduce
other ways to load the initrd, pass the soft and hard memory limits at
the same time, and let the code handling the initrd= command line option
deal with this.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

The file I/O routine that is used to load initrd or dtb files from
the EFI system partition suffers from a few issues:
- it converts the u8[] command line back to a UTF-16 string, which is
  pointless since we only handle initrd or dtb arguments provided via
  the loaded image protocol anyway, which is where we got the UTF-16[]
  command line from in the first place when booting via the PE entry
  point,
- in the far majority of cases, only a single initrd= option is present,
  but it optimizes for multiple options, by going over the command line
  twice, allocating heap buffers for dynamically sized arrays, etc.
- the coding style is hard to follow, with few comments, and all logic
  including string parsing etc all combined in a single routine.

Let's fix this by rewriting most of it, based on the idea that in the
case of multiple initrds, we can just allocate a new, bigger buffer
and copy over the data before freeing the old one.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Split off the file I/O support code into a separate source file so
it ends up in a separate object file in the static library, allowing
the linker to omit it if the routines are not used.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

get_dram_base() is only called from arm-stub.c so move it into
the same source file as its caller.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

efi_random_alloc() is only used on arm64, but as it shares a source
file with efi_random_get_seed(), the latter will pull in the former
on other architectures as well.

Let's take advantage of the fact that libstub is a static library,
and so the linker will only incorporate objects that are needed to
satisfy dependencies in other objects. This means we can move the
random alloc code to a separate source file that gets built
unconditionally, but only used when needed.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

We now support cmdline data that is located in memory that is not
32-bit addressable, so relax the allocation limit on systems where
this feature is enabled.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Move all the declarations that are only used in stub code from
linux/efi.h to efistub.h which is only included locally.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

We now support bootparams structures that are located in memory that
is not 32-bit addressable, so relax the allocation limit on systems
where this feature is enabled.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Align the naming of efi_file_io_interface_t and efi_file_handle_t with
the UEFI spec, and call them efi_simple_file_system_protocol_t and
efi_file_protocol_t, respectively, using the same convention we use
for all other type definitions that originate in the UEFI spec.

While at it, move the definitions to efistub.h, so they are only seen
by code that needs them.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Most of the EFI stub source files of all architectures reside under
drivers/firmware/efi/libstub, where they share a Makefile with special
CFLAGS and an include file with declarations that are only relevant
for stub code.

Currently, we carry a lot of stub specific stuff in linux/efi.h only
because eboot.c in arch/x86 needs them as well. So let's move eboot.c
into libstub/, and move the contents of eboot.h that we still care
about into efistub.h
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

The implementation of efi_high_alloc() uses a complicated way of
traversing the memory map to find an available region that is located
as close as possible to the provided upper limit, and calls AllocatePages
subsequently to create the allocation at that exact address.

This is precisely what the EFI_ALLOCATE_MAX_ADDRESS allocation type
argument to AllocatePages() does, and considering that EFI_ALLOC_ALIGN
only exceeds EFI_PAGE_SIZE on arm64, let's use AllocatePages() directly
and implement the alignment using code that the compiler can remove if
it does not exceed EFI_PAGE_SIZE.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Create a new source file mem.c to keep the routines involved in memory
allocation and deallocation and manipulation of the EFI memory map.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

The arm64 kernel no longer requires the FDT blob to fit inside a
naturally aligned 2 MB memory block, so remove the code that aligns
the allocation to 2 MB.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Instead of setting the visibility pragma for a small set of symbol
declarations that could result in absolute references that we cannot
support in the stub, declare hidden visibility for all code in the
EFI stub, which is more robust and future proof.

To ensure that the #pragma is taken into account before any other
includes are processed, put it in a header file of its own and
include it via the compiler command line using the -include option.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

When using the native PE entry point (as opposed to the EFI handover
protocol entry point that is used more widely), we set code32_start,
which is a 32-bit wide field, to the effective symbol address of
startup_32, which could overflow given that the EFI loader may have
located the running image anywhere in memory, and we haven't reached
the point yet where we relocate ourselves.

Since we relocate ourselves if code32_start != pref_address, this
isn't likely to lead to problems in practice, given how unlikely
it is that the truncated effective address of startup_32 happens
to equal pref_address. But it is better to defer the assignment
of code32_start to after the relocation, when it is guaranteed to
fit.

While at it, move the call to efi_relocate_kernel() to an earlier
stage so it is more likely that our preferred offset in memory has
not been occupied by other memory allocations done in the mean time.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

We have some code in the EFI stub entry point that takes the address
of the apm_bios_info struct in the newly allocated and zeroed out
boot_params structure, only to zero it out again. This is pointless
so remove it.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertenly introduced[3] to the codebase from now on.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20200211231421.GA15697@embeddedorSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

The UEFI spec defines (and deprecates) a misguided and shortlived
memory protection feature that is based on splitting memory regions
covering PE/COFF executables into separate code and data regions,
without annotating them as belonging to the same executable image.
When the OS assigns the virtual addresses of these regions, it may
move them around arbitrarily, without taking into account that the
PE/COFF code sections may contain relative references into the data
sections, which means the relative placement of these segments has
to be preserved or the executable image will be corrupted.

The original workaround on arm64 was to ensure that adjacent regions
of the same type were mapped adjacently in the virtual mapping, but
this requires sorting of the memory map, which we would prefer to
avoid.

Considering that the native physical mapping of the PE/COFF images
does not suffer from this issue, let's preserve it at runtime, and
install it as the virtual mapping as well.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Some (somewhat older) laptops have a correct BGRT table, except that the
version field is 0 instead of 1.

This has been seen on several Ivy Bridge based Lenovo models.

For now the spec. only defines version 1, so it is reasonably safe to
assume that tables with a version of 0 really are version 1 too,
which is what this commit does so that the BGRT table will be accepted
by the kernel on laptop models with this issue.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20200131130623.33875-1-hdegoede@redhat.comSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

This function is only called from efi_main in the same source file.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200130222004.1932152-1-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Rearrange the instructions a bit to use a 32-bit displacement once
instead of 2/3 times. This saves 8 bytes of machine code.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-8-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

The limit value for the GDTR should be such that adding it to the base
address gives the address of the last byte of the GDT, i.e. it should be
one less than the size, not the size.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-7-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

The 64-bit kernel will already load a GDT in startup_64, which is the
next function to execute after return from efi_main.

Add GDT setup code to the 32-bit kernel's startup_32 as well. Doing it
in the head code has the advantage that we can avoid potentially
corrupting the GDT during copy/decompression. This also removes
dependence on having a specific GDT layout setup by the bootloader.

Both startup_32 and startup_64 now clear interrupts on entry, so we can
remove that from efi_main as well.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-6-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

startup_32 already clears these flags on entry, do it in startup_64 as
well for consistency.

The direction flag in particular is not specified to be cleared in the
boot protocol documentation, and we currently call into C code
(paging_prepare) without explicitly clearing it.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-5-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

The GDT may get overwritten during the copy or during extract_kernel,
which will cause problems if any segment register is touched before the
GDTR is reloaded by the decompressed kernel. For safety update the GDTR
to point to the GDT within the copied kernel.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-4-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>