The number of slots can be 'unsigned int', since on 64-bit, the maximum
amount of memory is 2^52, the minimum alignment is 2^21, so the slot
number cannot be greater than 2^31. But in case future processors have
more than 52 physical address bits, make it 'unsigned long'.
The slot areas are limited by MAX_SLOT_AREA, currently 100. It is
indexed by an int, but the number of areas is stored as 'unsigned long'.
Change both to 'unsigned int' for consistency.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200728225722.67457-15-nivedita@alum.mit.edu
This check doesn't save anything. In the case when none of the
parameters are present, each strstr will scan args twice (once to find
the length and then for searching), six scans in total. Just going ahead
and parsing the arguments only requires three scans: strlen, memcpy, and
parsing. This will be the first malloc, so free will actually free up
the memory, so the check doesn't save heap space either.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200728225722.67457-14-nivedita@alum.mit.edu
Clip the start and end of the region to minimum and mem_limit prior to
the loop. region.start can only increase during the loop, so raising it
to minimum before the loop is enough.
A region that becomes empty due to this will get checked in
the first iteration of the loop.
Drop the check for overlap extending beyond the end of the region. This
will get checked in the next loop iteration anyway.
Rename end to region_end for symmetry with region.start.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200728225722.67457-10-nivedita@alum.mit.edu
On 64-bit, the kernel must be placed below MAXMEM (64TiB with 4-level
paging or 4PiB with 5-level paging). This is currently not enforced by
KASLR, which thus implicitly relies on physical memory being limited to
less than 64TiB.
On 32-bit, the limit is KERNEL_IMAGE_SIZE (512MiB). This is enforced by
special checks in __process_mem_region().
Initialize mem_limit to the maximum (depending on architecture), instead
of ULLONG_MAX, and make sure the command-line arguments can only
decrease it. This makes the enforcement explicit on 64-bit, and
eliminates the 32-bit specific checks to keep the kernel below 512M.
Check upfront to make sure the minimum address is below the limit before
doing any work.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200727230801.3468620-5-nivedita@alum.mit.edu
Pull x86 fixes from Thomas Gleixner:
"A pile of fixes for x86:
- Fix the I/O bitmap invalidation on XEN PV, which was overlooked in
the recent ioperm/iopl rework. This caused the TSS and XEN's I/O
bitmap to get out of sync.
- Use the proper vectors for HYPERV.
- Make disabling of stack protector for the entry code work with GCC
builds which enable stack protector by default. Removing the option
is not sufficient, it needs an explicit -fno-stack-protector to
shut it off.
- Mark check_user_regs() noinstr as it is called from noinstr code.
The missing annotation causes it to be placed in the text section
which makes it instrumentable.
- Add the missing interrupt disable in exc_alignment_check()
- Fixup a XEN_PV build dependency in the 32bit entry code
- A few fixes to make the Clang integrated assembler happy
- Move EFI stub build to the right place for out of tree builds
- Make prepare_exit_to_usermode() static. It's not longer called from
ASM code"
* tag 'x86-urgent-2020-07-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot: Don't add the EFI stub to targets
x86/entry: Actually disable stack protector
x86/ioperm: Fix io bitmap invalidation on Xen PV
x86: math-emu: Fix up 'cmp' insn for clang ias
x86/entry: Fix vectors to IDTENTRY_SYSVEC for CONFIG_HYPERV
x86/entry: Add compatibility with IAS
x86/entry/common: Make prepare_exit_to_usermode() static
x86/entry: Mark check_user_regs() noinstr
x86/traps: Disable interrupts in exc_aligment_check()
x86/entry/32: Fix XEN_PV build dependency
vmlinux-objs-y is added to targets, which currently means that the EFI
stub gets added to the targets as well. It shouldn't be added since it
is built elsewhere.
This confuses Makefile.build which interprets the EFI stub as a target
$(obj)/$(objtree)/drivers/firmware/efi/libstub/lib.a
and will create drivers/firmware/efi/libstub/ underneath
arch/x86/boot/compressed, to hold this supposed target, if building
out-of-tree. [0]
Fix this by pulling the stub out of vmlinux-objs-y into efi-obj-y.
[0] See scripts/Makefile.build near the end:
# Create directories for object files if they do not exist
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lkml.kernel.org/r/20200715032631.1562882-1-nivedita@alum.mit.edu
Some Makefiles already pass -ffreestanding unconditionally.
For example, arch/arm64/lib/Makefile, arch/x86/purgatory/Makefile.
No problem report so far about hard-coding this option. So, we can
assume all supported compilers know -ffreestanding.
I confirmed GCC 4.8 and Clang manuals document this option.
Get rid of cc-option from -ffreestanding.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Some Makefiles already pass -fno-stack-protector unconditionally.
For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile.
No problem report so far about hard-coding this option. So, we can
assume all supported compilers know -fno-stack-protector.
GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN)
Get rid of cc-option from -fno-stack-protector.
Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which is always 'y'.
Note:
arch/mips/vdso/Makefile adds -fno-stack-protector twice, first
unconditionally, and second conditionally. I removed the second one.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Commit
17054f492d ("efi/x86: Implement mixed mode boot without the handover protocol")
introduced a new entry point for the EFI stub to be booted in mixed mode
on 32-bit firmware.
When entered via efi32_pe_entry, control is first transferred to
startup_32 to setup for the switch to long mode, and then the EFI stub
proper is entered via efi_pe_entry. efi_pe_entry is an MS ABI function,
and the ABI requires 32 bytes of shadow stack space to be allocated by
the caller, as well as the stack being aligned to 8 mod 16 on entry.
Allocate 40 bytes on the stack before switching to 64-bit mode when
calling efi_pe_entry to account for this.
For robustness, explicitly align boot_stack_end to 16 bytes. It is
currently implicitly aligned since .bss is cacheline-size aligned,
head_64.o is the first object file with a .bss section, and the heap and
boot sizes are aligned.
Fixes: 17054f492d ("efi/x86: Implement mixed mode boot without the handover protocol")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200617131957.2507632-1-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Merge the state of the locking kcsan branch before the read/write_once()
and the atomics modifications got merged.
Squash the fallout of the rebase on top of the read/write once and atomic
fallback work into the merge. The history of the original branch is
preserved in tag locking-kcsan-2020-06-02.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Pull x86 build updates from Ingo Molnar:
"Misc dependency fixes, plus a documentation update about memory
protection keys support"
* tag 'x86-build-2020-06-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/Kconfig: Update config and kernel doc for MPK feature on AMD
x86/boot: Discard .discard.unreachable for arch/x86/boot/compressed/vmlinux
x86/boot/build: Add phony targets in arch/x86/boot/Makefile to PHONY
x86/boot/build: Make 'make bzlilo' not depend on vmlinux or $(obj)/bzImage
x86/boot/build: Add cpustr.h to targets and remove clean-files
Pull x86 boot updates from Ingo Molnar:
"Misc updates:
- Add the initrdmem= boot option to specify an initrd embedded in RAM
(flash most likely)
- Sanitize the CS value earlier during boot, which also fixes SEV-ES
- Various fixes and smaller cleanups"
* tag 'x86-boot-2020-06-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot: Correct relocation destination on old linkers
x86/boot/compressed/64: Switch to __KERNEL_CS after GDT is loaded
x86/boot: Fix -Wint-to-pointer-cast build warning
x86/boot: Add kstrtoul() from lib/
x86/tboot: Mark tboot static
x86/setup: Add an initrdmem= option to specify initrd physical address
With commit
ce5e3f909f ("efi/printf: Add 64-bit and 8-bit integer support")
arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable
section coming from drivers/firmware/efi/libstub/vsprintf.stub.o. That section
gets generated from unreachable() annotations when CONFIG_STACK_VALIDATION is
enabled.
.discard.unreachable contains an R_X86_64_PC32 relocation which will be
warned about by LLD: a non-SHF_ALLOC section (.discard.unreachable) is
not part of the memory image, thus conceptually the distance between a
non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at
link time:
% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux
ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''
Reuse the DISCARDS macro which includes .discard.* to drop
.discard.unreachable.
[ bp: Massage and complete the commit message. ]
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Fangrui Song <maskray@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Arvind Sankar <nivedita@alum.mit.edu>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Link: https://lkml.kernel.org/r/20200520182010.242489-1-maskray@google.com
For the 32-bit kernel, as described in
6d92bc9d48 ("x86/build: Build compressed x86 kernels as PIE"),
pre-2.26 binutils generates R_386_32 relocations in PIE mode. Since the
startup code does not perform relocation, any reloc entry with R_386_32
will remain as 0 in the executing code.
Commit
974f221c84 ("x86/boot: Move compressed kernel to the end of the
decompression buffer")
added a new symbol _end but did not mark it hidden, which doesn't give
the correct offset on older linkers. This causes the compressed kernel
to be copied beyond the end of the decompression buffer, rather than
flush against it. This region of memory may be reserved or already
allocated for other purposes by the bootloader.
Mark _end as hidden to fix. This changes the relocation from R_386_32 to
R_386_RELATIVE even on the pre-2.26 binutils.
For 64-bit, this is not strictly necessary, as the 64-bit kernel is only
built as PIE if the linker supports -z noreloc-overflow, which implies
binutils-2.27+, but for consistency, mark _end as hidden here too.
The below illustrates the before/after impact of the patch using
binutils-2.25 and gcc-4.6.4 (locally compiled from source) and QEMU.
Disassembly before patch:
48: 8b 86 60 02 00 00 mov 0x260(%esi),%eax
4e: 2d 00 00 00 00 sub $0x0,%eax
4f: R_386_32 _end
Disassembly after patch:
48: 8b 86 60 02 00 00 mov 0x260(%esi),%eax
4e: 2d 00 f0 76 00 sub $0x76f000,%eax
4f: R_386_RELATIVE *ABS*
Dump from extract_kernel before patch:
early console in extract_kernel
input_data: 0x0207c098 <--- this is at output + init_size
input_len: 0x0074fef1
output: 0x01000000
output_len: 0x00fa63d0
kernel_total_size: 0x0107c000
needed_size: 0x0107c000
Dump from extract_kernel after patch:
early console in extract_kernel
input_data: 0x0190d098 <--- this is at output + init_size - _end
input_len: 0x0074fef1
output: 0x01000000
output_len: 0x00fa63d0
kernel_total_size: 0x0107c000
needed_size: 0x0107c000
Fixes: 974f221c84 ("x86/boot: Move compressed kernel to the end of the decompression buffer")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200207214926.3564079-1-nivedita@alum.mit.edu
When the pre-decompression code loads its first GDT in startup_64(), it
is still running on the CS value of the previous GDT. In the case of
SEV-ES, this is the EFI GDT but it can be anything depending on what has
loaded the kernel (boot loader, container runtime, etc.)
To make exception handling work (especially IRET) the CPU needs to
switch to a CS value in the current GDT, so jump to __KERNEL_CS after
the first GDT is loaded. This is prudent also as a general sanitization
of CS to a known good value.
[ bp: Massage commit message. ]
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200428151725.31091-13-joro@8bytes.org
Fix this warning when building 32-bit with
CONFIG_RANDOMIZE_BASE=y
CONFIG_MEMORY_HOTREMOVE=y
arch/x86/boot/compressed/acpi.c:316:9: warning: \
cast to pointer from integer of different size [-Wint-to-pointer-cast]
Have get_cmdline_acpi_rsdp() return unsigned long which is the proper
type to convert to a pointer of the respective width.
[ bp: Rewrite commit message, touch ups. ]
Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1587645588-7130-3-git-send-email-vamshi.k.sthambamkadi@gmail.com
Instead of using __efistub_global to force variables into the .data
section, leave them in the .bss but pull the EFI stub's .bss section
into .data in the linker script for the compressed kernel.
Add relocation checking for x86 as well to catch non-PC-relative
relocations that require runtime processing, since the EFI stub does not
do any runtime relocation processing.
This will catch, for example, data relocations created by static
initializers of pointers.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200416151227.3360778-3-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Resolve these conflicts:
arch/x86/Kconfig
arch/x86/kernel/Makefile
Do a minor "evil merge" to move the KCSAN entry up a bit by a few lines
in the Kconfig to reduce the probability of future conflicts.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull SPDX updates from Greg KH:
"Here are three SPDX patches for 5.7-rc1.
One fixes up the SPDX tag for a single driver, while the other two go
through the tree and add SPDX tags for all of the .gitignore files as
needed.
Nothing too complex, but you will get a merge conflict with your
current tree, that should be trivial to handle (one file modified by
two things, one file deleted.)
All three of these have been in linux-next for a while, with no
reported issues other than the merge conflict"
* tag 'spdx-5.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx:
ASoC: MT6660: make spdxcheck.py happy
.gitignore: add SPDX License Identifier
.gitignore: remove too obvious comments
Pull x86 boot updates from Ingo Molnar:
"Misc cleanups and small enhancements all around the map"
* 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot/compressed: Fix debug_puthex() parameter type
x86/setup: Fix static memory detection
x86/vmlinux: Drop unneeded linker script discard of .eh_frame
x86/*/Makefile: Use -fno-asynchronous-unwind-tables to suppress .eh_frame sections
x86/boot/compressed: Remove .eh_frame section from bzImage
x86/boot/compressed/64: Remove .bss/.pgtable from bzImage
x86/boot/compressed/64: Use 32-bit (zero-extended) MOV for z_output_len
x86/boot/compressed/64: Use LEA to initialize boot stack pointer
In the CONFIG_X86_VERBOSE_BOOTUP=Y case, the debug_puthex() macro just
turns into __puthex(), which takes 'unsigned long' as parameter.
But in the CONFIG_X86_VERBOSE_BOOTUP=N case, it is a function which
takes 'unsigned char *', causing compile warnings when the function is
used. Fix the parameter type to get rid of the warnings.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200319091407.1481-11-joro@8bytes.org
code32_start is meant for 16-bit real-mode bootloaders to inform the
kernel where the 32-bit protected mode code starts. Nothing in the
protected mode kernel except the EFI stub uses it.
efi_main() currently returns boot_params, with code32_start set inside it
to tell efi_stub_entry() where startup_32 is located. Since it was invoked
by efi_stub_entry() in the first place, boot_params is already known.
Return the address of startup_32 instead.
This will allow a 64-bit kernel to live above 4Gb, for example, and it's
cleaner as well.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200301230436.2246909-5-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-13-ardb@kernel.org
The following commit:
ef5a7b5eb1 ("efi/x86: Remove GDT setup from efi_main")
introduced GDT setup into the 32-bit kernel's startup_32, and reloads
the GDTR after relocating the kernel for paranoia's sake.
A followup commit:
32d009137a ("x86/boot: Reload GDTR after copying to the end of the buffer")
introduced a similar GDTR reload in the 64-bit kernel as well.
The GDTR is adjusted by (init_size-_end), however this may not be the
correct offset to apply if the kernel was loaded at a misaligned address
or below LOAD_PHYSICAL_ADDR, as in that case the decompression buffer
has an additional offset from the original load address.
This should never happen for a conformant bootloader, but we're being
paranoid anyway, so just store the new GDT address in there instead of
adding any offsets, which is simpler as well.
Fixes: ef5a7b5eb1 ("efi/x86: Remove GDT setup from efi_main")
Fixes: 32d009137a ("x86/boot: Reload GDTR after copying to the end of the buffer")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Link: https://lore.kernel.org/r/20200226230031.3011645-2-nivedita@alum.mit.edu
Pull EFI updates for v5.7 from Ard Biesheuvel:
This time, the set of changes for the EFI subsystem is much larger than
usual. The main reasons are:
- Get things cleaned up before EFI support for RISC-V arrives, which will
increase the size of the validation matrix, and therefore the threshold to
making drastic changes,
- After years of defunct maintainership, the GRUB project has finally started
to consider changes from the distros regarding UEFI boot, some of which are
highly specific to the way x86 does UEFI secure boot and measured boot,
based on knowledge of both shim internals and the layout of bootparams and
the x86 setup header. Having this maintenance burden on other architectures
(which don't need shim in the first place) is hard to justify, so instead,
we are introducing a generic Linux/UEFI boot protocol.
Summary of changes:
- Boot time GDT handling changes (Arvind)
- Simplify handling of EFI properties table on arm64
- Generic EFI stub cleanups, to improve command line handling, file I/O,
memory allocation, etc.
- Introduce a generic initrd loading method based on calling back into
the firmware, instead of relying on the x86 EFI handover protocol or
device tree.
- Introduce a mixed mode boot method that does not rely on the x86 EFI
handover protocol either, and could potentially be adopted by other
architectures (if another one ever surfaces where one execution mode
is a superset of another)
- Clean up the contents of struct efi, and move out everything that
doesn't need to be stored there.
- Incorporate support for UEFI spec v2.8A changes that permit firmware
implementations to return EFI_UNSUPPORTED from UEFI runtime services at
OS runtime, and expose a mask of which ones are supported or unsupported
via a configuration table.
- Various documentation updates and minor code cleanups (Heinrich)
- Partial fix for the lack of by-VA cache maintenance in the decompressor
on 32-bit ARM. Note that these patches were deliberately put at the
beginning so they can be used as a stable branch that will be shared with
a PR containing the complete fix, which I will send to the ARM tree.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Now that .eh_frame sections for the files in setup.elf and realmode.elf
are not generated anymore, the linker scripts don't need the special
output section name /DISCARD/ any more.
Remove the one in the main kernel linker script as well, since there are
no .eh_frame sections already, and fix up a comment referencing .eh_frame.
Update the comment in asm/dwarf2.h referring to .eh_frame so it continues
to make sense, as well as being more specific.
[ bp: Touch up commit message. ]
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://lkml.kernel.org/r/20200224232129.597160-3-nivedita@alum.mit.edu
While discussing a patch to discard .eh_frame from the compressed
vmlinux using the linker script, Fangrui Song pointed out [1] that these
sections shouldn't exist in the first place because arch/x86/Makefile
uses -fno-asynchronous-unwind-tables.
It turns out this is because the Makefiles used to build the compressed
kernel redefine KBUILD_CFLAGS, dropping this flag.
Add the flag to the Makefile for the compressed kernel, as well as the
EFI stub Makefile to fix this.
Also add the flag to boot/Makefile and realmode/rm/Makefile so that the
kernel's boot code (boot/setup.elf) and realmode trampoline
(realmode/rm/realmode.elf) won't be compiled with .eh_frame sections,
since their linker scripts also just discard them.
[1] https://lore.kernel.org/lkml/20200222185806.ywnqhfqmy67akfsa@google.com/
Suggested-by: Fangrui Song <maskray@google.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://lkml.kernel.org/r/20200224232129.597160-2-nivedita@alum.mit.edu
Discarding unnecessary sections with "*(*)" (see thread at Link: below)
works fine with the bfd linker but fails with lld:
$ make -j$(nproc) -s CC=clang LD=ld.lld O=out.x86_64 distclean defconfig bzImage
ld.lld: error: discarding .shstrtab section is not allowed
lld tries to also discard essential sections like .shstrtab, .symtab and
.strtab, which results in the link failing since .shstrtab is required
by the ELF specification: the e_shstrndx field in the ELF header is the
index of .shstrtab, and each section in the section table is required to
have an sh_name that points into the .shstrtab.
.symtab and .strtab are also necessary to generate the zoffset.h file
for the bzImage header.
Since the only sizeable section that can be discarded is .eh_frame,
restrict the discard to only .eh_frame to be safe.
[ bp: Flesh out commit message and replace offending commit with this one. ]
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://lkml.kernel.org/r/20200109150218.16544-2-nivedita@alum.mit.edu
Add support for booting 64-bit x86 kernels from 32-bit firmware running
on 64-bit capable CPUs without requiring the bootloader to implement
the EFI handover protocol or allocate the setup block, etc etc, all of
which can be done by the stub itself, using code that already exists.
Instead, create an ordinary EFI application entrypoint but implemented
in 32-bit code [so that it can be invoked by 32-bit firmware], and stash
the address of this 32-bit entrypoint in the .compat section where the
bootloader can find it.
Note that we use the setup block embedded in the binary to go through
startup_32(), but it gets reallocated and copied in efi_pe_entry(),
using the same code that runs when the x86 kernel is booted in EFI
mode from native firmware. This requires the loaded image protocol to
be installed on the kernel image's EFI handle, and point to the kernel
image itself and not to its loader. This, in turn, requires the
bootloader to use the LoadImage() boot service to load the 64-bit
image from 32-bit firmware, which is in fact supported by firmware
based on EDK2. (Only StartImage() will fail, and instead, the newly
added entrypoint needs to be invoked)
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
