linux-toradex.git/arch/arm64/kernel/efi-header.S, branch v6.7 Linux kernel for Apalis and Colibri modules arm64: efi: Enable BTI codegen and add PE/COFF annotation 2023-04-20T13:43:45+00:00 Ard Biesheuvel ardb@kernel.org 2023-04-18T13:49:48+00:00 8358098b9787caab8bbc93fd78d046afaed43c16 UEFI heavily relies on so-called protocols, which are essentially tables populated with pointers to executable code, and these are invoked indirectly using BR or BLR instructions. This makes the EFI execution context vulnerable to attacks on forward edge control flow, and so it would help if we could enable hardware enforcement (BTI) on CPUs that implement it. So let's no longer disable BTI codegen for the EFI stub, and set the newly introduced PE/COFF header flag when the kernel is built with BTI landing pads. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Mark Brown <broonie@kernel.org> 
UEFI heavily relies on so-called protocols, which are essentially
tables populated with pointers to executable code, and these are invoked
indirectly using BR or BLR instructions.

This makes the EFI execution context vulnerable to attacks on forward
edge control flow, and so it would help if we could enable hardware
enforcement (BTI) on CPUs that implement it.

So let's no longer disable BTI codegen for the EFI stub, and set the
newly introduced PE/COFF header flag when the kernel is built with BTI
landing pads.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
arm64: efi: Set NX compat flag in PE/COFF header 2023-03-10T13:11:40+00:00 Ard Biesheuvel ardb@kernel.org 2023-03-10T12:30:05+00:00 3c66bb1918c262dd52fb4221a8d372619c5da70a The PE/COFF header has a NX compat flag which informs the firmware that the application does not rely on memory regions being mapped with both executable and writable permissions at the same time. This is typically used by the firmware to decide whether it can set the NX attribute on all allocations it returns, but going forward, it may be used to enforce a policy that only permits applications with the NX flag set to be loaded to begin wiht in some configurations, e.g., when Secure Boot is in effect. Even though the arm64 version of the EFI stub may relocate the kernel before executing it, it always did so after disabling the MMU, and so we were always in line with what the NX compat flag conveys, we just never bothered to set it. So let's set the flag now. Cc: <stable@vger.kernel.org> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> 
The PE/COFF header has a NX compat flag which informs the firmware that
the application does not rely on memory regions being mapped with both
executable and writable permissions at the same time.

This is typically used by the firmware to decide whether it can set the
NX attribute on all allocations it returns, but going forward, it may be
used to enforce a policy that only permits applications with the NX flag
set to be loaded to begin wiht in some configurations, e.g., when Secure
Boot is in effect.

Even though the arm64 version of the EFI stub may relocate the kernel
before executing it, it always did so after disabling the MMU, and so we
were always in line with what the NX compat flag conveys, we just never
bothered to set it.

So let's set the flag now.

Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
arm64: head: tidy up the Image header definition 2020-11-17T16:14:20+00:00 Ard Biesheuvel ardb@kernel.org 2020-11-17T12:47:29+00:00 7919385b9fb3cefe495310e5c44ca8a6d9c446e8 Even though support for EFI boot remains entirely optional for arm64, it is unlikely that we will ever be able to repurpose the image header fields that the EFI loader relies on, i.e., the magic NOP at offset 0x0 and the PE header address at offset 0x3c. So let's factor out the differences into a 'efi_signature_nop' macro and a local symbol representing the PE header address, and move the conditional definitions into efi-header.S, taking into account whether CONFIG_EFI is enabled or not. While at it, switch to a signature NOP that behaves more like a NOP, i.e., one that only clobbers the flags. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20201117124729.12642-4-ardb@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> 
Even though support for EFI boot remains entirely optional for arm64,
it is unlikely that we will ever be able to repurpose the image header
fields that the EFI loader relies on, i.e., the magic NOP at offset
0x0 and the PE header address at offset 0x3c.

So let's factor out the differences into a 'efi_signature_nop' macro and
a local symbol representing the PE header address, and move the
conditional definitions into efi-header.S, taking into account whether
CONFIG_EFI is enabled or not. While at it, switch to a signature NOP
that behaves more like a NOP, i.e., one that only clobbers the
flags.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201117124729.12642-4-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arm64/head: avoid symbol names pointing into first 64 KB of kernel image 2020-11-17T16:14:20+00:00 Ard Biesheuvel ardb@kernel.org 2020-11-17T12:47:28+00:00 b50a3225cdffef43b76b294fa7fb3cd1f32f50d0 We no longer map the first 64 KB of the kernel image, as there is nothing there that we ever need to refer back to once the kernel has booted. Even though facilities like kallsyms are very careful to only refer to the region that starts at _stext when mapping virtual addresses to symbol names, let's avoid any confusion by switching to local .L prefixed symbol names for the EFI header, as none of them have any significance to the rest of the kernel. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20201117124729.12642-3-ardb@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> 
We no longer map the first 64 KB of the kernel image, as there is nothing
there that we ever need to refer back to once the kernel has booted. Even
though facilities like kallsyms are very careful to only refer to the
region that starts at _stext when mapping virtual addresses to symbol
names, let's avoid any confusion by switching to local .L prefixed symbol
names for the EFI header, as none of them have any significance to the
rest of the kernel.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201117124729.12642-3-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arm64: omit [_text, _stext) from permanent kernel mapping 2020-11-17T16:14:20+00:00 Ard Biesheuvel ardb@kernel.org 2020-11-17T12:47:27+00:00 e2a073dde9218cdef3c5431bddabf4549dd65fea In a previous patch, we increased the size of the EFI PE/COFF header to 64 KB, which resulted in the _stext symbol to appear at a fixed offset of 64 KB into the image. Since 64 KB is also the largest page size we support, this completely removes the need to map the first 64 KB of the kernel image, given that it only contains the arm64 Image header and the EFI header, neither of which we ever access again after booting the kernel. More importantly, we should avoid an executable mapping of non-executable and not entirely predictable data, to deal with the unlikely event that we inadvertently emitted something that looks like an opcode that could be used as a gadget for speculative execution. So let's limit the kernel mapping of .text to the [_stext, _etext) region, which matches the view of generic code (such as kallsyms) when it reasons about the boundaries of the kernel's .text section. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20201117124729.12642-2-ardb@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> 
In a previous patch, we increased the size of the EFI PE/COFF header
to 64 KB, which resulted in the _stext symbol to appear at a fixed
offset of 64 KB into the image.

Since 64 KB is also the largest page size we support, this completely
removes the need to map the first 64 KB of the kernel image, given that
it only contains the arm64 Image header and the EFI header, neither of
which we ever access again after booting the kernel. More importantly,
we should avoid an executable mapping of non-executable and not entirely
predictable data, to deal with the unlikely event that we inadvertently
emitted something that looks like an opcode that could be used as a
gadget for speculative execution.

So let's limit the kernel mapping of .text to the [_stext, _etext)
region, which matches the view of generic code (such as kallsyms) when
it reasons about the boundaries of the kernel's .text section.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201117124729.12642-2-ardb@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arm64: efi: increase EFI PE/COFF header padding to 64 KB 2020-10-28T14:02:03+00:00 Ard Biesheuvel ardb@kernel.org 2020-10-27T07:32:06+00:00 a2d50c1c77aa879af24f9f67b33186737b3d4885 Commit 76085aff29f5 ("efi/libstub/arm64: align PE/COFF sections to segment alignment") increased the PE/COFF section alignment to match the minimum segment alignment of the kernel image, which ensures that the kernel does not need to be moved around in memory by the EFI stub if it was built as relocatable. However, the first PE/COFF section starts at _stext, which is only 4 KB aligned, and so the section layout is inconsistent. Existing EFI loaders seem to care little about this, but it is better to clean this up. So let's pad the header to 64 KB to match the PE/COFF section alignment. Fixes: 76085aff29f5 ("efi/libstub/arm64: align PE/COFF sections to segment alignment") Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20201027073209.2897-2-ardb@kernel.org Signed-off-by: Will Deacon <will@kernel.org> 
Commit 76085aff29f5 ("efi/libstub/arm64: align PE/COFF sections to segment
alignment") increased the PE/COFF section alignment to match the minimum
segment alignment of the kernel image, which ensures that the kernel does
not need to be moved around in memory by the EFI stub if it was built as
relocatable.

However, the first PE/COFF section starts at _stext, which is only 4 KB
aligned, and so the section layout is inconsistent. Existing EFI loaders
seem to care little about this, but it is better to clean this up.

So let's pad the header to 64 KB to match the PE/COFF section alignment.

Fixes: 76085aff29f5 ("efi/libstub/arm64: align PE/COFF sections to segment alignment")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20201027073209.2897-2-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux 2020-06-01T22:18:27+00:00 Linus Torvalds torvalds@linux-foundation.org 2020-06-01T22:18:27+00:00 533b220f7be4e461a5222a223d169b42856741ef Pull arm64 updates from Will Deacon: "A sizeable pile of arm64 updates for 5.8. Summary below, but the big two features are support for Branch Target Identification and Clang's Shadow Call stack. The latter is currently arm64-only, but the high-level parts are all in core code so it could easily be adopted by other architectures pending toolchain support Branch Target Identification (BTI): - Support for ARMv8.5-BTI in both user- and kernel-space. This allows branch targets to limit the types of branch from which they can be called and additionally prevents branching to arbitrary code, although kernel support requires a very recent toolchain. - Function annotation via SYM_FUNC_START() so that assembly functions are wrapped with the relevant "landing pad" instructions. - BPF and vDSO updates to use the new instructions. - Addition of a new HWCAP and exposure of BTI capability to userspace via ID register emulation, along with ELF loader support for the BTI feature in .note.gnu.property. - Non-critical fixes to CFI unwind annotations in the sigreturn trampoline. Shadow Call Stack (SCS): - Support for Clang's Shadow Call Stack feature, which reserves platform register x18 to point at a separate stack for each task that holds only return addresses. This protects function return control flow from buffer overruns on the main stack. - Save/restore of x18 across problematic boundaries (user-mode, hypervisor, EFI, suspend, etc). - Core support for SCS, should other architectures want to use it too. - SCS overflow checking on context-switch as part of the existing stack limit check if CONFIG_SCHED_STACK_END_CHECK=y. CPU feature detection: - Removed numerous "SANITY CHECK" errors when running on a system with mismatched AArch32 support at EL1. This is primarily a concern for KVM, which disabled support for 32-bit guests on such a system. - Addition of new ID registers and fields as the architecture has been extended. Perf and PMU drivers: - Minor fixes and cleanups to system PMU drivers. Hardware errata: - Unify KVM workarounds for VHE and nVHE configurations. - Sort vendor errata entries in Kconfig. Secure Monitor Call Calling Convention (SMCCC): - Update to the latest specification from Arm (v1.2). - Allow PSCI code to query the SMCCC version. Software Delegated Exception Interface (SDEI): - Unexport a bunch of unused symbols. - Minor fixes to handling of firmware data. Pointer authentication: - Add support for dumping the kernel PAC mask in vmcoreinfo so that the stack can be unwound by tools such as kdump. - Simplification of key initialisation during CPU bringup. BPF backend: - Improve immediate generation for logical and add/sub instructions. vDSO: - Minor fixes to the linker flags for consistency with other architectures and support for LLVM's unwinder. - Clean up logic to initialise and map the vDSO into userspace. ACPI: - Work around for an ambiguity in the IORT specification relating to the "num_ids" field. - Support _DMA method for all named components rather than only PCIe root complexes. - Minor other IORT-related fixes. Miscellaneous: - Initialise debug traps early for KGDB and fix KDB cacheflushing deadlock. - Minor tweaks to early boot state (documentation update, set TEXT_OFFSET to 0x0, increase alignment of PE/COFF sections). - Refactoring and cleanup" * tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (148 commits) KVM: arm64: Move __load_guest_stage2 to kvm_mmu.h KVM: arm64: Check advertised Stage-2 page size capability arm64/cpufeature: Add get_arm64_ftr_reg_nowarn() ACPI/IORT: Remove the unused __get_pci_rid() arm64/cpuinfo: Add ID_MMFR4_EL1 into the cpuinfo_arm64 context arm64/cpufeature: Add remaining feature bits in ID_AA64PFR1 register arm64/cpufeature: Add remaining feature bits in ID_AA64PFR0 register arm64/cpufeature: Add remaining feature bits in ID_AA64ISAR0 register arm64/cpufeature: Add remaining feature bits in ID_MMFR4 register arm64/cpufeature: Add remaining feature bits in ID_PFR0 register arm64/cpufeature: Introduce ID_MMFR5 CPU register arm64/cpufeature: Introduce ID_DFR1 CPU register arm64/cpufeature: Introduce ID_PFR2 CPU register arm64/cpufeature: Make doublelock a signed feature in ID_AA64DFR0 arm64/cpufeature: Drop TraceFilt feature exposure from ID_DFR0 register arm64/cpufeature: Add explicit ftr_id_isar0[] for ID_ISAR0 register arm64: mm: Add asid_gen_match() helper firmware: smccc: Fix missing prototype warning for arm_smccc_version_init arm64: vdso: Fix CFI directives in sigreturn trampoline arm64: vdso: Don't prefix sigreturn trampoline with a BTI C instruction ... 
Pull arm64 updates from Will Deacon:
 "A sizeable pile of arm64 updates for 5.8.

  Summary below, but the big two features are support for Branch Target
  Identification and Clang's Shadow Call stack. The latter is currently
  arm64-only, but the high-level parts are all in core code so it could
  easily be adopted by other architectures pending toolchain support

  Branch Target Identification (BTI):

   - Support for ARMv8.5-BTI in both user- and kernel-space. This allows
     branch targets to limit the types of branch from which they can be
     called and additionally prevents branching to arbitrary code,
     although kernel support requires a very recent toolchain.

   - Function annotation via SYM_FUNC_START() so that assembly functions
     are wrapped with the relevant "landing pad" instructions.

   - BPF and vDSO updates to use the new instructions.

   - Addition of a new HWCAP and exposure of BTI capability to userspace
     via ID register emulation, along with ELF loader support for the
     BTI feature in .note.gnu.property.

   - Non-critical fixes to CFI unwind annotations in the sigreturn
     trampoline.

  Shadow Call Stack (SCS):

   - Support for Clang's Shadow Call Stack feature, which reserves
     platform register x18 to point at a separate stack for each task
     that holds only return addresses. This protects function return
     control flow from buffer overruns on the main stack.

   - Save/restore of x18 across problematic boundaries (user-mode,
     hypervisor, EFI, suspend, etc).

   - Core support for SCS, should other architectures want to use it
     too.

   - SCS overflow checking on context-switch as part of the existing
     stack limit check if CONFIG_SCHED_STACK_END_CHECK=y.

  CPU feature detection:

   - Removed numerous "SANITY CHECK" errors when running on a system
     with mismatched AArch32 support at EL1. This is primarily a concern
     for KVM, which disabled support for 32-bit guests on such a system.

   - Addition of new ID registers and fields as the architecture has
     been extended.

  Perf and PMU drivers:

   - Minor fixes and cleanups to system PMU drivers.

  Hardware errata:

   - Unify KVM workarounds for VHE and nVHE configurations.

   - Sort vendor errata entries in Kconfig.

  Secure Monitor Call Calling Convention (SMCCC):

   - Update to the latest specification from Arm (v1.2).

   - Allow PSCI code to query the SMCCC version.

  Software Delegated Exception Interface (SDEI):

   - Unexport a bunch of unused symbols.

   - Minor fixes to handling of firmware data.

  Pointer authentication:

   - Add support for dumping the kernel PAC mask in vmcoreinfo so that
     the stack can be unwound by tools such as kdump.

   - Simplification of key initialisation during CPU bringup.

  BPF backend:

   - Improve immediate generation for logical and add/sub instructions.

  vDSO:

   - Minor fixes to the linker flags for consistency with other
     architectures and support for LLVM's unwinder.

   - Clean up logic to initialise and map the vDSO into userspace.

  ACPI:

   - Work around for an ambiguity in the IORT specification relating to
     the "num_ids" field.

   - Support _DMA method for all named components rather than only PCIe
     root complexes.

   - Minor other IORT-related fixes.

  Miscellaneous:

   - Initialise debug traps early for KGDB and fix KDB cacheflushing
     deadlock.

   - Minor tweaks to early boot state (documentation update, set
     TEXT_OFFSET to 0x0, increase alignment of PE/COFF sections).

   - Refactoring and cleanup"

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (148 commits)
  KVM: arm64: Move __load_guest_stage2 to kvm_mmu.h
  KVM: arm64: Check advertised Stage-2 page size capability
  arm64/cpufeature: Add get_arm64_ftr_reg_nowarn()
  ACPI/IORT: Remove the unused __get_pci_rid()
  arm64/cpuinfo: Add ID_MMFR4_EL1 into the cpuinfo_arm64 context
  arm64/cpufeature: Add remaining feature bits in ID_AA64PFR1 register
  arm64/cpufeature: Add remaining feature bits in ID_AA64PFR0 register
  arm64/cpufeature: Add remaining feature bits in ID_AA64ISAR0 register
  arm64/cpufeature: Add remaining feature bits in ID_MMFR4 register
  arm64/cpufeature: Add remaining feature bits in ID_PFR0 register
  arm64/cpufeature: Introduce ID_MMFR5 CPU register
  arm64/cpufeature: Introduce ID_DFR1 CPU register
  arm64/cpufeature: Introduce ID_PFR2 CPU register
  arm64/cpufeature: Make doublelock a signed feature in ID_AA64DFR0
  arm64/cpufeature: Drop TraceFilt feature exposure from ID_DFR0 register
  arm64/cpufeature: Add explicit ftr_id_isar0[] for ID_ISAR0 register
  arm64: mm: Add asid_gen_match() helper
  firmware: smccc: Fix missing prototype warning for arm_smccc_version_init
  arm64: vdso: Fix CFI directives in sigreturn trampoline
  arm64: vdso: Don't prefix sigreturn trampoline with a BTI C instruction
  ...
efi/libstub: Add missing prototype for PE/COFF entry point 2020-05-23T09:01:57+00:00 Ard Biesheuvel ardb@kernel.org 2020-05-23T09:01:57+00:00 6e99d3213b10ee18428d6d20715ad6c0e89ead4d Fix a missing prototype warning by adding a forward declaration for the PE/COFF entrypoint, and while at it, align the function name between the x86 and ARM versions of the stub. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> 
Fix a missing prototype warning by adding a forward declaration
for the PE/COFF entrypoint, and while at it, align the function
name between the x86 and ARM versions of the stub.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
efi/libstub/arm64: align PE/COFF sections to segment alignment 2020-04-28T16:36:52+00:00 Ard Biesheuvel ardb@kernel.org 2020-04-13T15:55:18+00:00 76085aff29f585139a37a10ea0a7daa63f70872c The arm64 kernel's segment alignment is fixed at 64 KB for any page size, and relocatable kernels are able to fix up any misalignment of the kernel image with respect to the 2 MB section alignment that is mandated by the arm64 boot protocol. Let's increase the PE/COFF section alignment to the same value, so that kernels loaded by the UEFI PE/COFF loader are guaranteed to end up at an address that doesn't require any reallocation to be done if the kernel is relocatable. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20200413155521.24698-6-ardb@kernel.org Signed-off-by: Will Deacon <will@kernel.org> 
The arm64 kernel's segment alignment is fixed at 64 KB for any page
size, and relocatable kernels are able to fix up any misalignment of
the kernel image with respect to the 2 MB section alignment that is
mandated by the arm64 boot protocol.

Let's increase the PE/COFF section alignment to the same value, so that
kernels loaded by the UEFI PE/COFF loader are guaranteed to end up at
an address that doesn't require any reallocation to be done if the
kernel is relocatable.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20200413155521.24698-6-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
efi/libstub: Introduce symbolic constants for the stub major/minor version 2020-02-23T20:59:42+00:00 Ard Biesheuvel ardb@kernel.org 2020-02-20T10:06:00+00:00 148d3f716c208738d2c7ff8c80be18d89ec8a06e Now that we have added new ways to load the initrd or the mixed mode kernel, we will also need a way to tell the loader about this. Add symbolic constants for the PE/COFF major/minor version numbers (which fortunately have always been 0x0 for all architectures), so that we can bump them later to document the capabilities of the stub. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> 
Now that we have added new ways to load the initrd or the mixed mode
kernel, we will also need a way to tell the loader about this. Add
symbolic constants for the PE/COFF major/minor version numbers (which
fortunately have always been 0x0 for all architectures), so that we
can bump them later to document the capabilities of the stub.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>