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/* Copyright (c) 2023, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#ifndef OPENSSL_HEADER_ASM_BASE_H
#define OPENSSL_HEADER_ASM_BASE_H
#include <openssl/target.h>
// This header contains symbols and common sections used by assembly files. It
// is included as a public header to simplify the build, but is not intended for
// external use.
//
// Every assembly file must include this header. Some linker features require
// all object files to be tagged with some section metadata. This header file,
// when included in assembly, adds that metadata. It also makes defines like
// |OPENSSL_X86_64| available and includes the prefixing macros.
//
// Including this header in an assembly file imples:
//
// - The file does not require an executable stack.
//
// - The file, on aarch64, uses the macros defined below to be compatible with
// BTI and PAC.
//
// - The file, on x86_64, requires the program to be compatible with Intel IBT
// and SHSTK
#if defined(__ASSEMBLER__)
#if defined(BORINGSSL_PREFIX)
#include <boringssl_prefix_symbols_asm.h>
#endif
#if defined(__ELF__)
// Every ELF object file, even empty ones, should disable executable stacks. See
// https://www.airs.com/blog/archives/518.
.pushsection .note.GNU-stack, "", %progbits
.popsection
#endif
#if defined(__CET__) && defined(OPENSSL_X86_64)
// Clang and GCC define __CET__ and provide <cet.h> when they support Intel's
// Indirect Branch Tracking.
// https://lpc.events/event/7/contributions/729/attachments/496/903/CET-LPC-2020.pdf
//
// cet.h defines _CET_ENDBR which is used to mark function entry points for IBT.
// and adds the assembly marker. The value of _CET_ENDBR is made dependant on if
// '-fcf-protection' is passed to the compiler. _CET_ENDBR is only required when
// the function is the target of an indirect jump, but BoringSSL chooses to mark
// all assembly entry points because it is easier, and allows BoringSSL's ABI
// tester to call the assembly entry points via an indirect jump.
#include <cet.h>
#else
#define _CET_ENDBR
#endif
#if defined(OPENSSL_ARM) || defined(OPENSSL_AARCH64)
// We require the ARM assembler provide |__ARM_ARCH| from Arm C Language
// Extensions (ACLE). This is supported in GCC 4.8+ and Clang 3.2+. MSVC does
// not implement ACLE, but we require Clang's assembler on Windows.
#if !defined(__ARM_ARCH)
#error "ARM assembler must define __ARM_ARCH"
#endif
// __ARM_ARCH__ is used by OpenSSL assembly to determine the minimum target ARM
// version.
//
// TODO(davidben): Switch the assembly to use |__ARM_ARCH| directly.
#define __ARM_ARCH__ __ARM_ARCH
// Even when building for 32-bit ARM, support for aarch64 crypto instructions
// will be included.
#define __ARM_MAX_ARCH__ 8
// Support macros for
// - Armv8.3-A Pointer Authentication and
// - Armv8.5-A Branch Target Identification
// features which require emitting a .note.gnu.property section with the
// appropriate architecture-dependent feature bits set.
//
// |AARCH64_SIGN_LINK_REGISTER| and |AARCH64_VALIDATE_LINK_REGISTER| expand to
// PACIxSP and AUTIxSP, respectively. |AARCH64_SIGN_LINK_REGISTER| should be
// used immediately before saving the LR register (x30) to the stack.
// |AARCH64_VALIDATE_LINK_REGISTER| should be used immediately after restoring
// it. Note |AARCH64_SIGN_LINK_REGISTER|'s modifications to LR must be undone
// with |AARCH64_VALIDATE_LINK_REGISTER| before RET. The SP register must also
// have the same value at the two points. For example:
//
// .global f
// f:
// AARCH64_SIGN_LINK_REGISTER
// stp x29, x30, [sp, #-96]!
// mov x29, sp
// ...
// ldp x29, x30, [sp], #96
// AARCH64_VALIDATE_LINK_REGISTER
// ret
//
// |AARCH64_VALID_CALL_TARGET| expands to BTI 'c'. Either it, or
// |AARCH64_SIGN_LINK_REGISTER|, must be used at every point that may be an
// indirect call target. In particular, all symbols exported from a file must
// begin with one of these macros. For example, a leaf function that does not
// save LR can instead use |AARCH64_VALID_CALL_TARGET|:
//
// .globl return_zero
// return_zero:
// AARCH64_VALID_CALL_TARGET
// mov x0, #0
// ret
//
// A non-leaf function which does not immediately save LR may need both macros
// because |AARCH64_SIGN_LINK_REGISTER| appears late. For example, the function
// may jump to an alternate implementation before setting up the stack:
//
// .globl with_early_jump
// with_early_jump:
// AARCH64_VALID_CALL_TARGET
// cmp x0, #128
// b.lt .Lwith_early_jump_128
// AARCH64_SIGN_LINK_REGISTER
// stp x29, x30, [sp, #-96]!
// mov x29, sp
// ...
// ldp x29, x30, [sp], #96
// AARCH64_VALIDATE_LINK_REGISTER
// ret
//
// .Lwith_early_jump_128:
// ...
// ret
//
// These annotations are only required with indirect calls. Private symbols that
// are only the target of direct calls do not require annotations. Also note
// that |AARCH64_VALID_CALL_TARGET| is only valid for indirect calls (BLR), not
// indirect jumps (BR). Indirect jumps in assembly are currently not supported
// and would require a macro for BTI 'j'.
//
// Although not necessary, it is safe to use these macros in 32-bit ARM
// assembly. This may be used to simplify dual 32-bit and 64-bit files.
//
// References:
// - "ELF for the Arm® 64-bit Architecture"
// https://github.com/ARM-software/abi-aa/blob/master/aaelf64/aaelf64.rst
// - "Providing protection for complex software"
// https://developer.arm.com/architectures/learn-the-architecture/providing-protection-for-complex-software
#if defined(__ARM_FEATURE_BTI_DEFAULT) && __ARM_FEATURE_BTI_DEFAULT == 1
#define GNU_PROPERTY_AARCH64_BTI (1 << 0) // Has Branch Target Identification
#define AARCH64_VALID_CALL_TARGET hint #34 // BTI 'c'
#else
#define GNU_PROPERTY_AARCH64_BTI 0 // No Branch Target Identification
#define AARCH64_VALID_CALL_TARGET
#endif
#if defined(__ARM_FEATURE_PAC_DEFAULT) && \
(__ARM_FEATURE_PAC_DEFAULT & 1) == 1 // Signed with A-key
#define GNU_PROPERTY_AARCH64_POINTER_AUTH \
(1 << 1) // Has Pointer Authentication
#define AARCH64_SIGN_LINK_REGISTER hint #25 // PACIASP
#define AARCH64_VALIDATE_LINK_REGISTER hint #29 // AUTIASP
#elif defined(__ARM_FEATURE_PAC_DEFAULT) && \
(__ARM_FEATURE_PAC_DEFAULT & 2) == 2 // Signed with B-key
#define GNU_PROPERTY_AARCH64_POINTER_AUTH \
(1 << 1) // Has Pointer Authentication
#define AARCH64_SIGN_LINK_REGISTER hint #27 // PACIBSP
#define AARCH64_VALIDATE_LINK_REGISTER hint #31 // AUTIBSP
#else
#define GNU_PROPERTY_AARCH64_POINTER_AUTH 0 // No Pointer Authentication
#if GNU_PROPERTY_AARCH64_BTI != 0
#define AARCH64_SIGN_LINK_REGISTER AARCH64_VALID_CALL_TARGET
#else
#define AARCH64_SIGN_LINK_REGISTER
#endif
#define AARCH64_VALIDATE_LINK_REGISTER
#endif
#if GNU_PROPERTY_AARCH64_POINTER_AUTH != 0 || GNU_PROPERTY_AARCH64_BTI != 0
.pushsection .note.gnu.property, "a";
.balign 8;
.long 4;
.long 0x10;
.long 0x5;
.asciz "GNU";
.long 0xc0000000; /* GNU_PROPERTY_AARCH64_FEATURE_1_AND */
.long 4;
.long (GNU_PROPERTY_AARCH64_POINTER_AUTH | GNU_PROPERTY_AARCH64_BTI);
.long 0;
.popsection;
#endif
#endif // ARM || AARCH64
#endif // __ASSEMBLER__
#endif // OPENSSL_HEADER_ASM_BASE_H
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