Files
FFmpeg/libavutil/aarch64/asm.S
Martin Storsjö 3ec48e4bc6 aarch64: Add Armv9.3-A GCS (Guarded Control Stack) support
Signal that our assembly is compliant with the GCS feature, if
the GCS feature is enabled in the compiler (available since Clang
18 and GCC 15) - this is enabled by -mbranch-protection=standard
with a new enough compiler.

GCS doesn't require any specific modifications to the assembly
code, but requires that all functions return to the expected call
address (checked through a shadow stack).

(cherry picked from commit 846746be4b)
2026-03-20 13:12:08 +02:00

341 lines
9.8 KiB
ArmAsm

/*
* Copyright (c) 2008 Mans Rullgard <mans@mansr.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#ifdef __ELF__
# define ELF
#else
# define ELF #
#endif
#if HAVE_AS_FUNC
# define FUNC
#else
# define FUNC #
#endif
#ifndef __has_feature
# define __has_feature(x) 0
#endif
#if HAVE_AS_ARCH_DIRECTIVE
.arch AS_ARCH_LEVEL
#endif
#if HAVE_AS_ARCHEXT_CRC_DIRECTIVE
#define ENABLE_ARM_CRC .arch_extension crc
#define DISABLE_ARM_CRC .arch_extension nocrc
#else
#define ENABLE_ARM_CRC
#define DISABLE_ARM_CRC
#endif
#if HAVE_AS_ARCHEXT_DOTPROD_DIRECTIVE
#define ENABLE_DOTPROD .arch_extension dotprod
#define DISABLE_DOTPROD .arch_extension nodotprod
#else
#define ENABLE_DOTPROD
#define DISABLE_DOTPROD
#endif
#if HAVE_AS_ARCHEXT_I8MM_DIRECTIVE
#define ENABLE_I8MM .arch_extension i8mm
#define DISABLE_I8MM .arch_extension noi8mm
#else
#define ENABLE_I8MM
#define DISABLE_I8MM
#endif
#if HAVE_AS_ARCHEXT_SVE_DIRECTIVE
#define ENABLE_SVE .arch_extension sve
#define DISABLE_SVE .arch_extension nosve
#else
#define ENABLE_SVE
#define DISABLE_SVE
#endif
#if HAVE_AS_ARCHEXT_SVE2_DIRECTIVE
#define ENABLE_SVE2 .arch_extension sve2
#define DISABLE_SVE2 .arch_extension nosve2
#else
#define ENABLE_SVE2
#define DISABLE_SVE2
#endif
#if HAVE_AS_ARCHEXT_SME_DIRECTIVE
#define ENABLE_SME .arch_extension sme
#define DISABLE_SME .arch_extension nosme
#else
#define ENABLE_SME
#define DISABLE_SME
#endif
#if HAVE_AS_ARCHEXT_SME_I16I64_DIRECTIVE
#define ENABLE_SME_I16I64 .arch_extension sme-i16i64
#define DISABLE_SME_I16I64 .arch_extension nosme-i16i64
#else
#define ENABLE_SME_I16I64
#define DISABLE_SME_I16I64
#endif
#if HAVE_AS_ARCHEXT_SME2_DIRECTIVE
#define ENABLE_SME2 .arch_extension sme2
#define DISABLE_SME2 .arch_extension nosme2
#else
#define ENABLE_SME2
#define DISABLE_SME2
#endif
DISABLE_ARM_CRC
DISABLE_DOTPROD
DISABLE_I8MM
DISABLE_SVE
DISABLE_SVE2
DISABLE_SME
DISABLE_SME_I16I64
DISABLE_SME2
#if HAVE_SME
.macro sme_entry
stp x29, x30, [sp, #-80]!
mov x29, sp
stp d8, d9, [sp, #16]
stp d10, d11, [sp, #32]
stp d12, d13, [sp, #48]
stp d14, d15, [sp, #64]
smstart
.endm
.macro sme_exit
smstop
ldp d8, d9, [sp, #16]
ldp d10, d11, [sp, #32]
ldp d12, d13, [sp, #48]
ldp d14, d15, [sp, #64]
ldp x29, x30, [sp], #80
.endm
#endif
/* 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 supported through
* |AARCH64_VALID_JUMP_TARGET|. Landing Pads which shall serve for jumps and
* calls can be created using |AARCH64_VALID_JUMP_CALL_TARGET|.
*
* 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 BTI
# define AARCH64_VALID_CALL_TARGET hint #34 // BTI 'c'
# define AARCH64_VALID_JUMP_TARGET hint #38 // BTI 'j'
#else
# define GNU_PROPERTY_AARCH64_BTI 0 // No BTI
# define AARCH64_VALID_CALL_TARGET
# define AARCH64_VALID_JUMP_TARGET
#endif
#if defined(__ARM_FEATURE_PAC_DEFAULT)
# if ((__ARM_FEATURE_PAC_DEFAULT & (1 << 0)) != 0) // authentication using key A
# define AARCH64_SIGN_LINK_REGISTER paciasp
# define AARCH64_VALIDATE_LINK_REGISTER autiasp
# elif ((__ARM_FEATURE_PAC_DEFAULT & (1 << 1)) != 0) // authentication using key B
# define AARCH64_SIGN_LINK_REGISTER pacibsp
# define AARCH64_VALIDATE_LINK_REGISTER autibsp
# else
# error Pointer authentication defines no valid key!
# endif
# if ((__ARM_FEATURE_PAC_DEFAULT & (1 << 2)) != 0)
# error Authentication of leaf functions is enabled but not supported in FFmpeg!
# endif
# define GNU_PROPERTY_AARCH64_PAC (1 << 1)
#else
# define GNU_PROPERTY_AARCH64_PAC 0
# define AARCH64_SIGN_LINK_REGISTER
# define AARCH64_VALIDATE_LINK_REGISTER
#endif
#if defined(__ARM_FEATURE_GCS_DEFAULT) && __ARM_FEATURE_GCS_DEFAULT == 1
#define GNU_PROPERTY_AARCH64_GCS (1 << 2)
#else
#define GNU_PROPERTY_AARCH64_GCS 0 /* No GCS */
#endif
#if (GNU_PROPERTY_AARCH64_BTI != 0 || GNU_PROPERTY_AARCH64_PAC != 0 || GNU_PROPERTY_AARCH64_GCS != 0) && defined(__ELF__)
.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_BTI | GNU_PROPERTY_AARCH64_PAC | GNU_PROPERTY_AARCH64_GCS)
.long 0
.popsection
#endif
.macro function name, export=0, align=4
.macro endfunc
ELF .size \name, . - \name
FUNC .endfunc
.purgem endfunc
.endm
.text
.align \align
.if \export
.global EXTERN_ASM\name
ELF .type EXTERN_ASM\name, %function
FUNC .func EXTERN_ASM\name
EXTERN_ASM\name:
AARCH64_VALID_CALL_TARGET
.else
ELF .type \name, %function
FUNC .func \name
\name:
.endif
.endm
.macro const name, align=4, relocate=0
.macro endconst
ELF .size \name, . - \name
.purgem endconst
.endm
#if HAVE_SECTION_DATA_REL_RO
.if \relocate
.section .data.rel.ro
.else
.section .rodata
.endif
#elif defined(_WIN32)
.section .rdata
#elif !defined(__MACH__)
.section .rodata
#else
.const_data
#endif
.align \align
\name:
.endm
.macro movrel rd, val, offset=0
#if CONFIG_PIC && defined(__APPLE__)
.if \offset < 0
adrp \rd, \val@PAGE
add \rd, \rd, \val@PAGEOFF
sub \rd, \rd, -(\offset)
.else
adrp \rd, \val+(\offset)@PAGE
add \rd, \rd, \val+(\offset)@PAGEOFF
.endif
#elif CONFIG_PIC && defined(_WIN32)
.if \offset < 0
adrp \rd, \val
add \rd, \rd, :lo12:\val
sub \rd, \rd, -(\offset)
.else
adrp \rd, \val+(\offset)
add \rd, \rd, :lo12:\val+(\offset)
.endif
#elif CONFIG_PIC
# if __has_feature(hwaddress_sanitizer)
adrp \rd, :pg_hi21_nc:\val+(\offset)
# else
adrp \rd, \val+(\offset)
# endif
add \rd, \rd, :lo12:\val+(\offset)
#else
ldr \rd, =\val+\offset
#endif
.endm
#define GLUE(a, b) a ## b
#define JOIN(a, b) GLUE(a, b)
#define X(s) JOIN(EXTERN_ASM, s)
#define x18 do_not_use_x18
#define w18 do_not_use_w18