glibc/sysdeps/arm/sysdep.h

/* Assembler macros for ARM.
   Copyright (C) 1997-2024 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library 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.

   The GNU C Library 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 the GNU C Library.  If not, see
   <https://www.gnu.org/licenses/>.  */

#include <sysdeps/generic/sysdep.h>
#include <features.h>

#ifndef __ASSEMBLER__
# include <stdint.h>
#else
# include <arm-features.h>
#endif

/* The __ARM_ARCH define is provided by gcc 4.8.  Construct it otherwise.  */
#ifndef __ARM_ARCH
# ifdef __ARM_ARCH_2__
#  define __ARM_ARCH 2
# elif defined (__ARM_ARCH_3__) || defined (__ARM_ARCH_3M__)
#  define __ARM_ARCH 3
# elif defined (__ARM_ARCH_4__) || defined (__ARM_ARCH_4T__)
#  define __ARM_ARCH 4
# elif defined (__ARM_ARCH_5__) || defined (__ARM_ARCH_5E__) \
       || defined(__ARM_ARCH_5T__) || defined(__ARM_ARCH_5TE__) \
       || defined(__ARM_ARCH_5TEJ__)
#  define __ARM_ARCH 5
# elif defined (__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) \
       || defined (__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__) \
       || defined (__ARM_ARCH_6K__) || defined(__ARM_ARCH_6T2__)
#  define __ARM_ARCH 6
# elif defined (__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) \
       || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) \
       || defined(__ARM_ARCH_7EM__)
#  define __ARM_ARCH 7
# else
#  error unknown arm architecture
# endif
#endif

#if __ARM_ARCH > 4 || defined (__ARM_ARCH_4T__)
# define ARCH_HAS_BX
#endif
#if __ARM_ARCH > 4
# define ARCH_HAS_BLX
#endif
#if __ARM_ARCH > 6 || defined (__ARM_ARCH_6K__) || defined (__ARM_ARCH_6ZK__)
# define ARCH_HAS_HARD_TP
#endif
#if __ARM_ARCH > 6 || defined (__ARM_ARCH_6T2__)
# define ARCH_HAS_T2
#endif

#ifdef	__ASSEMBLER__

/* Syntactic details of assembler.  */

#define ALIGNARG(log2) log2
#define ASM_SIZE_DIRECTIVE(name) .size name,.-name

#define PLTJMP(_x)	_x##(PLT)

#ifdef ARCH_HAS_BX
# define BX(R)		bx	R
# define BXC(C, R)	bx##C	R
# ifdef ARCH_HAS_BLX
#  define BLX(R)	blx	R
# else
#  define BLX(R)	mov	lr, pc; bx R
# endif
#else
# define BX(R)		mov	pc, R
# define BXC(C, R)	mov##C	pc, R
# define BLX(R)		mov	lr, pc; mov pc, R
#endif

#define DO_RET(R)	BX(R)
#define RETINSTR(C, R)	BXC(C, R)

/* Define an entry point visible from C.  */
#define	ENTRY(name)					\
	.globl	C_SYMBOL_NAME(name);			\
	.type	C_SYMBOL_NAME(name),%function;		\
	.align	ALIGNARG(4);				\
  C_LABEL(name)						\
	CFI_SECTIONS;					\
	cfi_startproc;					\
	CALL_MCOUNT

#define CFI_SECTIONS					\
	.cfi_sections .debug_frame

#undef	END
#define END(name)					\
	cfi_endproc;					\
	ASM_SIZE_DIRECTIVE(name)

/* If compiled for profiling, call `mcount' at the start of each function.  */
#ifdef	PROF
/* Call __gnu_mcount_nc (GCC >= 4.4).  */
#define CALL_MCOUNT					\
	push	{lr};					\
	cfi_adjust_cfa_offset (4);			\
	cfi_rel_offset (lr, 0);				\
	bl	PLTJMP(mcount);				\
	cfi_adjust_cfa_offset (-4);			\
	cfi_restore (lr)
#else
#define CALL_MCOUNT		/* Do nothing.  */
#endif

/* Since C identifiers are not normally prefixed with an underscore
   on this system, the asm identifier `syscall_error' intrudes on the
   C name space.  Make sure we use an innocuous name.  */
#define	syscall_error	__syscall_error
#define mcount		__gnu_mcount_nc

/* Tag_ABI_align8_preserved: This code preserves 8-byte
   alignment in any callee.  */
	.eabi_attribute 25, 1
/* Tag_ABI_align8_needed: This code may require 8-byte alignment from
   the caller.  */
	.eabi_attribute 24, 1

/* The thumb2 encoding is reasonably complete.  Unless suppressed, use it.  */
	.syntax unified
# if defined(__thumb2__) && !defined(NO_THUMB)
	.thumb
#else
#  undef __thumb__
#  undef __thumb2__
	.arm
# endif

/* Load or store to/from address X + Y into/from R, (maybe) using T.
   X or Y can use T freely; T can be R if OP is a load.  The first
   version eschews the two-register addressing mode, while the
   second version uses it.  */
# define LDST_INDEXED_NOINDEX(OP, R, T, X, Y)		\
	add	T, X, Y;				\
	OP	R, [T]
# define LDST_INDEXED_INDEX(OP, R, X, Y)		\
	OP	R, [X, Y]

# ifdef ARM_NO_INDEX_REGISTER
/* We're never using the two-register addressing mode, so this
   always uses an intermediate add.  */
#  define LDST_INDEXED(OP, R, T, X, Y)	LDST_INDEXED_NOINDEX (OP, R, T, X, Y)
#  define LDST_PC_INDEXED(OP, R, T, X)	LDST_INDEXED_NOINDEX (OP, R, T, pc, X)
# else
/* The two-register addressing mode is OK, except on Thumb with pc.  */
#  define LDST_INDEXED(OP, R, T, X, Y)	LDST_INDEXED_INDEX (OP, R, X, Y)
#  ifdef __thumb2__
#   define LDST_PC_INDEXED(OP, R, T, X)	LDST_INDEXED_NOINDEX (OP, R, T, pc, X)
#  else
#   define LDST_PC_INDEXED(OP, R, T, X)	LDST_INDEXED_INDEX (OP, R, pc, X)
#  endif
# endif

/* Load or store to/from a pc-relative EXPR into/from R, using T.  */
# ifdef __thumb2__
#  define LDST_PCREL(OP, R, T, EXPR) \
	ldr	T, 98f;					\
	.subsection 2;					\
98:	.word	EXPR - 99f - PC_OFS;			\
	.previous;					\
99:	add	T, T, pc;				\
	OP	R, [T]
# elif defined (ARCH_HAS_T2) && ARM_PCREL_MOVW_OK
#  define LDST_PCREL(OP, R, T, EXPR)			\
	movw	T, #:lower16:EXPR - 99f - PC_OFS;	\
	movt	T, #:upper16:EXPR - 99f - PC_OFS;	\
99:	LDST_PC_INDEXED (OP, R, T, T)
# else
#  define LDST_PCREL(OP, R, T, EXPR) \
	ldr	T, 98f;					\
	.subsection 2;					\
98:	.word	EXPR - 99f - PC_OFS;			\
	.previous;					\
99:	OP	R, [pc, T]
# endif

/* Load from a global SYMBOL + CONSTANT into R, using T.  */
# if defined (ARCH_HAS_T2) && !defined (PIC)
#  define LDR_GLOBAL(R, T, SYMBOL, CONSTANT)				\
	movw	T, #:lower16:SYMBOL;					\
	movt	T, #:upper16:SYMBOL;					\
	ldr	R, [T, $CONSTANT]
# elif defined (ARCH_HAS_T2) && defined (PIC) && ARM_PCREL_MOVW_OK
#  define LDR_GLOBAL(R, T, SYMBOL, CONSTANT)				\
	movw	R, #:lower16:_GLOBAL_OFFSET_TABLE_ - 97f - PC_OFS;	\
	movw	T, #:lower16:99f - 98f - PC_OFS;			\
	movt	R, #:upper16:_GLOBAL_OFFSET_TABLE_ - 97f - PC_OFS;	\
	movt	T, #:upper16:99f - 98f - PC_OFS;			\
	.pushsection .rodata.cst4, "aM", %progbits, 4;			\
	.balign 4;							\
99:	.word	SYMBOL##(GOT);						\
	.popsection;							\
97:	add	R, R, pc;						\
98:	LDST_PC_INDEXED (ldr, T, T, T);					\
	LDST_INDEXED (ldr, R, T, R, T);					\
	ldr	R, [R, $CONSTANT]
# else
#  define LDR_GLOBAL(R, T, SYMBOL, CONSTANT)		\
	ldr	T, 99f;					\
	ldr	R, 100f;				\
98:	add	T, T, pc;				\
	ldr	T, [T, R];				\
	.subsection 2;					\
99:	.word	_GLOBAL_OFFSET_TABLE_ - 98b - PC_OFS;	\
100:	.word	SYMBOL##(GOT);				\
	.previous;					\
	ldr	R, [T, $CONSTANT]
# endif

/* This is the same as LDR_GLOBAL, but for a SYMBOL that is known to
   be in the same linked object (as for one with hidden visibility).
   We can avoid the GOT indirection in the PIC case.  For the pure
   static case, LDR_GLOBAL is already optimal.  */
# ifdef PIC
#  define LDR_HIDDEN(R, T, SYMBOL, CONSTANT) \
  LDST_PCREL (ldr, R, T, SYMBOL + CONSTANT)
# else
#  define LDR_HIDDEN(R, T, SYMBOL, CONSTANT) \
  LDR_GLOBAL (R, T, SYMBOL, CONSTANT)
# endif

/* Cope with negative memory offsets, which thumb can't encode.
   Use NEGOFF_ADJ_BASE to (conditionally) alter the base register,
   and then NEGOFF_OFF1 to use 0 for thumb and the offset for arm,
   or NEGOFF_OFF2 to use A-B for thumb and A for arm.  */
# ifdef __thumb2__
#  define NEGOFF_ADJ_BASE(R, OFF)	add R, R, $OFF
#  define NEGOFF_ADJ_BASE2(D, S, OFF)	add D, S, $OFF
#  define NEGOFF_OFF1(R, OFF)		[R]
#  define NEGOFF_OFF2(R, OFFA, OFFB)	[R, $((OFFA) - (OFFB))]
# else
#  define NEGOFF_ADJ_BASE(R, OFF)
#  define NEGOFF_ADJ_BASE2(D, S, OFF)	mov D, S
#  define NEGOFF_OFF1(R, OFF)		[R, $OFF]
#  define NEGOFF_OFF2(R, OFFA, OFFB)	[R, $OFFA]
# endif

/* Helper to get the TLS base pointer.  The interface is that TMP is a
   register that may be used to hold the LR, if necessary.  TMP may be
   LR itself to indicate that LR need not be saved.  The base pointer
   is returned in R0.  Only R0 and TMP are modified.  */

# ifdef ARCH_HAS_HARD_TP
/* If the cpu has cp15 available, use it.  */
#  define GET_TLS(TMP)		mrc p15, 0, r0, c13, c0, 3
# else
/* At this generic level we have no tricks to pull.  Call the ABI routine.  */
#  define GET_TLS(TMP)					\
	push	{ r1, r2, r3, lr };			\
	cfi_remember_state;				\
	cfi_adjust_cfa_offset (16);			\
	cfi_rel_offset (r1, 0);				\
	cfi_rel_offset (r2, 4);				\
	cfi_rel_offset (r3, 8);				\
	cfi_rel_offset (lr, 12);			\
	bl	__aeabi_read_tp;			\
	pop	{ r1, r2, r3, lr };			\
	cfi_restore_state
# endif /* ARCH_HAS_HARD_TP */

/* These are the directives used for EABI unwind info.
   Wrap them in macros so another configuration's sysdep.h
   file can define them away if it doesn't use EABI unwind info.  */
# define eabi_fnstart		.fnstart
# define eabi_fnend		.fnend
# define eabi_save(...)		.save __VA_ARGS__
# define eabi_cantunwind	.cantunwind
# define eabi_pad(n)		.pad n

#endif	/* __ASSEMBLER__ */

/* This number is the offset from the pc at the current location.  */
#ifdef __thumb__
# define PC_OFS  4
#else
# define PC_OFS  8
#endif