arch/xtensa/lib/usercopy.S

Source file repositories/reference/linux-study-clean/arch/xtensa/lib/usercopy.S

File Facts

System
Linux kernel
Corpus path
arch/xtensa/lib/usercopy.S
Extension
.S
Size
7553 bytes
Lines
302
Domain
Architecture Layer
Bucket
arch/xtensa
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

#include <linux/linkage.h>
#include <asm/asmmacro.h>
#include <asm/core.h>

	.text
ENTRY(__xtensa_copy_user)

#if !XCHAL_HAVE_LOOPS && defined(__XTENSA_CALL0_ABI__)
#define STACK_SIZE 4
#else
#define STACK_SIZE 0
#endif
	abi_entry(STACK_SIZE)
	# a2/ dst, a3/ src, a4/ len
	mov	a5, a2		# copy dst so that a2 is return value
	mov	a11, a4		# preserve original len for error case
.Lcommon:
	bbsi.l	a2, 0, .Ldst1mod2 # if dst is 1 mod 2
	bbsi.l	a2, 1, .Ldst2mod4 # if dst is 2 mod 4
.Ldstaligned:	# return here from .Ldstunaligned when dst is aligned
	srli	a7, a4, 4	# number of loop iterations with 16B
				# per iteration
	movi	a8, 3		  # if source is also aligned,
	bnone	a3, a8, .Laligned # then use word copy
	__ssa8	a3		# set shift amount from byte offset
	bnez	a4, .Lsrcunaligned
	movi	a2, 0		# return success for len==0
	abi_ret(STACK_SIZE)

/*
 * Destination is unaligned
 */

.Ldst1mod2:	# dst is only byte aligned
	bltui	a4, 7, .Lbytecopy	# do short copies byte by byte

	# copy 1 byte
EX(10f)	l8ui	a6, a3, 0
	addi	a3, a3,  1
EX(10f)	s8i	a6, a5,  0
	addi	a5, a5,  1
	addi	a4, a4, -1
	bbci.l	a5, 1, .Ldstaligned	# if dst is now aligned, then
					# return to main algorithm
.Ldst2mod4:	# dst 16-bit aligned
	# copy 2 bytes
	bltui	a4, 6, .Lbytecopy	# do short copies byte by byte
EX(10f)	l8ui	a6, a3, 0
EX(10f)	l8ui	a7, a3, 1
	addi	a3, a3,  2
EX(10f)	s8i	a6, a5,  0
EX(10f)	s8i	a7, a5,  1
	addi	a5, a5,  2
	addi	a4, a4, -2
	j	.Ldstaligned	# dst is now aligned, return to main algorithm

/*
 * Byte by byte copy
 */
	.align	4
	.byte	0		# 1 mod 4 alignment for LOOPNEZ
				# (0 mod 4 alignment for LBEG)
.Lbytecopy:
#if XCHAL_HAVE_LOOPS
	loopnez	a4, .Lbytecopydone
#else /* !XCHAL_HAVE_LOOPS */
	beqz	a4, .Lbytecopydone
	add	a7, a3, a4	# a7 = end address for source
#endif /* !XCHAL_HAVE_LOOPS */
.Lnextbyte:

Annotation

Implementation Notes