/* * Copyright 2008 Vitaly Mayatskikh <vmayatsk@redhat.com> * Copyright 2002 Andi Kleen, SuSE Labs. * Subject to the GNU Public License v2. * * Functions to copy from and to user space. */ #include <linux/linkage.h> #include <asm/dwarf2.h> #define FIX_ALIGNMENT 1 #include <asm/current.h> #include <asm/asm-offsets.h> #include <asm/thread_info.h> #include <asm/cpufeature.h> #include <asm/alternative-asm.h> /* * By placing feature2 after feature1 in altinstructions section, we logically * implement: * If CPU has feature2, jmp to alt2 is used * else if CPU has feature1, jmp to alt1 is used * else jmp to orig is used. */ .macro ALTERNATIVE_JUMP feature1,feature2,orig,alt1,alt2 0: .byte 0xe9 /* 32bit jump */ .long \orig-1f /* by default jump to orig */ 1: .section .altinstr_replacement,"ax" 2: .byte 0xe9 /* near jump with 32bit immediate */ .long \alt1-1b /* offset */ /* or alternatively to alt1 */ 3: .byte 0xe9 /* near jump with 32bit immediate */ .long \alt2-1b /* offset */ /* or alternatively to alt2 */ .previous .section .altinstructions,"a" altinstruction_entry 0b,2b,\feature1,5,5 altinstruction_entry 0b,3b,\feature2,5,5 .previous .endm .macro ALIGN_DESTINATION #ifdef FIX_ALIGNMENT /* check for bad alignment of destination */ movl %edi,%ecx andl $7,%ecx jz 102f /* already aligned */ subl $8,%ecx negl %ecx subl %ecx,%edx 100: movb (%rsi),%al 101: movb %al,(%rdi) incq %rsi incq %rdi decl %ecx jnz 100b 102: .section .fixup,"ax" 103: addl %ecx,%edx /* ecx is zerorest also */ jmp copy_user_handle_tail .previous .section __ex_table,"a" .align 8 .quad 100b,103b .quad 101b,103b .previous #endif .endm /* Standard copy_to_user with segment limit checking */ ENTRY(_copy_to_user) CFI_STARTPROC GET_THREAD_INFO(%rax) movq %rdi,%rcx addq %rdx,%rcx jc bad_to_user cmpq TI_addr_limit(%rax),%rcx ja bad_to_user ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,X86_FEATURE_ERMS, \ copy_user_generic_unrolled,copy_user_generic_string, \ copy_user_enhanced_fast_string CFI_ENDPROC ENDPROC(_copy_to_user) /* Standard copy_from_user with segment limit checking */ ENTRY(_copy_from_user) CFI_STARTPROC GET_THREAD_INFO(%rax) movq %rsi,%rcx addq %rdx,%rcx jc bad_from_user cmpq TI_addr_limit(%rax),%rcx ja bad_from_user ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,X86_FEATURE_ERMS, \ copy_user_generic_unrolled,copy_user_generic_string, \ copy_user_enhanced_fast_string CFI_ENDPROC ENDPROC(_copy_from_user) .section .fixup,"ax" /* must zero dest */ ENTRY(bad_from_user) bad_from_user: CFI_STARTPROC movl %edx,%ecx xorl %eax,%eax rep stosb bad_to_user: movl %edx,%eax ret CFI_ENDPROC ENDPROC(bad_from_user) .previous /* * copy_user_generic_unrolled - memory copy with exception handling. * This version is for CPUs like P4 that don't have efficient micro * code for rep movsq * * Input: * rdi destination * rsi source * rdx count * * Output: * eax uncopied bytes or 0 if successful. */ ENTRY(copy_user_generic_unrolled) CFI_STARTPROC cmpl $8,%edx jb 20f /* less then 8 bytes, go to byte copy loop */ ALIGN_DESTINATION movl %edx,%ecx andl $63,%edx shrl $6,%ecx jz 17f 1: movq (%rsi),%r8 2: movq 1*8(%rsi),%r9 3: movq 2*8(%rsi),%r10 4: movq 3*8(%rsi),%r11 5: movq %r8,(%rdi) 6: movq %r9,1*8(%rdi) 7: movq %r10,2*8(%rdi) 8: movq %r11,3*8(%rdi) 9: movq 4*8(%rsi),%r8 10: movq 5*8(%rsi),%r9 11: movq 6*8(%rsi),%r10 12: movq 7*8(%rsi),%r11 13: movq %r8,4*8(%rdi) 14: movq %r9,5*8(%rdi) 15: movq %r10,6*8(%rdi) 16: movq %r11,7*8(%rdi) leaq 64(%rsi),%rsi leaq 64(%rdi),%rdi decl %ecx jnz 1b 17: movl %edx,%ecx andl $7,%edx shrl $3,%ecx jz 20f 18: movq (%rsi),%r8 19: movq %r8,(%rdi) leaq 8(%rsi),%rsi leaq 8(%rdi),%rdi decl %ecx jnz 18b 20: andl %edx,%edx jz 23f movl %edx,%ecx 21: movb (%rsi),%al 22: movb %al,(%rdi) incq %rsi incq %rdi decl %ecx jnz 21b 23: xor %eax,%eax ret .section .fixup,"ax" 30: shll $6,%ecx addl %ecx,%edx jmp 60f 40: lea (%rdx,%rcx,8),%rdx jmp 60f 50: movl %ecx,%edx 60: jmp copy_user_handle_tail /* ecx is zerorest also */ .previous .section __ex_table,"a" .align 8 .quad 1b,30b .quad 2b,30b .quad 3b,30b .quad 4b,30b .quad 5b,30b .quad 6b,30b .quad 7b,30b .quad 8b,30b .quad 9b,30b .quad 10b,30b .quad 11b,30b .quad 12b,30b .quad 13b,30b .quad 14b,30b .quad 15b,30b .quad 16b,30b .quad 18b,40b .quad 19b,40b .quad 21b,50b .quad 22b,50b .previous CFI_ENDPROC ENDPROC(copy_user_generic_unrolled) /* Some CPUs run faster using the string copy instructions. * This is also a lot simpler. Use them when possible. * * Only 4GB of copy is supported. This shouldn't be a problem * because the kernel normally only writes from/to page sized chunks * even if user space passed a longer buffer. * And more would be dangerous because both Intel and AMD have * errata with rep movsq > 4GB. If someone feels the need to fix * this please consider this. * * Input: * rdi destination * rsi source * rdx count * * Output: * eax uncopied bytes or 0 if successful. */ ENTRY(copy_user_generic_string) CFI_STARTPROC andl %edx,%edx jz 4f cmpl $8,%edx jb 2f /* less than 8 bytes, go to byte copy loop */ ALIGN_DESTINATION movl %edx,%ecx shrl $3,%ecx andl $7,%edx 1: rep movsq 2: movl %edx,%ecx 3: rep movsb 4: xorl %eax,%eax ret .section .fixup,"ax" 11: lea (%rdx,%rcx,8),%rcx 12: movl %ecx,%edx /* ecx is zerorest also */ jmp copy_user_handle_tail .previous .section __ex_table,"a" .align 8 .quad 1b,11b .quad 3b,12b .previous CFI_ENDPROC ENDPROC(copy_user_generic_string) /* * Some CPUs are adding enhanced REP MOVSB/STOSB instructions. * It's recommended to use enhanced REP MOVSB/STOSB if it's enabled. * * Input: * rdi destination * rsi source * rdx count * * Output: * eax uncopied bytes or 0 if successful. */ ENTRY(copy_user_enhanced_fast_string) CFI_STARTPROC andl %edx,%edx jz 2f movl %edx,%ecx 1: rep movsb 2: xorl %eax,%eax ret .section .fixup,"ax" 12: movl %ecx,%edx /* ecx is zerorest also */ jmp copy_user_handle_tail .previous .section __ex_table,"a" .align 8 .quad 1b,12b .previous CFI_ENDPROC ENDPROC(copy_user_enhanced_fast_string)