diff options
Diffstat (limited to 'arch/x86_64/lib/copy_user.S')
| -rw-r--r-- | arch/x86_64/lib/copy_user.S | 247 |
1 files changed, 226 insertions, 21 deletions
diff --git a/arch/x86_64/lib/copy_user.S b/arch/x86_64/lib/copy_user.S index 79422b6559c..f64569b83b5 100644 --- a/arch/x86_64/lib/copy_user.S +++ b/arch/x86_64/lib/copy_user.S @@ -4,9 +4,12 @@ * Functions to copy from and to user space. */ +#define FIX_ALIGNMENT 1 + #include <asm/current.h> #include <asm/asm-offsets.h> #include <asm/thread_info.h> + #include <asm/cpufeature.h> /* Standard copy_to_user with segment limit checking */ .globl copy_to_user @@ -18,7 +21,23 @@ copy_to_user: jc bad_to_user cmpq threadinfo_addr_limit(%rax),%rcx jae bad_to_user - jmp copy_user_generic +2: + .byte 0xe9 /* 32bit jump */ + .long .Lcug-1f +1: + + .section .altinstr_replacement,"ax" +3: .byte 0xe9 /* replacement jmp with 8 bit immediate */ + .long copy_user_generic_c-1b /* offset */ + .previous + .section .altinstructions,"a" + .align 8 + .quad 2b + .quad 3b + .byte X86_FEATURE_REP_GOOD + .byte 5 + .byte 5 + .previous /* Standard copy_from_user with segment limit checking */ .globl copy_from_user @@ -53,44 +72,230 @@ bad_to_user: * rsi source * rdx count * - * 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. - * * Output: * eax uncopied bytes or 0 if successful. */ - .globl copy_user_generic + .p2align 4 copy_user_generic: + .byte 0x66,0x66,0x90 /* 5 byte nop for replacement jump */ + .byte 0x66,0x90 +1: + .section .altinstr_replacement,"ax" +2: .byte 0xe9 /* near jump with 32bit immediate */ + .long copy_user_generic_c-1b /* offset */ + .previous + .section .altinstructions,"a" + .align 8 + .quad copy_user_generic + .quad 2b + .byte X86_FEATURE_REP_GOOD + .byte 5 + .byte 5 + .previous +.Lcug: + pushq %rbx + xorl %eax,%eax /*zero for the exception handler */ + +#ifdef FIX_ALIGNMENT + /* check for bad alignment of destination */ + movl %edi,%ecx + andl $7,%ecx + jnz .Lbad_alignment +.Lafter_bad_alignment: +#endif + + movq %rdx,%rcx + + movl $64,%ebx + shrq $6,%rdx + decq %rdx + js .Lhandle_tail + + .p2align 4 +.Lloop: +.Ls1: movq (%rsi),%r11 +.Ls2: movq 1*8(%rsi),%r8 +.Ls3: movq 2*8(%rsi),%r9 +.Ls4: movq 3*8(%rsi),%r10 +.Ld1: movq %r11,(%rdi) +.Ld2: movq %r8,1*8(%rdi) +.Ld3: movq %r9,2*8(%rdi) +.Ld4: movq %r10,3*8(%rdi) + +.Ls5: movq 4*8(%rsi),%r11 +.Ls6: movq 5*8(%rsi),%r8 +.Ls7: movq 6*8(%rsi),%r9 +.Ls8: movq 7*8(%rsi),%r10 +.Ld5: movq %r11,4*8(%rdi) +.Ld6: movq %r8,5*8(%rdi) +.Ld7: movq %r9,6*8(%rdi) +.Ld8: movq %r10,7*8(%rdi) + + decq %rdx + + leaq 64(%rsi),%rsi + leaq 64(%rdi),%rdi + + jns .Lloop + + .p2align 4 +.Lhandle_tail: + movl %ecx,%edx + andl $63,%ecx + shrl $3,%ecx + jz .Lhandle_7 + movl $8,%ebx + .p2align 4 +.Lloop_8: +.Ls9: movq (%rsi),%r8 +.Ld9: movq %r8,(%rdi) + decl %ecx + leaq 8(%rdi),%rdi + leaq 8(%rsi),%rsi + jnz .Lloop_8 + +.Lhandle_7: + movl %edx,%ecx + andl $7,%ecx + jz .Lende + .p2align 4 +.Lloop_1: +.Ls10: movb (%rsi),%bl +.Ld10: movb %bl,(%rdi) + incq %rdi + incq %rsi + decl %ecx + jnz .Lloop_1 + +.Lende: + popq %rbx + ret + +#ifdef FIX_ALIGNMENT + /* align destination */ + .p2align 4 +.Lbad_alignment: + movl $8,%r9d + subl %ecx,%r9d + movl %r9d,%ecx + cmpq %r9,%rdx + jz .Lhandle_7 + js .Lhandle_7 +.Lalign_1: +.Ls11: movb (%rsi),%bl +.Ld11: movb %bl,(%rdi) + incq %rsi + incq %rdi + decl %ecx + jnz .Lalign_1 + subq %r9,%rdx + jmp .Lafter_bad_alignment +#endif + + /* table sorted by exception address */ + .section __ex_table,"a" + .align 8 + .quad .Ls1,.Ls1e + .quad .Ls2,.Ls2e + .quad .Ls3,.Ls3e + .quad .Ls4,.Ls4e + .quad .Ld1,.Ls1e + .quad .Ld2,.Ls2e + .quad .Ld3,.Ls3e + .quad .Ld4,.Ls4e + .quad .Ls5,.Ls5e + .quad .Ls6,.Ls6e + .quad .Ls7,.Ls7e + .quad .Ls8,.Ls8e + .quad .Ld5,.Ls5e + .quad .Ld6,.Ls6e + .quad .Ld7,.Ls7e + .quad .Ld8,.Ls8e + .quad .Ls9,.Le_quad + .quad .Ld9,.Le_quad + .quad .Ls10,.Le_byte + .quad .Ld10,.Le_byte +#ifdef FIX_ALIGNMENT + .quad .Ls11,.Lzero_rest + .quad .Ld11,.Lzero_rest +#endif + .quad .Le5,.Le_zero + .previous + + /* compute 64-offset for main loop. 8 bytes accuracy with error on the + pessimistic side. this is gross. it would be better to fix the + interface. */ + /* eax: zero, ebx: 64 */ +.Ls1e: addl $8,%eax +.Ls2e: addl $8,%eax +.Ls3e: addl $8,%eax +.Ls4e: addl $8,%eax +.Ls5e: addl $8,%eax +.Ls6e: addl $8,%eax +.Ls7e: addl $8,%eax +.Ls8e: addl $8,%eax + addq %rbx,%rdi /* +64 */ + subq %rax,%rdi /* correct destination with computed offset */ + + shlq $6,%rdx /* loop counter * 64 (stride length) */ + addq %rax,%rdx /* add offset to loopcnt */ + andl $63,%ecx /* remaining bytes */ + addq %rcx,%rdx /* add them */ + jmp .Lzero_rest + + /* exception on quad word loop in tail handling */ + /* ecx: loopcnt/8, %edx: length, rdi: correct */ +.Le_quad: + shll $3,%ecx + andl $7,%edx + addl %ecx,%edx + /* edx: bytes to zero, rdi: dest, eax:zero */ +.Lzero_rest: + movq %rdx,%rcx +.Le_byte: + xorl %eax,%eax +.Le5: rep + stosb + /* when there is another exception while zeroing the rest just return */ +.Le_zero: + movq %rdx,%rax + jmp .Lende + + /* Some CPUs run faster using the string copy instructions. + This is also a lot simpler. Use them when possible. + Patch in jmps to this code instead of copying it fully + to avoid unwanted aliasing in the exception tables. */ + + /* rdi destination + * rsi source + * rdx count + * + * Output: + * eax uncopied bytes or 0 if successfull. + * + * 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. + */ +copy_user_generic_c: movl %edx,%ecx shrl $3,%ecx andl $7,%edx - jz 5f 1: rep movsq movl %edx,%ecx - xor %eax,%eax 2: rep movsb +4: movl %ecx,%eax ret - /* align here? */ -5: xorl %eax,%eax -6: rep movsq - ret - - .section .fixup,"ax" 3: lea (%rdx,%rcx,8),%rax ret -4: movl %ecx,%eax - ret - .previous .section __ex_table,"a" .quad 1b,3b .quad 2b,4b - .quad 6b,4b .previous |