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[PATCH] Fix zeroing on exception in copy_*_user
- Don't zero for __copy_from_user_inatomic following i386. This will prevent spurious zeros for parallel file system writers when one does a exception - The string instruction version didn't zero the output on exception. Oops. Also I cleaned up the code a bit while I was at it and added a minor optimization to the string instruction path. Signed-off-by: Andi Kleen <ak@suse.de>
This commit is contained in:
Andi Kleen
Andi Kleen
parent
f0f4c3432e
commit
3022d734a5
@ -29,6 +29,7 @@ EXPORT_SYMBOL(__put_user_8);
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EXPORT_SYMBOL(copy_user_generic);
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EXPORT_SYMBOL(copy_from_user);
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EXPORT_SYMBOL(copy_to_user);
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EXPORT_SYMBOL(__copy_from_user_inatomic);
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EXPORT_SYMBOL(copy_page);
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EXPORT_SYMBOL(clear_page);
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@ -9,10 +9,29 @@
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#define FIX_ALIGNMENT 1
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#include <asm/current.h>
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#include <asm/asm-offsets.h>
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#include <asm/thread_info.h>
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#include <asm/cpufeature.h>
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#include <asm/current.h>
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#include <asm/asm-offsets.h>
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#include <asm/thread_info.h>
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#include <asm/cpufeature.h>
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.macro ALTERNATIVE_JUMP feature,orig,alt
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0:
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.byte 0xe9 /* 32bit jump */
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.long \orig-1f /* by default jump to orig */
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1:
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.section .altinstr_replacement,"ax"
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2: .byte 0xe9 /* near jump with 32bit immediate */
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.long \alt-1b /* offset */ /* or alternatively to alt */
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.previous
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.section .altinstructions,"a"
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.align 8
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.quad 0b
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.quad 2b
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.byte \feature /* when feature is set */
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.byte 5
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.byte 5
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.previous
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.endm
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/* Standard copy_to_user with segment limit checking */
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ENTRY(copy_to_user)
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@ -23,25 +42,21 @@ ENTRY(copy_to_user)
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jc bad_to_user
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cmpq threadinfo_addr_limit(%rax),%rcx
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jae bad_to_user
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2:
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.byte 0xe9 /* 32bit jump */
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.long .Lcug-1f
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1:
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xorl %eax,%eax /* clear zero flag */
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ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
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CFI_ENDPROC
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ENDPROC(copy_to_user)
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.section .altinstr_replacement,"ax"
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3: .byte 0xe9 /* replacement jmp with 32 bit immediate */
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.long copy_user_generic_c-1b /* offset */
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.previous
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.section .altinstructions,"a"
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.align 8
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.quad 2b
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.quad 3b
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.byte X86_FEATURE_REP_GOOD
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.byte 5
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.byte 5
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.previous
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ENTRY(copy_user_generic)
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CFI_STARTPROC
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movl $1,%ecx /* set zero flag */
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ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
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CFI_ENDPROC
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ENTRY(__copy_from_user_inatomic)
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CFI_STARTPROC
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xorl %ecx,%ecx /* clear zero flag */
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ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
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CFI_ENDPROC
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/* Standard copy_from_user with segment limit checking */
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ENTRY(copy_from_user)
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@ -52,7 +67,8 @@ ENTRY(copy_from_user)
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jc bad_from_user
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cmpq threadinfo_addr_limit(%rax),%rcx
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jae bad_from_user
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/* FALL THROUGH to copy_user_generic */
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movl $1,%ecx /* set zero flag */
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ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
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CFI_ENDPROC
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ENDPROC(copy_from_user)
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@ -73,37 +89,26 @@ END(bad_from_user)
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/*
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* copy_user_generic - memory copy with exception handling.
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* copy_user_generic_unrolled - memory copy with exception handling.
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* This version is for CPUs like P4 that don't have efficient micro code for rep movsq
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*
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* Input:
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* rdi destination
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* rsi source
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* rdx count
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* ecx zero flag -- if true zero destination on error
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*
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* Output:
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* eax uncopied bytes or 0 if successful.
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*/
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ENTRY(copy_user_generic)
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ENTRY(copy_user_generic_unrolled)
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CFI_STARTPROC
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.byte 0x66,0x66,0x90 /* 5 byte nop for replacement jump */
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.byte 0x66,0x90
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1:
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.section .altinstr_replacement,"ax"
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2: .byte 0xe9 /* near jump with 32bit immediate */
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.long copy_user_generic_c-1b /* offset */
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.previous
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.section .altinstructions,"a"
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.align 8
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.quad copy_user_generic
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.quad 2b
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.byte X86_FEATURE_REP_GOOD
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.byte 5
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.byte 5
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.previous
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.Lcug:
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pushq %rbx
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CFI_ADJUST_CFA_OFFSET 8
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CFI_REL_OFFSET rbx, 0
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pushq %rcx
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CFI_ADJUST_CFA_OFFSET 8
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CFI_REL_OFFSET rcx, 0
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xorl %eax,%eax /*zero for the exception handler */
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#ifdef FIX_ALIGNMENT
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@ -179,6 +184,9 @@ ENTRY(copy_user_generic)
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CFI_REMEMBER_STATE
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.Lende:
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popq %rcx
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CFI_ADJUST_CFA_OFFSET -8
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CFI_RESTORE rcx
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popq %rbx
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CFI_ADJUST_CFA_OFFSET -8
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CFI_RESTORE rbx
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@ -265,6 +273,8 @@ ENTRY(copy_user_generic)
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addl %ecx,%edx
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/* edx: bytes to zero, rdi: dest, eax:zero */
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.Lzero_rest:
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cmpl $0,(%rsp)
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jz .Le_zero
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movq %rdx,%rcx
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.Le_byte:
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xorl %eax,%eax
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@ -286,6 +296,7 @@ ENDPROC(copy_user_generic)
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/* rdi destination
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* rsi source
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* rdx count
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* ecx zero flag
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*
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* Output:
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* eax uncopied bytes or 0 if successfull.
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@ -296,25 +307,48 @@ ENDPROC(copy_user_generic)
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* And more would be dangerous because both Intel and AMD have
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* errata with rep movsq > 4GB. If someone feels the need to fix
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* this please consider this.
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*/
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copy_user_generic_c:
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*/
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ENTRY(copy_user_generic_string)
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CFI_STARTPROC
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movl %ecx,%r8d /* save zero flag */
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movl %edx,%ecx
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shrl $3,%ecx
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andl $7,%edx
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jz 10f
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1: rep
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movsq
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movl %edx,%ecx
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2: rep
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movsb
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4: movl %ecx,%eax
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9: movl %ecx,%eax
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ret
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3: lea (%rdx,%rcx,8),%rax
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/* multiple of 8 byte */
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10: rep
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movsq
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xor %eax,%eax
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ret
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/* exception handling */
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3: lea (%rdx,%rcx,8),%rax /* exception on quad loop */
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jmp 6f
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5: movl %ecx,%eax /* exception on byte loop */
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/* eax: left over bytes */
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6: testl %r8d,%r8d /* zero flag set? */
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jz 7f
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movl %eax,%ecx /* initialize x86 loop counter */
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push %rax
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xorl %eax,%eax
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8: rep
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stosb /* zero the rest */
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11: pop %rax
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7: ret
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CFI_ENDPROC
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END(copy_user_generic_c)
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.section __ex_table,"a"
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.quad 1b,3b
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.quad 2b,4b
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.quad 2b,5b
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.quad 8b,11b
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.quad 10b,3b
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.previous
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@ -238,6 +238,7 @@ do { \
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/* Handles exceptions in both to and from, but doesn't do access_ok */
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extern unsigned long copy_user_generic(void *to, const void *from, unsigned len);
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extern unsigned long copy_user_generic_dontzero(void *to, const void *from, unsigned len);
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extern unsigned long copy_to_user(void __user *to, const void *from, unsigned len);
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extern unsigned long copy_from_user(void *to, const void __user *from, unsigned len);
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@ -303,7 +304,6 @@ static __always_inline int __copy_to_user(void __user *dst, const void *src, uns
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}
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}
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static __always_inline int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
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{
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int ret = 0;
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@ -352,7 +352,7 @@ long strlen_user(const char __user *str);
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unsigned long clear_user(void __user *mem, unsigned long len);
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unsigned long __clear_user(void __user *mem, unsigned long len);
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#define __copy_to_user_inatomic __copy_to_user
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#define __copy_from_user_inatomic __copy_from_user
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extern long __copy_from_user_inatomic(void *dst, const void __user *src, unsigned size);
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#define __copy_to_user_inatomic copy_user_generic
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#endif /* __X86_64_UACCESS_H */
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