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63bcff2a30
When Supervisor Mode Access Prevention (SMAP) is enabled, access to userspace from the kernel is controlled by the AC flag. To make the performance of manipulating that flag acceptable, there are two new instructions, STAC and CLAC, to set and clear it. This patch adds those instructions, via alternative(), when the SMAP feature is enabled. It also adds X86_EFLAGS_AC unconditionally to the SYSCALL entry mask; there is simply no reason to make that one conditional. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Link: http://lkml.kernel.org/r/1348256595-29119-9-git-send-email-hpa@linux.intel.com
102 lines
1.9 KiB
ArmAsm
102 lines
1.9 KiB
ArmAsm
/*
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* __put_user functions.
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*
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* (C) Copyright 2005 Linus Torvalds
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* (C) Copyright 2005 Andi Kleen
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* (C) Copyright 2008 Glauber Costa
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*
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* These functions have a non-standard call interface
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* to make them more efficient, especially as they
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* return an error value in addition to the "real"
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* return value.
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*/
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#include <linux/linkage.h>
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#include <asm/dwarf2.h>
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#include <asm/thread_info.h>
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#include <asm/errno.h>
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#include <asm/asm.h>
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#include <asm/smap.h>
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/*
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* __put_user_X
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*
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* Inputs: %eax[:%edx] contains the data
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* %ecx contains the address
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*
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* Outputs: %eax is error code (0 or -EFAULT)
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*
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* These functions should not modify any other registers,
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* as they get called from within inline assembly.
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*/
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#define ENTER CFI_STARTPROC ; \
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GET_THREAD_INFO(%_ASM_BX)
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#define EXIT ASM_CLAC ; \
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ret ; \
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CFI_ENDPROC
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.text
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ENTRY(__put_user_1)
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ENTER
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cmp TI_addr_limit(%_ASM_BX),%_ASM_CX
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jae bad_put_user
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ASM_STAC
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1: movb %al,(%_ASM_CX)
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xor %eax,%eax
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EXIT
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ENDPROC(__put_user_1)
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ENTRY(__put_user_2)
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ENTER
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mov TI_addr_limit(%_ASM_BX),%_ASM_BX
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sub $1,%_ASM_BX
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cmp %_ASM_BX,%_ASM_CX
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jae bad_put_user
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ASM_STAC
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2: movw %ax,(%_ASM_CX)
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xor %eax,%eax
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EXIT
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ENDPROC(__put_user_2)
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ENTRY(__put_user_4)
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ENTER
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mov TI_addr_limit(%_ASM_BX),%_ASM_BX
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sub $3,%_ASM_BX
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cmp %_ASM_BX,%_ASM_CX
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jae bad_put_user
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ASM_STAC
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3: movl %eax,(%_ASM_CX)
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xor %eax,%eax
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EXIT
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ENDPROC(__put_user_4)
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ENTRY(__put_user_8)
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ENTER
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mov TI_addr_limit(%_ASM_BX),%_ASM_BX
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sub $7,%_ASM_BX
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cmp %_ASM_BX,%_ASM_CX
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jae bad_put_user
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ASM_STAC
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4: mov %_ASM_AX,(%_ASM_CX)
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#ifdef CONFIG_X86_32
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5: movl %edx,4(%_ASM_CX)
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#endif
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xor %eax,%eax
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EXIT
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ENDPROC(__put_user_8)
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bad_put_user:
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CFI_STARTPROC
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movl $-EFAULT,%eax
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EXIT
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END(bad_put_user)
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_ASM_EXTABLE(1b,bad_put_user)
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_ASM_EXTABLE(2b,bad_put_user)
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_ASM_EXTABLE(3b,bad_put_user)
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_ASM_EXTABLE(4b,bad_put_user)
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#ifdef CONFIG_X86_32
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_ASM_EXTABLE(5b,bad_put_user)
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#endif
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