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fa697140f9
Let's make use of ARCH_HAS_SYSCALL_WRAPPER=y on pure 64-bit x86-64 systems:
Each syscall defines a stub which takes struct pt_regs as its only
argument. It decodes just those parameters it needs, e.g:
asmlinkage long sys_xyzzy(const struct pt_regs *regs)
{
return SyS_xyzzy(regs->di, regs->si, regs->dx);
}
This approach avoids leaking random user-provided register content down
the call chain.
For example, for sys_recv() which is a 4-parameter syscall, the assembly
now is (in slightly reordered fashion):
<sys_recv>:
callq <__fentry__>
/* decode regs->di, ->si, ->dx and ->r10 */
mov 0x70(%rdi),%rdi
mov 0x68(%rdi),%rsi
mov 0x60(%rdi),%rdx
mov 0x38(%rdi),%rcx
[ SyS_recv() is automatically inlined by the compiler,
as it is not [yet] used anywhere else ]
/* clear %r9 and %r8, the 5th and 6th args */
xor %r9d,%r9d
xor %r8d,%r8d
/* do the actual work */
callq __sys_recvfrom
/* cleanup and return */
cltq
retq
The only valid place in an x86-64 kernel which rightfully calls
a syscall function on its own -- vsyscall -- needs to be modified
to pass struct pt_regs onwards as well.
To keep the syscall table generation working independent of
SYSCALL_PTREGS being enabled, the stubs are named the same as the
"original" syscall stubs, i.e. sys_*().
This patch is based on an original proof-of-concept
| From: Linus Torvalds <torvalds@linux-foundation.org>
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
and was split up and heavily modified by me, in particular to base it on
ARCH_HAS_SYSCALL_WRAPPER, to limit it to 64-bit-only for the time being,
and to update the vsyscall to the new calling convention.
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180405095307.3730-4-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
247 lines
5.3 KiB
C
247 lines
5.3 KiB
C
/*
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* Access to user system call parameters and results
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*
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* Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the GNU General Public License v.2.
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*
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* See asm-generic/syscall.h for descriptions of what we must do here.
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*/
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#ifndef _ASM_X86_SYSCALL_H
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#define _ASM_X86_SYSCALL_H
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#include <uapi/linux/audit.h>
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#include <linux/sched.h>
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#include <linux/err.h>
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#include <asm/asm-offsets.h> /* For NR_syscalls */
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#include <asm/thread_info.h> /* for TS_COMPAT */
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#include <asm/unistd.h>
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#ifdef CONFIG_SYSCALL_PTREGS
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typedef asmlinkage long (*sys_call_ptr_t)(const struct pt_regs *);
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#else
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typedef asmlinkage long (*sys_call_ptr_t)(unsigned long, unsigned long,
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unsigned long, unsigned long,
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unsigned long, unsigned long);
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#endif /* CONFIG_SYSCALL_PTREGS */
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extern const sys_call_ptr_t sys_call_table[];
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#if defined(CONFIG_X86_32)
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#define ia32_sys_call_table sys_call_table
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#define __NR_syscall_compat_max __NR_syscall_max
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#define IA32_NR_syscalls NR_syscalls
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#endif
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#if defined(CONFIG_IA32_EMULATION)
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extern const sys_call_ptr_t ia32_sys_call_table[];
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#endif
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/*
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* Only the low 32 bits of orig_ax are meaningful, so we return int.
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* This importantly ignores the high bits on 64-bit, so comparisons
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* sign-extend the low 32 bits.
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*/
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static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
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{
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return regs->orig_ax;
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}
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static inline void syscall_rollback(struct task_struct *task,
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struct pt_regs *regs)
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{
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regs->ax = regs->orig_ax;
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}
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static inline long syscall_get_error(struct task_struct *task,
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struct pt_regs *regs)
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{
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unsigned long error = regs->ax;
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#ifdef CONFIG_IA32_EMULATION
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/*
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* TS_COMPAT is set for 32-bit syscall entries and then
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* remains set until we return to user mode.
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*/
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if (task->thread_info.status & (TS_COMPAT|TS_I386_REGS_POKED))
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/*
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* Sign-extend the value so (int)-EFOO becomes (long)-EFOO
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* and will match correctly in comparisons.
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*/
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error = (long) (int) error;
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#endif
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return IS_ERR_VALUE(error) ? error : 0;
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}
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static inline long syscall_get_return_value(struct task_struct *task,
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struct pt_regs *regs)
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{
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return regs->ax;
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}
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static inline void syscall_set_return_value(struct task_struct *task,
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struct pt_regs *regs,
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int error, long val)
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{
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regs->ax = (long) error ?: val;
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}
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#ifdef CONFIG_X86_32
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static inline void syscall_get_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned int i, unsigned int n,
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unsigned long *args)
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{
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BUG_ON(i + n > 6);
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memcpy(args, ®s->bx + i, n * sizeof(args[0]));
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}
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static inline void syscall_set_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned int i, unsigned int n,
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const unsigned long *args)
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{
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BUG_ON(i + n > 6);
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memcpy(®s->bx + i, args, n * sizeof(args[0]));
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}
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static inline int syscall_get_arch(void)
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{
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return AUDIT_ARCH_I386;
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}
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#else /* CONFIG_X86_64 */
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static inline void syscall_get_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned int i, unsigned int n,
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unsigned long *args)
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{
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# ifdef CONFIG_IA32_EMULATION
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if (task->thread_info.status & TS_COMPAT)
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switch (i) {
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case 0:
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if (!n--) break;
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*args++ = regs->bx;
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case 1:
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if (!n--) break;
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*args++ = regs->cx;
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case 2:
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if (!n--) break;
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*args++ = regs->dx;
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case 3:
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if (!n--) break;
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*args++ = regs->si;
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case 4:
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if (!n--) break;
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*args++ = regs->di;
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case 5:
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if (!n--) break;
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*args++ = regs->bp;
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case 6:
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if (!n--) break;
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default:
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BUG();
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break;
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}
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else
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# endif
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switch (i) {
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case 0:
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if (!n--) break;
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*args++ = regs->di;
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case 1:
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if (!n--) break;
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*args++ = regs->si;
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case 2:
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if (!n--) break;
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*args++ = regs->dx;
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case 3:
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if (!n--) break;
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*args++ = regs->r10;
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case 4:
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if (!n--) break;
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*args++ = regs->r8;
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case 5:
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if (!n--) break;
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*args++ = regs->r9;
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case 6:
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if (!n--) break;
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default:
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BUG();
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break;
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}
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}
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static inline void syscall_set_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned int i, unsigned int n,
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const unsigned long *args)
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{
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# ifdef CONFIG_IA32_EMULATION
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if (task->thread_info.status & TS_COMPAT)
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switch (i) {
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case 0:
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if (!n--) break;
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regs->bx = *args++;
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case 1:
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if (!n--) break;
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regs->cx = *args++;
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case 2:
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if (!n--) break;
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regs->dx = *args++;
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case 3:
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if (!n--) break;
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regs->si = *args++;
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case 4:
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if (!n--) break;
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regs->di = *args++;
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case 5:
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if (!n--) break;
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regs->bp = *args++;
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case 6:
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if (!n--) break;
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default:
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BUG();
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break;
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}
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else
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# endif
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switch (i) {
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case 0:
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if (!n--) break;
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regs->di = *args++;
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case 1:
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if (!n--) break;
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regs->si = *args++;
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case 2:
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if (!n--) break;
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regs->dx = *args++;
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case 3:
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if (!n--) break;
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regs->r10 = *args++;
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case 4:
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if (!n--) break;
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regs->r8 = *args++;
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case 5:
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if (!n--) break;
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regs->r9 = *args++;
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case 6:
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if (!n--) break;
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default:
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BUG();
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break;
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}
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}
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static inline int syscall_get_arch(void)
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{
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/* x32 tasks should be considered AUDIT_ARCH_X86_64. */
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return in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
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}
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#endif /* CONFIG_X86_32 */
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#endif /* _ASM_X86_SYSCALL_H */
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