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/*
 *  linux/arch/x86_64/entry.S
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002  Andi Kleen SuSE Labs
 *  Copyright (C) 2000  Pavel Machek <pavel@suse.cz>
 * 
 *  $Id$
 *
 *  Jun Nakajima <jun.nakajima@intel.com>
 *  Asit Mallick <asit.k.mallick@intel.com>
 *      Modified for Xen
 */

/*
 * entry.S contains the system-call and fault low-level handling routines.
 *
 * NOTE: This code handles signal-recognition, which happens every time
 * after an interrupt and after each system call.
 * 
 * Normal syscalls and interrupts don't save a full stack frame, this is 
 * only done for syscall tracing, signals or fork/exec et.al.
 * 
 * A note on terminology:	 
 * - top of stack: Architecture defined interrupt frame from SS to RIP 
 * at the top of the kernel process stack.	
 * - partial stack frame: partially saved registers upto R11.
 * - full stack frame: Like partial stack frame, but all register saved. 
 *	
 * TODO:	 
 * - schedule it carefully for the final hardware.
 */

#define ASSEMBLY 1
#include <linux/config.h>
#ifdef CONFIG_DEBUG_INFO
#undef CONFIG_DEBUG_INFO
#endif
#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/smp.h>
#include <asm/cache.h>
#include <asm/errno.h>
#include <asm/dwarf2.h>
#include <asm/calling.h>
#include <asm/asm-offsets.h>
#include <asm/msr.h>
#include <asm/unistd.h>
#include <asm/thread_info.h>
#include <asm/hw_irq.h>
#include <asm/page.h>
#include <asm/errno.h>
#include <xen/interface/arch-x86_64.h>
#include <xen/interface/features.h>

#include "irq_vectors.h"

#include "xen_entry.S"
	
	.code64

#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif	

NMI_MASK = 0x80000000
	
/*
 * C code is not supposed to know about undefined top of stack. Every time 
 * a C function with an pt_regs argument is called from the SYSCALL based 
 * fast path FIXUP_TOP_OF_STACK is needed.
 * RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs
 * manipulation.
 */        	
		
	/* %rsp:at FRAMEEND */ 
	.macro FIXUP_TOP_OF_STACK tmp
	movq    $__USER_CS,CS(%rsp)
	movq 	$-1,RCX(%rsp)
	.endm

	.macro RESTORE_TOP_OF_STACK tmp,offset=0
	.endm

	.macro FAKE_STACK_FRAME child_rip
	/* push in order ss, rsp, eflags, cs, rip */
	xorl %eax, %eax
	pushq %rax /* ss */
	CFI_ADJUST_CFA_OFFSET	8
	/*CFI_REL_OFFSET	ss,0*/
	pushq %rax /* rsp */
	CFI_ADJUST_CFA_OFFSET	8
	CFI_REL_OFFSET	rsp,0
	pushq $(1<<9) /* eflags - interrupts on */
	CFI_ADJUST_CFA_OFFSET	8
	/*CFI_REL_OFFSET	rflags,0*/
	pushq $__KERNEL_CS /* cs */
	CFI_ADJUST_CFA_OFFSET	8
	/*CFI_REL_OFFSET	cs,0*/
	pushq \child_rip /* rip */
	CFI_ADJUST_CFA_OFFSET	8
	CFI_REL_OFFSET	rip,0
	pushq	%rax /* orig rax */
	CFI_ADJUST_CFA_OFFSET	8
	.endm

	.macro UNFAKE_STACK_FRAME
	addq $8*6, %rsp
	CFI_ADJUST_CFA_OFFSET	-(6*8)
	.endm

	.macro	CFI_DEFAULT_STACK start=1
	.if \start
	CFI_STARTPROC	simple
	CFI_DEF_CFA	rsp,SS+8
	.else
	CFI_DEF_CFA_OFFSET SS+8
	.endif
	CFI_REL_OFFSET	r15,R15
	CFI_REL_OFFSET	r14,R14
	CFI_REL_OFFSET	r13,R13
	CFI_REL_OFFSET	r12,R12
	CFI_REL_OFFSET	rbp,RBP
	CFI_REL_OFFSET	rbx,RBX
	CFI_REL_OFFSET	r11,R11
	CFI_REL_OFFSET	r10,R10
	CFI_REL_OFFSET	r9,R9
	CFI_REL_OFFSET	r8,R8
	CFI_REL_OFFSET	rax,RAX
	CFI_REL_OFFSET	rcx,RCX
	CFI_REL_OFFSET	rdx,RDX
	CFI_REL_OFFSET	rsi,RSI
	CFI_REL_OFFSET	rdi,RDI
	CFI_REL_OFFSET	rip,RIP
	/*CFI_REL_OFFSET	cs,CS*/
	/*CFI_REL_OFFSET	rflags,EFLAGS*/
	CFI_REL_OFFSET	rsp,RSP
	/*CFI_REL_OFFSET	ss,SS*/
	.endm

        /*
         * Must be consistent with the definition in arch-x86_64.h:    
         *     struct iret_context {
         *        u64 rax, r11, rcx, flags, rip, cs, rflags, rsp, ss;
         *     };
         * #define VGCF_IN_SYSCALL (1<<8) 
         */
	.macro HYPERVISOR_IRET flag
	testb $3,1*8(%rsp)
	jnz   2f
	testl $NMI_MASK,2*8(%rsp)
	jnz   2f

	testb $1,(xen_features+XENFEAT_supervisor_mode_kernel)
	jnz   1f

	/* Direct iret to kernel space. Correct CS and SS. */
	orb   $3,1*8(%rsp)
	orb   $3,4*8(%rsp)
1:	iretq

2:	/* Slow iret via hypervisor. */
	andl  $~NMI_MASK, 16(%rsp)
	pushq $\flag
	jmp  hypercall_page + (__HYPERVISOR_iret * 32)
	.endm

        .macro SWITCH_TO_KERNEL ssoff,adjust=0
	jc  1f
	orb  $1,\ssoff-\adjust+4(%rsp)
1:
        .endm

/*
 * A newly forked process directly context switches into this.
 */ 	
/* rdi:	prev */	
ENTRY(ret_from_fork)
	CFI_DEFAULT_STACK
	call schedule_tail
	GET_THREAD_INFO(%rcx)
	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%rcx)
	jnz rff_trace
rff_action:	
	RESTORE_REST
	testl $3,CS-ARGOFFSET(%rsp)	# from kernel_thread?
	je   int_ret_from_sys_call
	testl $_TIF_IA32,threadinfo_flags(%rcx)
	jnz  int_ret_from_sys_call
	RESTORE_TOP_OF_STACK %rdi,ARGOFFSET
	jmp ret_from_sys_call
rff_trace:
	movq %rsp,%rdi
	call syscall_trace_leave
	GET_THREAD_INFO(%rcx)	
	jmp rff_action
	CFI_ENDPROC

/*
 * System call entry. Upto 6 arguments in registers are supported.
 *
 * SYSCALL does not save anything on the stack and does not change the
 * stack pointer.
 */
		
/*
 * Register setup:	
 * rax  system call number
 * rdi  arg0
 * rcx  return address for syscall/sysret, C arg3 
 * rsi  arg1
 * rdx  arg2	
 * r10  arg3 	(--> moved to rcx for C)
 * r8   arg4
 * r9   arg5
 * r11  eflags for syscall/sysret, temporary for C
 * r12-r15,rbp,rbx saved by C code, not touched. 		
 * 
 * Interrupts are off on entry.
 * Only called from user space.
 *
 * XXX	if we had a free scratch register we could save the RSP into the stack frame
 *      and report it properly in ps. Unfortunately we haven't.
 */ 			 		

ENTRY(system_call)
	CFI_STARTPROC	simple
	CFI_DEF_CFA	rsp,0
	CFI_REGISTER	rip,rcx
	/*CFI_REGISTER	rflags,r11*/
	SAVE_ARGS -8,0
	movq  %rax,ORIG_RAX-ARGOFFSET(%rsp) 
        XEN_UNBLOCK_EVENTS(%r11)        
	GET_THREAD_INFO(%rcx)
	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%rcx)
	CFI_REMEMBER_STATE
	jnz tracesys
	cmpq $__NR_syscall_max,%rax
	ja badsys
	movq %r10,%rcx
	call *sys_call_table(,%rax,8)  # XXX:	 rip relative
	movq %rax,RAX-ARGOFFSET(%rsp)
/*
 * Syscall return path ending with SYSRET (fast path)
 * Has incomplete stack frame and undefined top of stack. 
 */		
	.globl ret_from_sys_call
ret_from_sys_call:
	movl $_TIF_ALLWORK_MASK,%edi
	/* edi:	flagmask */
sysret_check:		
	GET_THREAD_INFO(%rcx)
        XEN_BLOCK_EVENTS(%rsi)        
	movl threadinfo_flags(%rcx),%edx
	andl %edi,%edx
	CFI_REMEMBER_STATE
	jnz  sysret_careful 
        XEN_UNBLOCK_EVENTS(%rsi)                
	CFI_REGISTER	rip,rcx
	RESTORE_ARGS 0,8,0
	/*CFI_REGISTER	rflags,r11*/
        HYPERVISOR_IRET VGCF_IN_SYSCALL

	/* Handle reschedules */
	/* edx:	work, edi: workmask */	
sysret_careful:
	CFI_RESTORE_STATE
	bt $TIF_NEED_RESCHED,%edx
	jnc sysret_signal
        XEN_BLOCK_EVENTS(%rsi)        
	pushq %rdi
	CFI_ADJUST_CFA_OFFSET 8
	call schedule
	popq  %rdi
	CFI_ADJUST_CFA_OFFSET -8
	jmp sysret_check

	/* Handle a signal */ 
sysret_signal:
/*	sti */
        XEN_UNBLOCK_EVENTS(%rsi)        
	testl $(_TIF_SIGPENDING|_TIF_NOTIFY_RESUME|_TIF_SINGLESTEP),%edx
	jz    1f

	/* Really a signal */
	/* edx:	work flags (arg3) */
	leaq do_notify_resume(%rip),%rax
	leaq -ARGOFFSET(%rsp),%rdi # &pt_regs -> arg1
	xorl %esi,%esi # oldset -> arg2
	call ptregscall_common
1:	movl $_TIF_NEED_RESCHED,%edi
	jmp sysret_check
	
badsys:
	movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
	jmp ret_from_sys_call

	/* Do syscall tracing */
tracesys:			 
	CFI_RESTORE_STATE
	SAVE_REST
	movq $-ENOSYS,RAX(%rsp)
	FIXUP_TOP_OF_STACK %rdi
	movq %rsp,%rdi
	call syscall_trace_enter
	LOAD_ARGS ARGOFFSET  /* reload args from stack in case ptrace changed it */
	RESTORE_REST
	cmpq $__NR_syscall_max,%rax
	ja  1f
	movq %r10,%rcx	/* fixup for C */