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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>
 */

/*
 * 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.
 *
 * Some macro usage:
 * - CFI macros are used to generate dwarf2 unwind information for better
 * backtraces. They don't change any code.
 * - SAVE_ALL/RESTORE_ALL - Save/restore all registers
 * - SAVE_ARGS/RESTORE_ARGS - Save/restore registers that C functions modify.
 * There are unfortunately lots of special cases where some registers
 * not touched. The macro is a big mess that should be cleaned up.
 * - SAVE_REST/RESTORE_REST - Handle the registers not saved by SAVE_ARGS.
 * Gives a full stack frame.
 * - ENTRY/END Define functions in the symbol table.
 * - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack
 * frame that is otherwise undefined after a SYSCALL
 * - TRACE_IRQ_* - Trace hard interrupt state for lock debugging.
 * - errorentry/paranoidentry/zeroentry - Define exception entry points.
 */

#include <linux/linkage.h>
#include <asm/segment.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/irqflags.h>
#include <asm/paravirt.h>
#include <asm/ftrace.h>

/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
#include <linux/elf-em.h>
#define AUDIT_ARCH_X86_64	(EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
#define __AUDIT_ARCH_64BIT 0x80000000
#define __AUDIT_ARCH_LE	   0x40000000

	.code64

#ifdef CONFIG_FUNCTION_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(mcount)
	retq
END(mcount)

ENTRY(ftrace_caller)

	/* taken from glibc */
	subq $0x38, %rsp
	movq %rax, (%rsp)
	movq %rcx, 8(%rsp)
	movq %rdx, 16(%rsp)
	movq %rsi, 24(%rsp)
	movq %rdi, 32(%rsp)
	movq %r8, 40(%rsp)
	movq %r9, 48(%rsp)

	movq 0x38(%rsp), %rdi
	movq 8(%rbp), %rsi
	subq $MCOUNT_INSN_SIZE, %rdi

.globl ftrace_call
ftrace_call:
	call ftrace_stub

	movq 48(%rsp), %r9
	movq 40(%rsp), %r8
	movq 32(%rsp), %rdi
	movq 24(%rsp), %rsi
	movq 16(%rsp), %rdx
	movq 8(%rsp), %rcx
	movq (%rsp), %rax
	addq $0x38, %rsp

.globl ftrace_stub
ftrace_stub:
	retq
END(ftrace_caller)

#else /* ! CONFIG_DYNAMIC_FTRACE */
ENTRY(mcount)
	cmpq $ftrace_stub, ftrace_trace_function
	jnz trace
.globl ftrace_stub
ftrace_stub:
	retq

trace:
	/* taken from glibc */
	subq $0x38, %rsp
	movq %rax, (%rsp)
	movq %rcx, 8(%rsp)
	movq %rdx, 16(%rsp)
	movq %rsi, 24(%rsp)
	movq %rdi, 32(%rsp)
	movq %r8, 40(%rsp)
	movq %r9, 48(%rsp)

	movq 0x38(%rsp), %rdi
	movq 8(%rbp), %rsi
	subq $MCOUNT_INSN_SIZE, %rdi

	call   *ftrace_trace_function

	movq 48(%rsp), %r9
	movq 40(%rsp), %r8
	movq 32(%rsp), %rdi
	movq 24(%rsp), %rsi
	movq 16(%rsp), %rdx
	movq 8(%rsp), %rcx
	movq (%rsp), %rax
	addq $0x38, %rsp

	jmp ftrace_stub
END(mcount)
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_TRACER */

#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif

#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret64)
	swapgs
	sysretq
#endif /* CONFIG_PARAVIRT */


.macro TRACE_IRQS_IRETQ offset=ARGOFFSET
#ifdef CONFIG_TRACE_IRQFLAGS
	bt   $9,EFLAGS-\offset(%rsp)	/* interrupts off? */
	jnc  1f
	TRACE_IRQS_ON
1:
#endif
.endm

/*
 * 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	%gs:pda_oldrsp,\tmp
	movq  	\tmp,RSP(%rsp)
	movq    $__USER_DS,SS(%rsp)
	movq    $__USER_CS,CS(%rsp)
	movq 	$-1,RCX(%rsp)
	movq	R11(%rsp),\tmp  /* get eflags */
	movq	\tmp,EFLAGS(%rsp)
	.endm

	.macro RESTORE_TOP_OF_STACK tmp,offset=0
	movq   RSP-\offset(%rsp),\tmp
	movq   \tmp,%gs:pda_oldrsp
	movq   EFLAGS-\offset(%rsp),\tmp
	movq   \tmp,R11-\offset(%rsp)
	.endm

	.macro FAKE_STACK_FRAME child_rip
	/* push in order ss, rsp, eflags, cs, rip */
	xorl %eax, %eax
	pushq $__KERNEL_DS /* 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_SIGNAL_FRAME
	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
/*
 * A newly forked process directly context switches into this.
 */
/* rdi:	prev */
ENTRY(ret_from_fork)
	CFI_DEFAULT_STACK
	push kernel_eflags(%rip)
	CFI_ADJUST_CFA_OFFSET 8
	popf				# reset kernel eflags
	CFI_ADJUST_CFA_OFFSET -8
	call schedule_tail
	GET_THREAD_INFO(%rcx)
	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
	CFI_REMEMBER_STATE
	jnz rff_trace
rff_action:
	RESTORE_REST
	testl $3,CS-ARGOFFSET(%rsp)	# from kernel_thread?
	je   int_ret_from_sys_call
	testl $_TIF_IA32,TI_flags(%rcx)
	jnz  int_ret_from_sys_call
	RESTORE_TOP_OF_STACK %rdi,ARGOFFSET
	jmp ret_from_sys_call
	CFI_RESTORE_STATE
rff_trace:
	movq %rsp,%rdi
	call syscall_trace_leave
	GET_THREAD_INFO(%rcx)
	jmp rff_action
	CFI_ENDPROC
END(ret_from_fork)

/*
 * 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.
 *
 * When user can change the frames always force IRET. That is because
 * it deals with uncanonical addresses better. SYSRET has trouble
 * with them due to bugs in both AMD and Intel CPUs.
 */

ENTRY(system_call)
	CFI_STARTPROC	simple
	CFI_SIGNAL_FRAME
	CFI_DEF_CFA	rsp,PDA_STACKOFFSET
	CFI_REGISTER	rip,rcx
	/*CFI_REGISTER	rflags,r11*/
	SWAPGS_UNSAFE_STACK
	/*
	 * A hypervisor implementation might want to use a label
	 * after the swapgs, so that it can do the swapgs
	 * for the guest and jump here on syscall.
	 */
ENTRY(system_call_after_swapgs)

	movq	%rsp,%gs:pda_oldrsp
	movq	%gs:pda_kernelstack,%rsp
	/*
	 * No need to follow this irqs off/on section - it's straight
	 * and short:
	 */
	ENABLE_INTERRUPTS(CLBR_NONE)
	SAVE_ARGS 8,1
	movq  %rax,ORIG_RAX-ARGOFFSET(%rsp)
	movq  %rcx,RIP-ARGOFFSET(%rsp)
	CFI_REL_OFFSET rip,RIP-ARGOFFSET
	GET_THREAD_INFO(%rcx)
	testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%rcx)
	jnz tracesys
system_call_fastpath:
	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.
 */
ret_from_sys_call:
	movl $_TIF_ALLWORK_MASK,%edi
	/* edi:	flagmask */
sysret_check:
	LOCKDEP_SYS_EXIT
	GET_THREAD_INFO(%rcx)
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	movl TI_flags(%rcx),%edx
	andl %edi,%edx
	jnz  sysret_careful
	CFI_REMEMBER_STATE
	/*
	 * sysretq will re-enable interrupts:
	 */
	TRACE_IRQS_ON
	movq RIP-ARGOFFSET(%rsp),%rcx
	CFI_REGISTER	rip,rcx
	RESTORE_ARGS 0,-ARG_SKIP,1
	/*CFI_REGISTER	rflags,r11*/
	movq	%gs:pda_oldrsp, %rsp
	USERGS_SYSRET64

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

	/* Handle a signal */
sysret_signal:
	TRACE_IRQS_ON
	ENABLE_INTERRUPTS(CLBR_NONE)
#ifdef CONFIG_AUDITSYSCALL
	bt $TIF_SYSCALL_AUDIT,%edx
	jc sysret_audit
#endif
	/* 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
	movl $_TIF_WORK_MASK,%edi
	/* Use IRET because user could have changed frame. This
	   works because ptregscall_common has called FIXUP_TOP_OF_STACK. */
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	jmp int_with_check

badsys:
	movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
	jmp ret_from_sys_call

#ifdef CONFIG_AUDITSYSCALL
	/*
	 * Fast path for syscall audit without full syscall trace.
	 * We just call audit_syscall_entry() directly, and then
	 * jump back to the normal fast path.
	 */
auditsys:
	movq %r10,%r9			/* 6th arg: 4th syscall arg */
	movq %rdx,%r8			/* 5th arg: 3rd syscall arg */
	movq %rsi,%rcx			/* 4th arg: 2nd syscall arg */
	movq %rdi,%rdx			/* 3rd arg: 1st syscall arg */
	movq %rax,%rsi			/* 2nd arg: syscall number */
	movl $AUDIT_ARCH_X86_64,%edi	/* 1st arg: audit arch */
	call audit_syscall_entry
	LOAD_ARGS 0		/* reload call-clobbered registers */
	jmp system_call_fastpath

	/*
	 * Return fast path for syscall audit.  Call audit_syscall_exit()
	 * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
	 * masked off.
	 */
sysret_audit:
	movq %rax,%rsi		/* second arg, syscall return value */
	cmpq $0,%rax		/* is it < 0? */
	setl %al		/* 1 if so, 0 if not */
	movzbl %al,%edi		/* zero-extend that into %edi */
	inc %edi /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */
	call audit_syscall_exit
	movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
	jmp sysret_check
#endif	/* CONFIG_AUDITSYSCALL */

	/* Do syscall tracing */
tracesys:
#ifdef CONFIG_AUDITSYSCALL
	testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
	jz auditsys
#endif
	SAVE_REST
	movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
	FIXUP_TOP_OF_STACK %rdi
	movq %rsp,%rdi
	call syscall_trace_enter
	/*
	 * Reload arg registers from stack in case ptrace changed them.
	 * We don't reload %rax because syscall_trace_enter() returned
	 * the value it wants us to use in the table lookup.
	 */
	LOAD_ARGS ARGOFFSET, 1
	RESTORE_REST
	cmpq $__NR_syscall_max,%rax
	ja   int_ret_from_sys_call	/* RAX(%rsp) set to -ENOSYS above */
	movq %r10,%rcx	/* fixup for C */
	call *sys_call_table(,%rax,8)
	movq %rax,RAX-ARGOFFSET(%rsp)
	/* Use IRET because user could have changed frame */

/*
 * Syscall return path ending with IRET.
 * Has correct top of stack, but partial stack frame.
 */
	.globl int_ret_from_sys_call
	.globl int_with_check
int_ret_from_sys_call:
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	testl $3,CS-ARGOFFSET(%rsp)
	je retint_restore_args
	movl $_TIF_ALLWORK_MASK,%edi
	/* edi:	mask to check */
int_with_check:
	LOCKDEP_SYS_EXIT_IRQ
	GET_THREAD_INFO(%rcx)
	movl TI_flags(%rcx),%edx
	andl %edi,%edx
	jnz   int_careful
	andl    $~TS_COMPAT,TI_status(%rcx)
	jmp   retint_swapgs

	/* Either reschedule or signal or syscall exit tracking needed. */
	/* First do a reschedule test. */
	/* edx:	work, edi: workmask */
int_careful:
	bt $TIF_NEED_RESCHED,%edx
	jnc  int_very_careful
	TRACE_IRQS_ON
	ENABLE_INTERRUPTS(CLBR_NONE)
	pushq %rdi
	CFI_ADJUST_CFA_OFFSET 8
	call schedule
	popq %rdi
	CFI_ADJUST_CFA_OFFSET -8
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	jmp int_with_check

	/* handle signals and tracing -- both require a full stack frame */
int_very_careful:
	TRACE_IRQS_ON
	ENABLE_INTERRUPTS(CLBR_NONE)
	SAVE_REST
	/* Check for syscall exit trace */
	testl $_TIF_WORK_SYSCALL_EXIT,%edx
	jz int_signal
	pushq %rdi
	CFI_ADJUST_CFA_OFFSET 8
	leaq 8(%rsp),%rdi	# &ptregs -> arg1
	call syscall_trace_leave
	popq %rdi
	CFI_ADJUST_CFA_OFFSET -8
	andl $~(_TIF_WORK_SYSCALL_EXIT|_TIF_SYSCALL_EMU),%edi
	jmp int_restore_rest

int_signal:
	testl $_TIF_DO_NOTIFY_MASK,%edx
	jz 1f
	movq %rsp,%rdi		# &ptregs -> arg1
	xorl %esi,%esi		# oldset -> arg2
	call do_notify_resume
1:	movl $_TIF_WORK_MASK,%edi
int_restore_rest:
	RESTORE_REST
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	jmp int_with_check
	CFI_ENDPROC
END(system_call)

/*
 * Certain special system calls that need to save a complete full stack frame.
 */

	.macro PTREGSCALL label,func,arg
	.globl \label
\label:
	leaq	\func(%rip),%rax
	leaq    -ARGOFFSET+8(%rsp),\arg /* 8 for return address */
	jmp	ptregscall_common
END(\label)
	.endm

	CFI_STARTPROC

	PTREGSCALL stub_clone, sys_clone, %r8
	PTREGSCALL stub_fork, sys_fork, %rdi
	PTREGSCALL stub_vfork, sys_vfork, %rdi
	PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx
	PTREGSCALL stub_iopl, sys_iopl, %rsi

ENTRY(ptregscall_common)
	popq %r11
	CFI_ADJUST_CFA_OFFSET -8
	CFI_REGISTER rip, r11
	SAVE_REST
	movq %r11, %r15
	CFI_REGISTER rip, r15
	FIXUP_TOP_OF_STACK %r11
	call *%rax
	RESTORE_TOP_OF_STACK %r11
	movq %r15, %r11
	CFI_REGISTER rip, r11
	RESTORE_REST
	pushq %r11
	CFI_ADJUST_CFA_OFFSET 8
	CFI_REL_OFFSET rip, 0
	ret
	CFI_ENDPROC
END(ptregscall_common)

ENTRY(stub_execve)
	CFI_STARTPROC
	popq %r11
	CFI_ADJUST_CFA_OFFSET -8
	CFI_REGISTER rip, r11
	SAVE_REST
	FIXUP_TOP_OF_STACK %r11
	movq %rsp, %rcx
	call sys_execve
	RESTORE_TOP_OF_STACK %r11
	movq %rax,RAX(%rsp)
	RESTORE_REST
	jmp int_ret_from_sys_call
	CFI_ENDPROC
END(stub_execve)

/*
 * sigreturn is special because it needs to restore all registers on return.
 * This cannot be done with SYSRET, so use the IRET return path instead.
 */
ENTRY(stub_rt_sigreturn)
	CFI_STARTPROC
	addq $8, %rsp
	CFI_ADJUST_CFA_OFFSET	-8
	SAVE_REST
	movq %rsp,%rdi
	FIXUP_TOP_OF_STACK %r11
	call sys_rt_sigreturn
	movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
	RESTORE_REST
	jmp int_ret_from_sys_call
	CFI_ENDPROC
END(stub_rt_sigreturn)

/*
 * initial frame state for interrupts and exceptions
 */
	.macro _frame ref
	CFI_STARTPROC simple
	CFI_SIGNAL_FRAME
	CFI_DEF_CFA rsp,SS+8-\ref
	/*CFI_REL_OFFSET ss,SS-\ref*/
	CFI_REL_OFFSET rsp,RSP-\ref
	/*CFI_REL_OFFSET rflags,EFLAGS-\ref*/
	/*CFI_REL_OFFSET cs,CS-\ref*/
	CFI_REL_OFFSET rip,RIP-\ref
	.endm

/* initial frame state for interrupts (and exceptions without error code) */