path: root/arch/x86_64/kernel/entry.S

/*
 *  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>

	.code64

#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif	


.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 %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_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 4
	popf				# reset kernel eflags
	CFI_ADJUST_CFA_OFFSET -4
	call schedule_tail
	GET_THREAD_INFO(