原创作品转载请注明出处《Linux内核分析》MOOC课程http://mooc.study.163.com/course/USTC-1000029000
如果我写的不好或者有误的地方请留言
题目自拟，内容围绕系统调用system_call的处理过程进行；
博客内容中需要仔细分析system_call对应的汇编代码的工作过程，特别注意系统调用返回iret之前的进程调度时机等。
总结部分需要阐明自己对“系统调用处理过程”的理解，进一步推广到一般的中断处理过程。
实验报告：
1.将myfork()和myasmfork()函数写入menu/text.c中
2.重新编译make rootfs
3.运行myfork和myasmfork
4.下断点sys_fork
5.查看上下文
6.单步调试
在sys_fork设置断点
定位到kernel/fork.c 1704行
n：我们可以看到sys_fork的执行流程：只有do_fork
我们进入do_fork
s：单步进入函数do_fork
通过单步调试
主要经历了以下函数
up_task_struct
alloc_task_struct_node
kmem_cache_alloc_node
alloc_kmem_pages_node
alloc_thread_info_node
clear_tsk_need_resched
clear_tsk_thread_flag
set_task_stack_end_magic
rt_mutex_init_task
copy_process
rt_mutex_init_task
最后创建了新的进程
pid = 868
7.分析entry_32.S
其中entry_32.S如下：
/*
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/ /*
* entry.S contains the system-call and fault low-level handling routines.
* This also contains the timer-interrupt handler, as well as all interrupts
* and faults that can result in a task-switch.
*
* NOTE: This code handles signal-recognition, which happens every time
* after a timer-interrupt and after each system call.
*
* I changed all the .align's to 4 (16 byte alignment), as that's faster
* on a 486.
*
* Stack layout in 'syscall_exit':
* ptrace needs to have all regs on the stack.
* if the order here is changed, it needs to be
* updated in fork.c:copy_process, signal.c:do_signal,
* ptrace.c and ptrace.h
*
* 0(%esp) - %ebx
* 4(%esp) - %ecx
* 8(%esp) - %edx
* C(%esp) - %esi
* 10(%esp) - %edi
* 14(%esp) - %ebp
* 18(%esp) - %eax
* 1C(%esp) - %ds
* 20(%esp) - %es
* 24(%esp) - %fs
* 28(%esp) - %gs saved iff !CONFIG_X86_32_LAZY_GS
* 2C(%esp) - orig_eax
* 30(%esp) - %eip
* 34(%esp) - %cs
* 38(%esp) - %eflags
* 3C(%esp) - %oldesp
* 40(%esp) - %oldss
*
* "current" is in register %ebx during any slow entries.
*/ #include <linux/linkage.h>
#include <linux/err.h>
#include <asm/thread_info.h>
#include <asm/irqflags.h>
#include <asm/errno.h>
#include <asm/segment.h>
#include <asm/smp.h>
#include <asm/page_types.h>
#include <asm/percpu.h>
#include <asm/dwarf2.h>
#include <asm/processor-flags.h>
#include <asm/ftrace.h>
#include <asm/irq_vectors.h>
#include <asm/cpufeature.h>
#include <asm/alternative-asm.h>
#include <asm/asm.h>
#include <asm/smap.h> /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
#include <linux/elf-em.h>
#define AUDIT_ARCH_I386 (EM_386|__AUDIT_ARCH_LE)
#define __AUDIT_ARCH_LE 0x40000000 #ifndef CONFIG_AUDITSYSCALL
#define sysenter_audit syscall_trace_entry
#define sysexit_audit syscall_exit_work
#endif .section .entry.text, "ax" /*
* We use macros for low-level operations which need to be overridden
* for paravirtualization. The following will never clobber any registers:
* INTERRUPT_RETURN (aka. "iret")
* GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")
* ENABLE_INTERRUPTS_SYSEXIT (aka "sti; sysexit").
*
* For DISABLE_INTERRUPTS/ENABLE_INTERRUPTS (aka "cli"/"sti"), you must
* specify what registers can be overwritten (CLBR_NONE, CLBR_EAX/EDX/ECX/ANY).
* Allowing a register to be clobbered can shrink the paravirt replacement
* enough to patch inline, increasing performance.
*/ #ifdef CONFIG_PREEMPT
#define preempt_stop(clobbers) DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF
#else
#define preempt_stop(clobbers)
#define resume_kernel restore_all
#endif .macro TRACE_IRQS_IRET
#ifdef CONFIG_TRACE_IRQFLAGS
testl $X86_EFLAGS_IF,PT_EFLAGS(%esp) # interrupts off?
jz 1f
TRACE_IRQS_ON
:
#endif
.endm /*
* User gs save/restore
*
* %gs is used for userland TLS and kernel only uses it for stack
* canary which is required to be at %gs:20 by gcc. Read the comment
* at the top of stackprotector.h for more info.
*
* Local labels 98 and 99 are used.
*/
#ifdef CONFIG_X86_32_LAZY_GS /* unfortunately push/pop can't be no-op */
.macro PUSH_GS
pushl_cfi $
.endm
.macro POP_GS pop=
addl $( + \pop), %esp
CFI_ADJUST_CFA_OFFSET -( + \pop)
.endm
.macro POP_GS_EX
.endm /* all the rest are no-op */
.macro PTGS_TO_GS
.endm
.macro PTGS_TO_GS_EX
.endm
.macro GS_TO_REG reg
.endm
.macro REG_TO_PTGS reg
.endm
.macro SET_KERNEL_GS reg
.endm #else /* CONFIG_X86_32_LAZY_GS */ .macro PUSH_GS
pushl_cfi %gs
/*CFI_REL_OFFSET gs, 0*/
.endm .macro POP_GS pop=
: popl_cfi %gs
/*CFI_RESTORE gs*/
.if \pop <>
add $\pop, %esp
CFI_ADJUST_CFA_OFFSET -\pop
.endif
.endm
.macro POP_GS_EX
.pushsection .fixup, "ax"
: movl $, (%esp)
jmp 98b
.popsection
_ASM_EXTABLE(98b,99b)
.endm .macro PTGS_TO_GS
: mov PT_GS(%esp), %gs
.endm
.macro PTGS_TO_GS_EX
.pushsection .fixup, "ax"
: movl $, PT_GS(%esp)
jmp 98b
.popsection
_ASM_EXTABLE(98b,99b)
.endm .macro GS_TO_REG reg
movl %gs, \reg
/*CFI_REGISTER gs, \reg*/
.endm
.macro REG_TO_PTGS reg
movl \reg, PT_GS(%esp)
/*CFI_REL_OFFSET gs, PT_GS*/
.endm
.macro SET_KERNEL_GS reg
movl $(__KERNEL_STACK_CANARY), \reg
movl \reg, %gs
.endm #endif /* CONFIG_X86_32_LAZY_GS */ .macro SAVE_ALL
cld
PUSH_GS
pushl_cfi %fs
/*CFI_REL_OFFSET fs, 0;*/
pushl_cfi %es
/*CFI_REL_OFFSET es, 0;*/
pushl_cfi %ds
/*CFI_REL_OFFSET ds, 0;*/
pushl_cfi %eax
CFI_REL_OFFSET eax,
pushl_cfi %ebp
CFI_REL_OFFSET ebp,
pushl_cfi %edi
CFI_REL_OFFSET edi,
pushl_cfi %esi
CFI_REL_OFFSET esi,
pushl_cfi %edx
CFI_REL_OFFSET edx,
pushl_cfi %ecx
CFI_REL_OFFSET ecx,
pushl_cfi %ebx
CFI_REL_OFFSET ebx,
movl $(__USER_DS), %edx
movl %edx, %ds
movl %edx, %es
movl $(__KERNEL_PERCPU), %edx
movl %edx, %fs
SET_KERNEL_GS %edx
.endm .macro RESTORE_INT_REGS
popl_cfi %ebx
CFI_RESTORE ebx
popl_cfi %ecx
CFI_RESTORE ecx
popl_cfi %edx
CFI_RESTORE edx
popl_cfi %esi
CFI_RESTORE esi
popl_cfi %edi
CFI_RESTORE edi
popl_cfi %ebp
CFI_RESTORE ebp
popl_cfi %eax
CFI_RESTORE eax
.endm .macro RESTORE_REGS pop=
RESTORE_INT_REGS
: popl_cfi %ds
/*CFI_RESTORE ds;*/
: popl_cfi %es
/*CFI_RESTORE es;*/
: popl_cfi %fs
/*CFI_RESTORE fs;*/
POP_GS \pop
.pushsection .fixup, "ax"
: movl $, (%esp)
jmp 1b
: movl $, (%esp)
jmp 2b
: movl $, (%esp)
jmp 3b
.popsection
_ASM_EXTABLE(1b,4b)
_ASM_EXTABLE(2b,5b)
_ASM_EXTABLE(3b,6b)
POP_GS_EX
.endm .macro RING0_INT_FRAME
CFI_STARTPROC simple
CFI_SIGNAL_FRAME
CFI_DEF_CFA esp, *
/*CFI_OFFSET cs, -2*4;*/
CFI_OFFSET eip, -*
.endm .macro RING0_EC_FRAME
CFI_STARTPROC simple
CFI_SIGNAL_FRAME
CFI_DEF_CFA esp, *
/*CFI_OFFSET cs, -2*4;*/
CFI_OFFSET eip, -*
.endm .macro RING0_PTREGS_FRAME
CFI_STARTPROC simple
CFI_SIGNAL_FRAME
CFI_DEF_CFA esp, PT_OLDESP-PT_EBX
/*CFI_OFFSET cs, PT_CS-PT_OLDESP;*/
CFI_OFFSET eip, PT_EIP-PT_OLDESP
/*CFI_OFFSET es, PT_ES-PT_OLDESP;*/
/*CFI_OFFSET ds, PT_DS-PT_OLDESP;*/
CFI_OFFSET eax, PT_EAX-PT_OLDESP
CFI_OFFSET ebp, PT_EBP-PT_OLDESP
CFI_OFFSET edi, PT_EDI-PT_OLDESP
CFI_OFFSET esi, PT_ESI-PT_OLDESP
CFI_OFFSET edx, PT_EDX-PT_OLDESP
CFI_OFFSET ecx, PT_ECX-PT_OLDESP
CFI_OFFSET ebx, PT_EBX-PT_OLDESP
.endm ENTRY(ret_from_fork)
CFI_STARTPROC
pushl_cfi %eax
call schedule_tail
GET_THREAD_INFO(%ebp)
popl_cfi %eax
pushl_cfi $0x0202 # Reset kernel eflags
popfl_cfi
jmp syscall_exit
CFI_ENDPROC
END(ret_from_fork) ENTRY(ret_from_kernel_thread)
CFI_STARTPROC
pushl_cfi %eax
call schedule_tail
GET_THREAD_INFO(%ebp)
popl_cfi %eax
pushl_cfi $0x0202 # Reset kernel eflags
popfl_cfi
movl PT_EBP(%esp),%eax
call *PT_EBX(%esp)
movl $,PT_EAX(%esp)
jmp syscall_exit
CFI_ENDPROC
ENDPROC(ret_from_kernel_thread) /*
* Return to user mode is not as complex as all this looks,
* but we want the default path for a system call return to
* go as quickly as possible which is why some of this is
* less clear than it otherwise should be.
*/ # userspace resumption stub bypassing syscall exit tracing
ALIGN
RING0_PTREGS_FRAME
ret_from_exception:
preempt_stop(CLBR_ANY)
ret_from_intr:
GET_THREAD_INFO(%ebp)
#ifdef CONFIG_VM86
movl PT_EFLAGS(%esp), %eax # mix EFLAGS and CS
movb PT_CS(%esp), %al
andl $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax
#else
/*
* We can be coming here from child spawned by kernel_thread().
*/
movl PT_CS(%esp), %eax
andl $SEGMENT_RPL_MASK, %eax
#endif
cmpl $USER_RPL, %eax
jb resume_kernel # not returning to v8086 or userspace ENTRY(resume_userspace)
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
andl $_TIF_WORK_MASK, %ecx # is there any work to be done on
# int/exception return?
jne work_pending
jmp restore_all
END(ret_from_exception) #ifdef CONFIG_PREEMPT
ENTRY(resume_kernel)
DISABLE_INTERRUPTS(CLBR_ANY)
need_resched:
cmpl $,PER_CPU_VAR(__preempt_count)
jnz restore_all
testl $X86_EFLAGS_IF,PT_EFLAGS(%esp) # interrupts off (exception path) ?
jz restore_all
call preempt_schedule_irq
jmp need_resched
END(resume_kernel)
#endif
CFI_ENDPROC /* SYSENTER_RETURN points to after the "sysenter" instruction in
the vsyscall page. See vsyscall-sysentry.S, which defines the symbol. */ # sysenter call handler stub
ENTRY(ia32_sysenter_target)
CFI_STARTPROC simple
CFI_SIGNAL_FRAME
CFI_DEF_CFA esp,
CFI_REGISTER esp, ebp
movl TSS_sysenter_sp0(%esp),%esp
sysenter_past_esp:
/*
* Interrupts are disabled here, but we can't trace it until
* enough kernel state to call TRACE_IRQS_OFF can be called - but
* we immediately enable interrupts at that point anyway.
*/
pushl_cfi $__USER_DS
/*CFI_REL_OFFSET ss, 0*/
pushl_cfi %ebp
CFI_REL_OFFSET esp,
pushfl_cfi
orl $X86_EFLAGS_IF, (%esp)
pushl_cfi $__USER_CS
/*CFI_REL_OFFSET cs, 0*/
/*
* Push current_thread_info()->sysenter_return to the stack.
* A tiny bit of offset fixup is necessary - 4*4 means the 4 words
* pushed above; +8 corresponds to copy_thread's esp0 setting.
*/
pushl_cfi ((TI_sysenter_return)-THREAD_SIZE++*)(%esp)
CFI_REL_OFFSET eip, pushl_cfi %eax
SAVE_ALL
ENABLE_INTERRUPTS(CLBR_NONE) /*
* Load the potential sixth argument from user stack.
* Careful about security.
*/
cmpl $__PAGE_OFFSET-,%ebp
jae syscall_fault
ASM_STAC
: movl (%ebp),%ebp
ASM_CLAC
movl %ebp,PT_EBP(%esp)
_ASM_EXTABLE(1b,syscall_fault) GET_THREAD_INFO(%ebp) testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
jnz sysenter_audit
sysenter_do_call:
cmpl $(NR_syscalls), %eax
jae sysenter_badsys
call *sys_call_table(,%eax,)
sysenter_after_call:
movl %eax,PT_EAX(%esp)
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testl $_TIF_ALLWORK_MASK, %ecx
jne sysexit_audit
sysenter_exit:
/* if something modifies registers it must also disable sysexit */
movl PT_EIP(%esp), %edx
movl PT_OLDESP(%esp), %ecx
xorl %ebp,%ebp
TRACE_IRQS_ON
: mov PT_FS(%esp), %fs
PTGS_TO_GS
ENABLE_INTERRUPTS_SYSEXIT #ifdef CONFIG_AUDITSYSCALL
sysenter_audit:
testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
jnz syscall_trace_entry
/* movl PT_EAX(%esp), %eax already set, syscall number: 1st arg to audit */
movl PT_EBX(%esp), %edx /* ebx/a0: 2nd arg to audit */
/* movl PT_ECX(%esp), %ecx already set, a1: 3nd arg to audit */
pushl_cfi PT_ESI(%esp) /* a3: 5th arg */
pushl_cfi PT_EDX+(%esp) /* a2: 4th arg */
call __audit_syscall_entry
popl_cfi %ecx /* get that remapped edx off the stack */
popl_cfi %ecx /* get that remapped esi off the stack */
movl PT_EAX(%esp),%eax /* reload syscall number */
jmp sysenter_do_call sysexit_audit:
testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %ecx
jne syscall_exit_work
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_ANY)
movl %eax,%edx /* second arg, syscall return value */
cmpl $-MAX_ERRNO,%eax /* is it an error ? */
setbe %al /* 1 if so, 0 if not */
movzbl %al,%eax /* zero-extend that */
call __audit_syscall_exit
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %ecx
jne syscall_exit_work
movl PT_EAX(%esp),%eax /* reload syscall return value */
jmp sysenter_exit
#endif CFI_ENDPROC
.pushsection .fixup,"ax"
: movl $,PT_FS(%esp)
jmp 1b
.popsection
_ASM_EXTABLE(1b,2b)
PTGS_TO_GS_EX
ENDPROC(ia32_sysenter_target) # system call handler stub
ENTRY(system_call)
RING0_INT_FRAME # can't unwind into user space anyway
ASM_CLAC
pushl_cfi %eax # save orig_eax
SAVE_ALL
GET_THREAD_INFO(%ebp)
# system call tracing in operation / emulation
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
jnz syscall_trace_entry
cmpl $(NR_syscalls), %eax
jae syscall_badsys
syscall_call:
call *sys_call_table(,%eax,)
syscall_after_call:
movl %eax,PT_EAX(%esp) # store the return value
syscall_exit:
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testl $_TIF_ALLWORK_MASK, %ecx # current->work
jne syscall_exit_work restore_all:
TRACE_IRQS_IRET
restore_all_notrace:
#ifdef CONFIG_X86_ESPFIX32
movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
# Warning: PT_OLDSS(%esp) contains the wrong/random values if we
# are returning to the kernel.
# See comments in process.c:copy_thread() for details.
movb PT_OLDSS(%esp), %ah
movb PT_CS(%esp), %al
andl $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << ) | SEGMENT_RPL_MASK), %eax
cmpl $((SEGMENT_LDT << ) | USER_RPL), %eax
CFI_REMEMBER_STATE
je ldt_ss # returning to user-space with LDT SS
#endif
restore_nocheck:
RESTORE_REGS # skip orig_eax/error_code
irq_return:
INTERRUPT_RETURN
.section .fixup,"ax"
ENTRY(iret_exc)
pushl $ # no error code
pushl $do_iret_error
jmp error_code
.previous
_ASM_EXTABLE(irq_return,iret_exc) #ifdef CONFIG_X86_ESPFIX32
CFI_RESTORE_STATE
ldt_ss:
#ifdef CONFIG_PARAVIRT
/*
* The kernel can't run on a non-flat stack if paravirt mode
* is active. Rather than try to fixup the high bits of
* ESP, bypass this code entirely. This may break DOSemu
* and/or Wine support in a paravirt VM, although the option
* is still available to implement the setting of the high
* 16-bits in the INTERRUPT_RETURN paravirt-op.
*/
cmpl $, pv_info+PARAVIRT_enabled
jne restore_nocheck
#endif /*
* Setup and switch to ESPFIX stack
*
* We're returning to userspace with a 16 bit stack. The CPU will not
* restore the high word of ESP for us on executing iret... This is an
* "official" bug of all the x86-compatible CPUs, which we can work
* around to make dosemu and wine happy. We do this by preloading the
* high word of ESP with the high word of the userspace ESP while
* compensating for the offset by changing to the ESPFIX segment with
* a base address that matches for the difference.
*/
#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8)
mov %esp, %edx /* load kernel esp */
mov PT_OLDESP(%esp), %eax /* load userspace esp */
mov %dx, %ax /* eax: new kernel esp */
sub %eax, %edx /* offset (low word is 0) */
shr $, %edx
mov %dl, GDT_ESPFIX_SS + /* bits 16..23 */
mov %dh, GDT_ESPFIX_SS + /* bits 24..31 */
pushl_cfi $__ESPFIX_SS
pushl_cfi %eax /* new kernel esp */
/* Disable interrupts, but do not irqtrace this section: we
* will soon execute iret and the tracer was already set to
* the irqstate after the iret */
DISABLE_INTERRUPTS(CLBR_EAX)
lss (%esp), %esp /* switch to espfix segment */
CFI_ADJUST_CFA_OFFSET -
jmp restore_nocheck
#endif
CFI_ENDPROC
ENDPROC(system_call) # perform work that needs to be done immediately before resumption
ALIGN
RING0_PTREGS_FRAME # can't unwind into user space anyway
work_pending:
testb $_TIF_NEED_RESCHED, %cl
jz work_notifysig
work_resched:
call schedule
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
andl $_TIF_WORK_MASK, %ecx # is there any work to be done other
# than syscall tracing?
jz restore_all
testb $_TIF_NEED_RESCHED, %cl
jnz work_resched work_notifysig: # deal with pending signals and
# notify-resume requests
#ifdef CONFIG_VM86
testl $X86_EFLAGS_VM, PT_EFLAGS(%esp)
movl %esp, %eax
jne work_notifysig_v86 # returning to kernel-space or
# vm86-space
:
#else
movl %esp, %eax
#endif
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
movb PT_CS(%esp), %bl
andb $SEGMENT_RPL_MASK, %bl
cmpb $USER_RPL, %bl
jb resume_kernel
xorl %edx, %edx
call do_notify_resume
jmp resume_userspace #ifdef CONFIG_VM86
ALIGN
work_notifysig_v86:
pushl_cfi %ecx # save ti_flags for do_notify_resume
call save_v86_state # %eax contains pt_regs pointer
popl_cfi %ecx
movl %eax, %esp
jmp 1b
#endif
END(work_pending) # perform syscall exit tracing
ALIGN
syscall_trace_entry:
movl $-ENOSYS,PT_EAX(%esp)
movl %esp, %eax
call syscall_trace_enter
/* What it returned is what we'll actually use. */
cmpl $(NR_syscalls), %eax
jnae syscall_call
jmp syscall_exit
END(syscall_trace_entry) # perform syscall exit tracing
ALIGN
syscall_exit_work:
testl $_TIF_WORK_SYSCALL_EXIT, %ecx
jz work_pending
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_ANY) # could let syscall_trace_leave() call
# schedule() instead
movl %esp, %eax
call syscall_trace_leave
jmp resume_userspace
END(syscall_exit_work)
CFI_ENDPROC RING0_INT_FRAME # can't unwind into user space anyway
syscall_fault:
ASM_CLAC
GET_THREAD_INFO(%ebp)
movl $-EFAULT,PT_EAX(%esp)
jmp resume_userspace
END(syscall_fault) syscall_badsys:
movl $-ENOSYS,%eax
jmp syscall_after_call
END(syscall_badsys) sysenter_badsys:
movl $-ENOSYS,%eax
jmp sysenter_after_call
END(sysenter_badsys)
CFI_ENDPROC .macro FIXUP_ESPFIX_STACK
/*
* Switch back for ESPFIX stack to the normal zerobased stack
*
* We can't call C functions using the ESPFIX stack. This code reads
* the high word of the segment base from the GDT and swiches to the
* normal stack and adjusts ESP with the matching offset.
*/
#ifdef CONFIG_X86_ESPFIX32
/* fixup the stack */
mov GDT_ESPFIX_SS + , %al /* bits 16..23 */
mov GDT_ESPFIX_SS + , %ah /* bits 24..31 */
shl $, %eax
addl %esp, %eax /* the adjusted stack pointer */
pushl_cfi $__KERNEL_DS
pushl_cfi %eax
lss (%esp), %esp /* switch to the normal stack segment */
CFI_ADJUST_CFA_OFFSET -
#endif
.endm
.macro UNWIND_ESPFIX_STACK
#ifdef CONFIG_X86_ESPFIX32
movl %ss, %eax
/* see if on espfix stack */
cmpw $__ESPFIX_SS, %ax
jne 27f
movl $__KERNEL_DS, %eax
movl %eax, %ds
movl %eax, %es
/* switch to normal stack */
FIXUP_ESPFIX_STACK
:
#endif
.endm /*
* Build the entry stubs and pointer table with some assembler magic.
* We pack 7 stubs into a single 32-byte chunk, which will fit in a
* single cache line on all modern x86 implementations.
*/
.section .init.rodata,"a"
ENTRY(interrupt)
.section .entry.text, "ax"
.p2align
.p2align CONFIG_X86_L1_CACHE_SHIFT
ENTRY(irq_entries_start)
RING0_INT_FRAME
vector=FIRST_EXTERNAL_VECTOR
.rept (NR_VECTORS-FIRST_EXTERNAL_VECTOR+)/
.balign
.rept
.if vector < NR_VECTORS
.if vector <> FIRST_EXTERNAL_VECTOR
CFI_ADJUST_CFA_OFFSET -
.endif
: pushl_cfi $(~vector+0x80) /* Note: always in signed byte range */
.if ((vector-FIRST_EXTERNAL_VECTOR)%) <>
jmp 2f
.endif
.previous
.long 1b
.section .entry.text, "ax"
vector=vector+
.endif
.endr
: jmp common_interrupt
.endr
END(irq_entries_start) .previous
END(interrupt)
.previous /*
* the CPU automatically disables interrupts when executing an IRQ vector,
* so IRQ-flags tracing has to follow that:
*/
.p2align CONFIG_X86_L1_CACHE_SHIFT
common_interrupt:
ASM_CLAC
addl $-0x80,(%esp) /* Adjust vector into the [-256,-1] range */
SAVE_ALL
TRACE_IRQS_OFF
movl %esp,%eax
call do_IRQ
jmp ret_from_intr
ENDPROC(common_interrupt)
CFI_ENDPROC #define BUILD_INTERRUPT3(name, nr, fn) \
ENTRY(name) \
RING0_INT_FRAME; \
ASM_CLAC; \
pushl_cfi $~(nr); \
SAVE_ALL; \
TRACE_IRQS_OFF \
movl %esp,%eax; \
call fn; \
jmp ret_from_intr; \
CFI_ENDPROC; \
ENDPROC(name) #ifdef CONFIG_TRACING
#define TRACE_BUILD_INTERRUPT(name, nr) \
BUILD_INTERRUPT3(trace_##name, nr, smp_trace_##name)
#else
#define TRACE_BUILD_INTERRUPT(name, nr)
#endif #define BUILD_INTERRUPT(name, nr) \
BUILD_INTERRUPT3(name, nr, smp_##name); \
TRACE_BUILD_INTERRUPT(name, nr) /* The include is where all of the SMP etc. interrupts come from */
#include <asm/entry_arch.h> ENTRY(coprocessor_error)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
pushl_cfi $do_coprocessor_error
jmp error_code
CFI_ENDPROC
END(coprocessor_error) ENTRY(simd_coprocessor_error)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
#ifdef CONFIG_X86_INVD_BUG
/* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
: pushl_cfi $do_general_protection
:
.section .altinstructions,"a"
altinstruction_entry 661b, 663f, X86_FEATURE_XMM, 662b-661b, 664f-663f
.previous
.section .altinstr_replacement,"ax"
: pushl $do_simd_coprocessor_error
:
.previous
#else
pushl_cfi $do_simd_coprocessor_error
#endif
jmp error_code
CFI_ENDPROC
END(simd_coprocessor_error) ENTRY(device_not_available)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $- # mark this as an int
pushl_cfi $do_device_not_available
jmp error_code
CFI_ENDPROC
END(device_not_available) #ifdef CONFIG_PARAVIRT
ENTRY(native_iret)
iret
_ASM_EXTABLE(native_iret, iret_exc)
END(native_iret) ENTRY(native_irq_enable_sysexit)
sti
sysexit
END(native_irq_enable_sysexit)
#endif ENTRY(overflow)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
pushl_cfi $do_overflow
jmp error_code
CFI_ENDPROC
END(overflow) ENTRY(bounds)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
pushl_cfi $do_bounds
jmp error_code
CFI_ENDPROC
END(bounds) ENTRY(invalid_op)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
pushl_cfi $do_invalid_op
jmp error_code
CFI_ENDPROC
END(invalid_op) ENTRY(coprocessor_segment_overrun)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
pushl_cfi $do_coprocessor_segment_overrun
jmp error_code
CFI_ENDPROC
END(coprocessor_segment_overrun) ENTRY(invalid_TSS)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $do_invalid_TSS
jmp error_code
CFI_ENDPROC
END(invalid_TSS) ENTRY(segment_not_present)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $do_segment_not_present
jmp error_code
CFI_ENDPROC
END(segment_not_present) ENTRY(stack_segment)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $do_stack_segment
jmp error_code
CFI_ENDPROC
END(stack_segment) ENTRY(alignment_check)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $do_alignment_check
jmp error_code
CFI_ENDPROC
END(alignment_check) ENTRY(divide_error)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $ # no error code
pushl_cfi $do_divide_error
jmp error_code
CFI_ENDPROC
END(divide_error) #ifdef CONFIG_X86_MCE
ENTRY(machine_check)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
pushl_cfi machine_check_vector
jmp error_code
CFI_ENDPROC
END(machine_check)
#endif ENTRY(spurious_interrupt_bug)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $
pushl_cfi $do_spurious_interrupt_bug
jmp error_code
CFI_ENDPROC
END(spurious_interrupt_bug) #ifdef CONFIG_XEN
/* Xen doesn't set %esp to be precisely what the normal sysenter
entrypoint expects, so fix it up before using the normal path. */
ENTRY(xen_sysenter_target)
RING0_INT_FRAME
addl $*, %esp /* remove xen-provided frame */
CFI_ADJUST_CFA_OFFSET -*
jmp sysenter_past_esp
CFI_ENDPROC ENTRY(xen_hypervisor_callback)
CFI_STARTPROC
pushl_cfi $- /* orig_ax = -1 => not a system call */
SAVE_ALL
TRACE_IRQS_OFF /* Check to see if we got the event in the critical
region in xen_iret_direct, after we've reenabled
events and checked for pending events. This simulates
iret instruction's behaviour where it delivers a
pending interrupt when enabling interrupts. */
movl PT_EIP(%esp),%eax
cmpl $xen_iret_start_crit,%eax
jb 1f
cmpl $xen_iret_end_crit,%eax
jae 1f jmp xen_iret_crit_fixup ENTRY(xen_do_upcall)
: mov %esp, %eax
call xen_evtchn_do_upcall
jmp ret_from_intr
CFI_ENDPROC
ENDPROC(xen_hypervisor_callback) # Hypervisor uses this for application faults while it executes.
# We get here for two reasons:
# . Fault while reloading DS, ES, FS or GS
# . Fault while executing IRET
# Category we fix up by reattempting the load, and zeroing the segment
# register if the load fails.
# Category we fix up by jumping to do_iret_error. We cannot use the
# normal Linux return path in this case because if we use the IRET hypercall
# to pop the stack frame we end up in an infinite loop of failsafe callbacks.
# We distinguish between categories by maintaining a status value in EAX.
ENTRY(xen_failsafe_callback)
CFI_STARTPROC
pushl_cfi %eax
movl $,%eax
: mov (%esp),%ds
: mov (%esp),%es
: mov (%esp),%fs
: mov (%esp),%gs
/* EAX == 0 => Category 1 (Bad segment)
EAX != 0 => Category 2 (Bad IRET) */
testl %eax,%eax
popl_cfi %eax
lea (%esp),%esp
CFI_ADJUST_CFA_OFFSET -
jz 5f
jmp iret_exc
: pushl_cfi $- /* orig_ax = -1 => not a system call */
SAVE_ALL
jmp ret_from_exception
CFI_ENDPROC .section .fixup,"ax"
: xorl %eax,%eax
movl %eax,(%esp)
jmp 1b
: xorl %eax,%eax
movl %eax,(%esp)
jmp 2b
: xorl %eax,%eax
movl %eax,(%esp)
jmp 3b
: xorl %eax,%eax
movl %eax,(%esp)
jmp 4b
.previous
_ASM_EXTABLE(1b,6b)
_ASM_EXTABLE(2b,7b)
_ASM_EXTABLE(3b,8b)
_ASM_EXTABLE(4b,9b)
ENDPROC(xen_failsafe_callback) BUILD_INTERRUPT3(xen_hvm_callback_vector, HYPERVISOR_CALLBACK_VECTOR,
xen_evtchn_do_upcall) #endif /* CONFIG_XEN */ #if IS_ENABLED(CONFIG_HYPERV) BUILD_INTERRUPT3(hyperv_callback_vector, HYPERVISOR_CALLBACK_VECTOR,
hyperv_vector_handler) #endif /* CONFIG_HYPERV */ #ifdef CONFIG_FUNCTION_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE ENTRY(mcount)
ret
END(mcount) ENTRY(ftrace_caller)
pushl %eax
pushl %ecx
pushl %edx
pushl $ /* Pass NULL as regs pointer */
movl *(%esp), %eax
movl 0x4(%ebp), %edx
movl function_trace_op, %ecx
subl $MCOUNT_INSN_SIZE, %eax .globl ftrace_call
ftrace_call:
call ftrace_stub addl $,%esp /* skip NULL pointer */
popl %edx
popl %ecx
popl %eax
ftrace_ret:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call
ftrace_graph_call:
jmp ftrace_stub
#endif .globl ftrace_stub
ftrace_stub:
ret
END(ftrace_caller) ENTRY(ftrace_regs_caller)
pushf /* push flags before compare (in cs location) */ /*
* i386 does not save SS and ESP when coming from kernel.
* Instead, to get sp, ®s->sp is used (see ptrace.h).
* Unfortunately, that means eflags must be at the same location
* as the current return ip is. We move the return ip into the
* ip location, and move flags into the return ip location.
*/
pushl (%esp) /* save return ip into ip slot */ pushl $ /* Load 0 into orig_ax */
pushl %gs
pushl %fs
pushl %es
pushl %ds
pushl %eax
pushl %ebp
pushl %edi
pushl %esi
pushl %edx
pushl %ecx
pushl %ebx movl *(%esp), %eax /* Get the saved flags */
movl %eax, *(%esp) /* Move saved flags into regs->flags location */
/* clobbering return ip */
movl $__KERNEL_CS,*(%esp) movl *(%esp), %eax /* Load ip (1st parameter) */
subl $MCOUNT_INSN_SIZE, %eax /* Adjust ip */
movl 0x4(%ebp), %edx /* Load parent ip (2nd parameter) */
movl function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
pushl %esp /* Save pt_regs as 4th parameter */ GLOBAL(ftrace_regs_call)
call ftrace_stub addl $, %esp /* Skip pt_regs */
movl *(%esp), %eax /* Move flags back into cs */
movl %eax, *(%esp) /* Needed to keep addl from modifying flags */
movl *(%esp), %eax /* Get return ip from regs->ip */
movl %eax, *(%esp) /* Put return ip back for ret */ popl %ebx
popl %ecx
popl %edx
popl %esi
popl %edi
popl %ebp
popl %eax
popl %ds
popl %es
popl %fs
popl %gs
addl $, %esp /* Skip orig_ax and ip */
popf /* Pop flags at end (no addl to corrupt flags) */
jmp ftrace_ret popf
jmp ftrace_stub
#else /* ! CONFIG_DYNAMIC_FTRACE */ ENTRY(mcount)
cmpl $__PAGE_OFFSET, %esp
jb ftrace_stub /* Paging not enabled yet? */ cmpl $ftrace_stub, ftrace_trace_function
jnz trace
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
cmpl $ftrace_stub, ftrace_graph_return
jnz ftrace_graph_caller cmpl $ftrace_graph_entry_stub, ftrace_graph_entry
jnz ftrace_graph_caller
#endif
.globl ftrace_stub
ftrace_stub:
ret /* taken from glibc */
trace:
pushl %eax
pushl %ecx
pushl %edx
movl 0xc(%esp), %eax
movl 0x4(%ebp), %edx
subl $MCOUNT_INSN_SIZE, %eax call *ftrace_trace_function popl %edx
popl %ecx
popl %eax
jmp ftrace_stub
END(mcount)
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_TRACER */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller)
pushl %eax
pushl %ecx
pushl %edx
movl 0xc(%esp), %edx
lea 0x4(%ebp), %eax
movl (%ebp), %ecx
subl $MCOUNT_INSN_SIZE, %edx
call prepare_ftrace_return
popl %edx
popl %ecx
popl %eax
ret
END(ftrace_graph_caller) .globl return_to_handler
return_to_handler:
pushl %eax
pushl %edx
movl %ebp, %eax
call ftrace_return_to_handler
movl %eax, %ecx
popl %edx
popl %eax
jmp *%ecx
#endif #ifdef CONFIG_TRACING
ENTRY(trace_page_fault)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $trace_do_page_fault
jmp error_code
CFI_ENDPROC
END(trace_page_fault)
#endif ENTRY(page_fault)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $do_page_fault
ALIGN
error_code:
/* the function address is in %gs's slot on the stack */
pushl_cfi %fs
/*CFI_REL_OFFSET fs, 0*/
pushl_cfi %es
/*CFI_REL_OFFSET es, 0*/
pushl_cfi %ds
/*CFI_REL_OFFSET ds, 0*/
pushl_cfi %eax
CFI_REL_OFFSET eax,
pushl_cfi %ebp
CFI_REL_OFFSET ebp,
pushl_cfi %edi
CFI_REL_OFFSET edi,
pushl_cfi %esi
CFI_REL_OFFSET esi,
pushl_cfi %edx
CFI_REL_OFFSET edx,
pushl_cfi %ecx
CFI_REL_OFFSET ecx,
pushl_cfi %ebx
CFI_REL_OFFSET ebx,
cld
movl $(__KERNEL_PERCPU), %ecx
movl %ecx, %fs
UNWIND_ESPFIX_STACK
GS_TO_REG %ecx
movl PT_GS(%esp), %edi # get the function address
movl PT_ORIG_EAX(%esp), %edx # get the error code
movl $-, PT_ORIG_EAX(%esp) # no syscall to restart
REG_TO_PTGS %ecx
SET_KERNEL_GS %ecx
movl $(__USER_DS), %ecx
movl %ecx, %ds
movl %ecx, %es
TRACE_IRQS_OFF
movl %esp,%eax # pt_regs pointer
call *%edi
jmp ret_from_exception
CFI_ENDPROC
END(page_fault) /*
* Debug traps and NMI can happen at the one SYSENTER instruction
* that sets up the real kernel stack. Check here, since we can't
* allow the wrong stack to be used.
*
* "TSS_sysenter_sp0+12" is because the NMI/debug handler will have
* already pushed 3 words if it hits on the sysenter instruction:
* eflags, cs and eip.
*
* We just load the right stack, and push the three (known) values
* by hand onto the new stack - while updating the return eip past
* the instruction that would have done it for sysenter.
*/
.macro FIX_STACK offset ok label
cmpw $__KERNEL_CS, (%esp)
jne \ok
\label:
movl TSS_sysenter_sp0 + \offset(%esp), %esp
CFI_DEF_CFA esp,
CFI_UNDEFINED eip
pushfl_cfi
pushl_cfi $__KERNEL_CS
pushl_cfi $sysenter_past_esp
CFI_REL_OFFSET eip,
.endm ENTRY(debug)
RING0_INT_FRAME
ASM_CLAC
cmpl $ia32_sysenter_target,(%esp)
jne debug_stack_correct
FIX_STACK , debug_stack_correct, debug_esp_fix_insn
debug_stack_correct:
pushl_cfi $- # mark this as an int
SAVE_ALL
TRACE_IRQS_OFF
xorl %edx,%edx # error code
movl %esp,%eax # pt_regs pointer
call do_debug
jmp ret_from_exception
CFI_ENDPROC
END(debug) /*
* NMI is doubly nasty. It can happen _while_ we're handling
* a debug fault, and the debug fault hasn't yet been able to
* clear up the stack. So we first check whether we got an
* NMI on the sysenter entry path, but after that we need to
* check whether we got an NMI on the debug path where the debug
* fault happened on the sysenter path.
*/
ENTRY(nmi)
RING0_INT_FRAME
ASM_CLAC
#ifdef CONFIG_X86_ESPFIX32
pushl_cfi %eax
movl %ss, %eax
cmpw $__ESPFIX_SS, %ax
popl_cfi %eax
je nmi_espfix_stack
#endif
cmpl $ia32_sysenter_target,(%esp)
je nmi_stack_fixup
pushl_cfi %eax
movl %esp,%eax
/* Do not access memory above the end of our stack page,
* it might not exist.
*/
andl $(THREAD_SIZE-),%eax
cmpl $(THREAD_SIZE-),%eax
popl_cfi %eax
jae nmi_stack_correct
cmpl $ia32_sysenter_target,(%esp)
je nmi_debug_stack_check
nmi_stack_correct:
/* We have a RING0_INT_FRAME here */
pushl_cfi %eax
SAVE_ALL
xorl %edx,%edx # zero error code
movl %esp,%eax # pt_regs pointer
call do_nmi
jmp restore_all_notrace
CFI_ENDPROC nmi_stack_fixup:
RING0_INT_FRAME
FIX_STACK , nmi_stack_correct,
jmp nmi_stack_correct nmi_debug_stack_check:
/* We have a RING0_INT_FRAME here */
cmpw $__KERNEL_CS,(%esp)
jne nmi_stack_correct
cmpl $debug,(%esp)
jb nmi_stack_correct
cmpl $debug_esp_fix_insn,(%esp)
ja nmi_stack_correct
FIX_STACK , nmi_stack_correct,
jmp nmi_stack_correct #ifdef CONFIG_X86_ESPFIX32
nmi_espfix_stack:
/* We have a RING0_INT_FRAME here.
*
* create the pointer to lss back
*/
pushl_cfi %ss
pushl_cfi %esp
addl $, (%esp)
/* copy the iret frame of 12 bytes */
.rept
pushl_cfi (%esp)
.endr
pushl_cfi %eax
SAVE_ALL
FIXUP_ESPFIX_STACK # %eax == %esp
xorl %edx,%edx # zero error code
call do_nmi
RESTORE_REGS
lss +(%esp), %esp # back to espfix stack
CFI_ADJUST_CFA_OFFSET -
jmp irq_return
#endif
CFI_ENDPROC
END(nmi) ENTRY(int3)
RING0_INT_FRAME
ASM_CLAC
pushl_cfi $- # mark this as an int
SAVE_ALL
TRACE_IRQS_OFF
xorl %edx,%edx # zero error code
movl %esp,%eax # pt_regs pointer
call do_int3
jmp ret_from_exception
CFI_ENDPROC
END(int3) ENTRY(general_protection)
RING0_EC_FRAME
pushl_cfi $do_general_protection
jmp error_code
CFI_ENDPROC
END(general_protection) #ifdef CONFIG_KVM_GUEST
ENTRY(async_page_fault)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $do_async_page_fault
jmp error_code
CFI_ENDPROC
END(async_page_fault)
#endif
entry_32.S
其中system_call如下：
ENTRY(system_call)
RING0_INT_FRAME # can't unwind into user space anyway
ASM_CLAC
pushl_cfi %eax # save orig_eax
SAVE_ALL
GET_THREAD_INFO(%ebp)
# system call tracing in operation / emulation
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
jnz syscall_trace_entry
cmpl $(NR_syscalls), %eax
jae syscall_badsys
syscall_call:
call *sys_call_table(,%eax,)
syscall_after_call:
movl %eax,PT_EAX(%esp) # store the return value
syscall_exit:
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testl $_TIF_ALLWORK_MASK, %ecx # current->work
jne syscall_exit_work restore_all:
TRACE_IRQS_IRET
restore_all_notrace:
#ifdef CONFIG_X86_ESPFIX32
movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
# Warning: PT_OLDSS(%esp) contains the wrong/random values if we
# are returning to the kernel.
# See comments in process.c:copy_thread() for details.
movb PT_OLDSS(%esp), %ah
movb PT_CS(%esp), %al
andl $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << ) | SEGMENT_RPL_MASK), %eax
cmpl $((SEGMENT_LDT << ) | USER_RPL), %eax
CFI_REMEMBER_STATE
je ldt_ss # returning to user-space with LDT SS
#endif
restore_nocheck:
RESTORE_REGS # skip orig_eax/error_code
irq_return:
INTERRUPT_RETURN
.section .fixup,"ax"
ENTRY(iret_exc)
pushl $ # no error code
pushl $do_iret_error
jmp error_code
.previous
_ASM_EXTABLE(irq_return,iret_exc) #ifdef CONFIG_X86_ESPFIX32
CFI_RESTORE_STATE
ldt_ss:
#ifdef CONFIG_PARAVIRT
/*
* The kernel can't run on a non-flat stack if paravirt mode
* is active. Rather than try to fixup the high bits of
* ESP, bypass this code entirely. This may break DOSemu
* and/or Wine support in a paravirt VM, although the option
* is still available to implement the setting of the high
* 16-bits in the INTERRUPT_RETURN paravirt-op.
*/
cmpl $, pv_info+PARAVIRT_enabled
jne restore_nocheck
#endif /*
* Setup and switch to ESPFIX stack
*
* We're returning to userspace with a 16 bit stack. The CPU will not
* restore the high word of ESP for us on executing iret... This is an
* "official" bug of all the x86-compatible CPUs, which we can work
* around to make dosemu and wine happy. We do this by preloading the
* high word of ESP with the high word of the userspace ESP while
* compensating for the offset by changing to the ESPFIX segment with
* a base address that matches for the difference.
*/
#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8)
mov %esp, %edx /* load kernel esp */
mov PT_OLDESP(%esp), %eax /* load userspace esp */
mov %dx, %ax /* eax: new kernel esp */
sub %eax, %edx /* offset (low word is 0) */
shr $, %edx
mov %dl, GDT_ESPFIX_SS + /* bits 16..23 */
mov %dh, GDT_ESPFIX_SS + /* bits 24..31 */
pushl_cfi $__ESPFIX_SS
pushl_cfi %eax /* new kernel esp */
/* Disable interrupts, but do not irqtrace this section: we
* will soon execute iret and the tracer was already set to
* the irqstate after the iret */
DISABLE_INTERRUPTS(CLBR_EAX)
lss (%esp), %esp /* switch to espfix segment */
CFI_ADJUST_CFA_OFFSET -
jmp restore_nocheck
#endif
CFI_ENDPROC
ENDPROC(system_call)
entry_call
精简其中主要的如下：
ENTRY(system_call)
SAVE_ALL #保存现场
syscall_call:
call *sys_call_table(,%eax,) #中断向量表
syscall_after_call:
movl %eax,PT_EAX(%esp) # 存储返回值
7 syscall_exit:
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY) # 确保不会错过中断
restore_all:
TRACE_IRQS_IRET
irq_return:
INTERRUPT_RETURN
ENDPROC(system_call)
借图 修改一下系统调用部分
流程图
