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Xen代码分析(一)x86_32.S

上一篇 / 下一篇 2007-12-12 00:32:24 / 个人分类：Virtualization

[http://hi.baidu.com/realvm]

XEN 只能由 grub 来引导，x86_32.S 是从GRUB进入XEN 的入口文件
tzl$x*RwI+uu!l051Testing软件测试网c}7}(fX K'H&D
    1   #include <xen/config.h>
E(bo/JzT T*a0    2   #include <xen/multiboot.h>
D5KB;p;E"t0    3   #include <public/xen.h>
mdm7Q'g$M^m0    4   #include <asm/asm_defns.h>
LL}X o n7rp{0    5   #include <asm/desc.h>
O)@9ZOyFB0    6   #include <asm/page.h>
    7   #include <asm/msr.h>
}Q @7y8i0    851Testing软件测试网2en J0nT/~
    9   #define SECONDARY_CPU_FLAG 0xA5A5A5A5
   10
M;XGFL{`fyW0X5HO0   11           .text51Testing软件测试网]&?,GyZH
   12
f@U2H+[2v6J oz0   13   ENTRY(start)51Testing软件测试网b}#g*O*pc"xp
   14   ENTRY(stext)
   15   ENTRY(_stext)
"iM9m7tE#zu1A0   16           jmp __start51Testing软件测试网(H&poL&n9U
/**
grub 根据xen的头信息获得入口地址，然后读入整个映像，最后把控制权交给xen。
FU~(\2R:Kbo0看一下xen的头：
.VvH-ThrU_k0# readelf -l xen
51Testing软件测试网Cu:?"qR!`
Elf 文件类型为 EXEC (可执行文件)
P~bS+? H3Z3yO0入口点 0x100000
共有 1 个程序头，开始于偏移量52
u/MY3iup0
C_p0PaA-`0程序头：
@URd[]fZ0Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz Flg Align51Testing软件测试网2]w9y-zr
LOAD           0x000080 0x00100000 0x00100000 0xb86e4 0x107000 RWE 0x4051Testing软件测试网3f,}5N)m}0h

b#@7OT\:L/]0Section to Segment mapping:
bJdv M5Jx R(f$h9SA0段节...
#`NAV`k Y P'io+w0   00     .text
%S4L!F3hG6rLu0当xen运行时，cpu已经处于保护模式
ZR:R \ThI5s(W0
#FF dk2Tr0**/
t!{%geWL:R/R6G0   17
E#p%x&B:a(j+I"ZT0   18           .align 4
}lVR4@"f*`0   19
h5h!QH ?f(Y+Pr1P[0   20   /*** MULTIBOOT HEADER ****/
oE8C}2d8Mq)EBe0   21   #define MULTIBOOT_HEADER_FLAGS (MULTIBOOT_HEADER_MODS_ALIGNED | \
   22                                   MULTIBOOT_HEADER_WANT_MEMORY)51Testing软件测试网$EPcB(_3[a
   23           /* Magic number indicating a Multiboot header. */51Testing软件测试网LobaPrL {
   24           .long MULTIBOOT_HEADER_MAGIC51Testing软件测试网&OOH5g a9pN
   25           /* Flags to bootloader (see Multiboot spec). */
xP0NM+{u c1Rh;]0   26           .long MULTIBOOT_HEADER_FLAGS
(Ap7z5zSn0   27           /* Checksum: must be the negated sum of the first two fields. */
/**
4p#bn!Fm|gf D0上面的定义是给grub看的，表明支持multiboot，详细内容见multiboot协议
AvYD0wt0**/
;I)SgEmf5x1K0   28           .long -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
k4tO(I'Q4PGD5z;K0   29
mX9K){ K;zH!]0   30   not_multiboot_msg:51Testing软件测试网/uFjMZ&B.t
   31           .asciz "ERR: Not a Multiboot bootloader!"51Testing软件测试网'iPFmp
   32   not_multiboot:
6R|D;gq ]qf$?-q(D1z1}.M0   33           mov     $not_multiboot_msg-__PAGE_OFFSET,%esi
'E2SI8OC3z0   34           mov     $0xB8000,%edi # VGA framebuffer
7YfpTTr/E0   35   1:      mov     (%esi),%bl51Testing软件测试网(V Wg_#XH2Sf
   36           test    %bl,%bl        # Terminate on '\0' sentinel
(g \]J8kf0   37   2:      je      2b51Testing软件测试网#g"H.w#oNxl(M
   38           mov     $0x3f8+5,%dx   # UART Line Status Register
vEh rN!f0   39   3:      in      %dx,%al
-UM]3a(NoD&G0   40           test    $0x20,%al      # Test THR Empty flag
   41           je      3b
p^\w2D\0   42           mov     $0x3f8+0,%dx   # UART Transmit Holding Register51Testing软件测试网5` ?*PxW5_
   43           mov     %bl,%al
   44           out     %al,%dx        # Send a character over the serial line
de'|(R Cq0   45           movsb                  # Write a character to the VGA framebuffer
te6kMv6z9x-Y0   46           mov     $7,%al
   47           stosb                  # Write an attribute to the VGA framebuffer51Testing软件测试网CFl5s BoG
   48           jmp     1b51Testing软件测试网 kK8zk5^x
   4951Testing软件测试网:k!S)i6gKfd
   50   __start:
aP SA!F0   51           /* Set up a few descrīptors: on entry only CS is guaranteed good. */
   52           lgdt    %cs:nopaging_gdt_descr-__PAGE_OFFSET51Testing软件测试网 crT8M,Lg
/**51Testing软件测试网.zWm)[uF
初始化gdt, 为什么要-__PAGE_OFFSET，前面已经说过，简单来说，编译时的代码位置和运行是不一样，因此要减一个偏移量。当使用页转换后就不需要-__PAGE_OFFSET了，那时的0xFF100000和0x00100000将映射到同一物理地址。
"TG3_1eXG0对比一下gdt_descr和nopaging_gdt_descr的内容也可以看出一点道道：
gdt_descr:
Yes0hJ:u0        .word   LAST_RESERVED_GDT_BYTE
O]3x c;C4f`0        .long   gdt_table - FIRST_RESERVED_GDT_BYTE
OQF3VNUL&pn0
4Ez3CBw"q!v8e0        .word   051Testing软件测试网9kNNcQu,X
nopaging_gdt_descr:51Testing软件测试网O4cL{Tk U
        .word   LAST_RESERVED_GDT_BYTE
        .long   gdt_table - FIRST_RESERVED_GDT_BYTE - __PAGE_OFFSET
7BNZ4u1W(Tka0这两个descr实际上指向同一个gdt_table.
t&`ff/cYm#C[+A0**/
)vdC7f%j:^g0
jVb W:C;UXH&t0   53           mov     $(__HYPERVISOR_DS),%ecx
_af4YJ \w0/**
e]tFR9b Q o0初始化ds, es, fs, gs
__HYPERVISOR_DS 的值可以在 ./include/asm/config.h 中找到：
#define __HYPERVISOR_CS 0xe00851Testing软件测试网(n.T"th,BO
#define __HYPERVISOR_DS 0xe010
"WC[#|2ZP-b UX$eFEL0每个表项是8个字节，换成十进制cs,ds分别是第7169和7170项。51Testing软件测试网C,U4MpINI
再看看nopaging_gdt_descr的内容：51Testing软件测试网6Rq-m2kXBl
nopaging_gdt_descr:
T#tp:pqnc5S0        .word   LAST_RESERVED_GDT_BYTE
FD&u#f)dy#l0        .long   gdt_table - FIRST_RESERVED_GDT_BYTE - __PAGE_OFFSET
gdt 的基地址位于gdt_table之前，空出了FIRST_RESERVED_GDT_BYTE个字节，51Testing软件测试网6?;@eI'cHj
#define FIRST_RESERVED_GDT_PAGE 14
#define FIRST_RESERVED_GDT_BYTE (FIRST_RESERVED_GDT_PAGE * 4096)
E;~ g3zku6?;R'r0F2q0实际是就是保留了14个页，算一下：51Testing软件测试网gZ+B6?6}c[T
14 * 4096 /8 ＝ 7168 项，所以第7169，7170项就是相对于gdt_table的第1，2项。
]"iJo7M%F0
3Dac&b5J-y0**/
   54           mov     %ecx,%ds51Testing软件测试网/[NBn7~ w
   55           mov     %ecx,%es
D4[bX1pgd"m0   56           mov     %ecx,%fs
   57           mov     %ecx,%gs
9F0?f#C$ly0   58           ljmp    $(__HYPERVISOR_CS),$(1f)-__PAGE_OFFSET
i [Nv4U%L!jW0   59   1:      lss     stack_start-__PAGE_OFFSET,%esp
2qo(P!A,Sjd0i0   60           add     $(STACK_SIZE-CPUINFO_sizeof-__PAGE_OFFSET),%esp
h#T4empN+T0/**
@PE(O2s(k"GZi0设置stack:51Testing软件测试网`/T+{ x/DZ|
ENTRY(stack_start)
pE-E}9d\1c"\0        .long cpu0_stack
t&MDW I8^Z:R9l0        .long __HYPERVISOR_DS51Testing软件测试网,P0Ct\6kVQ
...51Testing软件测试网CUm/HX6@c6U
ENTRY(cpu0_stack)
        .fill STACK_SIZE,1,0
2SC)r|*T]8^ Er0
4c0^0e;x&E*Jvb6l4_0这里为什么要多减一个CPUINFO_sizeof呢？原因是xen要在栈底保留出一点空间供cpu0 的 cpu_info 结构使用。51Testing软件测试网i'FHM0Aq*T
看看./include/asm-x86/current.h 中的 get_cpu_info 是如何实现的就更清楚了：
51Testing软件测试网G%[7[:G\5e
     23 static inline struct cpu_info *get_cpu_info(void)
0eX[oB!l+\-ha0     24 {
     25     struct cpu_info *cpu_info;
O]+?!Sdt%F0     26     __asm__ ( "and %%"__OP"sp,%0; or %2,%0"
     27               : "=r" (cpu_info)
n$Qd2zD'pD"r/`L0     28               : "0" (~(STACK_SIZE-1)), "i" (STACK_SIZE-sizeof(struct cpu_info))
1Y _(??m0     29         );
     30     return cpu_info;51Testing软件测试网 P0X:d4L*s2b g
     31 }
I#]Drs-c0用伪汇编指令表示，意思是这样：
t%c9J fs1ch]:^qx0mov (~(STACK_SIZE-1)), cpu_info
and %esp, cpu_info51Testing软件测试网?qg3acG'W
or (STACK_SIZE-sizeof(struct cpu_info)), cpu_info

8T-iBe2Hu4S8{0这里面有些小技巧， %esp and (~(STACK_SIZE-1)) 的值实际就是栈顶，再or (STACK_SIZE-sizeof(struct cpu_info))
就得到距栈底sizeof(struct cpu_info)的地址，该空间就是上面保留下来的。
@y F)O%~3}N \.V0]0
**/
h%mSEI{;d&_0
jn&m}+W6J{M0   6151Testing软件测试网c]'BMe }
   62           /* Reset EFLAGS (subsumes CLI and CLD). */51Testing软件测试网-Cr!sc]{
   63           pushl   $0
^"uGF.X!yI.R0   64           popf
   65
   66           /* Set up FPU. */
E7z'u-n%y}s:yRT0   67           fninit
T&v7a+K hj0   68
NG+h9JDDD0   69           /* Set up CR4, except global flag which Intel requires should be     */
;S8A2{9ul|$EEPf0   70           /* left until after paging is enabled (IA32 Manual Vol. 3, Sec. 2.5) */51Testing软件测试网GNF:c1T_
   71           mov     mmu_cr4_features-__PAGE_OFFSET,%ecx
%TXG_Mx[h0/**
$U aI x:h4iTZ]5Z0u0CR4:51Testing软件测试网?9~3u'x8?
31-------------------14   13       12 11 10 9 8      7     6       5      4      3      2      1      0
zM$WAfd0reserved(set to 0)         VMXE   0   0   | | PCE PGE MCE PAE PSE DE   TSD   PVI VME
q h5S3dpXP0W5r0                OSXMMEXCPT ________| |51Testing软件测试网\r$e9N(Qj f
                           OSFXSR___________|51Testing软件测试网2aY1_X7z2lB;`
mmu_cr4_features 在 ./arch/x86/setup.c 中有定义：
6a z5MC0u/^9QS0#if CONFIG_PAGING_LEVELS > 2
5hf^%N(H$R0unsigned long mmu_cr4_features = X86_CR4_PSE | X86_CR4_PGE | X86_CR4_PAE;
WKKi Yee,E#s0#else
x{vn9k]0`a(]0unsigned long mmu_cr4_features = X86_CR4_PSE;
#endif
\t4Cri0                                                  51Testing软件测试网1y'D _ }t}3e

0S*BS-\QG0**/
h^3v'GyV ys0
t)b,T;xV0   72           and     $0x7f,%cl   # CR4.PGE (global enable)
/**
3Mr&M:? \i0清除PGE位
VI/WST0**/
   73           mov     %ecx,%cr4
oCI'q4X|7r _eaO0   74
~v wEM3^ r0   75           cmp     $(SECONDARY_CPU_FLAG),%ebx
   76           je      start_paging51Testing软件测试网ui7kzl
/**
,n$An+Mx!b#~.B2n0SECONDARY_CPU_FLAG 的值是这样定义的
5R8eE/jW0#define SECONDARY_CPU_FLAG 0xA5A5A5A5
4`N6{-A0G/O)B Y0xen 3.x.y 以后支持SMP(包括xen0和xenU), 当％ebx值是0xA5A5A5A5时，意味着这段代码是从SMP上的从别的CPU执行过来的。
e5U jy }#c0

**/51Testing软件测试网r.AM`*Y p
   77
c7R"W)e5yK`vW0   78           /* Check for Multiboot bootloader */
atK([@(~+T!cIu0   79           cmp     $0x2BADB002,%eax
YV#W9NV+w5~2s/|0   80           jne     not_multiboot
bY,p~r4{rd0   81
5l0g w"]0H,QI0   82           /* Initialize BSS (no nasty surprises!) */
L#Z7Z"f-YIu0   83           mov     $__bss_start-__PAGE_OFFSET,%edi
)y"{el)sL0   84           mov     $_end-__PAGE_OFFSET,%ecx
:X.B7W-B0S WK0   85           sub     %edi,%ecx51Testing软件测试网|^is'} z$b
   86           xor     %eax,%eax
C3cddZ#`-Y"r0   87           rep     stosb
   88
{)^+e!Cm0   89           /* Save the Multiboot info structure for later use. */51Testing软件测试网6D8X4H,r~M
   90           add     $__PAGE_OFFSET,%ebx
   91           push    %ebx
"hG6ZD!u#c0   92
zrUq*O2W(^6~0   93   #ifdef CONFIG_X86_PAE51Testing软件测试网#r n9S8vH ^^
   94           /* Initialize low and high mappings of all memory with 2MB pages */
d}[PCsh0   95           mov     $idle_pg_table_l2-__PAGE_OFFSET,%edi51Testing软件测试网[#l-o_oNg
   96           mov     $0xe3,%eax                  /* PRESENT+RW+A+D+2MB */
R LX3jsz;`0   97   1:      mov     %eax,__PAGE_OFFSET>>18(%edi) /* high mapping */51Testing软件测试网?*Dtxamx*f
   98           stosl                                /* low mapping */
8Q2Y^4P]];X0   99           add     $4,%edi51Testing软件测试网UcoH`x6oD
100           add     $(1<<L2_PAGETABLE_SHIFT),%eax
101           cmp     $DIRECTMAP_PHYS_END+0xe3,%eax
102           jne     1b51Testing软件测试网H*oA_9w{iC
103   1:      stosl   /* low mappings cover as much physmem as possible */51Testing软件测试网#I(R#S,?'VX3Z
104           add     $4,%edi51Testing软件测试网y sK"paXC
105           add     $(1<<L2_PAGETABLE_SHIFT),%eax
\0~1Opp9^[N0106           cmp     $HYPERVISOR_VIRT_START+0xe3,%eax
.n$x7[8HR6Q0107           jne     1b
108   #else
C zU.sYA8F0L:Y0109           /* Initialize low and high mappings of all memory with 4MB pages */
)m[5V ?.c[ V5Rw ][`C0110           mov     $idle_pg_table-__PAGE_OFFSET,%edi
111           mov     $0xe3,%eax                  /* PRESENT+RW+A+D+4MB */
112   1:      mov     %eax,__PAGE_OFFSET>>20(%edi) /* high mapping */
3e Q+cz&\+WO0113           stosl                                /* low mapping */51Testing软件测试网d9Yj~/k.kW;a
114           add     $(1<<L2_PAGETABLE_SHIFT),%eax
rz5BVNP?H$wA's0115           cmp     $DIRECTMAP_PHYS_END+0xe3,%eax
116           jne     1b51Testing软件测试网1F3zq9CU j*`W
117   1:      stosl   /* low mappings cover as much physmem as possible */
118           add     $(1<<L2_PAGETABLE_SHIFT),%eax51Testing软件测试网tTO9^q9G
119           cmp     $HYPERVISOR_VIRT_START+0xe3,%eax
Oir!Q,r%\+sJy8xw0120           jne     1b51Testing软件测试网f~3}\,h"@4`I
121   #endif
12251Testing软件测试网RcI.S|H7X
123           /* Initialise IDT with simple error defaults. */
3Zk#s0uCX0124           lea     ignore_int,%edx
125           mov     $(__HYPERVISOR_CS << 16),%eax
126           mov     %dx,%ax            /* selector = 0x0010 = cs */
vKV.HG;EB r0127           mov     $0x8E00,%dx        /* interrupt gate - dpl=0, present */
+PyJrnJ9L,xf0128           lea     idt_table-__PAGE_OFFSET,%edi
7O[!q,G:f/v*X.u$wW0129           mov     $256,%ecx51Testing软件测试网jL![;nS@5o
130   1:      mov     %eax,(%edi)51Testing软件测试网?P t Pa
131           mov     %edx,4(%edi)
!o[#OI#d0r)QP0132           add     $8,%edi
133           loop    1b
bjG&o#_!XY-R013451Testing软件测试网C6w1o+ubF8v
135   start_paging:
136   #ifdef CONFIG_X86_PAE
/~^BE8s&}?g0137           /* Enable Execute-Disable (NX/XD) support if it is available. */
)FnS}b%e ~,lis0138           push    %ebx
7KVj@@P+g0139           mov     $0x80000000,%eax
8`&nqc(d"I0B0140           cpuid
,]6H.pk4V4Rbd1x A0141           cmp     $0x80000000,%eax    /* Any function > 0x80000000? */
142           jbe     no_execute_disable51Testing软件测试网LFS3o)GDw
143           mov     $0x80000001,%eax51Testing软件测试网n5Re*wIp
144           cpuid51Testing软件测试网2p'EsP1N[O
145           bt      $20,%edx            /* Execute Disable? */51Testing软件测试网Eel[0X7V
146           jnc     no_execute_disable
;}'g3np'mx&xC|}EL0147           movl    $MSR_EFER,%ecx
148           rdmsr51Testing软件测试网j,]'O^qM
149           bts     $_EFER_NX,%eax
.vg!WW#p'uWt6w0150           wrmsr
151   no_execute_disable:
152           pop     %ebx
7z.Ed"Xe9`k x0153   #endif
z"V?%Bi:aV%V.Z0154           mov     $idle_pg_table-__PAGE_OFFSET,%eax
!Aj/{@+yDa6m4J*h0155           mov     %eax,%cr3
(Q7UW|u/Y0156           mov     $0x80050033,%eax /* hi-to-lo: PG,AM,WP,NE,ET,MP,PE */
157           mov     %eax,%cr0
158           jmp     1f
wexw(o#^0159   1:      /* Install relocated selectors (FS/GS unused). */
Tb,z mL,s3Fr#|0160           lgdt    gdt_descr51Testing软件测试网D ~,P Wy,uW
161           mov     $(__HYPERVISOR_DS),%ecx51Testing软件测试网@W.e_xs
162           mov     %ecx,%ds
LX"d$J%n3{Mmm"Q@0163           mov     %ecx,%es
164           mov     %ecx,%ss
p~g u7m9c ^0165           ljmp    $(__HYPERVISOR_CS),$1f
0~F!v^x0k@ p3UN0166   1:      /* Paging enabled, so we can now enable GLOBAL mappings in CR4. */51Testing软件测试网5gzQt$aS9^
167           mov     mmu_cr4_features,%ecx
2W-]!XB5CBp&s;E0168           mov     %ecx,%cr4
o&E{TBD0169           /* Relocate ESP */
8CQG2v}#F0170           add     $__PAGE_OFFSET,%esp
0R5pu?&g0171
)g!ei&l6]B kl!U(E0172           lidt    idt_descr
e{0sD XsL017351Testing软件测试网5@9d8R'vQs
174           cmp     $(SECONDARY_CPU_FLAG),%ebx51Testing软件测试网G*~4`v{I`\
175           je      start_secondary51Testing软件测试网8U0\]a({RV
176
177           /* Call into main C routine. This should never return.*/51Testing软件测试网x6jk5xdedS
178           call    __start_xen
I/xI&G V,`I0179           ud2     /* Force a panic (invalid opcode). */
Y6`!O&C[!|z018051Testing软件测试网`U8_V8C4R e
181   /* This is the default interrupt handler. */
x0TJ_0X6M8w1w0182   int_msg:
_ T'`Q0pQ0183           .asciz "Unknown interrupt\n"
184           ALIGN
9@ {Kxt^?;RN0185   ignore_int:
5H1O7v4E$ty|0Uk5O0186           cld
^3D[\(s0187           mov     $(__HYPERVISOR_DS),%eax
188           mov     %eax,%ds
2scsw/Z'@y0189           mov     %eax,%es
190           pushl   $int_msg
"P3f&E:Uxyt%]s0191           call    printk
b}6}p N1c4];S0192   1:      jmp     1b
193
U-px#F'{+Sgnh0194   /*** STACK LOCATION ***/
*fJ3K/HY'sn0195
1?vB6B6e m^sK7UZ0196   ENTRY(stack_start)51Testing软件测试网1lw0uij)NA'e
197           .long cpu0_stack
198           .long __HYPERVISOR_DS
199
^6G^ ~|e{0200   /*** DEscrīptOR TABLES ***/
"x*Q c+{e:I[020151Testing软件测试网;O7`Os6l
202           ALIGN
U3Ji"[aV0203
JwcZ }0204           .word   0
3r:f Tq+Y\0205   idt_descr:
206           .word   256*8-1
C7MT Yv c0207           .long   idt_table
208
%N7O&}1KX|0209           .word   0
O3j_%OU,w0210   gdt_descr:
sF/R1}7q*qMV0211           .word   LAST_RESERVED_GDT_BYTE51Testing软件测试网}&O+pXO
212           .long   gdt_table - FIRST_RESERVED_GDT_BYTE51Testing软件测试网2V{pn-j,A
21351Testing软件测试网aHK`B
214           .word   051Testing软件测试网vZlg;\
215   nopaging_gdt_descr:
8| I%p!@y6F$eS A{6O0216           .word   LAST_RESERVED_GDT_BYTE
A SN4R1Eb0217           .long   gdt_table - FIRST_RESERVED_GDT_BYTE - __PAGE_OFFSET
21851Testing软件测试网Ca4p8ug-\`
219           .align PAGE_SIZE, 0
M#p.NO~ I},Im:E0220   /* NB. Rings != 0 get access up to MACH2PHYS_VIRT_END. This allows access to */51Testing软件测试网@mTF-@
221   /*     the machine->physical mapping table. Ring 0 can access all memory.    */
v0w6@1G'G0222   #define GUEST_DESC(d)                                                   \
y(A7fdC5nd0223           .long ((MACH2PHYS_VIRT_END - 1) >> 12) & 0xffff,                \
224                 ((MACH2PHYS_VIRT_END - 1) >> 12) & (0xf << 16) | (d)
pOs$]+j0225   ENTRY(gdt_table)
T8|1|]"k)Gw0226           .quad 0x0000000000000000     /* unused */
E s2e3o(V8d0227           .quad 0x00cf9a000000ffff     /* 0xe008 ring 0 4.00GB code at 0x0 */51Testing软件测试网LAbY%y
228           .quad 0x00cf92000000ffff     /* 0xe010 ring 0 4.00GB data at 0x0 */
4eU~$wt!]_+eL1~0229           GUEST_DESC(0x00c0ba00)       /* 0xe019 ring 1 3.xxGB code at 0x0 */
9G0Y/WJL!Po1Gub0230           GUEST_DESC(0x00c0b200)       /* 0xe021 ring 1 3.xxGB data at 0x0 */
4`5t5kn_r0231           GUEST_DESC(0x00c0fa00)       /* 0xe02b ring 3 3.xxGB code at 0x0 */51Testing软件测试网imP,Zp0m
232           GUEST_DESC(0x00c0f200)       /* 0xe033 ring 3 3.xxGB data at 0x0 */
.`R8l L/I`@0233           .quad 0x0000000000000000     /* unused                           */
$q3Uro4ej \,x0234           .fill 2*NR_CPUS,8,0          /* space for TSS and LDT per CPU    */
+\([Ni(dv$P+^+\M0235
i-{;T4bbC+l0236           .align PAGE_SIZE, 0
237
X^L7x*QpbO0238   #ifdef CONFIG_X86_PAE
HA,b6?G0W1e0239   ENTRY(idle_pg_table)
240   ENTRY(idle_pg_table_l3)
241           .long idle_pg_table_l2 + 0*PAGE_SIZE + 0x01 - __PAGE_OFFSET, 051Testing软件测试网I!G\5U1e"J
242           .long idle_pg_table_l2 + 1*PAGE_SIZE + 0x01 - __PAGE_OFFSET, 0
2p!qe#w'?0{N.D:^{zO0243           .long idle_pg_table_l2 + 2*PAGE_SIZE + 0x01 - __PAGE_OFFSET, 0
W [0v2T5wW9AIY0244           .long idle_pg_table_l2 + 3*PAGE_SIZE + 0x01 - __PAGE_OFFSET, 0
2jrA;ByPt0245   .section ".bss.page_aligned","w"51Testing软件测试网^gN iWi
246   ENTRY(idle_pg_table_l2)
u%g4F cK%g0247           .fill 4*PAGE_SIZE,1,0
248   #else51Testing软件测试网O^Ih?&F
249   .section ".bss.page_aligned","w"
250   ENTRY(idle_pg_table)51Testing软件测试网GN1LL}
251   ENTRY(idle_pg_table_l2)
&c4b!W%[%tV%Z0252           .fill 1*PAGE_SIZE,1,051Testing软件测试网%L.[9d`HU
253   #endif
d&m PL@o(~:Y'T2d&eF0A0254
!i3l/U/Nv(A{?,y0255   .section ".bss.stack_aligned","w"51Testing软件测试网 N-b N6~&|+y
256   ENTRY(cpu0_stack)
_8q?Q(t-R&s3V0257           .fill STACK_SIZE,1,0

Xen代码分析(一)x86_32.S

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