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/* arch/i386/gdt.c */
.set SEG_r0code, 1
.set SEG_r3code, 3
.set SEG_r3data, 4
.set IA32_SYSENTER_CS, 0x174
.set IA32_SYSENTER_ESP, 0x175
.set IA32_SYSENTER_EIP, 0x176
.section .text
.global sysexit
.type sysexit, @function
sysexit:
mov 4(%esp), %edx
mov 8(%esp), %ecx
mov $(SEG_r3data << 3 | 3), %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
// enable paging
mov %cr0, %eax
or $0x80000000, %eax
mov %eax, %cr0
sysexit
.global sysenter_setup
.type sysenter_setup, @function
sysenter_setup:
xor %edx, %edx
mov $(SEG_r0code << 3), %eax
mov $IA32_SYSENTER_CS, %ecx
wrmsr
mov $IA32_SYSENTER_ESP, %ecx
mov $_bss_end, %eax
wrmsr
mov $IA32_SYSENTER_EIP, %ecx
mov $sysenter_handler, %eax
wrmsr
ret
sysenter_handler:
pushal
push %edi
push %esi
push %ebx
push %eax
mov %cr0, %eax
and $0x7FFFFFFF, %eax // disable paging
mov %eax, %cr0
call syscall_handler
// save the return value
mov %eax, 44(%esp) // 16 [top of eflags] + 7*4 [skip until EAX]
mov %edx, 32(%esp) // 16 + 4*4 [skip until EBX]
mov %cr0, %eax
or $0x80000000, %eax // enable paging
mov %eax, %cr0
add $16, %esp
popal
sysexit
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