Guys,
I was looking at the SAVE_ALL code for kernel 2.6.
I am confused why SAVE_ALL restores __USER_DS to ds and es ?
#define SAVE_ALL \
cld; \
pushl %fs; \
pushl %es; \
pushl %ds; \
pushl %eax; \
pushl %ebp; \
pushl %edi; \
pushl %esi; \
pushl %edx; \
pushl %ecx; \
pushl %ebx; \
movl $(__USER_DS), %edx; \ <---- why __USER_DS ?
movl %edx, %ds; \
movl %edx, %es; \
movl $(__KERNEL_PDA), %edx; \
movl %edx, %fs
If you look at the linux 2.4, it restores __KERNEL_DS in SAVE_ALL.
#define SAVE_ALL \
cld; \
pushl %es; \
pushl %ds; \
pushl %eax; \
pushl %ebp; \
pushl %edi; \
pushl %esi; \
pushl %edx; \
pushl %ecx; \
pushl %ebx; \
movl $(__KERNEL_DS),%edx; \ <-- __KERNEL_DS is restored here.
movl %edx,%ds; \
movl %edx,%es;
Does anyone know why do we restore __USER_DS on context switch from user to kernel instead of __KERNEL_DS ?
thanks a lot for any help ...
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