First Linux Study

Linux first-Linux general technology-Linux programming and kernel information. The following is a detailed description. 1: # define FIRST_TSS_ENTRY 4

2: # define FIRST_LDT_ENTRY (FIRST_TSS_ENTRY + 1)

3: # define _ TSS (n) (unsigned long n) <4) + (FIRST_TSS_ENTRY <3 ))

4: # define _ LDT (n) (unsigned long n) <4) + (FIRST_LDT_ENTRY <3 ))

5: # define ltr (n) _ asm _ ("ltr % ax": "a" (_ TSS (n )))

6: # define lldt (n) _ asm _ ("lldt % ax": "a" (_ LDT (n )))

The above 4 indicates that each starting with 0 represents 4th bits of 8 bytes.

FIRST_TSS_ENTRY <3

The tss of the 1st tasks is 2 8 bytes offset from the 0th tasks, so 16 bytes are moved.

That is, (unsigned long n) <4

The loading of the nth task tr ldtr is the number of bytes of their offset


// Certificate //---------------------------------------------------------------------------------------------------------------------------------------------

Where is TSS? In the struct task_struct component struct tss_struct tss

Where is LDT? Also in struct task_struct, the component struct desc_struct ldt [3]

How does GDT manage TSS and LDT?

Struct tss_struct and struct desc_struct are both in the kernel, so they can be found through 32 offset addresses.

What are their attributes? That is, permission issues.

Therefore, you must set their location and permissions in GDT.

The Code is as follows:

# Define _ set_tssldt_desc (n, addr, type )\

_ Asm _ ("movw $104, % 1 \ n \ t "\

"Movw % ax, % 2 \ n \ t "\

"Rorl $16, % eax \ n \ t "\

"Movb % al, % 3 \ n \ t "\

"Movb $" type ", % 4 \ n \ t "\

"Movb $0x00, % 5 \ n \ t "\

"Movb % ah, % 6 \ n \ t "\

"Rorl $16, % eax "\

: "A" (addr), "m" (* (n), "m" (* (n + 2 )), "m" (* (n + 4 )),\

"M" (* (n + 5), "m" (* (n + 6), "m" (* (n + 7 )\

)

The same applies to other IDT.

I learned Linux because I am ignorant of Windows ~~~~

However, a lot of things make a headache During the learning process.