annotate src/proc-asm.S @ 62:38f768da2f31
added a comment in the tss showing the interesting bits
| author |
John Tsiombikas <nuclear@member.fsf.org> |
| date |
Wed, 17 Aug 2011 05:39:39 +0300 |
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437360696883 |
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line source |
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1 .text
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2 /* switch_stack(uint32_t new_stack, uint32_t *old_stack_ptr)
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3 * switches to the new stack and returns the old stack pointer, which is
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4 * also copied to the address passed as the second argument.
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5 */
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6 .globl switch_stack
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7 switch_stack:
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8 movl %esp, %eax /* old stack in eax */
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9 movl 8(%esp), %edx
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10 cmpl $0, %edx /* if old_stack_ptr is null, skip ahead */
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11 jz oldp_is_null
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12 movl %eax, (%edx) /* otherwise *old_stack_ptr = eax */
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13 oldp_is_null:
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14 movl 4(%esp), %esp /* set the new stack */
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15 ret
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16
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17 /* get_instr_stack_ptr(uint32_t *eip, uint32_t *esp)
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18 * returns the current instruction and stack pointers at the same
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19 * point in execution, so that a newly-forked process with these
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20 * values will just return from this function and continue on.
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21 */
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22 .globl get_instr_stack_ptr
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23 get_instr_stack_ptr:
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24 call get_instr_ptr
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25 movl %eax, 4(%esp)
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26 movl %esp, 8(%esp)
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27 ret
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28
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29 /* get_instr_ptr(void)
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30 * returns the address of the next instruction after the call to this function
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31 */
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32 .globl get_instr_ptr
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33 get_instr_ptr:
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34 movl (%esp), %eax
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35 ret
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36
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37 /* get_caller_instr_ptr(void)
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38 * returns the address of the next instruction after the call to the function that
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39 * called this function.
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40 * NOTE: will only work properly when called from a function that uses ebp to point
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41 * to its stack frame, which means all of the C functions but pretty much none of
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42 * our assembly functions.
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43 */
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44 .globl get_caller_instr_ptr
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45 get_caller_instr_ptr:
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46 movl 4(%ebp), %eax
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47 ret
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48
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49 /* this is where we end up when we first context_switch to a newly forked
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50 * process. The interrupt frame is already there, so we just call intr_ret
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51 * to return to user space
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52 */
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53 .globl just_forked
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54 just_forked:
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55 call intr_ret
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