| .text |
| |
| /* |
| Callee save registers: |
| ebp, ebx, esi, edi |
| |
| Caller save registers: |
| eax, ecx, edx |
| */ |
| |
| /* |
| Saves a set of registers. This is used by our implementation of |
| getcontext. |
| |
| The registers_t variable is in (%esp) |
| */ |
| |
| // swap_registers(registers_t *oregs, registers_t *regs) |
| .globl swap_registers |
| swap_registers: |
| // save the old context |
| movl 4(%esp), %eax |
| movl %ebx, 4(%eax) |
| movl %ebp, 16(%eax) |
| movl %esi, 20(%eax) |
| movl %edi, 24(%eax) |
| |
| // save the flags |
| pushf |
| popl %ecx |
| movl %ecx, 44(%eax) |
| |
| // save the return address as the instruction pointer |
| // and save the stack pointer of the caller |
| popl %ecx |
| movl %esp, 28(%eax) |
| movl %ecx, 48(%eax) |
| |
| // restore the new context |
| movl 4(%esp), %eax |
| |
| movl 4(%eax), %ebx |
| movl 16(%eax), %ebp |
| movl 20(%eax), %esi |
| movl 24(%eax), %edi |
| movl 28(%eax), %esp |
| |
| // restore the flags |
| movl 44(%eax), %ecx |
| push %ecx |
| popf |
| |
| // Return! |
| jmp *48(%eax) |
| |
| |
