Lab3 User Environment

[Preface] A Hope That My Crude Remarks May Draw Forth By Abler People
[前言]拋磚引玉

• How to do the following lab3?
• Read following list:
• Lec4 JOS memory layout.
• Lec5: Process Creation System call／Interrupt, and Exception Handling
• Hw5 Hw4
• Ch.9 of 80386 Programmer's Manual／Ch05 of the IA-32 Developer's Manual.
• Lab3 assignment.
• Dig everything unknown more:
• Think about debugging!
• Basic setup:
• IDT.
• Breakpoint exception.
• System call exception.
• Other exceptions.
• Allocate the memory space for Env structure.
• Be cared about address mapping.
• Link each element in the right order.
• Exercise 1 & 2 is done
• More setup 
• Make programs run.
• Setup the env's virtual memory mapping
• Map only user level's need address mapping from kern_pgdir.
• Load ELF file.
• Stack.
• Entry address.
• Set the env's fields well
• env_status/env_type...etc
• Let user programs be capable of trapping into kernel.
• Push the needed variable/registers into kernel stack!
• Default error handling: Not supported exceptions.
• Get PartA's grade.
• Setup exception handlers:
• Trap entries to support user's functionality.
• page_fault_handler.
• breakpoint handler.
• Pass exercise 5&6
• system call setup
• Handle 0x30 IDT entry.
• Organize the trap frame..
• Push the right esp as the trap call's input parameter(trap frame address).
• Dispatch the eax (syscall num) to the corresponding handler.
• Extract parameters in the right slot.
• Return value.
• User level's this env assignment.
• Pass exercise 7&8
• kdebug.c not yet.
• Protections
• user_mem_check
•  permission.
• legal contiguous memory coverage.
• evilhello: address' permission setup must be right.
• Pass All
• Challenge implementation: fast system call
• Read carefully about sysenter/sysexit/wrmsr/rdmsr in Intel manual.
• Setup the following slot in the right vale.
• MSR_IA32_SYSTEM_CS.
• GDT must own the right order between ring0/ring3's cs ss
• ring0:CS
• ring0:SS
• ring3:CS
• ring3:SS
• MSR_IA32_SYSTEM_EIP.
• MSR_IA32_SYSTEM_ESP
• library wrapper
• Assign the right value into regs.
• ebp(stack pointer used by sysenter).
• esi (intruction pointer used by sysenter).
• place arguments into the right registers.
• Be careful about push/restore clobber registers.
• Trap entry's handler
• Before calling system call function.
• push the needed vars into stack to organize the Trapframe.
• push the organize trapframe pointer into stack
• After calling system call function.
• Assign the right value into regs.
• edx(stack pointer used by sysenter).
• ecx (intruction pointer used by sysenter).
• Retroe the needed regs
• Finish Fast Syscall Challenge