42328ead0b
- Added paging_clone_directory_from(): deep-copies user-space pages so parent and child have independent memory. Kernel pages are shared. - Fixed process_fork() to accept registers_t* for accurate child state, and to clone from the parent's page directory (not the kernel's). - Refactored process_exit() to properly context-switch to next process using new process_switch_to_user assembly stub (loads full registers_t and performs iret), instead of halting unconditionally. - Fixed sys_waitpid() to use proper blocking: marks process BLOCKED, invokes scheduler, and resumes with exit code when child dies. - Added SYSCALL_SWITCHED mechanism to prevent syscall_handler from clobbering the next process's EAX after a context switch. - Created fork-test user app that validates fork + waitpid. - Added docs/fork.md with architecture documentation. Tested: fork-test creates child, both print messages, parent waits for child exit (code 7), parent reaps and exits (code 0). hello-world also verified to still work correctly after the process_exit refactor.
80 lines
1.7 KiB
ArmAsm
80 lines
1.7 KiB
ArmAsm
#
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# fork-test: Tests the fork system call.
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#
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# 1. Calls SYS_FORK
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# 2. Parent prints "Parent: pid=<pid>\n" and waits for child
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# 3. Child prints "Child: pid=0\n" and exits with code 7
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# 4. Parent exits with code 0
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#
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.section .text
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.global _start
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# System call numbers
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.equ SYS_EXIT, 0
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.equ SYS_WRITE, 1
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.equ SYS_FORK, 3
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.equ SYS_GETPID, 4
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.equ SYS_WAITPID, 6
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_start:
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# Fork
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movl $SYS_FORK, %eax
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int $0x80
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# EAX = 0 in child, child PID in parent
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testl %eax, %eax
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jz .child
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.parent:
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# Save child PID on the stack
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pushl %eax
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# Print "Parent\n"
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movl $SYS_WRITE, %eax
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movl $1, %ebx # fd = stdout
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movl $parent_msg, %ecx
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movl $parent_msg_len, %edx
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int $0x80
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# Waitpid for child
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popl %ebx # child PID
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movl $SYS_WAITPID, %eax
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int $0x80
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# EAX now has child's exit code (should be 7)
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# Print "Reaped\n"
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pushl %eax # save exit code
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movl $SYS_WRITE, %eax
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movl $1, %ebx
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movl $reaped_msg, %ecx
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movl $reaped_msg_len, %edx
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int $0x80
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popl %ebx # exit code (unused, exit with 0)
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# Exit with code 0
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movl $SYS_EXIT, %eax
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movl $0, %ebx
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int $0x80
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.child:
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# Print "Child\n"
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movl $SYS_WRITE, %eax
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movl $1, %ebx # fd = stdout
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movl $child_msg, %ecx
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movl $child_msg_len, %edx
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int $0x80
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# Exit with code 7
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movl $SYS_EXIT, %eax
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movl $7, %ebx
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int $0x80
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.section .rodata
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parent_msg: .ascii "Parent\n"
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.equ parent_msg_len, . - parent_msg
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child_msg: .ascii "Child\n"
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.equ child_msg_len, . - child_msg
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reaped_msg: .ascii "Reaped\n"
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.equ reaped_msg_len, . - reaped_msg
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