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.
202 lines
4.3 KiB
ArmAsm
202 lines
4.3 KiB
ArmAsm
.section .text
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.global idt_load
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.type idt_load, @function
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idt_load:
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mov 4(%esp), %eax
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lidt (%eax)
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ret
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/* Common ISR stub */
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isr_common_stub:
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pusha
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/* Save segment registers */
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mov %ds, %ax
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push %eax
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/* Load kernel data segment */
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mov $0x10, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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/* Push pointer to stack structure as argument for C handler */
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push %esp
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call isr_handler
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add $4, %esp /* Clean up pushed pointer */
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/* Restore segment registers */
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pop %eax
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mov %eax, %ds
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mov %eax, %es
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mov %eax, %fs
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mov %eax, %gs
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popa
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add $8, %esp /* Cleans up error code and ISR number */
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iret
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/* Macro for exceptions with NO Error Code */
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.macro ISR_NOERRCODE num
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.global isr\num
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.type isr\num, @function
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isr\num:
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cli
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push $0
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push $\num
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jmp isr_common_stub
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.endm
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/* Macro for exceptions WITH Error Code */
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.macro ISR_ERRCODE num
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.global isr\num
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.type isr\num, @function
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isr\num:
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cli
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push $\num
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jmp isr_common_stub
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.endm
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ISR_NOERRCODE 0
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ISR_NOERRCODE 1
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ISR_NOERRCODE 2
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ISR_NOERRCODE 3
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ISR_NOERRCODE 4
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ISR_NOERRCODE 5
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ISR_NOERRCODE 6
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ISR_NOERRCODE 7
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ISR_ERRCODE 8
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ISR_NOERRCODE 9
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ISR_ERRCODE 10
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ISR_ERRCODE 11
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ISR_ERRCODE 12
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ISR_ERRCODE 13
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ISR_ERRCODE 14
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ISR_NOERRCODE 15
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ISR_NOERRCODE 16
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ISR_ERRCODE 17
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ISR_NOERRCODE 18
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ISR_NOERRCODE 19
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ISR_NOERRCODE 20
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ISR_NOERRCODE 21
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ISR_NOERRCODE 22
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ISR_NOERRCODE 23
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ISR_NOERRCODE 24
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ISR_NOERRCODE 25
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ISR_NOERRCODE 26
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ISR_NOERRCODE 27
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ISR_NOERRCODE 28
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ISR_NOERRCODE 29
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ISR_ERRCODE 30
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ISR_NOERRCODE 31
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/* Macro for IRQs (Hardware Interrupts) */
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.macro ISR_IRQ num, idt_index
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.global irq\num
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.type irq\num, @function
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irq\num:
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cli
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push $0
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push $\idt_index
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jmp isr_common_stub
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.endm
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/* Hardware Interrupts */
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ISR_IRQ 0, 32
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ISR_IRQ 1, 33
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ISR_IRQ 2, 34
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ISR_IRQ 3, 35
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ISR_IRQ 4, 36
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ISR_IRQ 5, 37
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ISR_IRQ 6, 38
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ISR_IRQ 7, 39
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ISR_IRQ 8, 40
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ISR_IRQ 9, 41
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ISR_IRQ 10, 42
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ISR_IRQ 11, 43
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ISR_IRQ 12, 44
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ISR_IRQ 13, 45
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ISR_IRQ 14, 46
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ISR_IRQ 15, 47
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/*
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* INT 0x80 - System call entry point.
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* Uses the same isr_common_stub so the register layout matches registers_t.
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*/
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.global isr128
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.type isr128, @function
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isr128:
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cli
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push $0 /* Fake error code */
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push $0x80 /* Interrupt number 128 */
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jmp isr_common_stub
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/*
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* tss_flush - Load the Task Register with the TSS selector.
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* TSS is GDT entry 5, selector = 5*8 = 0x28. With RPL=0: 0x28.
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*/
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.global tss_flush
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.type tss_flush, @function
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tss_flush:
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mov $0x28, %ax
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ltr %ax
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ret
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/*
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* enter_usermode - Switch to Ring 3 user mode via iret.
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* void enter_usermode(uint32_t eip, uint32_t esp);
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*
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* Builds an iret frame on the stack:
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* SS = 0x23 (user data)
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* ESP = user stack pointer
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* EFLAGS = IF=1
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* CS = 0x1B (user code)
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* EIP = user entry point
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*/
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.global enter_usermode
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.type enter_usermode, @function
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enter_usermode:
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mov 4(%esp), %ecx /* user EIP */
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mov 8(%esp), %edx /* user ESP */
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/* Set data segment registers to user data segment */
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mov $0x23, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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/* Build iret frame */
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push $0x23 /* SS (user data) */
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push %edx /* ESP (user stack) */
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pushf /* EFLAGS */
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orl $0x200, (%esp) /* Ensure IF (Interrupt Flag) is set */
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push $0x1B /* CS (user code) */
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push %ecx /* EIP (entry point) */
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iret
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/*
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* process_switch_to_user - Restore full register state and iret to user mode.
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* void process_switch_to_user(registers_t *regs);
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*
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* Used by process_exit to context-switch to the next process when the normal
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* interrupt-return path isn't available (because we're not returning through
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* an ISR stub). Loads all registers from the registers_t struct and performs
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* iret to enter user mode.
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*/
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.global process_switch_to_user
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.type process_switch_to_user, @function
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process_switch_to_user:
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movl 4(%esp), %esp /* Point ESP to the registers_t struct */
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/* Restore segment register (ds → all data segments) */
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pop %eax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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popa /* Restore EAX-EDI */
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addl $8, %esp /* Skip int_no and err_code */
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iret /* Pops EIP, CS, EFLAGS, UserESP, SS */
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