From aa30d9c6b56f843f15de609653e6a95c0e604412 Mon Sep 17 00:00:00 2001 From: xamidev Date: Thu, 2 Apr 2026 17:05:51 +0200 Subject: [PATCH] user program (still many #PF) --- include/arch/x86.h | 1 - include/config.h | 1 + include/mem/vmm.h | 2 ++ include/sched/process.h | 3 +++ src/arch/x86/idt.c | 7 ++--- src/arch/x86/init.c | 2 +- src/kmain.c | 13 ++++----- src/mem/paging.c | 22 +++++++++++++--- src/mem/vmm.c | 11 ++++++++ src/sched/process.c | 58 +++++++++++++++++++++++++++++++++++++++++ user/hello.S | 3 +-- 11 files changed, 107 insertions(+), 16 deletions(-) diff --git a/include/arch/x86.h b/include/arch/x86.h index d6900e3..b0b9029 100644 --- a/include/arch/x86.h +++ b/include/arch/x86.h @@ -10,7 +10,6 @@ void wrmsr(uint32_t msr, uint64_t value); bool x86_has_msr(); void x86_arch_init(); - void x86_cpu_identification(); int cpuid_get_vendor_string(char* str); diff --git a/include/config.h b/include/config.h index 811ad4d..f3564ec 100644 --- a/include/config.h +++ b/include/config.h @@ -43,6 +43,7 @@ /* user */ #define USER_STACK_TOP 0x80000000 #define USER_STACK_PAGES 16 // 16*4096 = 64kb +#define USER_CODE_START 0x400000 // like linux /* paging */ #define PAGING_MAX_PHYS 0x200000000 diff --git a/include/mem/vmm.h b/include/mem/vmm.h index 64e1f0c..5383622 100644 --- a/include/mem/vmm.h +++ b/include/mem/vmm.h @@ -22,6 +22,8 @@ void vmm_unmap(uint64_t* pml4, uint64_t virt); void* vmm_map(uint64_t* pml4, uint64_t virt, uint64_t flags); uint64_t* vmm_create_address_space(); uint64_t vmm_virt_to_phys(uint64_t* pml4, uint64_t virt); +uintptr_t vmm_alloc_user_stack(uint64_t* pml4); +uintptr_t vmm_alloc_user_code(uint64_t* pml4, void* code_addr, uint64_t code_size); #define VMM_USER_SPACE_START 0x0000000000001000 #define VMM_USER_SPACE_END 0x00007FFFFFFFF000 diff --git a/include/sched/process.h b/include/sched/process.h index c42bf0d..ef00d3e 100644 --- a/include/sched/process.h +++ b/include/sched/process.h @@ -10,6 +10,7 @@ #include #include #include +#include typedef enum { READY, @@ -37,4 +38,6 @@ void process_exit(void); void process_display_list(struct process* processes_list); +void process_create_user(struct limine_file* file); + #endif diff --git a/src/arch/x86/idt.c b/src/arch/x86/idt.c index 75d5514..4a29524 100644 --- a/src/arch/x86/idt.c +++ b/src/arch/x86/idt.c @@ -77,7 +77,7 @@ void idt_init() idt_set_entry(i, vector_0_handler + (i*16), 0); } - idt_set_entry(0x80, vector_128_handler, 0); + idt_set_entry(0x80, vector_128_handler, 3); idt_load(&idt); DEBUG("IDT initialized"); @@ -264,9 +264,10 @@ struct cpu_status* interrupt_dispatch(struct cpu_status* context) // Send an EOI so that we can continue having interrupts outb(0x20, 0x20); - if (ticks % SCHEDULER_QUANTUM == 0) { + // Scheduler is temporarily disabled to test user trampoline + /* if (ticks % SCHEDULER_QUANTUM == 0) { return scheduler_schedule(context); - } + } */ break; diff --git a/src/arch/x86/init.c b/src/arch/x86/init.c index e1736c3..997793a 100644 --- a/src/arch/x86/init.c +++ b/src/arch/x86/init.c @@ -45,7 +45,7 @@ static void x86_enable_fpu() __asm__ volatile("mov %%cr4, %0" : "=r"(cr4)); cr4 |= 0x200; __asm__ volatile("mov %0, %%cr4" :: "r"(cr4)); - uint16_t cw = 0x37F; + uint16_t cw = 0x37F; // control word asm volatile("fldcw %0" :: "m"(cw)); } diff --git a/src/kmain.c b/src/kmain.c index 6d7cd21..89bd3b0 100644 --- a/src/kmain.c +++ b/src/kmain.c @@ -124,15 +124,16 @@ void kmain() if (!boot_ctx.module) { panic(NULL, "could not load 'hello' executable :("); - } - - if (boot_ctx.module->module_count == 1) { - file = boot_ctx.module->modules[0]; - DEBUG("file: addr=%p size=%u", file->address, file->size); - } + } printf(PEPPEROS_SPLASH); init.all = true; + if (boot_ctx.module->module_count == 1) { + file = boot_ctx.module->modules[0]; + DEBUG("file: addr=%p size=%u", file->address, file->size); + process_create_user(file); + } + idle(); } diff --git a/src/mem/paging.c b/src/mem/paging.c index 4b76536..bd0b812 100644 --- a/src/mem/paging.c +++ b/src/mem/paging.c @@ -99,30 +99,46 @@ void paging_map_page(uint64_t* root_table, uint64_t virt, uint64_t phys, uint64_ uint64_t *pdpt, *pd, *pt; + // Any parent entry on a userspace mapping must also carry PTE_USER, + // otherwise CPL3 accesses fault even if the final PTE is user. + uint64_t parent_flags = PTE_PRESENT | PTE_WRITABLE; + if (flags & PTE_USER) { + parent_flags |= PTE_USER; + } + // PML4 // If the entry at index is not present, allocate enough space for it // then populate the entry with correct addr + flags if (!(root_table[pml4_i] & PTE_PRESENT)) { pdpt = alloc_page_table(); - root_table[pml4_i] = VIRT_TO_PHYS(pdpt) | PTE_PRESENT | PTE_WRITABLE; + root_table[pml4_i] = VIRT_TO_PHYS(pdpt) | parent_flags; } else { pdpt = (uint64_t *)PHYS_TO_VIRT(root_table[pml4_i] & PTE_ADDR_MASK); + if (flags & PTE_USER) { + root_table[pml4_i] |= PTE_USER; + } } // PDPT: same here if (!(pdpt[pdpt_i] & PTE_PRESENT)) { pd = alloc_page_table(); - pdpt[pdpt_i] = VIRT_TO_PHYS(pd) | PTE_PRESENT | PTE_WRITABLE; + pdpt[pdpt_i] = VIRT_TO_PHYS(pd) | parent_flags; } else { pd = (uint64_t *)PHYS_TO_VIRT(pdpt[pdpt_i] & PTE_ADDR_MASK); + if (flags & PTE_USER) { + pdpt[pdpt_i] |= PTE_USER; + } } // PD: and here if (!(pd[pd_i] & PTE_PRESENT)) { pt = alloc_page_table(); - pd[pd_i] = VIRT_TO_PHYS(pt) | PTE_PRESENT | PTE_WRITABLE; + pd[pd_i] = VIRT_TO_PHYS(pt) | parent_flags; } else { pt = (uint64_t *)PHYS_TO_VIRT(pd[pd_i] & PTE_ADDR_MASK); + if (flags & PTE_USER) { + pd[pd_i] |= PTE_USER; + } } // PT: finally, populate the page table entry diff --git a/src/mem/vmm.c b/src/mem/vmm.c index ec20a39..d17970a 100644 --- a/src/mem/vmm.c +++ b/src/mem/vmm.c @@ -250,6 +250,17 @@ uintptr_t vmm_alloc_user_stack(uint64_t* pml4) return stack_top; } +uintptr_t vmm_alloc_user_code(uint64_t* pml4, void* code_addr, uint64_t code_size) +{ + uintptr_t code_start = USER_CODE_START; + + for (size_t i=code_start; i #include #include @@ -13,6 +15,7 @@ #include #include #include +#include extern struct flanterm_context* ft_ctx; @@ -196,4 +199,59 @@ void process_exit() for (;;) { asm("hlt"); } +} + +/* + * process_jump_to_user - Jump to userland + * @stack_top: Address of the top of the user stack + * @user_code: Address of the first instruction of user code + */ +void process_jump_to_user(uintptr_t stack_top, uintptr_t user_code) +{ + // 0x20 | 3 = 0x23 (user data segment | 3) + // 0x18 | 3 = 0x1B (user code segment | 3) + asm volatile(" \ + push $0x23 \n\ + push %0 \n\ + push $0x202 \n\ + push $0x1B \n\ + push %1 \n\ + iretq \n\ + " :: "r"(stack_top), "r"(user_code)); +} + +// Kernel stack used for interrupts from userland process. +// Should be set in TSS.RSP0 when switching to userland process. +uint8_t interrupt_stack[0x8000]; + +extern struct tss tss; + +/* + * process_create_user - Create a new user process + * @file: pointer to Limine file structure + * + * This function takes a loaded Limine executable + * module, and maps its code, a user stack, sets the + * TSS RSP0 for interrupts, and finally jumps to the + * user code. + */ +void process_create_user(struct limine_file* file) +{ + void* exec_addr = file->address; + uint64_t exec_size = file->size; + + uint64_t* user_pml4 = vmm_create_address_space(); + uintptr_t stack_top = vmm_alloc_user_stack(user_pml4); + uint64_t code = vmm_alloc_user_code(user_pml4, exec_addr, exec_size); + + // Could be kalloc_stack()ed PER PROCESS when we grow that + tss.rsp0 = (uint64_t)(interrupt_stack + sizeof(interrupt_stack)); + + // Load user_pml4 into cr3 along here?? + load_cr3(VIRT_TO_PHYS((uint64_t)user_pml4)); + + // Copy code into user pages + memcpy((uint64_t*)code, exec_addr, exec_size); + + process_jump_to_user(stack_top, code); } \ No newline at end of file diff --git a/user/hello.S b/user/hello.S index be06990..2520195 100644 --- a/user/hello.S +++ b/user/hello.S @@ -1,5 +1,4 @@ bits 64 hello: - mov qword rax, 0xcafebabe - jmp hello \ No newline at end of file + mov rax, 0xcafebabe \ No newline at end of file