mem: Implement safe copy functions

.github/workflows/it-compiles-test.yml

@@ -1,5 +1,5 @@
 name: It Compiles!
-on: [push]
+on: [push, workflow_dispatch]
 jobs:
   Compile:
     runs-on: ubuntu-latest

CMakeLists.txt

@@ -10,7 +10,6 @@ set(FILES
         ${PROJECT_SOURCE_DIR}/limine.cfg
 		crescent
         user_tty
-		initramfs.tar
         )
 
 add_executable(crescent src/main.c)
@@ -26,7 +25,7 @@ target_compile_options(crescent PRIVATE
         -mgeneral-regs-only -mno-red-zone -mcmodel=kernel
         -fno-stack-protector -fno-exceptions -fno-rtti
         -fno-omit-frame-pointer
-        -fPIC -nostdlibinc -fno-builtin>)
+        -fPIC -nostdlibinc -Werror=switch -Werror=noderef>)
 target_compile_options(crescent PRIVATE $<$<COMPILE_LANGUAGE:ASM>: -Wno-unused-command-line-argument>)
 target_link_options(crescent PRIVATE -T ${PROJECT_SOURCE_DIR}/.config/kernel.ld)
 

include/crescent/handle.h

@@ -0,0 +1,10 @@
+#ifndef CRESCENT_HANDLE_H
+#define CRESCENT_HANDLE_H
+
+#include <stdint.h>
+
+#define INVALID_HANDLE ((Handle) -1)
+
+typedef uint64_t Handle;
+
+#endif

include/crescent/sys.h

@@ -1,10 +1,6 @@
 #ifndef CRESCENT_SYS_H
 #define CRESCENT_SYS_H
-#include <stdint.h>
-
-#define INVALID_HANDLE ((Handle) -1)
-
-typedef uint64_t Handle;
+#include "handle.h"
 
 typedef enum {
 	SHUTDOWN_TYPE_REBOOT

limine.cfg

@@ -11,7 +11,4 @@ MODULE_CMDLINE=Tamsyn8x16r.psf
 MODULE_PATH=boot:///user_tty
 MODULE_CMDLINE=user_tty
 
-MODULE_PATH=boot:///initramfs.tar
-MODULE_CMDLINE=initramfs.tar
-
 KASLR=no

src/arch/misc.h

@@ -1,6 +1,12 @@
 #pragma once
+#include "types.h"
 
 void arch_hlt();
 void arch_spinloop_hint();
 
-void arch_reboot();
+void arch_reboot();
+
+#define __user __attribute__((address_space(1), noderef))
+
+bool arch_mem_copy_to_user(__user void* restrict user, const void* restrict kernel, usize size);
+bool arch_mem_copy_to_kernel(void* restrict kernel, __user const void* restrict user, usize size);

src/arch/x86/CMakeLists.txt

@@ -6,6 +6,7 @@ target_sources(crescent PRIVATE
         mod.c
         mem/map.c
         mem/mem.c
+		mem/misc.S
         interrupts/interrupts.c
         interrupts/idt.c
 		interrupts/int_stubs.S

src/arch/x86/interrupts/exceptions.c

@@ -61,6 +61,14 @@ GENERIC_EX(security, "security exception")
 IrqStatus ex_pf(void* void_ctx, void*) {
 	InterruptCtx* ctx = (InterruptCtx*) void_ctx;
 
+	Task* self = arch_get_cur_task();
+	if (self->handler_ip) {
+		ctx->ip = (usize) self->handler_ip;
+		ctx->sp = (usize) self->handler_sp;
+		self->handler_ip = 0;
+		return IRQ_ACK;
+	}
+
 	bool present = ctx->error & 1;
 	bool write = ctx->error & 1 << 1;
 	bool user = ctx->error & 1 << 2;
@@ -92,21 +100,11 @@ IrqStatus ex_pf(void* void_ctx, void*) {
 	backtrace_display(false);
 	spinlock_unlock(&PRINT_LOCK);
 
-	Task* self = arch_get_cur_task();
 	if (ctx->cs == 0x2b) {
 		kprintf("killing user task '%s'\n", self->name);
 		__asm__ volatile("sti");
 		sched_kill_cur();
 	}
-	else if (self->inside_syscall) {
-		ctx->sp = ctx->rbp + 8;
-		ctx->rbp = *(const u64*) ctx->rbp;
-		ctx->ip = *(const u64*) ctx->sp;
-		ctx->sp += 8;
-		ctx->rax = ERR_FAULT;
-		kprintf("%" PRIfg, COLOR_RESET);
-		return IRQ_ACK;
-	}
 
 	lapic_ipi_all(LAPIC_MSG_PANIC);
 

src/arch/x86/mem/misc.S

@@ -0,0 +1,45 @@
+// bool arch_mem_copy_to_user(__user void* restrict user, const void* restrict kernel, usize size);
+// bool arch_mem_copy_to_kernel(void* restrict kernel, __user const void* restrict user, usize size);
+
+#include <arch/x86/sched/usermode.inc>
+
+.globl arch_mem_copy_to_user
+.globl arch_mem_copy_to_kernel
+
+.type arch_mem_copy_to_user, @function
+arch_mem_copy_to_user:
+	push %rbp
+	mov %rsp, %rbp
+
+	lea 1f(%rip), %rax
+	mov %rax, %gs:X86TASK_HANDLER_IP_OFF
+	mov %rsp, %gs:X86TASK_HANDLER_SP_OFF
+
+	call memcpy
+
+	pop %rbp
+	mov $1, %eax
+	ret
+1:
+	pop %rbp
+	xor %eax, %eax
+	ret
+
+.type arch_mem_copy_to_kernel, @function
+arch_mem_copy_to_kernel:
+	push %rbp
+	mov %rsp, %rbp
+
+	lea 1f(%rip), %rax
+	mov %rax, %gs:X86TASK_HANDLER_IP_OFF
+	mov %rsp, %gs:X86TASK_HANDLER_SP_OFF
+
+	call memcpy
+
+	pop %rbp
+	mov $1, %eax
+	ret
+1:
+	pop %rbp
+	xor %eax, %eax
+	ret

src/arch/x86/sched/usermode.inc

@@ -1,6 +1,7 @@
 #ifndef USERMODE_INC
 #define USERMODE_INC
 
-#define X86TASK_INSIDE_SYSCALL_OFFSET 380
+#define X86TASK_HANDLER_IP_OFF 368
+#define X86TASK_HANDLER_SP_OFF 376
 
 #endif

src/arch/x86/sched/x86_task.h

@@ -18,10 +18,16 @@ typedef struct X86Task {
 	bool user;
 } X86Task;
 
+#define X86TASK_COMMON_OFF 72
+#define TASK_HANDLER_IP_OFF 296
+#define TASK_HANDLER_SP_OFF 304
+
 #include "usermode.inc"
-static_assert(offsetof(X86Task, common) + offsetof(Task, inside_syscall) == X86TASK_INSIDE_SYSCALL_OFFSET);
-static_assert(offsetof(Task, inside_syscall) == 308);
-static_assert(offsetof(X86Task, common) == 72);
+static_assert(offsetof(X86Task, common) == X86TASK_COMMON_OFF);
+static_assert(offsetof(Task, handler_ip) == TASK_HANDLER_IP_OFF);
+static_assert(offsetof(Task, handler_sp) == TASK_HANDLER_SP_OFF);
+static_assert(X86TASK_COMMON_OFF + TASK_HANDLER_IP_OFF == X86TASK_HANDLER_IP_OFF);
+static_assert(X86TASK_COMMON_OFF + TASK_HANDLER_SP_OFF == X86TASK_HANDLER_SP_OFF);
 
 void x86_task_add_map_page(X86Task* task, struct Page* page);
 void x86_task_remove_map_page(X86Task* task, struct Page* page);

src/mem/user.h

@@ -0,0 +1,10 @@
+#pragma once
+#include "arch/misc.h"
+
+static inline bool mem_copy_to_user(__user void* restrict user, const void* restrict kernel, usize size) {
+	return arch_mem_copy_to_user(user, kernel, size);
+}
+
+static inline bool mem_copy_to_kernel(void* restrict kernel, __user const void* restrict user, usize size) {
+	return arch_mem_copy_to_kernel(kernel, user, size);
+}

src/mem/vm.c

@@ -106,7 +106,7 @@ void* vm_user_alloc_backed(Process* process, usize count, PageFlags flags, void*
 	}
 
 	mutex_lock(&process->mapping_lock);
-	if (!process_add_mapping(process, (usize) vm, count * PAGE_SIZE)) {
+	if (!process_add_mapping(process, (usize) vm, count * PAGE_SIZE, flags & PF_WRITE)) {
 		mutex_unlock(&process->mapping_lock);
 		vm_user_dealloc(process, vm, count);
 		if (kernel_vm) {
@@ -192,7 +192,3 @@ bool vm_user_dealloc_backed(Process* process, void* ptr, usize count, void* kern
 	}
 	return true;
 }
-
-bool vm_user_verify(Process* process, void* ptr, size_t len) {
-	return process_is_mapped(process, (usize) ptr, len);
-}

src/mem/vm.h

@@ -19,5 +19,3 @@ void vm_user_dealloc(Process* process, void* ptr, usize count);
 void* vm_user_alloc_backed(Process* process, usize count, PageFlags flags, void** kernel_mapping);
 void vm_user_dealloc_kernel(void* kernel_mapping, usize count);
 bool vm_user_dealloc_backed(Process* process, void* ptr, usize count, void* kernel_mapping);
-
-bool vm_user_verify(Process* process, void* ptr, size_t len);

src/sched/process.c

@@ -22,35 +22,36 @@ Mapping* process_find_mapping(Process* self, usize addr) {
 	return NULL;
 }
 
-bool process_is_mapped(Process* self, usize start, usize size) {
-	usize end = start + size;
+bool process_is_mapped(Process* self, const void* start, usize size, bool rw) {
+	usize end = (usize) start + size;
 
 	const Mapping* mapping = (const Mapping*) self->mappings.hook.root;
 	while (mapping) {
 		usize mapping_start = mapping->base;
 		usize mapping_end = mapping_start + mapping->size;
 
-		if (start < mapping_end && mapping_start < end) {
-			return true;
+		if ((usize) start < mapping_end && mapping_start < end) {
+			return !rw || mapping->rw;
 		}
 
-		if (start < mapping->base) {
+		if ((usize) start < mapping->base) {
 			mapping = (const Mapping*) mapping->hook.left;
 		}
-		else if (start > mapping->base) {
+		else if ((usize) start > mapping->base) {
 			mapping = (const Mapping*) mapping->hook.right;
 		}
 	}
 	return false;
 }
 
-bool process_add_mapping(Process* self, usize base, usize size) {
+bool process_add_mapping(Process* self, usize base, usize size, bool rw) {
 	Mapping* mapping = kcalloc(sizeof(Mapping));
 	if (!mapping) {
 		return false;
 	}
 	mapping->base = base;
 	mapping->size = size;
+	mapping->rw = rw;
 
 	Mapping* m = (Mapping*) self->mappings.hook.root;
 	if (!m) {

src/sched/process.h

@@ -7,6 +7,7 @@ typedef struct {
 	RbTreeNode hook;
 	usize base;
 	usize size;
+	bool rw;
 } Mapping;
 
 typedef struct {
@@ -30,8 +31,8 @@ typedef struct Process {
 
 Process* process_new();
 Process* process_new_user();
-bool process_add_mapping(Process* self, usize base, usize size);
+bool process_add_mapping(Process* self, usize base, usize size, bool rw);
 bool process_remove_mapping(Process* self, usize base);
-bool process_is_mapped(Process* self, usize start, usize size);
+bool process_is_mapped(Process* self, const void* start, usize size, bool rw);
 void process_add_thread(Process* self, Task* task);
 void process_remove_thread(Process* self, Task* task);

src/sched/task.h

@@ -40,13 +40,14 @@ typedef struct Task {
 	struct Task* signal_waiters;
 	Mutex signal_waiters_lock;
 	EventQueue event_queue;
+	void* handler_ip;
+	void* handler_sp;
 	TaskStatus status;
 	u32 caps;
 	u8 level;
 	u8 priority;
 	bool pin_level;
 	bool pin_cpu;
-	bool inside_syscall;
 	atomic_bool killed;
 } Task;