kernel/arm: implement entering userspace

Change-Id: Icf3945db979a8f4444856fc7157649f48b297c29
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5037
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Fredrik Holmqvist <fredrik.holmqvist@gmail.com>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

headers/private/kernel/arch/arm/arch_thread_types.h

@@ -37,4 +37,15 @@ struct arch_fork_arg {
 	char	dummy;
 };
 
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void arch_return_to_userland(struct iframe *);
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif	/* KERNEL_ARCH_ARM_THREAD_TYPES_H */

headers/private/system/arch/arm/arch_commpage_defs.h

@@ -1,15 +1,17 @@
 /*
+ * Copyright 2022, Haiku Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
  * Copyright 2007, Travis Geiselbrecht. All rights reserved.
  * Distributed under the terms of the MIT License.
  */
-#ifndef _SYSTEM_ARCH_M68K_COMMPAGE_DEFS_H
-#define _SYSTEM_ARCH_M68K_COMMPAGE_DEFS_H
+#ifndef _SYSTEM_ARCH_ARM_COMMPAGE_DEFS_H
+#define _SYSTEM_ARCH_ARM_COMMPAGE_DEFS_H
 
 #ifndef _SYSTEM_COMMPAGE_DEFS_H
 #	error Must not be included directly. Include <commpage_defs.h> instead!
 #endif
 
-//#define COMMPAGE_ENTRY_M68K_SYSCALL	(COMMPAGE_ENTRY_FIRST_ARCH_SPECIFIC + 0)
-//#define COMMPAGE_ENTRY_M68K_MEMCPY	(COMMPAGE_ENTRY_FIRST_ARCH_SPECIFIC + 1)
+#define COMMPAGE_ENTRY_ARM_THREAD_EXIT	(COMMPAGE_ENTRY_FIRST_ARCH_SPECIFIC + 0)
 
-#endif	/* _SYSTEM_ARCH_M68K_COMMPAGE_DEFS_H */
+#endif	/* _SYSTEM_ARCH_ARM_COMMPAGE_DEFS_H */

headers/private/system/arch/arm/arch_cpu_defs.h

@@ -13,6 +13,12 @@
 
 #define CPSR_MODE_MASK		0x1f
 #define CPSR_MODE_USR		0x10
+#define CPSR_MODE_SVC		0x13
+#define CPSR_MODE_SYS		0x1f
+
+#define CPSR_T				0x20
+#define CPSR_F				0x40
+#define CPSR_I				0x80
 
 #define FSR_WNR				0x800
 

src/system/kernel/arch/arm/arch_asm.S

@@ -1,4 +1,7 @@
 /*
+ * Copyright 2022, Haiku Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
  * Copyright 2009, Wischert, johanneswi@gmail.com.
  * All rights reserved. Distributed under the terms of the MIT License.
  *
@@ -7,10 +10,12 @@
  */
 
 #include <arch/arm/arch_cpu.h>
+#include <arch/arm/arch_cpu_defs.h>
 
 #include <asm_defs.h>
 
 #include "asm_offsets.h"
+#include "syscall_numbers.h"
 
 .text
 
@@ -253,3 +258,42 @@ FUNCTION(arch_debug_call_with_fault_handler):
 	mov	r1, #1
 	b	longjmp
 FUNCTION_END(arch_debug_call_with_fault_handler)
+
+
+FUNCTION(arch_return_to_userland):
+	// set SPSR to user mode, IRQ enabled, FIQ disabled
+	mrs		ip, cpsr
+	bic		ip, ip, #(CPSR_MODE_MASK | CPSR_T | CPSR_F | CPSR_I)
+	orr		ip, ip, #(CPSR_MODE_USR | CPSR_F)
+	msr		spsr, ip
+
+	// use system mode to load user mode SP and LR
+	ldr		r4, [r0, #IFRAME_usr_sp]
+	ldr		r5, [r0, #IFRAME_usr_lr]
+	mrs		ip, cpsr
+	bic		ip, ip, #(CPSR_MODE_MASK)
+	orr		ip, ip, #(CPSR_MODE_SYS)
+	msr		cpsr, ip
+	mov		sp, r4
+	mov		lr, r5
+	bic		ip, ip, #(CPSR_MODE_MASK)
+	orr		ip, ip, #(CPSR_MODE_SVC)
+	msr		cpsr, ip
+
+	// load user mode entry point in LR
+	ldr		lr, [r0, #IFRAME_pc]
+
+	// load general purpose registers
+	mov		sp, r0
+	add		sp, sp, #4
+	ldmfd	sp!, { r0-r12 }
+
+	// jump to user mode entry point
+	movs	pc, lr
+FUNCTION_END(arch_return_to_userland)
+
+
+FUNCTION(arch_user_thread_exit):
+	svc		SYSCALL_EXIT_THREAD
+	bx		lr
+FUNCTION_END(arch_user_thread_exit)

src/system/kernel/arch/arm/arch_commpage.cpp

@@ -1,4 +1,7 @@
 /*
+ * Copyright 2022, Haiku Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
  * Copyright 2009, Johannes Wischert, johanneswi@gmail.com.
  * Distributed under the terms of the MIT License.
  */
@@ -15,14 +18,36 @@
 #include <smp.h>
 
 
+extern "C" void arch_user_thread_exit();
+
+
+static void
+register_commpage_function(const char* functionName, int32 commpageIndex,
+	const char* commpageSymbolName, addr_t expectedAddress)
+{
+	// get address and size of function
+	elf_symbol_info symbolInfo;
+	if (elf_lookup_kernel_symbol(functionName, &symbolInfo) != B_OK) {
+		panic("register_commpage_function(): Failed to find "
+			"function \"%s\"!", functionName);
+	}
+
+	ASSERT(expectedAddress == symbolInfo.address);
+
+	// fill in the commpage table entry
+	addr_t position = fill_commpage_entry(commpageIndex,
+		(void*)symbolInfo.address, symbolInfo.size);
+
+	// add symbol to the commpage image
+	image_id image = get_commpage_image();
+	elf_add_memory_image_symbol(image, commpageSymbolName, position,
+		symbolInfo.size, B_SYMBOL_TYPE_TEXT);
+}
+
+
 status_t
 arch_commpage_init(void)
 {
-	/* no optimized memcpy or anything yet */
-	/* we don't use it for syscall yet either */
-	// add syscall to the commpage image
-//	image_id image = get_commpage_image();
-#warning ARM:IMPLEMENTME
 	return B_OK;
 }
 
@@ -30,7 +55,10 @@ arch_commpage_init(void)
 status_t
 arch_commpage_init_post_cpus(void)
 {
-#warning ARM:IMPLEMENTME
+	register_commpage_function("arch_user_thread_exit",
+		COMMPAGE_ENTRY_ARM_THREAD_EXIT, "commpage_thread_exit",
+		(addr_t)&arch_user_thread_exit);
+
 	return B_OK;
 }
 

src/system/kernel/arch/arm/arch_thread.cpp

@@ -18,6 +18,7 @@
 #include <arch_cpu.h>
 #include <arch/thread.h>
 #include <boot/stage2.h>
+#include <commpage.h>
 #include <kernel.h>
 #include <thread.h>
 #include <tls.h>
@@ -198,9 +199,37 @@ arch_thread_dump_info(void *info)
 
 status_t
 arch_thread_enter_userspace(Thread *thread, addr_t entry,
-	void *arg1, void *arg2)
+	void *args1, void *args2)
 {
-	panic("arch_thread_enter_uspace(): not yet implemented\n");
+	arm_set_tls_context(thread);
+
+	addr_t stackTop = thread->user_stack_base + thread->user_stack_size;
+
+	TRACE(("arch_thread_enter_userspace: entry 0x%" B_PRIxADDR ", args %p %p, "
+		"ustack_top 0x%" B_PRIxADDR "\n", entry, args1, args2, stackTop));
+
+	//stackTop = arch_randomize_stack_pointer(stackTop - sizeof(args));
+
+	// Copy the address of the stub that calls exit_thread() when the thread
+	// entry function returns to LR to act as the return address.
+	// The stub is inside commpage.
+	addr_t commPageAddress = (addr_t)thread->team->commpage_address;
+
+	disable_interrupts();
+
+	// prepare the user iframe
+	iframe frame = {};
+	frame.r0 = (uint32)args1;
+	frame.r1 = (uint32)args2;
+	frame.usr_sp = stackTop;
+	frame.usr_lr = ((addr_t*)commPageAddress)[COMMPAGE_ENTRY_ARM_THREAD_EXIT]
+		+ commPageAddress;
+	frame.pc = entry;
+
+	// return to userland
+	arch_return_to_userland(&frame);
+
+	// normally we don't get here
 	return B_ERROR;
 }
 

src/system/kernel/arch/arm/asm_offsets.cpp

@@ -46,6 +46,9 @@ dummy()
 
 	// struct iframe
 	DEFINE_SIZEOF_MACRO(IFRAME, iframe);
+	DEFINE_OFFSET_MACRO(IFRAME, iframe, pc);
+	DEFINE_OFFSET_MACRO(IFRAME, iframe, usr_sp);
+	DEFINE_OFFSET_MACRO(IFRAME, iframe, usr_lr);
 
 	// struct signal_frame_data
 	DEFINE_SIZEOF_MACRO(SIGNAL_FRAME_DATA, signal_frame_data);