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extending example task, fix bug in handling of the TSS

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This commit is contained in:
Stefan Lankes 2014-01-22 10:28:14 +01:00
parent b83bc1d261
commit eb8859d706
12 changed files with 180 additions and 78 deletions
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11
arch/x86/include/asm/processor.h
View file

@ -82,6 +82,17 @@ inline static void rmb(void) { asm volatile("lfence" ::: "memory"); }
/// Force strict CPU ordering, serializes store operations.
inline static void wmb(void) { asm volatile("sfence" ::: "memory"); }
/** @brief Read EFLAGS
*
* @return The EFLAGS value
*/
static inline uint32_t read_eflags(void)
{
uint32_t result;
asm volatile ("pushf; pop %0" : "=r"(result));
return result;
}
/** @brief search the first most significant bit
*
* @param i source operand

21
arch/x86/include/asm/tasks.h
View file

@ -59,7 +59,10 @@ void switch_context(size_t** stack);
* - 0 on success
* - -EINVAL (-22) on failure
*/
int create_default_frame(task_t* task, entry_point_t ep, void* arg, uint8_t user);
int create_default_frame(task_t* task, entry_point_t ep, void* arg);
/** @brief Copy kernel stack pointer to TSS */
void set_kernel_stack(size_t stack);
/** @brief Register a task's TSS at GDT
*
@ -75,6 +78,22 @@ static inline int register_task(void)
return 0;
}
/** @brief Jump back to user code
*
* This function runs the user code after stopping it just as if
* it was a return from a procedure.
*
* @return 0 in any case
*/
static inline int jump_to_user_code(uint32_t ep, uint32_t stack)
{
asm volatile ("mov %0, %%ds; mov %0, %%fs; mov %0, %%gs; mov %0, %%es" :: "r"(0x23));
asm volatile ("push $0x23; push %0; push $0x1B; push %1" :: "r"(stack), "r"(ep));
asm volatile ("lret" ::: "cc");
return 0;
}
#ifdef __cplusplus
}
#endif

13
arch/x86/kernel/gdt.c
View file

@ -46,6 +46,11 @@ static gdt_entry_t gdt[GDT_ENTRIES] = {[0 ... GDT_ENTRIES-1] = {0, 0, 0, 0, 0,
*/
extern void gdt_flush(void);
void set_kernel_stack(size_t stack)
{
task_state_segment.esp0 = stack;
}
/* Setup a descriptor in the Global Descriptor Table */
void gdt_set_gate(int num, unsigned long base, unsigned long limit,
unsigned char access, unsigned char gran)
@ -122,13 +127,15 @@ void gdt_install(void)
* Create data segement for userspace applications (ring 3)
*/
gdt_set_gate(4, 0, limit,
GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
GDT_FLAG_4K_GRAN | mode);
GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
GDT_FLAG_4K_GRAN | mode);
/* set default values */
task_state_segment.eflags = 0x1202;
task_state_segment.ss0 = 0x10; // data segment
task_state_segment.ss0 = 0x10; // data segment
task_state_segment.esp0 = 0xDEADBEEF; // invalid pseudo address
task_state_segment.cs = 0x0b;
task_state_segment.ss = task_state_segment.ds = task_state_segment.es = task_state_segment.fs = task_state_segment.gs = 0x13;
gdt_set_gate(5, (unsigned long) (&task_state_segment), sizeof(tss_t)-1,
GDT_FLAG_PRESENT | GDT_FLAG_TSS | GDT_FLAG_RING0, mode);

38
arch/x86/kernel/tasks.c
View file

@ -32,8 +32,6 @@
#include <eduos/errno.h>
#include <eduos/processor.h>
static unsigned char ustacks[MAX_TASKS][KERNEL_STACK_SIZE] __attribute__ ((aligned (PAGE_SIZE)));
size_t* get_current_stack(void)
{
task_t* curr_task = current_task;
@ -41,11 +39,9 @@ size_t* get_current_stack(void)
return curr_task->last_stack_pointer;
}
int create_default_frame(task_t* task, entry_point_t ep, void* arg, uint8_t user)
int create_default_frame(task_t* task, entry_point_t ep, void* arg)
{
uint16_t cs = user ? 0x1B : 0x08;
uint16_t ds = user ? 0x23 : 0x10;
size_t *stack, *ustack;
size_t *stack;
struct state *stptr;
size_t state_size;
@ -56,16 +52,12 @@ int create_default_frame(task_t* task, entry_point_t ep, void* arg, uint8_t user
return -EINVAL;
memset(task->stack, 0xCD, KERNEL_STACK_SIZE);
memset(ustacks[task->id] , 0xCD, KERNEL_STACK_SIZE);
/* The difference between setting up a task for SW-task-switching
* and not for HW-task-switching is setting up a stack and not a TSS.
* This is the stack which will be activated and popped off for iret later.
*/
if (user)
stack = (size_t*) (ustacks[task->id] + KERNEL_STACK_SIZE - 16); // => stack is 16byte aligned
else
stack = (size_t*) (task->stack + KERNEL_STACK_SIZE - 16); // => stack is 16byte aligned
stack = (size_t*) (task->stack + KERNEL_STACK_SIZE - 16); // => stack is 16byte aligned
/* Only marker for debugging purposes, ... */
*stack-- = 0xDEADBEEF;
@ -74,21 +66,13 @@ int create_default_frame(task_t* task, entry_point_t ep, void* arg, uint8_t user
/* and the "caller" we shall return to.
* This procedure cleans the task after exit. */
if (user)
*stack = (size_t) leave_user_task;
else
*stack = (size_t) leave_kernel_task;
*stack = (size_t) leave_kernel_task;
/* Next bunch on the stack is the initial register state.
* The stack must look like the stack of a task which was
* scheduled away previously. */
if (user) {
ustack = stack;
stack = (size_t*) (task->stack + KERNEL_STACK_SIZE - 16);
state_size = sizeof(struct state);
} else state_size = sizeof(struct state) - 2*sizeof(size_t);
state_size = sizeof(struct state) - 2*sizeof(size_t);
stack = (size_t*) ((size_t) stack - state_size);
stptr = (struct state *) stack;
@ -101,16 +85,12 @@ int create_default_frame(task_t* task, entry_point_t ep, void* arg, uint8_t user
/* The instruction pointer shall be set on the first function to be called
after IRETing */
stptr->eip = (size_t)ep;
stptr->cs = cs;
stptr->ds = stptr->es = ds;
stptr->cs = 0x08;
stptr->ds = stptr->es = 0x10;
stptr->eflags = 0x1202;
if (user) {
// the creation of a user-level tasks change the IOPL level
// => useresp & ss is required
stptr->ss = ds;
stptr->useresp = (size_t)ustack;
}
// the creation of a kernel-level tasks don't change the IOPL level
// => useresp & ss isn't required
/* Set the task's stack pointer entry to the stack we have crafted right now. */
task->last_stack_pointer = (size_t*)stack;

7
arch/x86/kernel/timer.c
View file

@ -60,9 +60,9 @@ static void timer_handler(struct state *s)
* Every TIMER_FREQ clocks (approximately 1 second), we will
* display a message on the screen
*/
if (timer_ticks % TIMER_FREQ == 0) {
vga_puts("One second has passed\n");
}
//if (timer_ticks % TIMER_FREQ == 0) {
// vga_puts("One second has passed\n");
//}
}
#define LATCH(f) ((CLOCK_TICK_RATE + f/2) / f)
@ -108,4 +108,3 @@ int timer_init(void)
return 0;
}

10
include/eduos/stdio.h
View file

@ -62,6 +62,16 @@ int kprintf(const char*, ...);
*/
int koutput_init(void);
/**
* Works like the ANSI c function sprintf
*/
int ksprintf(char *str, const char *format, ...);
/**
* Works like the ANSI c function sprintf
*/
int ksnprintf(char *str, size_t size, const char *format, ...);
/**
* Scaled down version of printf(3)
*/

13
include/eduos/tasks.h
View file

@ -81,19 +81,6 @@ int multitasking_init(void);
*/
int create_kernel_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio);
/** @brief create a user-level task.
*
* @param id The value behind this pointer will be set to the new task's id
* @param ep Pointer to the entry function for the new task
* @param args Arguments the task shall start with
* @param prio Desired priority of the new kernel task
*
* @return
* - 0 on success
* - -EINVAL (-22) on failure
*/
int create_user_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio);
/** @brief determine the highest priority of all tasks, which are ready
*
* @return

28
kernel/main.c
View file

@ -47,13 +47,29 @@ extern const void bss_end;
extern char __BUILD_DATE;
extern char __BUILD_TIME;
/*static*/ int userfoo(void* arg)
static void userfoo(void* arg)
{
//SYSCALL1(__NR_write, "hello from userfoo\n");
//kprintf("hello from %s\n", (char*) arg);
while(1) { }
char str[256];
return 0;
ksnprintf(str, 256, "hello from %s\n", (char*) arg);
SYSCALL1(__NR_write, "hello from userfoo\n");
//kprintf("hello from %s\n", (char*) arg);
}
static char ustack[KERNEL_STACK_SIZE];
static int wrapper(void* arg)
{
size_t* stack = (size_t*) (ustack+KERNEL_STACK_SIZE-16);
memset(ustack, 0xCD, KERNEL_STACK_SIZE);
*stack-- = (size_t) arg;
*stack = (size_t) leave_user_task; // add dummy return value
set_kernel_stack((size_t) &stack);
return jump_to_user_code((uint32_t) userfoo, (uint32_t) stack);
}
static int foo(void* arg)
@ -101,7 +117,7 @@ int main(void)
kprintf("Processor frequency: %u MHz\n", get_cpu_frequency());
create_kernel_task(&id1, foo, "foo1", NORMAL_PRIO);
create_user_task(&id2, userfoo, "userfoo", NORMAL_PRIO);
create_kernel_task(&id2, wrapper, "userfoo", NORMAL_PRIO);
while(1) {
HALT;

1
kernel/syscall.c
View file

@ -33,7 +33,6 @@
static int sys_write(const char* buff)
{
kputs("bbba\n");
kputs(buff);
return 0;

32
kernel/tasks.c
View file

@ -132,15 +132,6 @@ static void NORETURN do_exit(int arg)
}
}
/** @brief A procedure to be called by user-level tasks */
void NORETURN leave_user_task(void)
{
SYSCALL1(__NR_exit, 0);
// we should never reach this point
while(1) { HALT; }
}
/** @brief A procedure to be called by kernel tasks */
void NORETURN leave_kernel_task(void) {
int result;
@ -149,6 +140,15 @@ void NORETURN leave_kernel_task(void) {
do_exit(result);
}
/** @brief This function shall be called by leaving user-level tasks */
void NORETURN leave_user_task(void)
{
SYSCALL1(__NR_exit, 0);
// this point should never reached
while(1) {}
}
/** @brief To be called by the systemcall to exit tasks */
void NORETURN sys_exit(int arg) {
do_exit(arg);
@ -171,7 +171,7 @@ void NORETURN abort(void) {
* - 0 on success
* - -ENOMEM (-12) or -EINVAL (-22) on failure
*/
static int create_task(tid_t* id, entry_point_t ep, void* arg, uint8_t prio, uint8_t user)
static int create_task(tid_t* id, entry_point_t ep, void* arg, uint8_t prio)
{
int ret = -ENOMEM;
uint32_t i;
@ -196,7 +196,7 @@ static int create_task(tid_t* id, entry_point_t ep, void* arg, uint8_t prio, uin
if (id)
*id = i;
ret = create_default_frame(task_table+i, ep, arg, user);
ret = create_default_frame(task_table+i, ep, arg);
// add task in the readyqueues
spinlock_irqsave_lock(&readyqueues.lock);
@ -227,15 +227,7 @@ int create_kernel_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio)
if (prio > MAX_PRIO)
prio = NORMAL_PRIO;
return create_task(id, ep, args, prio, 0);
}
int create_user_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio)
{
if (prio > MAX_PRIO)
prio = NORMAL_PRIO;
return create_task(id, ep, args, prio, 1);
return create_task(id, ep, args, prio);
}
/** @brief Wakeup a blocked task

2
libkern/Makefile
View file

@ -1,4 +1,4 @@
C_source := string.c stdio.c printf.c moddi3.c umoddi3.c divdi3.c udivdi3.c qdivrem.c
C_source := string.c stdio.c printf.c sprintf.c moddi3.c umoddi3.c divdi3.c udivdi3.c qdivrem.c
MODULE := libkern
include $(TOPDIR)/Makefile.inc

82
libkern/sprintf.c Normal file
View file

@ -0,0 +1,82 @@
/*
* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <eduos/stdio.h>
typedef struct {
char *str;
size_t pos;
size_t max;
} sputchar_arg_t;
static void sputchar(int c, void *arg)
{
sputchar_arg_t *dest = (sputchar_arg_t *) arg;
if (dest->pos < dest->max) {
dest->str[dest->pos] = (char)c;
dest->pos++;
}
}
int ksnprintf(char *str, size_t size, const char *format, ...)
{
int ret;
va_list ap;
sputchar_arg_t dest;
dest.str = str;
dest.pos = 0;
dest.max = size;
va_start(ap, format);
ret = kvprintf(format, sputchar, &dest, 10, ap);
va_end(ap);
str[ret] = 0;
return ret;
}
int ksprintf(char *str, const char *format, ...)
{
int ret;
va_list ap;
sputchar_arg_t dest;
dest.str = str;
dest.pos = 0;
dest.max = (size_t) -1;
va_start(ap, format);
ret = kvprintf(format, sputchar, &dest, 10, ap);
va_end(ap);
str[ret] = 0;
return ret;
}