blob: a35ca3de7717a3bafed840689e3fdea40e5c3611 [file] [log] [blame]
// Code for manipulating stack locations.
//
// Copyright (C) 2009 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU LGPLv3 license.
#include "biosvar.h" // get_ebda_seg
#include "util.h" // dprintf
#include "bregs.h" // CR0_PE
static inline u32 getcr0(void) {
u32 cr0;
asm("movl %%cr0, %0" : "=r"(cr0));
return cr0;
}
static inline void sgdt(struct descloc_s *desc) {
asm("sgdtl %0" : "=m"(*desc));
}
static inline void lgdt(struct descloc_s *desc) {
asm("lgdtl %0" : : "m"(*desc) : "memory");
}
// Call a 32bit SeaBIOS function from a 16bit SeaBIOS function.
static inline int
call32(void *func)
{
ASSERT16();
u32 cr0 = getcr0();
if (cr0 & CR0_PE)
// Called in 16bit protected mode?!
return -1;
// Backup cmos index register and disable nmi
u8 cmosindex = inb(PORT_CMOS_INDEX);
outb(cmosindex | NMI_DISABLE_BIT, PORT_CMOS_INDEX);
inb(PORT_CMOS_DATA);
// Backup fs/gs and gdt
u16 fs = GET_SEG(FS), gs = GET_SEG(GS);
struct descloc_s gdt;
sgdt(&gdt);
func -= BUILD_BIOS_ADDR;
u32 bkup_ss, bkup_esp;
asm volatile(
// Backup ss/esp / set esp to flat stack location
" movl %%ss, %0\n"
" movl %%esp, %1\n"
" shll $4, %0\n"
" addl %0, %%esp\n"
" movl %%ss, %0\n"
// Transition to 32bit mode, call func, return to 16bit
" pushl $(" __stringify(BUILD_BIOS_ADDR) " + 1f)\n"
" jmp transition32\n"
" .code32\n"
"1:calll %2\n"
" pushl $2f\n"
" jmp transition16big\n"
// Restore ds/ss/esp
" .code16gcc\n"
"2:movl %0, %%ds\n"
" movl %0, %%ss\n"
" movl %1, %%esp\n"
: "=&r" (bkup_ss), "=&r" (bkup_esp)
: "m" (*(u8*)func)
: "eax", "ecx", "edx", "cc", "memory");
// Restore gdt and fs/gs
lgdt(&gdt);
SET_SEG(FS, fs);
SET_SEG(GS, gs);
// Restore cmos index register
outb(cmosindex, PORT_CMOS_INDEX);
inb(PORT_CMOS_DATA);
return 0;
}
/****************************************************************
* Stack in EBDA
****************************************************************/
// Switch to the extra stack in ebda and call a function.
inline u32
stack_hop(u32 eax, u32 edx, u32 ecx, void *func)
{
ASSERT16();
u16 ebda_seg = get_ebda_seg(), bkup_ss;
u32 bkup_esp;
asm volatile(
// Backup current %ss/%esp values.
"movw %%ss, %w3\n"
"movl %%esp, %4\n"
// Copy ebda seg to %ds/%ss and set %esp
"movw %w6, %%ds\n"
"movw %w6, %%ss\n"
"movl %5, %%esp\n"
// Call func
"calll %7\n"
// Restore segments and stack
"movw %w3, %%ds\n"
"movw %w3, %%ss\n"
"movl %4, %%esp"
: "+a" (eax), "+d" (edx), "+c" (ecx), "=&r" (bkup_ss), "=&r" (bkup_esp)
: "i" (EBDA_OFFSET_TOP_STACK), "r" (ebda_seg), "m" (*(u8*)func)
: "cc", "memory");
return eax;
}
/****************************************************************
* Threads
****************************************************************/
#define THREADSTACKSIZE 4096
struct thread_info {
struct thread_info *next;
void *stackpos;
};
struct thread_info VAR16VISIBLE MainThread;
int VAR16VISIBLE CanPreempt;
void
thread_setup(void)
{
MainThread.next = &MainThread;
MainThread.stackpos = NULL;
CanPreempt = 0;
}
// Return the 'struct thread_info' for the currently running thread.
struct thread_info *
getCurThread(void)
{
u32 esp = getesp();
if (esp <= BUILD_STACK_ADDR)
return &MainThread;
return (void*)ALIGN_DOWN(esp, THREADSTACKSIZE);
}
// Switch to next thread stack.
static void
switch_next(struct thread_info *cur)
{
struct thread_info *next = cur->next;
if (cur == next)
// Nothing to do.
return;
asm volatile(
" pushl $1f\n" // store return pc
" pushl %%ebp\n" // backup %ebp
" movl %%esp, 4(%%eax)\n" // cur->stackpos = %esp
" movl 4(%%ecx), %%esp\n" // %esp = next->stackpos
" popl %%ebp\n" // restore %ebp
" retl\n" // restore pc
"1:\n"
: "+a"(cur), "+c"(next)
:
: "ebx", "edx", "esi", "edi", "cc", "memory");
}
// Briefly permit irqs to occur.
void
yield(void)
{
if (MODESEGMENT || !CONFIG_THREADS) {
// Just directly check irqs.
check_irqs();
return;
}
struct thread_info *cur = getCurThread();
if (cur == &MainThread)
// Permit irqs to fire
check_irqs();
// Switch to the next thread
switch_next(cur);
}
// Last thing called from a thread (called on "next" stack).
static void
__end_thread(struct thread_info *old)
{
struct thread_info *pos = &MainThread;
while (pos->next != old)
pos = pos->next;
pos->next = old->next;
free(old);
dprintf(DEBUG_thread, "\\%08x/ End thread\n", (u32)old);
}
// Create a new thread and start executing 'func' in it.
void
run_thread(void (*func)(void*), void *data)
{
ASSERT32FLAT();
if (! CONFIG_THREADS)
goto fail;
struct thread_info *thread;
thread = memalign_tmphigh(THREADSTACKSIZE, THREADSTACKSIZE);
if (!thread)
goto fail;
thread->stackpos = (void*)thread + THREADSTACKSIZE;
struct thread_info *cur = getCurThread();
thread->next = cur->next;
cur->next = thread;
dprintf(DEBUG_thread, "/%08x\\ Start thread\n", (u32)thread);
asm volatile(
// Start thread
" pushl $1f\n" // store return pc
" pushl %%ebp\n" // backup %ebp
" movl %%esp, 4(%%edx)\n" // cur->stackpos = %esp
" movl 4(%%ebx), %%esp\n" // %esp = thread->stackpos
" calll *%%ecx\n" // Call func
// End thread
" movl (%%ebx), %%ecx\n" // %ecx = thread->next
" movl 4(%%ecx), %%esp\n" // %esp = next->stackpos
" movl %%ebx, %%eax\n"
" calll %4\n" // call __end_thread(thread)
" popl %%ebp\n" // restore %ebp
" retl\n" // restore pc
"1:\n"
: "+a"(data), "+c"(func), "+b"(thread), "+d"(cur)
: "m"(*(u8*)__end_thread)
: "esi", "edi", "cc", "memory");
return;
fail:
func(data);
}
// Wait for all threads (other than the main thread) to complete.
void
wait_threads(void)
{
ASSERT32FLAT();
if (! CONFIG_THREADS)
return;
while (MainThread.next != &MainThread)
yield();
}
/****************************************************************
* Thread preemption
****************************************************************/
static u32 PreemptCount;
// Turn on RTC irqs and arrange for them to check the 32bit threads.
void
start_preempt(void)
{
if (! CONFIG_THREADS || ! CONFIG_THREAD_OPTIONROMS)
return;
CanPreempt = 1;
PreemptCount = 0;
useRTC();
}
// Turn off RTC irqs / stop checking for thread execution.
void
finish_preempt(void)
{
if (! CONFIG_THREADS || ! CONFIG_THREAD_OPTIONROMS)
return;
CanPreempt = 0;
releaseRTC();
dprintf(1, "Done preempt - %d checks\n", PreemptCount);
}
extern void yield_preempt(void);
#if MODESEGMENT == 0
// Try to execute 32bit threads.
void VISIBLE32FLAT
yield_preempt(void)
{
PreemptCount++;
switch_next(&MainThread);
}
#endif
// 16bit code that checks if threads are pending and executes them if so.
void
check_preempt(void)
{
if (! CONFIG_THREADS || ! CONFIG_THREAD_OPTIONROMS
|| !GET_GLOBAL(CanPreempt)
|| GET_GLOBAL(MainThread.next) == &MainThread)
return;
call32(yield_preempt);
}