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seabios/src/stacks.c

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// Code for manipulating stack locations.
//
// Copyright (C) 2009-2015 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU LGPLv3 license.
#include "biosvar.h" // GET_GLOBAL
#include "bregs.h" // CR0_PE
#include "fw/paravirt.h" // PORT_SMI_CMD
#include "hw/rtc.h" // rtc_use
#include "list.h" // hlist_node
#include "malloc.h" // free
#include "output.h" // dprintf
#include "romfile.h" // romfile_loadint
#include "stacks.h" // struct mutex_s
#include "string.h" // memset
#include "util.h" // useRTC
#define MAIN_STACK_MAX (1024*1024)
/****************************************************************
* 16bit / 32bit calling
****************************************************************/
struct {
u8 method;
u8 cmosindex;
u8 a20;
u16 ss, fs, gs;
u32 cr0;
struct descloc_s gdt;
} Call16Data VARLOW;
#define C16_BIG 1
#define C16_SMM 2
int HaveSmmCall32 VARFSEG;
// Backup state in preparation for call32
static int
call32_prep(u8 method)
{
if (!CONFIG_CALL32_SMM || method != C16_SMM) {
// Backup cr0
u32 cr0 = cr0_read();
if (cr0 & CR0_PE)
// Called in 16bit protected mode?!
return -1;
SET_LOW(Call16Data.cr0, cr0);
// Backup fs/gs and gdt
SET_LOW(Call16Data.fs, GET_SEG(FS));
SET_LOW(Call16Data.gs, GET_SEG(GS));
struct descloc_s gdt;
sgdt(&gdt);
SET_LOW(Call16Data.gdt.length, gdt.length);
SET_LOW(Call16Data.gdt.addr, gdt.addr);
// Enable a20 and backup its previous state
SET_LOW(Call16Data.a20, set_a20(1));
}
// Backup ss
SET_LOW(Call16Data.ss, GET_SEG(SS));
// Backup cmos index register and disable nmi
u8 cmosindex = inb(PORT_CMOS_INDEX);
if (!(cmosindex & NMI_DISABLE_BIT)) {
outb(cmosindex | NMI_DISABLE_BIT, PORT_CMOS_INDEX);
inb(PORT_CMOS_DATA);
}
SET_LOW(Call16Data.cmosindex, cmosindex);
SET_LOW(Call16Data.method, method);
return 0;
}
// Restore state backed up during call32
static u8
call32_post(void)
{
u8 method = GET_LOW(Call16Data.method);
SET_LOW(Call16Data.method, 0);
SET_LOW(Call16Data.ss, 0);
if (!CONFIG_CALL32_SMM || method != C16_SMM) {
// Restore a20
u8 a20 = GET_LOW(Call16Data.a20);
if (!a20)
set_a20(0);
// Restore gdt and fs/gs
struct descloc_s gdt;
gdt.length = GET_LOW(Call16Data.gdt.length);
gdt.addr = GET_LOW(Call16Data.gdt.addr);
lgdt(&gdt);
SET_SEG(FS, GET_LOW(Call16Data.fs));
SET_SEG(GS, GET_LOW(Call16Data.gs));
// Restore cr0
u32 cr0_caching = GET_LOW(Call16Data.cr0) & (CR0_CD|CR0_NW);
if (cr0_caching)
cr0_mask(CR0_CD|CR0_NW, cr0_caching);
}
// Restore cmos index register
u8 cmosindex = GET_LOW(Call16Data.cmosindex);
if (!(cmosindex & NMI_DISABLE_BIT)) {
outb(cmosindex, PORT_CMOS_INDEX);
inb(PORT_CMOS_DATA);
}
return method;
}
// Force next call16() to restore to a pristine cpu environment state
static void
call16_override(int big)
{
ASSERT32FLAT();
if (getesp() > BUILD_STACK_ADDR)
panic("call16_override with invalid stack\n");
memset(&Call16Data, 0, sizeof(Call16Data));
if (big) {
Call16Data.method = C16_BIG;
Call16Data.a20 = 1;
} else {
Call16Data.a20 = !CONFIG_DISABLE_A20;
}
}
// 16bit handler code called from call16() / call16_smm()
u32 VISIBLE16
call16_helper(u32 eax, u32 edx, u32 (*func)(u32 eax, u32 edx))
{
u8 method = call32_post();
u32 ret = func(eax, edx);
call32_prep(method);
return ret;
}
#define ASM32_SWITCH16 " .pushsection .text.32fseg." UNIQSEC "\n .code16\n"
#define ASM32_BACK32 " .popsection\n .code32\n"
#define ASM16_SWITCH32 " .code32\n"
#define ASM16_BACK16 " .code16gcc\n"
// Call a SeaBIOS C function in 32bit mode using smm trampoline
static u32
call32_smm(void *func, u32 eax)
{
ASSERT16();
dprintf(9, "call32_smm %p %x\n", func, eax);
call32_prep(C16_SMM);
u32 bkup_esp;
asm volatile(
// Backup esp / set esp to flat stack location
" movl %%esp, %0\n"
" movl %%ss, %%eax\n"
" shll $4, %%eax\n"
" addl %%eax, %%esp\n"
// Transition to 32bit mode, call func, return to 16bit
" movl $" __stringify(CALL32SMM_CMDID) ", %%eax\n"
" movl $" __stringify(CALL32SMM_ENTERID) ", %%ecx\n"
" movl $(" __stringify(BUILD_BIOS_ADDR) " + 1f), %%ebx\n"
" outb %%al, $" __stringify(PORT_SMI_CMD) "\n"
" rep; nop\n"
" hlt\n"
ASM16_SWITCH32
"1:movl %1, %%eax\n"
" calll *%2\n"
" movl %%eax, %1\n"
" movl $" __stringify(CALL32SMM_CMDID) ", %%eax\n"
" movl $" __stringify(CALL32SMM_RETURNID) ", %%ecx\n"
" movl $2f, %%ebx\n"
" outb %%al, $" __stringify(PORT_SMI_CMD) "\n"
" rep; nop\n"
" hlt\n"
// Restore esp
ASM16_BACK16
"2:movl %0, %%esp\n"
: "=&r" (bkup_esp), "+r" (eax)
: "r" (func)
: "eax", "ecx", "edx", "ebx", "cc", "memory");
call32_post();
dprintf(9, "call32_smm done %p %x\n", func, eax);
return eax;
}
static u32
call16_smm(u32 eax, u32 edx, void *func)
{
ASSERT32FLAT();
if (!CONFIG_CALL32_SMM)
return eax;
func -= BUILD_BIOS_ADDR;
dprintf(9, "call16_smm %p %x %x\n", func, eax, edx);
u32 stackoffset = Call16Data.ss << 4;
asm volatile(
// Restore esp
" subl %0, %%esp\n"
// Transition to 16bit mode, call func, return to 32bit
" movl $" __stringify(CALL32SMM_CMDID) ", %%eax\n"
" movl $" __stringify(CALL32SMM_RETURNID) ", %%ecx\n"
" movl $(1f - " __stringify(BUILD_BIOS_ADDR) "), %%ebx\n"
" outb %%al, $" __stringify(PORT_SMI_CMD) "\n"
" rep; nop\n"
" hlt\n"
ASM32_SWITCH16
"1:movl %1, %%eax\n"
" movl %3, %%ecx\n"
" calll _cfunc16_call16_helper\n"
" movl %%eax, %1\n"
" movl $" __stringify(CALL32SMM_CMDID) ", %%eax\n"
" movl $" __stringify(CALL32SMM_ENTERID) ", %%ecx\n"
" movl $2f, %%ebx\n"
" outb %%al, $" __stringify(PORT_SMI_CMD) "\n"
" rep; nop\n"
" hlt\n"
// Set esp to flat stack location
ASM32_BACK32
"2:addl %0, %%esp\n"
: "+r" (stackoffset), "+r" (eax), "+d" (edx)
: "r" (func)
: "eax", "ecx", "ebx", "cc", "memory");
return eax;
}
// Call a 32bit SeaBIOS function from a 16bit SeaBIOS function.
u32 VISIBLE16
__call32(void *func, u32 eax, u32 errret)
{
ASSERT16();
if (CONFIG_CALL32_SMM && GET_GLOBAL(HaveSmmCall32))
return call32_smm(func, eax);
// Jump direclty to 32bit mode - this clobbers the 16bit segment
// selector registers.
int ret = call32_prep(C16_BIG);
if (ret)
return errret;
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"
" shrl $4, %0\n"
// Transition to 32bit mode, call func, return to 16bit
" movl $(" __stringify(BUILD_BIOS_ADDR) " + 1f), %%edx\n"
" jmp transition32_nmi_off\n"
ASM16_SWITCH32
"1:calll *%3\n"
" movl $2f, %%edx\n"
" jmp transition16big\n"
// Restore ds/ss/esp
ASM16_BACK16
"2:movl %0, %%ds\n"
" movl %0, %%ss\n"
" movl %1, %%esp\n"
: "=&r" (bkup_ss), "=&r" (bkup_esp), "+a" (eax)
: "r" (func)
: "ecx", "edx", "cc", "memory");
call32_post();
return eax;
}
// Call a 16bit SeaBIOS function, restoring the mode from last call32().
static u32
call16(u32 eax, u32 edx, void *func)
{
ASSERT32FLAT();
if (getesp() > MAIN_STACK_MAX)
panic("call16 with invalid stack\n");
if (CONFIG_CALL32_SMM && Call16Data.method == C16_SMM)
return call16_smm(eax, edx, func);
extern void transition16big(void);
extern void transition16(void);
void *thunk = transition16;
if (Call16Data.method == C16_BIG || in_post())
thunk = transition16big;
func -= BUILD_BIOS_ADDR;
u32 stackseg = Call16Data.ss;
asm volatile(
// Transition to 16bit mode
" movl $(1f - " __stringify(BUILD_BIOS_ADDR) "), %%edx\n"
" jmp *%%ecx\n"
// Setup ss/esp and call func
ASM32_SWITCH16
"1:movl %2, %%ecx\n"
" shll $4, %2\n"
" movw %%cx, %%ss\n"
" subl %2, %%esp\n"
" movw %%cx, %%ds\n"
" movl %4, %%edx\n"
" movl %3, %%ecx\n"
" calll _cfunc16_call16_helper\n"
// Return to 32bit and restore esp
" movl $2f, %%edx\n"
" jmp transition32_nmi_off\n"
ASM32_BACK32
"2:addl %2, %%esp\n"
: "+a" (eax), "+c"(thunk), "+r"(stackseg)
: "r" (func), "r" (edx)
: "edx", "cc", "memory");
return eax;
}
/****************************************************************
* Extra 16bit stack
****************************************************************/
// Space for a stack for 16bit code.
u8 ExtraStack[BUILD_EXTRA_STACK_SIZE+1] VARLOW __aligned(8);
u8 *StackPos VARLOW;
// Test if currently on the extra stack
int
on_extra_stack(void)
{
return MODE16 && GET_SEG(SS) == SEG_LOW && getesp() > (u32)ExtraStack;
}
// Switch to the extra stack and call a function.
u32
__stack_hop(u32 eax, u32 edx, void *func)
{
if (on_extra_stack())
return ((u32 (*)(u32, u32))func)(eax, edx);
ASSERT16();
u16 stack_seg = SEG_LOW;
u32 bkup_ss, bkup_esp;
asm volatile(
// Backup current %ss/%esp values.
"movw %%ss, %w3\n"
"movl %%esp, %4\n"
// Copy stack seg to %ds/%ss and set %esp
"movw %w6, %%ds\n"
"movw %w6, %%ss\n"
"movl %5, %%esp\n"
"pushl %3\n"
"pushl %4\n"
// Call func
"calll *%2\n"
"popl %4\n"
"popl %3\n"
// Restore segments and stack
"movw %w3, %%ds\n"
"movw %w3, %%ss\n"
"movl %4, %%esp"
: "+a" (eax), "+d" (edx), "+c" (func), "=&r" (bkup_ss), "=&r" (bkup_esp)
: "m" (StackPos), "r" (stack_seg)
: "cc", "memory");
return eax;
}
// Switch back to original caller's stack and call a function.
u32
__stack_hop_back(u32 eax, u32 edx, void *func)
{
if (!MODESEGMENT)
return call16(eax, edx, func);
if (!MODE16 || !on_extra_stack())
return ((u32 (*)(u32, u32))func)(eax, edx);
ASSERT16();
u16 bkup_ss;
u32 bkup_stack_pos, temp;
asm volatile(
// Backup stack_pos and current %ss/%esp
"movl %6, %4\n"
"movw %%ss, %w3\n"
"movl %%esp, %6\n"
// Restore original callers' %ss/%esp
"movl -4(%4), %5\n"
"movl %5, %%ss\n"
"movw %%ds:-8(%4), %%sp\n"
"movl %5, %%ds\n"
// Call func
"calll *%2\n"
// Restore %ss/%esp and stack_pos
"movw %w3, %%ds\n"
"movw %w3, %%ss\n"
"movl %6, %%esp\n"
"movl %4, %6"
: "+a" (eax), "+d" (edx), "+c" (func), "=&r" (bkup_ss)
, "=&r" (bkup_stack_pos), "=&r" (temp), "+m" (StackPos)
:
: "cc", "memory");
return eax;
}
/****************************************************************
* External 16bit interface calling
****************************************************************/
// Far call 16bit code with a specified register state.
void VISIBLE16
_farcall16(struct bregs *callregs, u16 callregseg)
{
if (need_hop_back()) {
stack_hop_back(_farcall16, callregs, callregseg);
return;
}
ASSERT16();
asm volatile(
"calll __farcall16\n"
: "+a" (callregs), "+m" (*callregs), "+d" (callregseg)
:
: "ebx", "ecx", "esi", "edi", "cc", "memory");
}
// Invoke external 16bit code.
void
farcall16(struct bregs *callregs)
{
call16_override(0);
_farcall16(callregs, 0);
}
// Invoke external 16bit code in "big real" mode.
void
farcall16big(struct bregs *callregs)
{
call16_override(1);
_farcall16(callregs, 0);
}
// Invoke a 16bit software interrupt.
void
__call16_int(struct bregs *callregs, u16 offset)
{
callregs->code.offset = offset;
if (!MODESEGMENT) {
callregs->code.seg = SEG_BIOS;
_farcall16((void*)callregs - Call16Data.ss * 16, Call16Data.ss);
return;
}
callregs->code.seg = GET_SEG(CS);
_farcall16(callregs, GET_SEG(SS));
}
// Reset the machine
void
reset(void)
{
extern void reset_vector(void) __noreturn;
if (!MODE16)
call16(0, 0, reset_vector);
reset_vector();
}
/****************************************************************
* Threads
****************************************************************/
// Thread info - stored at bottom of each thread stack - don't change
// without also updating the inline assembler below.
struct thread_info {
void *stackpos;
struct hlist_node node;
};
struct thread_info MainThread VARFSEG = {
NULL, { &MainThread.node, &MainThread.node.next }
};
#define THREADSTACKSIZE 4096
// Check if any threads are running.
static int
have_threads(void)
{
return (CONFIG_THREADS
&& GET_FLATPTR(MainThread.node.next) != &MainThread.node);
}
// Return the 'struct thread_info' for the currently running thread.
struct thread_info *
getCurThread(void)
{
u32 esp = getesp();
if (esp <= MAIN_STACK_MAX)
return &MainThread;
return (void*)ALIGN_DOWN(esp, THREADSTACKSIZE);
}
static u8 CanInterrupt, ThreadControl;
// Initialize the support for internal threads.
void
thread_setup(void)
{
CanInterrupt = 1;
call16_override(1);
if (! CONFIG_THREADS)
return;
ThreadControl = romfile_loadint("etc/threads", 1);
}
// Should hardware initialization threads run during optionrom execution.
int
threads_during_optionroms(void)
{
return CONFIG_THREADS && CONFIG_RTC_TIMER && ThreadControl == 2 && in_post();
}
// Switch to next thread stack.
static void
switch_next(struct thread_info *cur)
{
struct thread_info *next = container_of(
cur->node.next, struct thread_info, node);
if (cur == next)
// Nothing to do.
return;
asm volatile(
" pushl $1f\n" // store return pc
" pushl %%ebp\n" // backup %ebp
" movl %%esp, (%%eax)\n" // cur->stackpos = %esp
" movl (%%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");
}
// Last thing called from a thread (called on MainThread stack).
static void
__end_thread(struct thread_info *old)
{
hlist_del(&old->node);
dprintf(DEBUG_thread, "\\%08x/ End thread\n", (u32)old);
free(old);
if (!have_threads())
dprintf(1, "All threads complete.\n");
}
void VISIBLE16 check_irqs(void);
// Create a new thread and start executing 'func' in it.
void
run_thread(void (*func)(void*), void *data)
{
ASSERT32FLAT();
if (! CONFIG_THREADS || ! ThreadControl)
goto fail;
struct thread_info *thread;
thread = memalign_tmphigh(THREADSTACKSIZE, THREADSTACKSIZE);
if (!thread)
goto fail;
dprintf(DEBUG_thread, "/%08x\\ Start thread\n", (u32)thread);
thread->stackpos = (void*)thread + THREADSTACKSIZE;
struct thread_info *cur = getCurThread();
struct thread_info *edx = cur;
hlist_add_after(&thread->node, &cur->node);
asm volatile(
// Start thread
" pushl $1f\n" // store return pc
" pushl %%ebp\n" // backup %ebp
" movl %%esp, (%%edx)\n" // cur->stackpos = %esp
" movl (%%ebx), %%esp\n" // %esp = thread->stackpos
" calll *%%ecx\n" // Call func
// End thread
" movl %%ebx, %%eax\n" // %eax = thread
" movl 4(%%ebx), %%ebx\n" // %ebx = thread->node.next
" movl (%5), %%esp\n" // %esp = MainThread.stackpos
" calll %4\n" // call __end_thread(thread)
" movl -4(%%ebx), %%esp\n" // %esp = next->stackpos
" popl %%ebp\n" // restore %ebp
" retl\n" // restore pc
"1:\n"
: "+a"(data), "+c"(func), "+b"(thread), "+d"(edx)
: "m"(*(u8*)__end_thread), "m"(MainThread)
: "esi", "edi", "cc", "memory");
if (cur == &MainThread)
// Permit irqs to fire
check_irqs();
return;
fail:
func(data);
}
/****************************************************************
* Thread helpers
****************************************************************/
// Low-level irq enable.
void VISIBLE16
check_irqs(void)
{
if (!MODESEGMENT && !CanInterrupt) {
// Can't enable interrupts (PIC and/or IVT not yet setup)
cpu_relax();
return;
}
if (need_hop_back()) {
stack_hop_back(check_irqs, 0, 0);
return;
}
if (MODE16)
clock_poll_irq();
asm volatile("sti ; nop ; rep ; nop ; cli ; cld" : : :"memory");
}
// Briefly permit irqs to occur.
void
yield(void)
{
if (MODESEGMENT || !CONFIG_THREADS) {
check_irqs();
return;
}
struct thread_info *cur = getCurThread();
// Switch to the next thread
switch_next(cur);
if (cur == &MainThread)
// Permit irqs to fire
check_irqs();
}
void VISIBLE16
wait_irq(void)
{
if (need_hop_back()) {
stack_hop_back(wait_irq, 0, 0);
return;
}
asm volatile("sti ; hlt ; cli ; cld": : :"memory");
}
// Wait for next irq to occur.
void
yield_toirq(void)
{
if (!CONFIG_HARDWARE_IRQ
|| (!MODESEGMENT && (have_threads() || !CanInterrupt))) {
// Threads still active or irqs not available - do a yield instead.
yield();
return;
}
wait_irq();
}
// Wait for all threads (other than the main thread) to complete.
void
wait_threads(void)
{
ASSERT32FLAT();
while (have_threads())
yield();
}
void
mutex_lock(struct mutex_s *mutex)
{
ASSERT32FLAT();
if (! CONFIG_THREADS)
return;
while (mutex->isLocked)
yield();
mutex->isLocked = 1;
}
void
mutex_unlock(struct mutex_s *mutex)
{
ASSERT32FLAT();
if (! CONFIG_THREADS)
return;
mutex->isLocked = 0;
}
/****************************************************************
* Thread preemption
****************************************************************/
int CanPreempt VARFSEG;
static u32 PreemptCount;
// Turn on RTC irqs and arrange for them to check the 32bit threads.
void
start_preempt(void)
{
if (! threads_during_optionroms())
return;
CanPreempt = 1;
PreemptCount = 0;
rtc_use();
}
// Turn off RTC irqs / stop checking for thread execution.
void
finish_preempt(void)
{
if (! threads_during_optionroms()) {
yield();
return;
}
CanPreempt = 0;
rtc_release();
dprintf(9, "Done preempt - %d checks\n", PreemptCount);
yield();
}
// Check if preemption is on, and wait for it to complete if so.
int
wait_preempt(void)
{
if (MODESEGMENT || !CONFIG_THREADS || !CanPreempt
|| getesp() < MAIN_STACK_MAX)
return 0;
while (CanPreempt)
yield();
return 1;
}
// Try to execute 32bit threads.
void VISIBLE32INIT
yield_preempt(void)
{
PreemptCount++;
switch_next(&MainThread);
}
// 16bit code that checks if threads are pending and executes them if so.
void
check_preempt(void)
{
if (CONFIG_THREADS && GET_GLOBAL(CanPreempt) && have_threads())
call32(yield_preempt, 0, 0);
}
/****************************************************************
* call32 helper
****************************************************************/
struct call32_params_s {
void *func;
u32 eax, edx, ecx;
};
u32 VISIBLE32FLAT
call32_params_helper(struct call32_params_s *params)
{
return ((u32 (*)(u32, u32, u32))params->func)(
params->eax, params->edx, params->ecx);
}
u32
__call32_params(void *func, u32 eax, u32 edx, u32 ecx, u32 errret)
{
ASSERT16();
struct call32_params_s params = {func, eax, edx, ecx};
return call32(call32_params_helper, MAKE_FLATPTR(GET_SEG(SS), &params)
, errret);
}
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