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This is taken from SOS
This commit is contained in:
Mathieu Maret 2019-05-15 23:22:28 +02:00
parent 03c74c68d6
commit 3bca737990
5 changed files with 637 additions and 1 deletions
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6
Makefile
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@ -15,7 +15,7 @@ CPPFLAGS += $(foreach dir, $(SUBDIRS), -I$(dir))
asmsrc=$(wildcard *.asm)
asmobj=$(asmsrc:%.asm=%.o)
csrc=$(shell find $(SUBDIRS) -type f -name "*.c")# $(wildcard *.c)
cobj=$(csrc:%.c=%.o)
cobj=$(csrc:%.c=%.o) core/cpu_context_switch.o
deps = $(csrc:%.c=%.d)
kernel:$(asmobj) $(cobj) linker.ld
@ -39,6 +39,10 @@ core/irq_handler.o:core/irq_handler.c
%.o:%.asm
$(AS) $(ASFLAGS) -o $@ $<
%.o: %.S
$(CC) "-I$(PWD)" -c "$<" $(CFLAGS) -o "$@"
self_test: CFLAGS += -DRUN_TEST -DDEBUG
self_test: clean kernel
qemu-system-x86_64 -kernel kernel -serial stdio

240
core/cpu_context.c Normal file
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@ -0,0 +1,240 @@
/* Copyright (C) 2005 David Decotigny
Copyright (C) 2000-2004, The KOS team
Initially taken from SOS
*/
#include "assert.h"
#include "klibc.h"
#include "segment.h"
#include "cpu_context.h"
/**
* Here is the definition of a CPU context for IA32 processors. This
* is a Matos/SOS convention, not a specification given by the IA32
* spec. However there is a strong constraint related to the x86
* interrupt handling specification: the top of the stack MUST be
* compatible with the 'iret' instruction, ie there must be the
* err_code (might be 0), eip, cs and eflags of the destination
* context in that order (see Intel x86 specs vol 3, figure 5-4).
*
* @note IMPORTANT: This definition MUST be consistent with the way
* the registers are stored on the stack in
* irq_wrappers.S/exception_wrappers.S !!! Hence the constraint above.
*/
struct cpu_state {
/* (Lower addresses) */
/* These are Matos/SOS convention */
uint16_t gs;
uint16_t fs;
uint16_t es;
uint16_t ds;
uint16_t cpl0_ss; /* This is ALWAYS the Stack Segment of the
Kernel context (CPL0) of the interrupted
thread, even for a user thread */
uint16_t alignment_padding; /* unused */
uint32_t eax;
uint32_t ebx;
uint32_t ecx;
uint32_t edx;
uint32_t esi;
uint32_t edi;
uint32_t ebp;
/* MUST NEVER CHANGE (dependent on the IA32 iret instruction) */
uint32_t error_code;
vaddr_t eip;
uint32_t cs; /* 32bits according to the specs ! However, the CS
register is really 16bits long */
uint32_t eflags;
/* (Higher addresses) */
} __attribute__((packed));
/**
* The CS value pushed on the stack by the CPU upon interrupt, and
* needed by the iret instruction, is 32bits long while the real CPU
* CS register is 16bits only: this macro simply retrieves the CPU
* "CS" register value from the CS value pushed on the stack by the
* CPU upon interrupt.
*
* The remaining 16bits pushed by the CPU should be considered
* "reserved" and architecture dependent. IMHO, the specs don't say
* anything about them. Considering that some architectures generate
* non-zero values for these 16bits (at least Cyrix), we'd better
* ignore them.
*/
#define GET_CPU_CS_REGISTER_VALUE(pushed_ui32_cs_value) ((pushed_ui32_cs_value)&0xffff)
/**
* Structure of an interrupted Kernel thread's context
*/
struct cpu_kstate {
struct cpu_state regs;
} __attribute__((packed));
/**
* THE main operation of a kernel thread. This routine calls the
* kernel thread function start_func and calls exit_func when
* start_func returns.
*/
static void core_routine(cpu_kstate_function_arg1_t *start_func, void *start_arg,
cpu_kstate_function_arg1_t *exit_func, void *exit_arg)
__attribute__((noreturn));
static void core_routine(cpu_kstate_function_arg1_t *start_func, void *start_arg,
cpu_kstate_function_arg1_t *exit_func, void *exit_arg)
{
start_func(start_arg);
exit_func(exit_arg);
assert(!"The exit function of the thread should NOT return !");
for (;;)
;
}
int cpu_kstate_init(struct cpu_state **ctxt, cpu_kstate_function_arg1_t *start_func,
uint32_t start_arg, vaddr_t stack_bottom, size_t stack_size,
cpu_kstate_function_arg1_t *exit_func, uint32_t exit_arg)
{
/* We are initializing a Kernel thread's context */
struct cpu_kstate *kctxt;
/* This is a critical internal function, so that it is assumed that
the caller knows what he does: we legitimally assume that values
for ctxt, start_func, stack_* and exit_func are allways VALID ! */
/* Setup the stack.
*
* On x86, the stack goes downward. Each frame is configured this
* way (higher addresses first):
*
* - (optional unused space. As of gcc 3.3, this space is 24 bytes)
* - arg n
* - arg n-1
* - ...
* - arg 1
* - return instruction address: The address the function returns to
* once finished
* - local variables
*
* The remaining of the code should be read from the end upward to
* understand how the processor will handle it.
*/
vaddr_t tmp_vaddr = stack_bottom + stack_size;
uint32_t *stack = (uint32_t *)tmp_vaddr;
/* If needed, poison the stack */
#ifdef CPU_STATE_DETECT_UNINIT_KERNEL_VARS
memset((void *)stack_bottom, CPU_STATE_STACK_POISON, stack_size);
#elif defined(CPU_STATE_DETECT_KERNEL_STACK_OVERFLOW)
cpu_state_prepare_detect_kernel_stack_overflow(stack_bottom, stack_size);
#endif
/* Simulate a call to the core_routine() function: prepare its
arguments */
*(--stack) = exit_arg;
*(--stack) = (uint32_t)exit_func;
*(--stack) = start_arg;
*(--stack) = (uint32_t)start_func;
*(--stack) = 0; /* Return address of core_routine => force page fault */
/*
* Setup the initial context structure, so that the CPU will execute
* the function core_routine() once this new context has been
* restored on CPU
*/
/* Compute the base address of the structure, which must be located
below the previous elements */
tmp_vaddr = ((vaddr_t)stack) - sizeof(struct cpu_kstate);
kctxt = (struct cpu_kstate *)tmp_vaddr;
/* Initialize the CPU context structure */
memset(kctxt, 0x0, sizeof(struct cpu_kstate));
/* Tell the CPU context structure that the first instruction to
execute will be that of the core_routine() function */
kctxt->regs.eip = (uint32_t)core_routine;
/* Setup the segment registers */
kctxt->regs.cs = BUILD_SEGMENT_REG_VALUE(0, FALSE, SEG_KCODE); /* Code */
kctxt->regs.ds = BUILD_SEGMENT_REG_VALUE(0, FALSE, SEG_KDATA); /* Data */
kctxt->regs.es = BUILD_SEGMENT_REG_VALUE(0, FALSE, SEG_KDATA); /* Data */
kctxt->regs.cpl0_ss = BUILD_SEGMENT_REG_VALUE(0, FALSE, SEG_KDATA); /* Stack */
/* fs and gs unused for the moment. */
/* The newly created context is initially interruptible */
kctxt->regs.eflags = (1 << 9); /* set IF bit */
/* Finally, update the generic kernel/user thread context */
*ctxt = (struct cpu_state *)kctxt;
return 0;
}
#if defined(CPU_STATE_DETECT_KERNEL_STACK_OVERFLOW)
void cpu_state_prepare_detect_kernel_stack_overflow(const struct cpu_state *ctxt,
vaddr_t stack_bottom, size_t stack_size)
{
(void)ctxt;
size_t poison_size = CPU_STATE_DETECT_KERNEL_STACK_OVERFLOW;
if (poison_size > stack_size)
poison_size = stack_size;
memset((void *)stack_bottom, CPU_STATE_STACK_POISON, poison_size);
}
void cpu_state_detect_kernel_stack_overflow(const struct cpu_state *ctxt, vaddr_t stack_bottom,
size_t stack_size)
{
unsigned char *c;
size_t i;
/* On Matos/SOS, "ctxt" corresponds to the address of the esp register of
the saved context in Kernel mode (always, even for the interrupted
context of a user thread). Here we make sure that this stack
pointer is within the allowed stack area */
assert(((vaddr_t)ctxt) >= stack_bottom);
assert(((vaddr_t)ctxt) + sizeof(struct cpu_kstate) <= stack_bottom + stack_size);
/* Check that the bottom of the stack has not been altered */
for (c = (unsigned char *)stack_bottom, i = 0;
(i < CPU_STATE_DETECT_KERNEL_STACK_OVERFLOW) && (i < stack_size); c++, i++) {
assert(CPU_STATE_STACK_POISON == *c);
}
}
#endif
/* =======================================================================
* Public Accessor functions
*/
vaddr_t cpu_context_get_PC(const struct cpu_state *ctxt)
{
assert(NULL != ctxt);
/* This is the PC of the interrupted context (ie kernel or user
context). */
return ctxt->eip;
}
vaddr_t cpu_context_get_SP(const struct cpu_state *ctxt)
{
assert(NULL != ctxt);
/* On Matos/SOS, "ctxt" corresponds to the address of the esp register of
the saved context in Kernel mode (always, even for the interrupted
context of a user thread). */
return (vaddr_t)ctxt;
}
void cpu_context_dump(const struct cpu_state *ctxt)
{
printf("CPU: eip=%x esp=%x eflags=%x cs=%x ds=%x ss=%x err=%x", (unsigned)ctxt->eip,
(unsigned)ctxt, (unsigned)ctxt->eflags, (unsigned)GET_CPU_CS_REGISTER_VALUE(ctxt->cs),
(unsigned)ctxt->ds, (unsigned)ctxt->cpl0_ss, (unsigned)ctxt->error_code);
}

207
core/cpu_context.h Normal file
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@ -0,0 +1,207 @@
/* Copyright (C) 2005 David Decotigny
Copyright (C) 2000-2004, The KOS team
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA.
*/
#pragma once
/**
* @file cpu_context.h
*
* Low level API to manage kernel and user thread CPU contexts. Should
* be some kind of architecture-independent.
*/
#include "types.h"
#include "errno.h"
/**
* Opaque structure storing the CPU context of an inactive kernel or
* user thread, as saved by the low level primitives below or by the
* interrupt/exception handlers.
*
* @note This is an (architecture-independent) forward declaration:
* see cpu_context.c and the *.S files for its
* (architecture-dependent) definition.
*/
struct cpu_state;
/**
* The type of the functions passed as arguments to the Kernel thread
* related functions.
*/
typedef void (cpu_kstate_function_arg1_t(void * arg1));
/**
* Function to create an initial context for a kernel thread starting
* its execution at function start_func with the argument initial_arg,
* and having the stack defined by stack_bottom/stack_size. When the
* start_func function returns, the function exit_func is called with
* argument exit_arg.
*
* @param kctxt The kernel thread CPU context to initialize. The
* address of the newly-initialized struct cpu_state will be
* stored in this variable. The contents of this struct cpu_state
* are actually located /inside/ the stack.
*
* @param start_func The address of the first instruction that will be
* executed when this context will be first transferred on
* CPU. Practically speaking, this is the address of a function that
* is assumed to take 1 argument.
*
* @param start_arg The value that will be passed as the argument to
* start_func when the thread starts. The stack will be setup
* accordingly to simulate a real call to the function and really
* passing this arguement.
*
* @param stack_bottom The lowest address of the stack.
*
* @param stack_size The size of the stack.
*
* @param exit_func The address of the instruction executed after the
* function start_func has returned. This function takes 1 parameter
* as argument: exit_arg.
*
* @param exit_arg The argument passed to the function exit_func.
*
* @note the newly created context is INTERRUPTIBLE by default !
*/
int cpu_kstate_init(struct cpu_state **kctxt,
cpu_kstate_function_arg1_t *start_func,
uint32_t start_arg,
vaddr_t stack_bottom,
size_t stack_size,
cpu_kstate_function_arg1_t *exit_func,
uint32_t exit_arg);
/**
* Function that performs an immediate context-switch from one
* kernel/user thread to another one. It stores the current executing
* context in from_ctxt, and restores to_context on CPU.
*
* @param from_ctxt The address of the struct cpu_state will be
* stored in this variable. Must NOT be NULL.
*
* @param to_ctxt The CPU will resume its execution with the struct
* cpu_state located at this address. Must NOT be NULL.
*/
void cpu_context_switch(struct cpu_state **from_ctxt,
struct cpu_state *to_ctxt);
/*
* Switch to the new given context (of a kernel/user thread) without
* saving the old context (of another kernel/user thread), and call
* the function reclaiming_func passing it the recalining_arg
* argument. The reclaining function is called from within the stack
* of the new context, so that it can (among other things) safely
* destroy the stack of the former context.
*
* @param switch_to_ctxt The context that will be restored on the CPU
*
* @param reclaiming_func The address of the function that will be
* called after having changed the stack, but before restoring the CPU
* context to switch_to_ctxt.
*/
void
cpu_context_exit_to(struct cpu_state *switch_to_ctxt,
cpu_kstate_function_arg1_t *reclaiming_func,
uint32_t reclaiming_arg) __attribute__((noreturn));
/* =======================================================================
* Public Accessor functions
*/
/**
* Return Program Counter stored in the saved kernel/user context
*/
vaddr_t cpu_context_get_PC(const struct cpu_state *ctxt);
/**
* Return Stack Pointer stored in the saved kernel/user context
*/
vaddr_t cpu_context_get_SP(const struct cpu_state *ctxt);
/**
* Dump the contents of the CPU context (bochs + x86_videomem)
*/
void cpu_context_dump(const struct cpu_state *ctxt);
/* =======================================================================
* Public Accessor functions TO BE USED ONLY BY Exception handlers
*/
/**
* Return the argument passed by the CPU upon exception, as stored in the
* saved context
*/
uint32_t cpu_context_get_EX_info(const struct cpu_state *ctxt);
/**
* Return the faulting address of the exception
*/
vaddr_t
cpu_context_get_EX_faulting_vaddr(const struct cpu_state *ctxt);
/* =======================================================================
* Macros controlling stack poisoning.
* Stack poisoning can be used to detect:
* - unitialized local variables
* - when the thread might have gone too deep in the stack
*/
/** The signature of the poison */
#define CPU_STATE_STACK_POISON 0xa5
/**
* When set, mean that the whole stack is poisoned to detect use of
* unititialized variables
*/
#define CPU_STATE_DETECT_UNINIT_KERNEL_VARS
/* #undef CPU_STATE_DETECT_UNINIT_KERNEL_VARS */
/**
* When set, mean that the bottom of the stack is poisoned to detect
* probable stack overflow. Its value indicates the number of bytes
* used for this detection.
*/
#define CPU_STATE_DETECT_KERNEL_STACK_OVERFLOW 64
/* #undef CPU_STATE_DETECT_KERNEL_STACK_OVERFLOW */
#if defined(CPU_STATE_DETECT_KERNEL_STACK_OVERFLOW)
void
cpu_state_prepare_detect_kernel_stack_overflow(const struct cpu_state *ctxt,
vaddr_t kernel_stack_bottom,
size_t kernel_stack_size);
void cpu_state_detect_kernel_stack_overflow(const struct cpu_state *ctxt,
vaddr_t kernel_stack_bottom,
size_t kernel_stack_size);
#else
# define cpu_state_prepare_detect_kernel_stack_overflow(ctxt,stkbottom,stksize) \
({ /* nop */ })
# define cpu_state_detect_kernel_stack_overflow(ctxt,stkbottom,stksize) \
({ /* nop */ })
#endif

107
core/cpu_context_switch.S Normal file
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@ -0,0 +1,107 @@
.file "cpu_context_switch.S"
.text
.globl cpu_context_switch
.type cpu_context_switch, @function
cpu_context_switch:
// arg2= to_context -- esp+64
// arg1= from_context -- esp+60
// caller ip -- esp+56
pushf // (eflags) esp+52
pushl %cs // (cs) esp+48
pushl $resume_pc // (ip) esp+44
pushl $0 // (error code) esp+40
pushl %ebp // esp+36
pushl %edi // esp+32
pushl %esi // esp+28
pushl %edx // esp+24
pushl %ecx // esp+20
pushl %ebx // esp+16
pushl %eax // esp+12
subl $2, %esp // (alignment) esp+10
pushw %ss // esp+8
pushw %ds // esp+6
pushw %es // esp+4
pushw %fs // esp+2
pushw %gs // esp
/*
* Now that the original eax/ebx are stored, we can use them safely
*/
/* Store the address of the saved context */
movl 60(%esp), %ebx
movl %esp, (%ebx)
/* This is the proper context switch ! We change the stack here */
movl 64(%esp), %esp
/* Restore the CPU context */
popw %gs
popw %fs
popw %es
popw %ds
popw %ss
addl $2,%esp
popl %eax
popl %ebx
popl %ecx
popl %edx
popl %esi
popl %edi
popl %ebp
addl $4, %esp /* Ignore "error code" */
/* This restores the eflags, the cs and the eip registers */
iret /* equivalent to: popfl ; ret */
resume_pc:
// Same context as that when cpu_context_switch got called
// arg2= to_context -- esp+8
// arg1= from_context -- esp+4
// caller ip -- esp
ret
/* ------------------------- */
.globl cpu_context_exit_to
.type cpu_context_exit_to, @function
cpu_context_exit_to:
// arg3= reclaiming_arg -- esp+12
// arg2= reclaiming_func -- esp+8
// arg1= to_context -- esp+4
// caller ip -- esp
/* Store the current SP in a temporary register */
movl %esp, %eax
/* This is the proper context switch ! We change the stack here */
movl 4(%eax), %esp
/* Call the reclaiming function (remember: the old frame address
is stored in eax) */
pushl 12(%eax)
call *8(%eax)
addl $4, %esp
/* Restore the CPU context */
popw %gs
popw %fs
popw %es
popw %ds
popw %ss
addl $2,%esp
popl %eax
popl %ebx
popl %ecx
popl %edx
popl %esi
popl %edi
popl %ebp
addl $4, %esp /* Ignore "error code" */
/* This restores the eflags, the cs and the eip registers */
iret /* equivalent to: popfl ; ret */

78
tests/test.c
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@ -1,5 +1,6 @@
#include "alloc.h"
#include "assert.h"
#include "cpu_context.h"
#include "klibc.h"
#include "list.h"
#include "mem.h"
@ -141,6 +142,82 @@ void test_backtrace()
test_backtrace_1(2);
}
/* ======================================================================
* Demonstrate the use of the CPU kernet context management API:
* - A coroutine prints "Hlowrd" and switches to the other after each
* letter
* - A coroutine prints "el ol\n" and switches back to the other after
* each letter.
* The first to reach the '\n' returns back to main.
*/
struct cpu_state *ctxt_hello1;
struct cpu_state *ctxt_hello2;
struct cpu_state *ctxt_main;
vaddr_t hello1_stack, hello2_stack;
static void reclaim_stack(void * stack_vaddr)
{
free(stack_vaddr);
}
static void exit_hello12(void * stack_vaddr)
{
cpu_context_exit_to(ctxt_main, (cpu_kstate_function_arg1_t *)reclaim_stack, (vaddr_t)stack_vaddr);
}
static void hello1(void *strIn)
{
char *str = (char *)strIn;
for (; *str != '\n'; str++) {
printf("hello1: %c\n", *str);
cpu_context_switch(&ctxt_hello1, ctxt_hello2);
}
/* You can uncomment this in case you explicitly want to exit
now. But returning from the function will do the same */
/* cpu_context_exit_to(ctxt_main,
(cpu_kstate_function_arg1_t*) reclaim_stack,
hello1_stack); */
}
static void hello2(void *strIn)
{
char *str = (char *)strIn;
for (; *str != '\n'; str++) {
printf("hello2: %c\n", *str);
cpu_context_switch(&ctxt_hello2, ctxt_hello1);
}
/* You can uncomment this in case you explicitly want to exit
now. But returning from the function will do the same */
/* cpu_context_exit_to(ctxt_main,
(cpu_kstate_function_arg1_t*) reclaim_stack,
hello2_stack); */
}
void testCoroutine()
{
#define DEMO_STACK_SIZE 1024
/* Allocate the stacks */
hello1_stack = (vaddr_t)malloc(DEMO_STACK_SIZE);
hello2_stack = (vaddr_t)malloc(DEMO_STACK_SIZE);
/* Initialize the coroutines' contexts */
cpu_kstate_init(&ctxt_hello1, (cpu_kstate_function_arg1_t *)hello1, (uint32_t) "Hlowrd",
(vaddr_t)hello1_stack, DEMO_STACK_SIZE,
(cpu_kstate_function_arg1_t *)exit_hello12, (uint32_t)hello1_stack);
cpu_kstate_init(&ctxt_hello2, (cpu_kstate_function_arg1_t *)hello2, (uint32_t) "el ol\n",
(vaddr_t)hello2_stack, DEMO_STACK_SIZE,
(cpu_kstate_function_arg1_t *)exit_hello12, (uint32_t)hello2_stack);
/* Go to first coroutine */
printf("Printing Hello World\\n...\n");
cpu_context_switch(&ctxt_main, ctxt_hello1);
/* The first coroutine to reach the '\n' switched back to us */
printf("Back in main !\n");
}
void run_test(void)
{
testPaging();
@ -153,4 +230,5 @@ void run_test(void)
testAlloc();
printf("Testing backtrace\n");
test_backtrace();
testCoroutine();
}