分类：
2008-04-23 11:18:58
ARM系统中MMU和Memory的系统结构如图 0 1所示。不过具体的CPU在实现MMU时差别较大，可能对其做简化和扩展, SkyEye的MMU模拟实现基于此，在提供一个标准的接口基础上,分成与具体CPU类型无关的MMU模拟子模块和与具体CPU类型相关的MMU模拟子模块两个主要部分。
ARM CPU进行数据访问的基本流程如图 0-2所示。
数据结构
typedef struct mmu_state_t {
ARMword control; //CP15 control register
ARMword translation_table_base; //CP15 translation table base register
ARMword domain_access_control; //CP15 domain access control register
ARMword fault_status; //CP15 fault status register
ARMword fault_address; //CP15 fault address register
ARMword last_domain; //last access domain
ARMword process_id; //CP15 process id register
mmu_ops_t ops;
union{
sa_mmu_t sa_mmu;
arm7100_mmu_t arm7100_mmu;
}u;
} mmu_state_t;
typedef struct mmu_ops_s{
int (*init)(ARMul_State *state);/*initilization*/
void (*exit)(ARMul_State *state);/*free on exit*/
fault_t (*read_byte)(ARMul_State *state, ARMword va, ARMword *data);
fault_t (*write_byte)(ARMul_State *state, ARMword va, ARMword data);
fault_t (*read_halfword)(ARMul_State *state, ARMword va, ARMword *data);
fault_t (*write_halfword)(ARMul_State *state, ARMword va,ARMword data);
fault_t (*read_word)(ARMul_State *state, ARMword va,ARMword *data);
fault_t (*write_word)(ARMul_State *state, ARMword va,ARMword data);
fault_t (*load_instr)(ARMul_State *state, ARMword va, ARMword *instr);
void (*mcr)(ARMul_State *state, ARMword instr, ARMword val);
ARMword (*mrc)(ARMul_State *state, ARMword instr);
}mmu_ops_t;
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数据结构ARMul_State中类型为mmu_state_t的mmu代表模拟中MMU的状态。mmu_state_t中的ops提供具体mmu的接口函数，同时包括一个联合结构u用于具体mmu实现的数据结构。
与具体CPU类型无关的MMU模拟子模块是实现MMU模拟的基础，它实现了TLB，TTW, 访问控制，CACHE, Write Buffer，Read Buffer等MMU要素的模拟,并且提供了较统一的接口，可以较灵活地组合实现具体MMU模拟。
TLB的实现（mmu/tlb.[ch]）
TLB是一个表，它的表项包含地址映射信息和访问控制信息，地址转换信息只有在该表中查询不到时，才通过TTW在内存中查找。
数据结构
TLB 映射类型
typedef enum tlb_mapping_t {
TLB_INVALID = 0,
TLB_SMALLPAGE = 1,
TLB_LARGEPAGE = 2,
TLB_SECTION = 3
} tlb_mapping_t;
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TLB 表项
typedef struct tlb_entry_t {
ARMword virt_addr; //virtual address
ARMword phys_addr; //physical address
ARMword perms; //access permission
ARMword domain; //access domain
tlb_mapping_t mapping; //tlb mapping type
} tlb_entry_t;
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TLB 表
typedef struct tlb_s{
int num; /*num of tlb entry*/
int cycle; /*current tlb cycle，used for allocate tlb_entry*/
tlb_entry_t *entrys;
}tlb_t;
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接口函数
int mmu_tlb_init(tlb_t *tlb_t, int num); 初始化TLB void mmu_tlb_exit(tlb_t *tlb_t); 释放TLB void mmu_tlb_invalidate_all(ARMul_State *state, tlb_t *tlb_t); 无效所有的tlb_entry void mmu_tlb_invalidate_entry(ARMul_State *state, tlb_t *tlb_t, ARMword virt_addr); 无效包含指定virt_addr的tlb_entry. tlb_entry_t * mmu_tlb_search(ARMul_State *state, tlb_t *tlb_t, ARMword virt_addr); 根据virt_addr查找tlb_entry |
TTW的实现(mmu/tlb.[ch])
ARM系统中通过2级映射，实现了页式地址转换。
接口函数
fault_t translate(ARMul_State *state, ARMword virt_addr, tlb_t *tlb_t, tlb_entry_t **tlb)
{
/*首先查找TLB表，如果没有找到，执行TTW并更新TLB表*/
*tlb = mmu_tlb_search(state, tlb_t, virt_addr);/*查找tlb*/
if (!*tlb) {
/* 没有找到,进行TTW*/
ARMword l1addr, l1desc; /*一级描述符地址、一级描述符*/
tlb_entry_t entry;
l1addr = state->mmu.translation_table_base & 0xFFFFC000;
l1addr = (l1addr | (virt_addr >> 18)) & ~3; /*计算一级描述符地址*/
l1desc = mem_read_word(state, l1addr); /*读取一级描述符*/
switch (l1desc & 3) {
case 0:
case 3:
return SECTION_TRANSLATION_FAULT;
case 1:
/*页式变换*/
{
ARMword l2addr, l2desc; /*二级描述符的地址，二级描述符*/
l2addr = l1desc & 0xFFFFFC00;
/*计算二级描述符的地址*/
l2addr = (l2addr | ((virt_addr & 0x000FF000) >> 10)) & ~3;
/*读取二级描述符*/
l2desc = mem_read_word(state, l2addr);
entry.virt_addr = virt_addr;
entry.phys_addr = l2desc;
entry.perms = l2desc & 0x00000FFC;
entry.domain = (l1desc >> 5) & 0x0000000F;
switch (l2desc & 3) {
case 0:
case 3:
state->mmu.last_domain = entry.domain;
return PAGE_TRANSLATION_FAULT;
case 1:
entry.mapping = TLB_LARGEPAGE; /*大页*/
break;
case 2:
entry.mapping = TLB_SMALLPAGE; /*小页*/
break;
}
}
break;
case 2:
/*段变换*/
entry.virt_addr = virt_addr;
entry.phys_addr = l1desc;
entry.perms = l1desc & 0x00000C0C;
entry.domain = (l1desc >> 5) & 0x0000000F;
entry.mapping = TLB_SECTION;
break;
}
entry.virt_addr &= tlb_masks[entry.mapping];
entry.phys_addr &= tlb_masks[entry.mapping];
/* 更新tlb*/
*tlb = &tlb_t->entrys[tlb_t->cycle];
tlb_t->cycle = (tlb_t->cycle + 1) % tlb_t->num;
**tlb = entry;
}
state->mmu.last_domain = (*tlb)->domain;
return NO_FAULT;
}
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访问控制的实现(mmu/tlb.[ch])
接口函数
fault_t check_access(ARMul_State *state, ARMword virt_addr, tlb_entry_t *tlb, int read); |
CACHE的实现(mmu/cache.[ch])
ARM系统中一般只实现组相联CACHE。组相联CACHE分成多组，一个组有包括多个CACHE line，一个32位地址可以由下图表示。
| Tag | Set | Word | 1 | 0 |
数据结构
Cache行
typedef struct cache_line_t{
ARMword tag; /* cache line align address |
bit2: last half dirty
bit1: first half dirty
bit0: cache valid flag
*/
ARMword pa; /*physical address*/
ARMword *data; /*array of cached data*/
}cache_line_t;
#define TAG_VALID_FLAG 0x00000001
#define TAG_FIRST_HALF_DIRTY 0x00000002
#define TAG_LAST_HALF_DIRTY 0x00000004
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Cache 组
typedef struct cache_set_s{
cache_line_t *lines;
int cycle; /*used for cache line allocation*/
}cache_set_t;
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Cache 结构
typedef struct cache_s{
int width; /*bytes in a line*/
int way; /*way of set asscociate*/
int set; /*num of set*/
int w_mode; /*write back or write through*/
//int a_mode; /*alloc mode: random or round-bin*/
cache_set_t *sets;
}cache_t;
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接口函数
/*Cache的初始化和释放*/ int mmu_cache_init(cache_t *cache_t, int width, int way, int set, int w_mode); void mmu_cache_exit(cache_t *cache_t); /*Cache 查找和分配*/ cache_line_t * mmu_cache_search(ARMul_State *state, cache_t *cache_t, ARMword va); cache_line_t * mmu_cache_alloc(ARMul_State *state, cache_t *cache_t, ARMword va, ARMword pa); /*Cache 操作*/ void mmu_cache_write_back(ARMul_State *state, cache_t *cache_t, cache_line_t *cache); void mmu_cache_clean(ARMul_State *state, cache_t *cache_t, ARMword va); void mmu_cache_invalidate(ARMul_State *state, cache_t *cache_t, ARMword va); void mmu_cache_invalidate_all(ARMul_State *state, cache_t *cache_t); void mmu_cache_soft_flush(ARMul_State *state, cache_t *cache_t, ARMword pa); |
Write Buffer的实现(mmu/wb.[hc])
用一个循环队列模拟Write Buffer。
数据结构
typedef struct wb_entry_s{
ARMword pa; //phy_addr
ARMbyte *data;//data
int nb; //number byte to write
}wb_entry_t;
typedef struct wb_s{
int num; //wb_entry_t的总数
int nb; //wb_entry_t中最大字节数
int first; //循环队列头
int last; //循环队列尾
int used; //循环队列中已用wb_entry_t的个数
wb_entry_t *entrys;
}wb_t;
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接口函数
/*初始化和释放*/ int mmu_wb_init(wb_t *wb_t, int num, int nb); void mmu_wb_exit(wb_t *wb); /*数据入Write Buffer*/ void mmu_wb_write_bytess(ARMul_State *state, wb_t *wb_t, ARMword pa, ARMbyte *data, int n); /*将Write Buffer中数据全部写入内存*/ void mmu_wb_drain_all(ARMul_State *state, wb_t *wb_t); |
Read Buffer的实现(mmu/rb.[hc])
数据结构
typedef struct rb_entry_s{
ARMword data[RB_WORD_NUM];//array to store data
ARMword va; //first word va
int type; //rb type
fault_t fault; //fault set by rb alloc
}rb_entry_t;
typedef struct rb_s{
int num;
rb_entry_t *entrys;
}rb_t;
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接口函数
/*初始化和释放*/ int mmu_rb_init(rb_t *rb_t, int num); void mmu_rb_exit(rb_t *rb_t); rb_entry_t *mmu_rb_search(rb_t *rb_t, ARMword va);/*查找*/ void mmu_rb_invalidate_entry(rb_t *rb_t, int i);/*无效*/ void mmu_rb_invalidate_all(rb_t *rb_t); void mmu_rb_load(ARMul_State *state, rb_t *rb_t, int i_rb, int type, ARMword va);/*装入*/ |
与具体CPU类型相关的MMU模拟子模块建立在与具体CPU无关的MMU模拟实现子模块的基础上，通过实现具体CPU的mmu_ops_t，完成具体CPU的MMU模拟。以下详细介绍StrongARM的MMU实现。
StrongARM的MMU分成指令和数据两部分。指令部分包括一个指令TLB和一个指令CACHE,数据部分包括一个数据TLB，两个数据CACHE(main CACHE和 mini CACHE)，一个Write Buffer和一个Read Buffer。如图 0-3所示：
mmu_ops_t sa_mmu_ops = {
sa_mmu_init,
sa_mmu_exit,
sa_mmu_read_byte,
sa_mmu_write_byte,
sa_mmu_read_halfword,
sa_mmu_write_halfword,
sa_mmu_read_word,
sa_mmu_write_word,
sa_mmu_load_instr,
sa_mmu_mcr,
sa_mmu_mrc,
};
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SA MMU的初始化
typedef struct sa_mmu_desc_s{
int i_tlb;
cache_desc_t i_cache;
int d_tlb;
cache_desc_t main_d_cache;
cache_desc_t mini_d_cache;
int rb;
wb_desc_t wb;
}sa_mmu_desc_t;
static sa_mmu_desc_t sa11xx_mmu_desc ={
32,
{32, 32, 16, CACHE_WRITE_BACK},
32,
{32, 32, 8, CACHE_WRITE_BACK},
{32, 2, 8, CACHE_WRITE_BACK},
4,
{8, 16}
};
typedef struct sa_mmu_s{
/*指令部分*/
tlb_t i_tlb; /*指令tlb*/
cache_t i_cache; /*指令cache*/
/*数据部分*/
tlb_t d_tlb; /*数据tlb*/
cache_t main_d_cache;/*main cache*/
cache_t mini_d_cache;/*mini cache*/
rb_t rb_t; /*Read Buffer*/
wb_t wb_t; /*Write Buffer*/
}sa_mmu_t;
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int sa_mmu_init(ARMul_State *state);
sa_mmu_desc_t 是SA MMU参数描述的数据结构，sa_mmu_t实现SA MMU 的数据表示。sa_mmu_init根据sa11xx_mmu_desc，完成对state->u.sa_mmu的初始化。
SA MMU的数据读操作
static fault_t
sa_mmu_read(ARMul_State *state, ARMword va, ARMword *data, ARMword datatype)
{
fault_t fault;
rb_entry_t *rb;
tlb_entry_t *tlb;
cache_line_t *cache;
ARMword pa, real_va,temp,offset;
/*根据CP15 process id register转换地址*/
va = mmu_pid_va_map(va);
real_va=va;
if (MMU_Disabled){
/*如果MMU关闭,直接从内存读取*/
if (datatype==ARM_BYTE_TYPE)
*data = mem_read_byte(state, va);
else if (datatype==ARM_HALFWORD_TYPE)
*data = mem_read_halfword(state, va);
else if (datatype==ARM_WORD_TYPE)
*data = mem_read_word(state, va);
else {
printf("SKYEYE:1 sa_mmu_read error: unknown data type %d\n",datatype);
exit(-1);
}
return 0;
}
/*align 异常检查*/
if (((va & 3 ) && (datatype==ARM_WORD_TYPE) && MMU_Aligned) || \
((va & 1 ) && (datatype==ARM_HALFWORD_TYPE) && MMU_Aligned) ){
d_msg("align\n");
return ALIGNMENT_FAULT;
} // else
va &= ~(WORD_SIZE - 1);
/*TTW得到tlb*/
fault = translate(state, va, D_TLB(), &tlb);
if (fault){
d_msg("translate\n");
return fault;
}
/*访问控制检查*/
fault = check_access(state, va, tlb, 1);
if (fault)
return fault;
/*首先在Read Buffer中查找数据*/
rb = mmu_rb_search(RB(), va);
if (rb){
if (rb->fault)
return rb->fault;
*data = rb->data[(va & (rb_masks[rb->type]-1))>>WORD_SHT];
goto datatrans;
//return 0;
};
/*其次查找main cache*/
cache = mmu_cache_search(state, MAIN_D_CACHE(), va);
if (cache){
*data = cache->data[va_cache_index(va, MAIN_D_CACHE())];
goto datatrans;
//return 0;
}
/*最后查找mini cache*/
cache = mmu_cache_search(state, MINI_D_CACHE(), va);
if (cache){
*data = cache->data[va_cache_index(va, MINI_D_CACHE())];
goto datatrans;
//return 0;
}
/*计算物理地址*/
pa = tlb_va_to_pa(tlb, va);
/*如果在[0xe0000000, 0xe8000000]区间，执行mmu_cache_soft_flush*/
if ((pa >= 0xe0000000) && (pa < 0xe8000000)){
if (tlb_c_flag(tlb)){
if (tlb_b_flag(tlb)){
mmu_cache_soft_flush(state, MAIN_D_CACHE(), pa);
}else{
mmu_cache_soft_flush(state, MINI_D_CACHE(), pa);
}
}
return 0;
}
/*如果B＝1，必须先清空Write Buffer*/
if (tlb_b_flag(tlb))
mmu_wb_drain_all(state, WB());
if (tlb_c_flag(tlb) && MMU_DCacheEnabled){
/*如果C=1,并且Data Cache开启，将数据读入Cache*/
cache_t *cache_t;
if (tlb_b_flag(tlb))
cache_t = MAIN_D_CACHE();
else
cache_t = MINI_D_CACHE();
cache = mmu_cache_alloc(state, cache_t, va, pa);
*data = cache->data[va_cache_index(va, cache_t)];
}else{
/*直接从内存读取*/
if (datatype==ARM_BYTE_TYPE)
*data = mem_read_byte(state, pa|(real_va&3));
else if (datatype==ARM_HALFWORD_TYPE)
*data = mem_read_halfword(state,
pa|(real_va&2));
else if (datatype==ARM_WORD_TYPE)
*data = mem_read_word(state, pa);
else {
printf("SKYEYE:2 sa_mmu_read error: unknown
data type %d\n", datatype);
exit(-1);
}
return 0;
}
/*根据读类型和Endian模式整理结果*/
datatrans:
if (datatype==ARM_HALFWORD_TYPE){
temp = *data;
offset = (((ARMword) state->bigendSig * 2) ^ (real_va & 2)) <<
3; /* bit offset into the word */
*data= (temp>> offset) & 0xffff;
} else if (datatype==ARM_BYTE_TYPE) {
temp = *data;
offset = (((ARMword) state->bigendSig * 3) ^ (real_va & 3)) <<
3; /* bit offset into the word */
*data=(temp >> offset & 0xffL);
}
end:
return 0;
}
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SA MMU的mcr操作
static void
sa_mmu_mcr(ARMul_State *state, ARMword instr, ARMword value)
{
mmu_regnum_t creg = BITS(16, 19) & 15;
if (!strncmp(skyeye_config.cpu->cpu_arch_name, "armv4", 5) )
{
switch (creg) {
………………….
case MMU_CACHE_OPS:
sa_mmu_cache_ops(state, instr, value);
break;
case MMU_TLB_OPS:
sa_mmu_tlb_ops(state, instr, value);
break;
case MMU_SA_RB_OPS:
sa_mmu_rb_ops(state, instr, value);
break;
case MMU_SA_DEBUG:
break;
case MMU_SA_CP15_R15:
break;
case MMU_PID:
state->mmu.process_id = value & 0x8e000000;
break;
default:
printf("mmu_mcr wrote UNKNOWN - reg %d\n", creg);
break;
}
}
}
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sa_mmu_mcr实现SA MMU特定的cache, tlb, read buffer, write buffer等操作。
SkyEye memory系统的模拟实现的基本思想是：
1． 地址划分，每个划分区域都提供对应的读写函数
2． 通过skyeye.conf配置文件配置memory地址区域
数据结构
typedef struct mem_bank_t {
ARMword (*read_byte)(ARMul_State *state, ARMword addr);
void (*write_byte)(ARMul_State *state, ARMword addr, ARMword data);
ARMword (*read_halfword)(ARMul_State *state, ARMword addr);
void (*write_halfword)(ARMul_State *state, ARMword addr, ARMword data);
ARMword (*read_word)(ARMul_State *state, ARMword addr);
void (*write_word)(ARMul_State *state, ARMword addr, ARMword data);
unsigned long addr, len;
char filename[MAX_STR];
} mem_bank_t;
typedef struct {
int bank_num;
int current_num; /*current num of bank*/
mem_bank_t mem_banks[MAX_BANK];
} mem_config_t;
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配置函数
int do_mem_bank_option(skyeye_option_t *this_option, int num_params, const char *params[])； /*完成memory bank的配置*/
读写接口函数
ARMword mem_read_byte(ARMul_State *state, ARMword addr); ARMword mem_read_halfword(ARMul_State *state, ARMword addr); ARMword mem_read_word(ARMul_State *state, ARMword addr); void mem_write_byte(ARMul_State *state, ARMword addr, ARMword data); void mem_write_halfword(ARMul_State *state, ARMword addr, ARMword data); void mem_write_word(ARMul_State *state, ARMword addr, ARMword data); |
实现方式都是先根据地址在mem_config_t中找到对应的mem_bank,再调用mem_bank对应的读写函数。
内存区域的读写函数
ARMword real_read_byte(ARMul_State *state, ARMword addr); void real_write_byte(ARMul_State *state, ARMword addr, ARMword data); ARMword real_read_halfword(ARMul_State *state, ARMword addr); void real_write_halfword(ARMul_State *state, ARMword addr, ARMword data); ARMword real_read_word(ARMul_State *state, ARMword addr); void real_write_word(ARMul_State *state, ARMword addr, ARMword data); |
IO区域的读写函数
ARMword io_read_byte(ARMul_State *state, ARMword addr); void io_write_byte(ARMul_State *state, ARMword addr, ARMword data); ARMword io_read_halfword(ARMul_State *state, ARMword addr); void io_write_halfword(ARMul_State *state, ARMword addr, ARMword data); ARMword io_read_word(ARMul_State *state, ARMword addr); void io_write_word(ARMul_State *state, ARMword addr, ARMword data); |
