什么是更新 MMU 转换表的正确方法 [英] what is the right way to update MMU translation table
问题描述
我在我的 s3c2440 板上启用了 MMU(3G - 4G 内存 :: 故障属性)，当我没有读/写 3G - 4G 内存时一切都很好.所以为了测试页面错误向量，我写信给一个 0xFF 到 3G 地址，正如我所料，我从 FSR 得到了正确的值，所以我在 _do_page_fault() 中做了这个，步骤是这样的:
I enabled MMU on my s3c2440 board (3G - 4G memory :: the fault attribute),everything was just fine when I didn't read/write 3G - 4G memory .So to test the page fault vector ,I wrote to a 0xFF to the 3G address,as I expected ,I got the right value from FSR ,So I did this in _do_page_fault (), the step was like this :
..... // set new page to translation table
.....
invlidate_icache (); // clear icache
clr_dcache (); // wb is used ,clear dcache
invalidate_ttb (); // invalidate translation table
然后 ISR_dataabort 返回，我读取 3G 地址以获取我之前 wote 的 0xFF.不幸的是，我再次中止了数据.(我确定我设置的转换表值没问题)
and then ISR_dataabort returned ,I read the 3G address to get the 0xFF which I wote before . Unfortunately I got a data abort again .(I am sure the translation table value I set is ok)
那么更新 MMU 转换表的正确方法是什么.感谢您的帮助！谢谢
So what is the correct way to update the MMU translation table .Any help is appreciate ! thanks
这是我使用的主要代码(仅用于一些测试)，(我对 ARM ARCH 有点陌生，所以这段代码可能很粗糙)
here is the Main code I used (just for some test), (I am a littlte strange to ARM ARCH,so this code might be urgly )
/* MMU TTB 0 BASE ATTR */
#define TTB0_FAULT (0|(1<<4)) /* TTB FAULT */
#define TTB0_COARSE (1|(1<<4)) /* COARSE PAGE BASE ADDR */
#define TTB0_SEG (2|(1<<4)) /* SEG BASE ADDR */
#define TTB0_FINE (3|(1<<4)) /* FINE PAGE BASE ADDR */
/* MMU TTB 1 BASE ATTR */
#define TTB1_FAULT (0)
#define TTB1_LPG (1) /* Large page */
#define TTB1_SPG (2) /* small page */
#define TTB1_TPG (3) /* tiny page */
/* domain access priority level */
#define FAULT_PL (0x0) /* domain fault */
#define USR_PL (0x1) /* usr mode */
#define RSV_PL (0x2) /* reserved */
#define SYS_PL (0x3) /* sys mode */
#define DOMAIN_FAULT (0x0<<5) /* fault 0*/
#define DOMAIN_SYS (0x1<<5) /* sys 1*/
#define DOMAIN_USR (0x2<<5) /* usr 2*/
/* C,B bit */
#define CB (3<<2) /* cache_on, write_back */
#define CNB (2<<2) /* cache_on, write_through */
#define NCB (1<<2) /* cache_off,WR_BUF on */
#define NCNB (0<<2) /* cache_off,WR_BUF off */
/* ap 2 bits */
#define AP_FAULT (0<<10) /* access deny */
#define AP_SU_ONLY (1<<10) /* rw su only */
#define AP_USR_RO (2<<10) /* sup=RW, user=RO */
#define AP_RW (3<<10) /* su=RW, user=RW */
/* page dir 1 ap0 */
#define AP0_SU_ONLY (1<<4) /* rw su only */
#define AP0_USR_RO (2<<4) /* sup=RW, user=RO */
#define AP0_RW (3<<4) /* su=RW, user=RW */
/* page dir 1 ap1 */
#define AP1_SU_ONLY (1<<6) /* rw su only */
#define AP1_USR_RO (2<<6) /* sup=RW, user=RO */
#define AP1_RW (3<<6) /* su=RW, user=RW */
/* page dir 1 ap2 */
#define AP2_SU_ONLY (1<<8) /* rw su only */
#define AP2_USR_RO (2<<8) /* sup=RW, user=RO */
#define AP2_RW (3<<8) /* su=RW, user=RW */
/* page dir 1 ap3 */
#define AP3_SU_ONLY (1<<10) /* rw su only */
#define AP3_USR_RO (2<<10) /* sup=RW, user=RO */
#define AP3_RW (3<<10) /* su=RW, user=RW */
#define RAM_START (0x30000000)
#define KERNEL_ENTRY (0x30300000) /* BANK 6 (3M) */
#define KERNEL_STACK (0x3001A000) /* BANK 6 (16K + 64K + 16K + 8K) (8k kernel stack) */
#define IRQ_STACK (0x3001B000) /* 4K IRQ STACK */
#define KERNEL_IMG_SIZE (0x20000)
#define IRQ_STACK (0x3001B000)
/* 16K aignment */
#define TTB_BASE (0x30000000)
#define PAGE_DIR0 (TTB_BASE)
#define TTB_FULL_SIZE (0x4000)
#define PAGE_DIR1 (TTB_BASE+TTB_FULL_SIZE)
#define PAGE_DIR0_SIZE (0x4000) /* 16k */
void _do_page_fault (void)
{
//
...........
//
// read the FSR && get the vaddr && type here
volatile unsigned *page_dir = (volatile unsigned*)(TTB_BASE);
unsigned index = vaddr >> 20,i = 0, j = 0;
unsigned page = 0;
if (!(page_dir[index] & ~(0x3FF) && (type == 0x0B))) { /* page_dir empty */
i = index & ~0x03;
if ( (page_dir[i+0] & ~(0x3FF)) || (page_dir [i+1] & ~(0x3FF))
|| (page_dir[i+2] & ~(0x3FF)) || (page_dir [i+3] & ~(0x3FF)) )
{
panic ( "page dir is bad !\n" ); /* 4 continuous page_dir must be 0 */
}
if (!(page = find_free_page ()))
panic ( "no more free page !\n" ); /* alloc a page page dir*/
page_dir[i+0] = (page + 0x000) | DOMAIN_USR | TTB0_COARSE ; /* small page 1st 1KB */
page_dir[i+1] = (page + 0x400) | DOMAIN_USR | TTB0_COARSE ; /* small page 2nd 1KB */
page_dir[i+2] = (page + 0x800) | DOMAIN_USR | TTB0_COARSE ; /* small page 3rd 1KB */
page_dir[i+3] = (page + 0xC00) | DOMAIN_USR | TTB0_COARSE ; /* small page 4th 1KB */
if (!(page = find_free_page ()))
panic ( "no more free page !\n" ); /* alloc a page page table*/
volatile unsigned *page_tbl = (volatile unsigned*) (page_dir[index] & ~(0x3FF));
*page_tbl = page|AP0_RW|AP1_RW|AP2_RW|AP3_RW| NCNB|TTB1_SPG;/* small page is used */
invalidate_icache ();
for (i = 0; i < 64; i++)
{
for (j = 0;j < 8;j ++)
clr_invalidate_dcache ( (i<<26)|(j<<5) );
}
invalidate_tlb ();
}
........
//
}
/* here is the macros */
#define invalidate_tlb() \
{\
__asm__ __volatile__ (\
"mov r0,#0\n"\
"mcr p15,0,r0,c8,c7,0\n"\
:::"r0" \
);\
}
#define clr_invalidate_dcache(index) \
{\
__asm__ __volatile__ (\
"mcr p15,0,%[i],c7,c14,2\n"\
:: [i]"r"(index)\
);\
}
#define invalidate_icache() \
{\
__asm__ __volatile__ (\
"mov r0,#0\n"\
"mcr p15,0,r0,c7,c5,0\n"\
::: "r0"\
);\
}
#define invalidate_dcache() \
{\
__asm__ __volatile__ (\
"mov r0,#0\n"\
"mcr p15,0,r0,c7,c6,0\n"\
::: "r0"\
);\
}
#define invalidate_idcache() \
{\
__asm__ __volatile__ (\
"mov r0,#0\n"\
"mcr p15,0,r0,c7,c7,0\n"\
:::"r0"\
);\
}\
推荐答案
注意: 我假设 TTB_BASE 是主要的 ARM L1 页表.如果是阴影，则需要按照 unixsmurf 显示更多代码.这是我最好的猜测...
Note: I assume TTB_BASE is the primary ARM L1 page table. If it is some shadow, you need to show more code as per unixsmurf. Here is my best guess...
您的 page_dir 既用作主要 L1 条目，也用作 L2 精细页表.TTB_BASE 应该只包含节、超级节或指向子页表的指针.您需要为 L2 页表分配更多的物理内存.
Your The page_dir is functioning as both the primary L1 entries and as the L2 fine page table.TTB_BASE should only contain sections, super sections or pointers to sub-page tables. You need to allocate more physical memory for the L2 page tables.
我猜你的 你的 page_dir[i+0]、page_dir[i+1] 等正在覆盖其他 L1 部分条目和 invalidate_tlb() 使它具体到 CPU.您应该使用 L2 page_tbl 指针来设置/索引小/精细页面.也许您的内核代码在 3G-4G 空间中，并且您正在那里覆盖一些关键的 L1 映射；任何数量的奇怪的事情都可能发生.page_tbl 目前的用途尚不清楚.
I guess your Your page_dir[i+0], page_dir[i+1], etc are overwriting other L1 section entries and invalidate_tlb() make this concrete to the CPU. You should be using the L2 page_tbl pointer to set/index the small/fine pages. Perhaps your kernel code is in the 3G-4G space and your are over-writing some critical L1 mappings there; any number of strange things could happen. The current use of page_tbl is unclear.
你不能重复使用主要的L1表，因为它们对硬件有意义.我猜这只是一个错误?
You can not double use the primary L1 tables as they have meaning to hardware. I guess that this is just a mistake?
主L1页表中只有三种类型的条目，
There are only three types of entries in the primary L1 page tables,
- Sections - 1MB 内存直接将 virt 映射到 phys，没有 2nd 页表.
- 超级部分 - 每个部分的 4MB 内存映射，但最大限度地减少了 TLB 压力.
- 第 2nd 页表.条目可以是 1k、4k 和 64k.精细页表的表大小为 4k，不在现代 ARM 设计中.每个条目是精细页表中的 1k 地址.
- Sections - a 1MB memory mapping straight virt to phys, with no 2nd page table.
- Super-sections - a 4MB memory mapping as per sections, but minimizing TLB pressure.
- A 2nd page table. Entries can be 1k,4k,and 64k. Fine page tables are 4k in table size and are not in modern ARM designs. Each entry is 1k of address in a fine page table.
主页表必须位于16k对齐的物理地址上，这也是它的大小.16k/(4bytes/entry)*1MB 给出了 L1 表的 4GB 地址范围.所以主L1页表中的每个条目总是引用一个1MB条目.粗页表是较新 ARM 上的唯一选项，它们指的是 1K L2 表.
The primary page table must be on a physical address that is 16k aligned, which is also it's size. 16k/(4bytes/entry)*1MB gives a 4GB address range of the L1 tables. So each entry in the primary L1 page table always refers to a 1MB entry. Coarse page tables are the only option on newer ARMs and they refer to a 1K L2 table.
1K_L2_size * 4K_entry / (4bytes_per_entry) gives 1MB address space.
1K_L2_size * 64K_entry / (16bytes_per_entry) gives 1MB address space.
在主要 L1 中有四个 1MB 条目，每个条目都用于超级部分.L2 表中的 64k 大页面各有四个条目.如果您使用超级部分，则没有L2 条目.
There are four entries of 1MB each in the primary L1 for a super-section. There are four entries each for a 64k large page in the L2 table. If you are using super-sections, you do not have L2 entries.
我认为您可能将超级部分和大页面混淆了?对于某些格式不正确的页表只会在 TLB 无效 上出现，因此 MMU 映射是通过遍历从表中重新获取的.
I think you may have Super-sections and large pages mixed up? For certain having improperly formatted page tables will only manifest on a TLB invalidate, so that MMU mappings are re-fetched from the tables via a walk.
最后，您应该刷新D缓存并排空写缓冲区以确保与内存的一致性.您可能还希望有一个内存屏障.
Finally, you should flush the D cache and drain the write buffer to ensure consistency with memory. You may wish to have a memory barrier as well.
static inline void dcache_clean(void)
{
const int zero = 0;
asm volatile ("" ::: "memory"); /* barrier */
/* clean entire D cache -> push to external memory. */
asm volatile ("1: mrc p15, 0, r15, c7, c10, 3\n"
" bne 1b\n" ::: "cc");
/* drain the write buffer */
asm volatile ("mcr 15, 0, %0, c7, c10, 4"::"r" (zero));
}
还有一些协处理器命令可以使单个 TLB 条目无效，因为您只更改了数据故障中 vaddr/paddr 映射的一部分.
There are also co-processor commands to invalidate single TLB entries as you are only changing a portion of the vaddr/paddr mappings in the data fault.
另见:ARM MMU教程，虚拟内存结构，以及您的ARM 架构参考手册.
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