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浅析armlinux-setup_arch()->bootmem_init()函数4
文章来源:http://gliethttp.cublog.cn
建议首先参考《浅析armlinux2_4_19启动程序[head-armv.s文件]》[http://gliethttp.cublog.cn]
//----------------------------------------
//1.arch/arm/mm/Init.c->bootmem_init()
void __init bootmem_init(struct meminfo *mi)
{
struct node_info node_info[NR_NODES], *np = node_info;
unsigned int bootmap_pages, bootmap_pfn, map_pg;
int node, initrd_node;
//计算为了管理所有mem内存,需管理位图占据页数目bootmap_pages,np中存储mem对应的页帧号
bootmap_pages = find_memend_and_nodes(mi, np);
//查找存放位图管理页的物理页帧号,实际是存放到_end后的后续页中
bootmap_pfn = find_bootmap_pfn(0, mi, bootmap_pages);
//检查initrd的合法性,同时将initrd所在内存bank的node返回给initrd_node
initrd_node = check_initrd(mi);
map_pg = bootmap_pfn;//位图页帧号
np += numnodes - 1;
for (node = numnodes - 1; node >= 0; node--, np--) {
/*
* If there are no pages in this node, ignore it.
* Note that node 0 must always have some pages.
*/
if (np->end == 0) {
if (node == 0)
BUG();
continue;
}
//将map_pg开始的位图管理空间全部置0xff
init_bootmem_node(NODE_DATA(node), map_pg, np->start, np->end);
//释放虚拟地址node_bootmem_map开始的位图管理的所有页,使相应页可用[gliethttp]
free_bootmem_node_bank(node, mi);
map_pg += np->bootmap_pages;
/*
* If this is node 0, we need to reserve some areas ASAP -
* we may use bootmem on node 0 to setup the other nodes.
*/
if (node == 0)//我的at91rm9200开发板仅仅有一个node=0
//将kernel自身和位图管理页占用的页对应的页位图置1,标识相应页已被占用
reserve_node_zero(bootmap_pfn, bootmap_pages);
}
#ifdef CONFIG_BLK_DEV_INITRD//在我的at91rm9200开发板中,initrd是开启的
//并且phys_initrd_start=0x21100000
//phys_initrd_size=6000000=0x5B8D80=5.73M
//initrd_node=0;
if (phys_initrd_size && initrd_node >= 0) {
//将initrd占用的页对应的页位图置1,标识相应页已被占用
reserve_bootmem_node(NODE_DATA(initrd_node), phys_initrd_start,
phys_initrd_size);
initrd_start = __phys_to_virt(phys_initrd_start);//转成虚拟地址
initrd_end = initrd_start + phys_initrd_size;
}
#endif
if (map_pg != bootmap_pfn + bootmap_pages)//保证所有bootmap都已经被遍历
BUG();
}
//----------------------------------------
//2.arch/arm/mm/Init.c->find_memend_and_nodes()
static unsigned int __init find_memend_and_nodes(struct meminfo *mi, struct node_info *np)
{unsigned int i, bootmem_pages = 0, memend_pfn = 0;
for (i = 0; i < NR_NODES; i++) {//默认失效
np[i].start = -1U;
np[i].end = 0;
np[i].bootmap_pages = 0;
}
for (i = 0; i < mi->nr_banks; i++) {
unsigned long start, end;
int node;
if (mi->bank[i].size == 0) {
mi->bank[i].node = -1;//该bank的node无效-1
continue;
}
node = mi->bank[i].node;//at91rm9200dk中mem连续node=0
if (node >= numnodes) {
numnodes = node + 1;
if (numnodes > NR_NODES)
BUG();
}
//获取当前bank的pfns
//#define PAGE_ALIGN(addr) (((addr)+PAGE_SIZE-1)&PAGE_MASK)//页边界对齐
//define O_PFN_UP(x) (PAGE_ALIGN(x) >> PAGE_SHIFT)
start = O_PFN_UP(mi->bank[i].start);//获取该bank.start对应物理页帧号
//同理,//获取该bank.end对应物理页帧号
end = O_PFN_DOWN(mi->bank[i].start + mi->bank[i].size);
if (np[node].start > start)
np[node].start = start;//存储
if (np[node].end < end)
np[node].end = end;//存储
if (memend_pfn < end)
memend_pfn = end;
}
for (i = 0; i < numnodes; i++) {
if (np[i].end == 0)
continue;
//bootmem_bootmap_pages计算pages个页需要多少个页来存储其位图管理信息
np[i].bootmap_pages = bootmem_bootmap_pages(np[i].end - np[i].start);
bootmem_pages += np[i].bootmap_pages;//累计位图管理信息页总数
}
/*
* This doesn't seem to be used by the Linux memory
* manager any more. If we can get rid of it, we
* also get rid of some of the stuff above as well.
*/
max_low_pfn = memend_pfn - O_PFN_DOWN(PHYS_OFFSET);
// max_pfn = memend_pfn - O_PFN_DOWN(PHYS_OFFSET);
mi->end = memend_pfn << PAGE_SHIFT;//所管理的物理内存结束地址
return bootmem_pages;
}
//----------------------------------------
//3.mm/Bootmem.c->bootmem_bootmap_pages()
//计算pages个页需要多少个页来存储其位图管理信息
unsigned long __init bootmem_bootmap_pages (unsigned long pages)
{unsigned long mapsize;
mapsize = (pages+7)/8;//所需8bits个数
mapsize = (mapsize + ~PAGE_MASK) & PAGE_MASK;//mapsize个字节页对齐
mapsize >>= PAGE_SHIFT;//mapsize个字节对应页数目
return mapsize;
}
//----------------------------------------
//4.arch/arm/mm/Init.c->find_bootmap_pfn()
//查找存放位图管理页的物理页帧号-init_mm.brk
static unsigned int __init
find_bootmap_pfn(int node, struct meminfo *mi, unsigned int bootmap_pages)
{unsigned int start_pfn, bank, bootmap_pfn;
start_pfn = V_PFN_UP(&_end);//将_end虚拟内存转换为对应的物理页帧号
bootmap_pfn = 0;
for (bank = 0; bank < mi->nr_banks; bank ++) {
unsigned int start, end;
if (mi->bank[bank].node != node)
continue;
start = O_PFN_UP(mi->bank[bank].start);
end = O_PFN_DOWN(mi->bank[bank].size +
mi->bank[bank].start);
if (end < start_pfn)
continue;
if (start < start_pfn)
start = start_pfn;//_end对应init_mm.brk临界点
if (end <= start)
continue;
if (end - start >= bootmap_pages) {
bootmap_pfn = start;//从init_mm.brk开始存放位图管理页
break;
}
}
if (bootmap_pfn == 0)
BUG();
return bootmap_pfn;//ok[gliethttp]
}
//----------------------------------------
//5.arch/arm/mm/Init.c->check_initrd()
//检查initrd的合法性
static int __init check_initrd(struct meminfo *mi)
{
int initrd_node = -2;
unsigned long end = phys_initrd_start + phys_initrd_size;
#ifdef CONFIG_BLK_DEV_INITRD
/*
* Make sure that the initrd is within a valid area of
* memory.
*/
if (phys_initrd_size) {
unsigned int i;
initrd_node = -1;
for (i = 0; i < mi->nr_banks; i++) {
unsigned long bank_end;
bank_end = mi->bank[i].start + mi->bank[i].size;
if (mi->bank[i].start <= phys_initrd_start &&
end <= bank_end)
initrd_node = mi->bank[i].node;
}
}
if (initrd_node == -1) {
printk(KERN_ERR "initrd (0x%08lx - 0x%08lx) extends beyond "
"physical memory - disabling initrd\n",
phys_initrd_start, end);
phys_initrd_start = phys_initrd_size = 0;
}
#endif
return initrd_node;//将initrd所在内存bank对应的node返回
}
//----------------------------------------
//6.mm/Bootmem.c->init_bootmem_node()
unsigned long __init init_bootmem_node (pg_data_t *pgdat, unsigned long freepfn, unsigned long startpfn, unsigned long endpfn)
{
return(init_bootmem_core(pgdat, freepfn, startpfn, endpfn));
}
//mm/Bootmem.c->init_bootmem_core()
static unsigned long __init init_bootmem_core (pg_data_t *pgdat,
unsigned long mapstart, unsigned long start, unsigned long end)
{
bootmem_data_t *bdata = pgdat->bdata;//读取&node_bootmem_data[0]
unsigned long mapsize = ((end - start)+7)/8;
pgdat->node_next = pgdat_list;
pgdat_list = pgdat;
mapsize = (mapsize + (sizeof(long) - 1UL)) & ~(sizeof(long) - 1UL);//4字节对齐
bdata->node_bootmem_map = phys_to_virt(mapstart << PAGE_SHIFT);//位图页帧号转为系统用的虚拟地址
bdata->node_boot_start = (start << PAGE_SHIFT);//本map所处物理内存起始地址
bdata->node_low_pfn = end;//本map所处物理内存结束地址
//用0xff填充map位图页帧后,mapsize个字节数据
//arch/arm/lib/memset.S->memset(),对虚拟地址bdata->node_bootmem_map进行赋值
memset(bdata->node_bootmem_map, 0xff, mapsize);
return mapsize;
}
//----------------------------------------
//7.mm/Bootmem.c->free_bootmem_node_bank()
static inline void free_bootmem_node_bank(int node, struct meminfo *mi)
{
pg_data_t *pgdat = NODE_DATA(node);//读取&node_bootmem_data[0]
int bank;
for (bank = 0; bank < mi->nr_banks; bank++)
if (mi->bank[bank].node == node)
free_bootmem_node(pgdat, mi->bank[bank].start,
mi->bank[bank].size);
}
void __init free_bootmem_node (pg_data_t *pgdat, unsigned long physaddr, unsigned long size)
{
return(free_bootmem_core(pgdat->bdata, physaddr, size));
}
static void __init free_bootmem_core(bootmem_data_t *bdata, unsigned long addr, unsigned long size)
{
unsigned long i;
unsigned long start;
/*
* round down end of usable mem, partially free pages are
* considered reserved.
*/
unsigned long sidx;
unsigned long eidx = (addr + size - bdata->node_boot_start)/PAGE_SIZE;
unsigned long end = (addr + size)/PAGE_SIZE;
if (!size) BUG();
if (end > bdata->node_low_pfn)//一般相等
BUG();
start = (addr + PAGE_SIZE-1) / PAGE_SIZE;//mem起始物理地址对应的页帧号
sidx = start - (bdata->node_boot_start/PAGE_SIZE);//起始大小
for (i = sidx; i < eidx; i++) {///sidx=0,eidx=size/PAGE_SIZE[gliethttp]
//清0各位图管理位,使相应页可用
//如i=4,那么第4物理页可用,清0bdata->node_bootmem_map[0]的第4位
if (!test_and_clear_bit(i, bdata->node_bootmem_map))//node_bootmem_map位图管理起始虚拟地址
BUG();
}
}
///arch/arm/lib/testclearbit.S->test_and_clear_bit()
ENTRY(test_and_clear_bit)
add r1, r1, r0, lsr #3//获取第r0位,对应字节对应的地址
and r3, r0, #7//获取字节中偏移
mov r0, #1
//include/asm-arm/proc-armv/Assembler.h->save_and_disable_irqs[gliethttp]
//.macro save_and_disable_irqs, oldcpsr, temp
//mrs \oldcpsr, cpsr//
//mov \temp, #I_BIT | MODE_SVC
//msr cpsr_c, \temp
//.endm
save_and_disable_irqs ip, r2//将cpsr保存到ip
ldrb r2, [r1]//取出字节数据
tst r2, r0, lsl r3//先测一次,我感觉没用
bic r2, r2, r0, lsl r3//将r2的第r3位清0,成功清0后Z=0,因为硬件故障未能成功那么Z=1,返回后会halt系统
strb r2, [r1]//存储清0后的结果
restore_irqs ip//恢复cpsr
moveq r0, #0//如果因为硬件故障导致不能清0,那么r0=0;清0失败
RETINSTR(mov,pc,lr)
//----------------------------------------
//8.arch/arm/mm/Init.c->reserve_node_zero()
//将kernel自身和位图管理页占用的页对应的页位图置1,标识相应页已被占用
static __init void reserve_node_zero(unsigned int bootmap_pfn, unsigned int bootmap_pages)
{
pg_data_t *pgdat = NODE_DATA(0);//获取node0的所有物理内存管理单元pgdat
//对于_end和_stext,参考arch/arm/vmlinux-armv.lds.in链接脚本
//_end为init_mm.brk,是kernel最末端地址
//__pa(&_stext)物理地址开始的&_end - &_stext个数据,对应页位图置1标识相应页已被占用
reserve_bootmem_node(pgdat, __pa(&_stext), &_end - &_stext);
#ifdef CONFIG_CPU_32
//将arch/arm/kernel/head-armv.s中4M保留页swapper_pg_dir,我的at91rm9200板子对应的物理地址为0x20004000~0x20008000
//swapper_pg_dir~swapper_pg_dir+4k*4的页对应的页位图置1标识相应页已被占用
//#define PTRS_PER_PGD 4096
reserve_bootmem_node(pgdat, __pa(swapper_pg_dir),
PTRS_PER_PGD * sizeof(pgd_t));
#endif
//将_end即init_mm.brk之后存放node物理页位图的位图管理空间也保护起来
//bootmap_pfn << PAGE_SHIFT~(bootmap_pfn << PAGE_SHIFT)+(bootmap_pages << PAGE_SHIFT)的页对应的页位图置1标识相应页已被占用
reserve_bootmem_node(pgdat, bootmap_pfn << PAGE_SHIFT,
bootmap_pages << PAGE_SHIFT);
//以下代码在at91rm9200dk下均不被编译进vmlinuz
if (machine_is_integrator())//if(0),否则会因为reserve_bootmem_node回环,halt系统
reserve_bootmem_node(pgdat, 0, __pa(swapper_pg_dir));
if (machine_is_archimedes() || machine_is_a5k())
reserve_bootmem_node(pgdat, 0x02000000, 0x00080000);
if (machine_is_edb7211() || machine_is_fortunet())
reserve_bootmem_node(pgdat, 0xc0000000, 0x00020000);
if (machine_is_p720t())
reserve_bootmem_node(pgdat, PHYS_OFFSET, 0x00014000);
#ifdef CONFIG_SA1111//非SA1111
reserve_bootmem_node(pgdat, PHYS_OFFSET, __pa(swapper_pg_dir)-PHYS_OFFSET);
#endif
}
void __init reserve_bootmem_node (pg_data_t *pgdat, unsigned long physaddr, unsigned long size)
{//使pgdat管理的物理内存,physaddr~(physaddr+size)之间的物理内存不可使用--占用保留
//physaddr~(physaddr+size)对应页位图置1标识相应页已被占用
reserve_bootmem_core(pgdat->bdata, physaddr, size);
}
static void __init reserve_bootmem_core(bootmem_data_t *bdata, unsigned long addr, unsigned long size)
{
unsigned long i;
/*
* round up, partially reserved pages are considered
* fully reserved.
*/
//bdata->node_boot_start该bdata对应node物理内存的起始地址
unsigned long sidx = (addr - bdata->node_boot_start)/PAGE_SIZE;//计算addr所处页帧号
unsigned long eidx = (addr + size - bdata->node_boot_start +
PAGE_SIZE-1)/PAGE_SIZE;//计算addr+size对应的页帧号
unsigned long end = (addr + size + PAGE_SIZE-1)/PAGE_SIZE;
if (!size) BUG();
if (sidx < 0)
BUG();
if (eidx < 0)
BUG();
if (sidx >= eidx)//数据回环
BUG();
//bdata->node_low_pfn为本node物理内存的地址上限
if ((addr >> PAGE_SHIFT) >= bdata->node_low_pfn)
BUG();
if (end > bdata->node_low_pfn)
BUG();
//条件符合,那么实行保护措施
//将sidx页到eidx页对应的位图置1,位图置1标识相应页已被占用(保护起来,不被kernel使用)
for (i = sidx; i < eidx; i++)
if (test_and_set_bit(i, bdata->node_bootmem_map))
printk("hm, page %08lx reserved twice.\n", i*PAGE_SIZE);
}
///arch/arm/lib/testclearbit.S->test_and_set_bit()
//ENTRY(test_and_set_bit)
// add r1, r1, r0, lsr #3//获取第r0位对应的字节地址
// and r3, r0, #7//计算处于字节的第几位
// mov r0, #1
// save_and_disable_irqs ip, r2//ip=cpsr
// ldrb r2, [r1]
// tst r2, r0, lsl r3
//orr操作,成功操作后Z=0,因为硬件故障未能成功那么Z=1,返回后会halt系统
// orr r2, r2, r0, lsl r3//将r2中的第r3位置1
// strb r2, [r1]//回写
// restore_irqs ip
// moveq r0, #0
// RETINSTR(mov,pc,lr)
//include/asm-arm/proc-armv/Assembler.h->save_and_disable_irqs[gliethttp]
//.macro save_and_disable_irqs, oldcpsr, temp
//mrs \oldcpsr, cpsr//
//mov \temp, #I_BIT | MODE_SVC
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