設置Linux保留物理內存並使用（1）

阅读量：5973 次

发布时间：2019-06-19

本文共 11443 字，大约阅读时间需要 38 分钟。

在Linux系統中可以通過memblock來設置系統保留物理內存，防止這些內存被內存管理系統分配出去。

作者：彭東林

郵箱： pengdonglin137@163.com

平臺

硬件平臺： TQ2440

Linux版本：Linux 3.14.45

說明

1. 在tq2440上，物理內存的起始地址是0x30000000，一共有64MB的內存，所以物理內存地址範圍是: 0x30000000 -> 0x33ffffff

2. 可以在uboot傳給kernel的參數bootargs中添加一個"memblock=debug"，這樣在Linux啓動的時候，會將設置memblock的信息打印出來

參考博文

代碼調用

在Linux啓動的時候會調用machine相關的代碼定製部分系統保留內存，函數調用如下：

start_kernel

----> setup_arch

----> arm_memblock_init

----> mdesc->reserve()

所以我們可以修改machine相關的代碼，添加reserve函數的實現。

方法一

修改mach-tq2440.c如下：

1 diff --git a/arch/arm/mach-s3c24xx/mach-tq2440.c b/arch/arm/mach-s3c24xx/mach-tq2440.c 2 index f9679fb..da75db2 100644 3 --- a/arch/arm/mach-s3c24xx/mach-tq2440.c 4 +++ b/arch/arm/mach-s3c24xx/mach-tq2440.c 5 @@ -23,6 +23,7 @@ 6  #include 
     
       7  #include 
      
        8  #include 
       
         9 +#include 
        
         10  11  #include 
         
          12  #include 
          
           13 @@ -503,11 +504,28 @@ static void __init tq2440_machine_init(void)14 s3c_pm_init();15 }16 17 +static void __init tq2440_reserve(void) {18 + u32 paddr,size;19 +20 + printk("%s enter.\n", __func__);21 +22 + paddr = 0x32000000;23 + size = 0x200000;24 +25 + if (memblock_reserve(paddr, size) < 0) {26 + pr_err("failed to reserve DRAM - no memory\n");27 + return;28 + }29 +30 + printk("reserve : reserve %dM mem\n", size>>20);31 +}32 +33 MACHINE_START(TQ2440, "TQ2440")34 /* Maintainer: Ben Dooks 
           
             */35 .atag_offset = 0x100,36 37 .init_irq = s3c2440_init_irq,38 + .reserve = tq2440_reserve,39 .map_io = tq2440_map_io,40 .init_machine = tq2440_machine_init,41 .init_time = samsung_timer_init,

上面我們在0x32000000開始的地方保留了2MB的物理內存，然後調用memblock_reserve告訴系統。這個在系統的啓動信息中可以看到：

1 [    0.000000] Machine: TQ2440 2 [    0.000000] memblock_reserve: [0x00000030008200-0x0000003057fc03] flags 0x0 arm_memblock_init+0x4c/0x1bc 3 [    0.000000] memblock_reserve: [0x00000030004000-0x00000030007fff] flags 0x0 arm_memblock_init+0x158/0x1bc 4 [    0.000000] tq2440_reserve enter. 5 [    0.000000] memblock_reserve: [0x00000032000000-0x000000321fffff] flags 0x0 tq2440_reserve+0x1c/0x50 6 [    0.000000] reserve : reserve 2M mem 7 [    0.000000] MEMBLOCK configuration: 8 [    0.000000]  memory size = 0x4000000 reserved size = 0x77ba04 9 [    0.000000]  memory.cnt  = 0x110 [    0.000000]  memory[0x0]    [0x00000030000000-0x00000033ffffff], 0x4000000 bytes flags: 0x011 [    0.000000]  reserved.cnt  = 0x312 [    0.000000]  reserved[0x0]    [0x00000030004000-0x00000030007fff], 0x4000 bytes flags: 0x013 [    0.000000]  reserved[0x1]    [0x00000030008200-0x0000003057fc03], 0x577a04 bytes flags: 0x014 [    0.000000]  reserved[0x2]    [0x00000032000000-0x000000321fffff], 0x200000 bytes flags: 0x0

上面的第5行和第14行就是我們自己設置的保留內存範圍信息。在Linux啓動後，在debugfs中也可以看到memblock的信息：

[root@TQ2440 /]# cat /sys/kernel/debug/memblock/memory    0: 0x30000000..0x33ffffff[root@TQ2440 /]# cat /sys/kernel/debug/memblock/reserved    0: 0x30004000..0x30007fff   1: 0x30008200..0x3057fc03   2: 0x32000000..0x321fffff   3: 0x33f60000..0x33ffbfff   4: 0x33ffc540..0x33ffc96b   5: 0x33ffc980..0x33ffc9f7   6: 0x33ffca00..0x33ffca03   7: 0x33ffca20..0x33ffca23   8: 0x33ffca40..0x33ffca43   9: 0x33ffca60..0x33ffca63  10: 0x33ffca80..0x33ffcad2  11: 0x33ffcae0..0x33ffcb32  12: 0x33ffcb40..0x33ffcb92  13: 0x33ffcba0..0x33ffcbbb  14: 0x33ffcbc0..0x33ffcdc7  15: 0x33ffcdd0..0x33ffffff

其中memory節點中存放的是可用的物理內存地址範圍，reserved表示已經分配出去的物理地址，第2行記錄的就是我們設置的。

既然添加了保留物理內存，那麼如何使用呢？下面我寫了一個簡單的內核模塊，使用我們添加的保留物理內存，下面是內核模塊的代碼：

1 #include 
     
       2  3 #define RESERVE_PHY  0x32000000 4 #define RESERVE_SIZE 0x200000 5  6 static char str[] = "pengdonglin137@163.com\n"; 7  8 static __init int reserve_demo_init(void) 9 {10     memcpy(phys_to_virt(RESERVE_PHY), str, sizeof(str));11 12     printk("%s: virt: %p\n", __func__, phys_to_virt(RESERVE_PHY));13 14     return 0;15 }16 17 static __exit void reserve_demo_exit(void)18 {19     printk("%s: %s\n", __func__, (char *)phys_to_virt(RESERVE_PHY));20 }21 22 module_init(reserve_demo_init);23 module_exit(reserve_demo_exit);24 MODULE_LICENSE("GPL");

可以看到，我們直接調用函數phys_to_virt將物理地址轉換成虛擬地址，然後直接向這個虛擬地址中寫入數據，在模塊卸載時再將內容打印出出來。

1 [root@TQ2440 /]# insmod nfs/demo.ko 2 [ 1417.153362] reserve_demo_init: virt: c20000003 [root@TQ2440 /]# 4 [root@TQ2440 /]# rmmod demo5 [ 1420.986938] reserve_demo_exit: pengdonglin137@163.com6 [ 1420.986938]

可以看到，第2行中得到物理地址0x32000000對應的虛擬地址是0xC2000000。在模塊卸載時打印出了我們之前寫入的內容。

這種方法使用與物理內存在Normal區域的情況。

方法二

修改mach-tq2440.c

1 diff --git a/arch/arm/mach-s3c24xx/mach-tq2440.c b/arch/arm/mach-s3c24xx/mach-tq2440.c 2 index f9679fb..345a868 100644 3 --- a/arch/arm/mach-s3c24xx/mach-tq2440.c 4 +++ b/arch/arm/mach-s3c24xx/mach-tq2440.c 5 @@ -23,6 +23,7 @@ 6  #include 
     
       7  #include 
      
        8  #include 
       
         9 +#include 
        
         10  11  #include 
         
          12  #include 
          
           13 @@ -503,11 +504,31 @@ static void __init tq2440_machine_init(void)14 s3c_pm_init();15 }16 17 +static void __init tq2440_reserve(void) {18 + u32 paddr,size;19 +20 + printk("%s enter.\n", __func__);21 +22 + paddr = 0x32000000;23 + size = 0x200000;24 +25 + if (memblock_reserve(paddr, size) < 0) {26 + pr_err("failed to reserve DRAM - no memory\n");27 + return;28 + }29 +30 + memblock_free(paddr, size);31 + memblock_remove(paddr, size);32 +33 + printk("reserve : reserve %dM mem\n", size>>20);34 +}35 +36 MACHINE_START(TQ2440, "TQ2440")37 /* Maintainer: Ben Dooks 
           
             */38 .atag_offset = 0x100,39 40 .init_irq = s3c2440_init_irq,41 + .reserve = tq2440_reserve,42 .map_io = tq2440_map_io,43 .init_machine = tq2440_machine_init,44 .init_time = samsung_timer_init,

用新kernel啓動，在啓動信息中可以看到：

1 [    0.000000] Machine: TQ2440 2 [    0.000000] memblock_reserve: [0x00000030008200-0x0000003057fc03] flags 0x0 arm_memblock_init+0x4c/0x1bc 3 [    0.000000] memblock_reserve: [0x00000030004000-0x00000030007fff] flags 0x0 arm_memblock_init+0x158/0x1bc 4 [    0.000000] tq2440_reserve enter. 5 [    0.000000] memblock_reserve: [0x00000032000000-0x000000321fffff] flags 0x0 tq2440_reserve+0x1c/0x68 6 [    0.000000]    memblock_free: [0x00000032000000-0x000000321fffff] tq2440_reserve+0x3c/0x68 7 [    0.000000] reserve : reserve 2M mem 8 [    0.000000] MEMBLOCK configuration: 9 [    0.000000]  memory size = 0x3e00000 reserved size = 0x57ba0410 [    0.000000]  memory.cnt  = 0x211 [    0.000000]  memory[0x0]    [0x00000030000000-0x00000031ffffff], 0x2000000 bytes flags: 0x012 [    0.000000]  memory[0x1]    [0x00000032200000-0x00000033ffffff], 0x1e00000 bytes flags: 0x013 [    0.000000]  reserved.cnt  = 0x214 [    0.000000]  reserved[0x0]    [0x00000030004000-0x00000030007fff], 0x4000 bytes flags: 0x015 [    0.000000]  reserved[0x1]    [0x00000030008200-0x0000003057fc03], 0x577a04 bytes flags: 0x0

在kernel啓動後，在memory和reserved節點中：

[root@TQ2440 /]# cat /sys/kernel/debug/memblock/memory    0: 0x30000000..0x31ffffff   1: 0x32200000..0x33ffffff

可以看到，此時系統中有兩塊物理內存，但是這兩塊物理內存的地址之間不連續，中間有一個大小爲2MB的“洞”。此時在reserved節點看不到這部分內存。

[root@TQ2440 /]# cat /sys/kernel/debug/memblock/reserved    0: 0x30004000..0x30007fff   1: 0x30008200..0x3057fc03   2: 0x33f60000..0x33ffbfff   3: 0x33ffc520..0x33ffc94b   4: 0x33ffc960..0x33ffc9d7   5: 0x33ffc9e0..0x33ffc9e3   6: 0x33ffca00..0x33ffca03   7: 0x33ffca20..0x33ffca23   8: 0x33ffca40..0x33ffca43   9: 0x33ffca60..0x33ffcab2  10: 0x33ffcac0..0x33ffcb12  11: 0x33ffcb20..0x33ffcb72  12: 0x33ffcb80..0x33ffcb9b  13: 0x33ffcba0..0x33ffcbbb  14: 0x33ffcbc0..0x33ffcdc7  15: 0x33ffcdd0..0x33ffffff

此時在使用這部分保留內存時就不能直接使用了，需要申請，然後映射後才能使用，如下：

1 #include 
     
       2 #include 
      
        3 #include 
       
         4  5 #define RESERVE_PHY  0x32000000 6 #define RESERVE_SIZE 0x200000 7  8 static char str[] = "pengdonglin137@163.com\n"; 9 static void __iomem *addr;10 11 static __init int reserve_demo_init(void)12 {13 14     if (!request_mem_region(RESERVE_PHY, RESERVE_SIZE, "my reserve"))15         return  -EBUSY;16 17     addr = ioremap_nocache(RESERVE_PHY, RESERVE_SIZE);18     memcpy(addr, str, sizeof(str));19 20     printk("%s: virt: %p\n", __func__, addr);21 22     return 0;23 }24 25 static __exit void reserve_demo_exit(void)26 {27     printk("%s: %s\n", __func__, (char *)addr);28 29     iounmap(addr);30     release_mem_region(RESERVE_PHY, RESERVE_SIZE);31 }32 33 module_init(reserve_demo_init);34 module_exit(reserve_demo_exit);35 MODULE_LICENSE("GPL");

然後加載這個模塊，此時會向addr中寫入字符串，在卸載時再打印出來。log如下：

1 [root@TQ2440 /]# insmod nfs/demo.ko 2 [   43.853848] reserve_demo_init: virt: c50000003 [root@TQ2440 /]# 4 [root@TQ2440 /]# rmmod demo5 [   49.247204] reserve_demo_exit: pengdonglin137@163.com6 [   49.247204] 7 [root@TQ2440 /]#

方法三

在uboot可以通過在bootargs中設置mem參數，告訴kernel可用的物理內存。

修改uboot傳給kernel的bootargs，如下：

setenv bootargs "memblock=debug noinitrd root=/dev/mtdblock2 init=/linuxrc console=ttySAC0,115200n8 mem=32M"

此時啓動Linux，啓動信息中可以看到：

[    0.000000] memblock_reserve: [0x00000030008200-0x00000030589c83] flags 0x0 arm_memblock_init+0x5c/0x1d8[    0.000000] memblock_reserve: [0x00000030004000-0x00000030007fff] flags 0x0 arm_memblock_init+0x8c/0x1d8[    0.000000] MEMBLOCK configuration:[    0.000000]  memory size = 0x2000000 reserved size = 0x585a84[    0.000000]  memory.cnt  = 0x1[    0.000000]  memory[0x0]    [0x00000030000000-0x00000031ffffff], 0x2000000 bytes flags: 0x0[    0.000000]  reserved.cnt  = 0x2[    0.000000]  reserved[0x0]    [0x00000030004000-0x00000030007fff], 0x4000 bytes flags: 0x0[    0.000000]  reserved[0x1]    [0x00000030008200-0x00000030589c83], 0x581a84 bytes flags: 0x0... ...[    0.000000] Memory: 26752K/32768K available (3912K kernel code, 214K rwdata, 1176K rodata, 155K init, 176K bss, 6016K reserved)

可以看到，此時Linux只知道有32MB的物理內存，而實際上板子上有64MB的物理內存。

可以看到memory和reserved節點的內容如下：

1 [root@TQ2440 /]# cat /d/memblock/memory  2    0: 0x30000000..0x31ffffff 3 [root@TQ2440 /]#  4 [root@TQ2440 /]# cat /d/memblock/reserved  5    0: 0x30004000..0x30007fff 6    1: 0x30008200..0x30589c83 7    2: 0x31fa6000..0x31ffbfff 8    3: 0x31ffc840..0x31ffca6b 9    4: 0x31ffca80..0x31ffcaf710    5: 0x31ffcb00..0x31ffcb0311    6: 0x31ffcb20..0x31ffcb2312    7: 0x31ffcb40..0x31ffcb4313    8: 0x31ffcb60..0x31ffcb6314    9: 0x31ffcb80..0x31ffcbda15   10: 0x31ffcbe0..0x31ffcc3a16   11: 0x31ffcc40..0x31ffcc9a17   12: 0x31ffcca0..0x31ffccbb18   13: 0x31ffccc0..0x31ffcdc319   14: 0x31ffcdd0..0x31ffffff

使用剩餘的物理內存，同樣需要先申請，再映射，然後再使用：

1 #include 
     
       2 #include 
      
        3 #include 
       
         4  5 #define RESERVE_PHY  0x32000000 6 #define RESERVE_SIZE 0x200000 7  8 static char str[] = "pengdonglin137@163.com\n"; 9 static void __iomem *addr;10 11 static __init int reserve_demo_init(void)12 {13 14     if (!request_mem_region(RESERVE_PHY, RESERVE_SIZE, "my reserve"))15         return  -EBUSY;16 17     addr = ioremap_nocache(RESERVE_PHY, RESERVE_SIZE);18     memcpy(addr, str, sizeof(str));19 20     printk("%s: virt: %p\n", __func__, addr);21 22     return 0;23 }24 25 static __exit void reserve_demo_exit(void)26 {27     printk("%s: %s\n", __func__, (char *)addr);28 29     iounmap(addr);30     release_mem_region(RESERVE_PHY, RESERVE_SIZE);31 }32 33 module_init(reserve_demo_init);34 module_exit(reserve_demo_exit);35 MODULE_LICENSE("GPL");

加載模塊，然後卸載，可以看到log：

1 root@TQ2440 /]# insmod /nfs/demo.ko 2 [  266.998897] reserve_demo_init: virt: c30000003 [root@TQ2440 /]# 4 [root@TQ2440 /]# rmmod demo5 [  271.735731] reserve_demo_exit: pengdonglin137@163.com6 [  271.735731]

完

转载地址：http://zqbox.baihongyu.com/

你可能感兴趣的文章

手动配置 ESXi 主机挂载 NFS 的最大值

一步一步学习SignalR进行实时通信_7_非代理