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設置Linux保留物理內存並使用 (1)

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

Linux内核---41.arm 内存初始化

http://bbs.chinaunix.net/thread-4143403-1-1.html

 

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 <linux/platform_device.h> 7  #include <linux/io.h> 8  #include <linux/dm9000.h> 9 +#include <linux/memblock.h>10  11  #include <asm/mach/arch.h>12  #include <asm/mach/map.h>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 <ben-linux@fluff.org> */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 <linux/module.h> 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 <linux/platform_device.h> 7  #include <linux/io.h> 8  #include <linux/dm9000.h> 9 +#include <linux/memblock.h>10  11  #include <asm/mach/arch.h>12  #include <asm/mach/map.h>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 <ben-linux@fluff.org> */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 <linux/module.h> 2 #include <linux/ioport.h> 3 #include <linux/io.h> 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 <linux/module.h> 2 #include <linux/ioport.h> 3 #include <linux/io.h> 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] 

 

設置Linux保留物理內存並使用 (1)