設置Linux保留物理內存並使用（1）

2022-12-18 14:35:21

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：

 diff --git a/arch/arm/mach-s3c24xx/mach-tq2440.c b/arch/arm/mach-s3c24xx/mach-tq2440.c

 index f9679fb..da75db2

 --- a/arch/arm/mach-s3c24xx/mach-tq2440.c

 +++ b/arch/arm/mach-s3c24xx/mach-tq2440.c

 @@ -, +, @@

  #include <linux/platform_device.h>

  #include <linux/io.h>

  #include <linux/dm9000.h>

 +#include <linux/memblock.h>

  #include <asm/mach/arch.h>

  #include <asm/mach/map.h>

 @@ -, +, @@ static void __init tq2440_machine_init(void)

         s3c_pm_init();

  }

 +static void __init tq2440_reserve(void) {

 +    u32 paddr,size;

 +

 +    printk("%s enter.\n", __func__);

 +

 +    paddr = 0x32000000;

 +    size = 0x200000;

 +

 +    if (memblock_reserve(paddr, size) < ) {

 +        pr_err("failed to reserve DRAM - no memory\n");

 +               return;

 +    }

 +

 +    printk("reserve : reserve %dM mem\n", size>>);

 +}

 +

  MACHINE_START(TQ2440, "TQ2440")

         /* Maintainer: Ben Dooks <ben-linux@fluff.org> */

         .atag_offset    = 0x100,

         .init_irq       = s3c2440_init_irq,

 +    .reserve    = tq2440_reserve,

         .map_io         = tq2440_map_io,

         .init_machine   = tq2440_machine_init,

         .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：

 [    0.000000] Machine: TQ2440

 [    0.000000] memblock_reserve: [0x00000030008200-0x0000003057fc03] flags 0x0 arm_memblock_init+0x4c/0x1bc

 [    0.000000] memblock_reserve: [0x00000030004000-0x00000030007fff] flags 0x0 arm_memblock_init+0x158/0x1bc

 [    0.000000] tq2440_reserve enter.

 [    0.000000] memblock_reserve: [0x00000032000000-0x000000321fffff] flags 0x0 tq2440_reserve+0x1c/0x50

 [    0.000000] reserve : reserve 2M mem

 [    0.000000] MEMBLOCK configuration:

 [    0.000000]  memory size = 0x4000000 reserved size = 0x77ba04

 [    0.000000]  memory.cnt  = 0x1

 [    0.000000]  memory[0x0]    [0x00000030000000-0x00000033ffffff], 0x4000000 bytes flags: 0x0

 [    0.000000]  reserved.cnt  = 0x3

 [    0.000000]  reserved[0x0]    [0x00000030004000-0x00000030007fff], 0x4000 bytes flags: 0x0

 [    0.000000]  reserved[0x1]    [0x00000030008200-0x0000003057fc03], 0x577a04 bytes flags: 0x0

 [    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

   : 0x30000000..0x33ffffff

[root@TQ2440 /]# cat /sys/kernel/debug/memblock/reserved

   : 0x30004000..0x30007fff

   : 0x30008200..0x3057fc03

   : 0x32000000..0x321fffff

   : 0x33f60000..0x33ffbfff

   : 0x33ffc540..0x33ffc96b

   : 0x33ffc980..0x33ffc9f7

   : 0x33ffca00..0x33ffca03

   : 0x33ffca20..0x33ffca23

   : 0x33ffca40..0x33ffca43

   : 0x33ffca60..0x33ffca63

  : 0x33ffca80..0x33ffcad2

  : 0x33ffcae0..0x33ffcb32

  : 0x33ffcb40..0x33ffcb92

  : 0x33ffcba0..0x33ffcbbb

  : 0x33ffcbc0..0x33ffcdc7

  : 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：

 #include <linux/module.h>

 #define RESERVE_PHY  0x32000000

 #define RESERVE_SIZE 0x200000

 static char str[] = "pengdonglin137@163.com\n";

 static __init int reserve_demo_init(void)

 {

     memcpy(phys_to_virt(RESERVE_PHY), str, sizeof(str));

     printk("%s: virt: %p\n", __func__, phys_to_virt(RESERVE_PHY));

     return ;

 }

 static __exit void reserve_demo_exit(void)

 {

     printk("%s: %s\n", __func__, (char *)phys_to_virt(RESERVE_PHY));

 }

 module_init(reserve_demo_init);

 module_exit(reserve_demo_exit);

 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。

 [root@TQ2440 /]# insmod nfs/demo.ko

 [ 1417.153362] reserve_demo_init: virt: c2000000

 [root@TQ2440 /]#

 [root@TQ2440 /]# rmmod demo

 [ 1420.986938] reserve_demo_exit: pengdonglin137@.com

 [ 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

 diff --git a/arch/arm/mach-s3c24xx/mach-tq2440.c b/arch/arm/mach-s3c24xx/mach-tq2440.c

 index f9679fb..345a868

 --- a/arch/arm/mach-s3c24xx/mach-tq2440.c

 +++ b/arch/arm/mach-s3c24xx/mach-tq2440.c

 @@ -, +, @@

  #include <linux/platform_device.h>

  #include <linux/io.h>

  #include <linux/dm9000.h>

 +#include <linux/memblock.h>

  #include <asm/mach/arch.h>

  #include <asm/mach/map.h>

 @@ -, +, @@ static void __init tq2440_machine_init(void)

         s3c_pm_init();

  }

 +static void __init tq2440_reserve(void) {

 +    u32 paddr,size;

 +

 +    printk("%s enter.\n", __func__);

 +

 +    paddr = 0x32000000;

 +    size = 0x200000;

 +

 +    if (memblock_reserve(paddr, size) < ) {

 +        pr_err("failed to reserve DRAM - no memory\n");

 +               return;

 +    }

 +

 +    memblock_free(paddr, size);

 +    memblock_remove(paddr, size);

 +

 +    printk("reserve : reserve %dM mem\n", size>>);

 +}

 +

  MACHINE_START(TQ2440, "TQ2440")

         /* Maintainer: Ben Dooks <ben-linux@fluff.org> */

         .atag_offset    = 0x100,

         .init_irq       = s3c2440_init_irq,

 +    .reserve    = tq2440_reserve,

         .map_io         = tq2440_map_io,

         .init_machine   = tq2440_machine_init,

         .init_time      = samsung_timer_init,

用新kernel啓動，在啓動信息中可以看到：

 [    0.000000] Machine: TQ2440

 [    0.000000] memblock_reserve: [0x00000030008200-0x0000003057fc03] flags 0x0 arm_memblock_init+0x4c/0x1bc

 [    0.000000] memblock_reserve: [0x00000030004000-0x00000030007fff] flags 0x0 arm_memblock_init+0x158/0x1bc

 [    0.000000] tq2440_reserve enter.

 [    0.000000] memblock_reserve: [0x00000032000000-0x000000321fffff] flags 0x0 tq2440_reserve+0x1c/0x68

 [    0.000000]    memblock_free: [0x00000032000000-0x000000321fffff] tq2440_reserve+0x3c/0x68

 [    0.000000] reserve : reserve 2M mem

 [    0.000000] MEMBLOCK configuration:

 [    0.000000]  memory size = 0x3e00000 reserved size = 0x57ba04

 [    0.000000]  memory.cnt  = 0x2

 [    0.000000]  memory[0x0]    [0x00000030000000-0x00000031ffffff], 0x2000000 bytes flags: 0x0

 [    0.000000]  memory[0x1]    [0x00000032200000-0x00000033ffffff], 0x1e00000 bytes flags: 0x0

 [    0.000000]  reserved.cnt  = 0x2

 [    0.000000]  reserved[0x0]    [0x00000030004000-0x00000030007fff], 0x4000 bytes flags: 0x0

 [    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

   : 0x30000000..0x31ffffff

   : 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

   : 0x30004000..0x30007fff

   : 0x30008200..0x3057fc03

   : 0x33f60000..0x33ffbfff

   : 0x33ffc520..0x33ffc94b

   : 0x33ffc960..0x33ffc9d7

   : 0x33ffc9e0..0x33ffc9e3

   : 0x33ffca00..0x33ffca03

   : 0x33ffca20..0x33ffca23

   : 0x33ffca40..0x33ffca43

   : 0x33ffca60..0x33ffcab2

  : 0x33ffcac0..0x33ffcb12

  : 0x33ffcb20..0x33ffcb72

  : 0x33ffcb80..0x33ffcb9b

  : 0x33ffcba0..0x33ffcbbb

  : 0x33ffcbc0..0x33ffcdc7

  : 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：

 #include <linux/module.h>

 #include <linux/ioport.h>

 #include <linux/io.h>

 #define RESERVE_PHY  0x32000000

 #define RESERVE_SIZE 0x200000

 static char str[] = "pengdonglin137@163.com\n";

 static void __iomem *addr;

 static __init int reserve_demo_init(void)

 {

     if (!request_mem_region(RESERVE_PHY, RESERVE_SIZE, "my reserve"))

         return  -EBUSY;

     addr = ioremap_nocache(RESERVE_PHY, RESERVE_SIZE);

     memcpy(addr, str, sizeof(str));

     printk("%s: virt: %p\n", __func__, addr);

     return ;

 }

 static __exit void reserve_demo_exit(void)

 {

     printk("%s: %s\n", __func__, (char *)addr);

     iounmap(addr);

     release_mem_region(RESERVE_PHY, RESERVE_SIZE);

 }

 module_init(reserve_demo_init);

 module_exit(reserve_demo_exit);

 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：

 [root@TQ2440 /]# insmod nfs/demo.ko

 [   43.853848] reserve_demo_init: virt: c5000000

 [root@TQ2440 /]#

 [root@TQ2440 /]# rmmod demo

 [   49.247204] reserve_demo_exit: pengdonglin137@.com

 [   49.247204]

 [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：

 [root@TQ2440 /]# cat /d/memblock/memory

    : 0x30000000..0x31ffffff

 [root@TQ2440 /]#

 [root@TQ2440 /]# cat /d/memblock/reserved

    : 0x30004000..0x30007fff

    : 0x30008200..0x30589c83

    : 0x31fa6000..0x31ffbfff

    : 0x31ffc840..0x31ffca6b

    : 0x31ffca80..0x31ffcaf7

    : 0x31ffcb00..0x31ffcb03

    : 0x31ffcb20..0x31ffcb23

    : 0x31ffcb40..0x31ffcb43

    : 0x31ffcb60..0x31ffcb63

    : 0x31ffcb80..0x31ffcbda

   : 0x31ffcbe0..0x31ffcc3a

   : 0x31ffcc40..0x31ffcc9a

   : 0x31ffcca0..0x31ffccbb

   : 0x31ffccc0..0x31ffcdc3

   : 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：

 #include <linux/module.h>

 #include <linux/ioport.h>

 #include <linux/io.h>

 #define RESERVE_PHY  0x32000000

 #define RESERVE_SIZE 0x200000

 static char str[] = "pengdonglin137@163.com\n";

 static void __iomem *addr;

 static __init int reserve_demo_init(void)

 {

     if (!request_mem_region(RESERVE_PHY, RESERVE_SIZE, "my reserve"))

         return  -EBUSY;

     addr = ioremap_nocache(RESERVE_PHY, RESERVE_SIZE);

     memcpy(addr, str, sizeof(str));

     printk("%s: virt: %p\n", __func__, addr);

     return ;

 }

 static __exit void reserve_demo_exit(void)

 {

     printk("%s: %s\n", __func__, (char *)addr);

     iounmap(addr);

     release_mem_region(RESERVE_PHY, RESERVE_SIZE);

 }

 module_init(reserve_demo_init);

 module_exit(reserve_demo_exit);

 MODULE_LICENSE("GPL");

加載模塊，然後卸載，可以看到log：

 root@TQ2440 /]# insmod /nfs/demo.ko

 [  266.998897] reserve_demo_init: virt: c3000000

 [root@TQ2440 /]#

 [root@TQ2440 /]# rmmod demo

 [  271.735731] reserve_demo_exit: pengdonglin137@.com

 [  271.735731]

完

码农公寓

平臺

參考博文

代碼調用

方法一

方法二

方法三

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