設置Linux保留物理內存並使用（1）【转】

转自：https://www.cnblogs.com/pengdonglin137/p/5837115.html

阅读目录(Content)

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

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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

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參考博文

Linux内核---41.arm 内存初始化

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

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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。

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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.
", __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
");
27 +               return;
28 +    }
29 +
30 +    printk("reserve : reserve %dM mem
", 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  = 0x1
10 [    0.000000]  memory[0x0]    [0x00000030000000-0x00000033ffffff], 0x4000000 bytes flags: 0x0
11 [    0.000000]  reserved.cnt  = 0x3
12 [    0.000000]  reserved[0x0]    [0x00000030004000-0x00000030007fff], 0x4000 bytes flags: 0x0
13 [    0.000000]  reserved[0x1]    [0x00000030008200-0x0000003057fc03], 0x577a04 bytes flags: 0x0
14 [    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
";
 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
", __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
", __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: c2000000
3 [root@TQ2440 /]# 
4 [root@TQ2440 /]# rmmod demo
5 [ 1420.986938] reserve_demo_exit: pengdonglin137@163.com
6 [ 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。

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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.
", __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
");
27 +               return;
28 +    }
29 +
30 +    memblock_free(paddr, size);
31 +    memblock_remove(paddr, size);
32 +
33 +    printk("reserve : reserve %dM mem
", 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 = 0x57ba04
10 [    0.000000]  memory.cnt  = 0x2
11 [    0.000000]  memory[0x0]    [0x00000030000000-0x00000031ffffff], 0x2000000 bytes flags: 0x0
12 [    0.000000]  memory[0x1]    [0x00000032200000-0x00000033ffffff], 0x1e00000 bytes flags: 0x0
13 [    0.000000]  reserved.cnt  = 0x2
14 [    0.000000]  reserved[0x0]    [0x00000030004000-0x00000030007fff], 0x4000 bytes flags: 0x0
15 [    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
";
 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
", __func__, addr);
21 
22     return 0;
23 }
24 
25 static __exit void reserve_demo_exit(void)
26 {
27     printk("%s: %s
", __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: c5000000
3 [root@TQ2440 /]# 
4 [root@TQ2440 /]# rmmod demo
5 [   49.247204] reserve_demo_exit: pengdonglin137@163.com
6 [   49.247204] 
7 [root@TQ2440 /]#

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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..0x31ffcaf7
10    5: 0x31ffcb00..0x31ffcb03
11    6: 0x31ffcb20..0x31ffcb23
12    7: 0x31ffcb40..0x31ffcb43
13    8: 0x31ffcb60..0x31ffcb63
14    9: 0x31ffcb80..0x31ffcbda
15   10: 0x31ffcbe0..0x31ffcc3a
16   11: 0x31ffcc40..0x31ffcc9a
17   12: 0x31ffcca0..0x31ffccbb
18   13: 0x31ffccc0..0x31ffcdc3
19   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
";
 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
", __func__, addr);
21 
22     return 0;
23 }
24 
25 static __exit void reserve_demo_exit(void)
26 {
27     printk("%s: %s
", __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: c3000000
3 [root@TQ2440 /]# 
4 [root@TQ2440 /]# rmmod demo
5 [  271.735731] reserve_demo_exit: pengdonglin137@163.com
6 [  271.735731]

完

【作者】张昺华

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