ReserveLinuxMemory

Reserve memory in linux at boot time and then map it to user level program.

Dependencies

Linux Kernel 4.0+
CONFIG_STRICT_DEVMEM=n (if on x86: CONFIG_x86_PAT=n)

Getting Started

Reserve memory at boot time in the kernel. Pass mem=2G memmap=30M$2G. mem= sets the kernel to run only within 2G and memmap= requests the kernel to reserve 30M starting at 2G
Check if memory has been reserved after kernel boots up using cat /proc/iomem. This shows you the physical map and you shoud see a "reserved" section.
Set the parameters for the driver in simple.c to match the boot parameters. The parameters of interest are in simple.c to match the memmap and mem.
```
#define RAW_DATA_SIZE 31457280
#define RAW_DATA_OFFSET 0x80000000UL
```

Build

In makefile modify the following lines to set the kernel source to build against and where the module file should be copied.

export KERNEL_SOURCE := /Kernel/linux-4.4.0/
PUBLIC_DRIVER_PWD=/modules

$ make.

If thing went well you will find a .ko file under PUBLIC_DRIVER_PWD/
To install module

$ sudo insmod simple.ko

Check if module is installed. dmesg should return a line with "RawdataStart..".

$ dmesg | tail -1

User level program and mmap.

The driver has been mapped to /sys/kernel/debug/mmap_example. When mmaping the RAW_DATA_SIZE has to match the parameter set at boot time.

#define RAW_DATA_SIZE 31457280
open("/sys/kernel/debug/mmap_example", O_RDWR);
 address = (unsigned char*) mmap(NULL, RAW_DATA_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE, configfd, 0);

Thanks

The code here was derived from this example on stackoverflow. http://stackoverflow.com/questions/37919223/map-reserver-memory-at-boot-to-user-space-using-remap-pfn-range

singhchn/ReserveLinuxMemory

ReserveLinuxMemory

Dependencies

Getting Started

Build

User level program and mmap.

Thanks