How do we Load Linux Image to appropiate location in Memory
bootloader, bootstrapping, linux, linux-kernel
Solution
`from file position 0x1000` means what it says. You have it in the dump:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
...
[ 1] .text PROGBITS c5000000 001000 5ac13e 00 AX 0 0 4096
It's where the `.text` section starts in the file, at offset `0x1000`.
But one thing we can see here .text section is greater than DRAM end address
Nope, it's not greater (not in the sense of bigger, at least), it's compiled in the expectation that it'll be loaded at address `0xc5000000` in the memory.
so image should not be loded properly though we are not getting any error after loading first section it keeps on loading other sections
The image can be loaded anywhere, it's just data for the purpose of loading.
OTOH, if `loading section to address 0xc5000000` means what it says, the file gets loaded into nowhere since your RAM ends at `0x7fffffff`.
but after this message it hangs.
And that's expected. Machine code is rarely position-independent and so if you load it at a location different from where it's supposed to be loaded, it'll not work. Or if it doesn't even get loaded, then what are you going to execute? Garbage.
Is there any way to set these section addresses before compilation??
Depending on the system you may have one of the two below options or both:
- set up page translation in such a way that virtual addresses from `0xc5000000` and up map to physical addresses from `0x5000000` and up for the entire program
- find the linker script that your compiler is using and change the initial section address from `0xc5000000` to `0x5000000`, google this up, see compiler/linker documentation
Also, it's a bit odd that the entry point is at `0x5000000`. Not that this is necessarily wrong, it's just that it's rarely the case. I'd make sure that the `start` label (or `_start` or whatever it is) indeed receives the same address as the beginning of the `.text` section. If, for some reason, it's not the case, there's something wrong either with the linker script or the compiler/linker command-line options or with the loader.
Problem
We are trying to load a linux image into our DRAM at a specific location ,DRAM end address is 0x80000000 which we come to know from boot log which says "mem device ending address is 0x80000000".We are loading our image at address "0x5000000" and before that variuos section in image getting loaded at some address which is greater than "0x80000000",for eaxmple again from boot logs ``` loading section to address 0xc5000000 from file position 0x1000, size is 0x5ac13e ``` Whats meaning of "from file position 0x1000" in above line. first section that loaded is .text section ,below is our vmlinux image dump of section header ``` [Nr] Name Type Addr Off Size ES Flg Lk Inf Al [ 0] NULL 00000000 000000 000000 00 0 0 0 [ 1] .text PROGBITS c5000000 001000 5ac13e 00 AX 0 0 4096 [ 2] .notes NOTE c55ac140 5ad140 000168 00 AX 0 0 4 [ 3] __ex_table PROGBITS c55ac2b0 5ad2b0 000fe0 00 A 0 0 4 [ 4] .rodata PROGBITS c55ae000 5af000 20a930 00 A 0 0 64 [ 5] __bug_table PROGBITS c57b8930 7b9930 0075fc 00 A 0 0 1 [ 6] .pci_fixup PROGBITS c57bff2c 7c0f2c 001a90 00 A 0 0 4 [ 7] .builtin_fw PROGBITS c57c19bc 7c29bc 0000cc 00 A 0 0 4 ``` Its quite a big list, so didn't post full .But one thing we can see here .text section is greater than DRAM end address ,so image should not be loded properly though we are not getting any error after loading first section it keeps on loading other sections but after this message it hangs. ``` program load complete, entry point: 0x5000000, size: 0x92e7fc ``` My question is how can I align these different sections address to our DRAM address, Is objcopy utility could be used here to change address of these Different sections. Is there any way to set these section addresses before compilation?? Second thing what could be reason for this Hang afer program load complete.