Messages in this thread | | | Date | Mon, 18 Jun 2012 21:23:54 +0200 | From | Michal Simek <> | Subject | Re: [RFC PATCH 7/8] ARM: vmlinux.lds: Setup physical load address not virtual |
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On 06/18/2012 09:02 PM, Nicolas Pitre wrote: > On Mon, 18 Jun 2012, Michal Simek wrote: > >> 2012/6/18 Nicolas Pitre<nicolas.pitre@linaro.org> >> >>> On Mon, 18 Jun 2012, Michal Simek wrote: >>> >>>> Setup correct virtual and physical address in ELF LOAD section. >>> >>> We are moving to a single kernel binary for multiple targets, including >>> targets with different physical load addresses. The kernel code figures >>> out at run time what the actual physical address is when >>> CONFIG_ARM_PATCH_PHYS_VIRT is set which is the default these days. In >>> other words, we don't know the physical offset at build time in that >>> case and CONFIG_PHYS_OFFSET is simply not defined. >>> >> >> ok. good to know and nice features. In that case I expect that you are >> using any binary format and you copy it to memory and run it. Code >> find out where it runs and based on that setup things. > > Exact.
ok. One more question about this feature. What is the alignment for it? I mean I have done the similar feature for Xilinx ppc440 and alignment depends on MMU TLB size.
> >> (BTW: This is very interesting for me to implement it on Microblaze. Can >> you point me to that kernel code part? or any doc?) > > You could have a look at https://wiki.ubuntu.com/Specs/ARMSingleKernel, > especially the section "Optimized virt_to_phys() with a runtime > determined PHYS_OFFSET". > > Then the following commits should be of interest: > > 72a20e22f4 "ARM: P2V: eliminate head.S use of PHYS_OFFSET for !XIP_KERNEL" > > dc21af99fa "ARM: P2V: introduce phys_to_virt/virt_to_phys runtime patching"
ok. Thanks will look at it.
> >> But can you do it with elf? > > No.
ok
> >> Please correct me if I am wrong IRC ARM Qemu uses zImage but it is no >> problem to use elf file. For this case >> Qemu elf loader also uses physical addresses from ELF and also entry point. > > If you want to use the ELF image, then you need to hardcode the physical > memory location in its header, and that's something we want to get away > from because it prevents a single kernel binary image from being used on > different targets with different memory layouts. Same issue with > u-Boot's legacy uImage format.
And are you able to get these information away from ELF? Or you just need to set it up to any default value. I would expect to 0x0.
> >> I haven't played with CONFIG_ARM_PATCH_PHYS_VIRT option but what is elf >> entry point for this case? > > For the kernel image itself it is the kernel virtual address.
Is it used somewhere? Or is it just setup to virtual address and no code use it? I mean that kernel virtual entry point.
I expect that if CONFIG_ARM_PATCH_PHYS_VIRT=y then CONFIG_PHYS_OFFSET is not setup Then LOAD_OFFSET should be equal to CONFIG_PAGE_OFFSET.
> > For the relocatable zImage decompressor wrapper it is 0.
ok.
Thanks, Michal
-- Michal Simek, Ing. (M.Eng) w: www.monstr.eu p: +42-0-721842854 Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/ Microblaze U-BOOT custodian
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