RE: [ARMv8] kernel entry point

RE: [ARMv8] kernel entry point

[Pankaj Bansal]

+ Ard,
Hi Ard,

Can you please check below mail? We are not able to boot linux loading Image at 16MB offset (0x81000000) from DDR start address (0x80000000)
I have tested with both u-boot as well as atf.

This issue is occurring with latest kernel (5.1) Image.
If I revert kernel code to commit a7f8de168ace ("arm64: allow kernel Image to be loaded anywhere in physical memory "), then this issue doesn't occur.

Do you know why the support of "loading kernel Image anywhere in memory" has been removed in latest kernel ?

Regards,
Pankaj Bansal

> -----Original Message-----
> From: Pankaj Bansal
> Sent: Tuesday, 7 May, 2019 04:03 PM
> To: 'Catalin Marinas' <catalin.marinas@arm.com>; 'Will Deacon'
> <will.deacon@arm.com>
> Cc: 'linux-arm-kernel@lists.infradead.org' <linux-arm-
> kernel@lists.infradead.org>; Varun Sethi <V.Sethi@nxp.com>
> Subject: [ARMv8] kernel entry point
> 
> Hi Catalin/Will et. Al,
> 
> I am s/w engineer from NXP India Pvt. Ltd.
> I am facing an issue while booting linux on our ARMv8 based platform.
> In our platform DDR address starts from 0x80000000.
> If I load kernel image @ address 0x80080000 and then try to boot linux image
> from this address, then linux is booting fine.
> BUT if I load kernel image @ address 0x81000000 and then try to boot linux
> image from this address, then linux is not booting.
> I have tried to boot linux using u-boot as well as arm trusted firmware.
> Linux is not booting with either of these if the linux load address is 0x81000000.
> 
> I get no kernel logs like "[    0.000000] Booting Linux on physical CPU 0x0"
> 
> The linux version that I am using is 4.14.53 Can you please help me in debugging
> this issue?
> 
> Regards,
> Pankaj Bansal

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Re: [ARMv8] kernel entry point

[Mark Rutland]

Hi Pankaj,

On Fri, May 10, 2019 at 01:24:55PM +0000, Pankaj Bansal wrote:
> + Ard,
> Hi Ard,
> 
> Can you please check below mail? We are not able to boot linux loading
> Image at 16MB offset (0x81000000) from DDR start address (0x80000000)
> I have tested with both u-boot as well as atf.
> 
> This issue is occurring with latest kernel (5.1) Image.  If I revert
> kernel code to commit a7f8de168ace ("arm64: allow kernel Image to be
> loaded anywhere in physical memory "), then this issue doesn't occur.

That commit allows the 2MiB base to be arbitrary, but the text_offset
must still be taken into account. That's all documented in:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm64/booting.txt?h=v5.1#n125

.. where we say:

| The Image must be placed text_offset bytes from a 2MB aligned base
| address anywhere in usable system RAM and called there. The region
| between the 2 MB aligned base address and the start of the image has no
| special significance to the kernel, and may be used for other purposes.
| At least image_size bytes from the start of the image must be free for
| use by the kernel.

... and where text_offset is defined in the Image header:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm64/booting.txt?h=v5.1#n73

On a contemporary defconfig kernel, text_offset is 0x80000, so
0x81000000 is not a valid address to load the kernel at.

I suspect that things will work if you load your kernel at 0x81080000.

I would strongly recommend you use a bootloader that parses the kernel
Image header, and respects text_offset automatically.

Thanks,
Mark.

> 
> Do you know why the support of "loading kernel Image anywhere in
> memory" has been removed in latest kernel ?
> 
> Regards,
> Pankaj Bansal
> 
> > -----Original Message-----
> > From: Pankaj Bansal
> > Sent: Tuesday, 7 May, 2019 04:03 PM
> > To: 'Catalin Marinas' <catalin.marinas@arm.com>; 'Will Deacon'
> > <will.deacon@arm.com>
> > Cc: 'linux-arm-kernel@lists.infradead.org' <linux-arm-
> > kernel@lists.infradead.org>; Varun Sethi <V.Sethi@nxp.com>
> > Subject: [ARMv8] kernel entry point
> > 
> > Hi Catalin/Will et. Al,
> > 
> > I am s/w engineer from NXP India Pvt. Ltd.
> > I am facing an issue while booting linux on our ARMv8 based platform.
> > In our platform DDR address starts from 0x80000000.
> > If I load kernel image @ address 0x80080000 and then try to boot linux image
> > from this address, then linux is booting fine.
> > BUT if I load kernel image @ address 0x81000000 and then try to boot linux
> > image from this address, then linux is not booting.
> > I have tried to boot linux using u-boot as well as arm trusted firmware.
> > Linux is not booting with either of these if the linux load address is 0x81000000.
> > 
> > I get no kernel logs like "[    0.000000] Booting Linux on physical CPU 0x0"
> > 
> > The linux version that I am using is 4.14.53 Can you please help me in debugging
> > this issue?
> > 
> > Regards,
> > Pankaj Bansal
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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RE: [ARMv8] kernel entry point

[Pankaj Bansal]

Hi Mark,

> -----Original Message-----
> From: Mark Rutland <mark.rutland@arm.com>
> Sent: Friday, 10 May, 2019 07:11 PM
> To: Pankaj Bansal <pankaj.bansal@nxp.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>; Will Deacon
> <will.deacon@arm.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>; Wasim
> Khan <wasim.khan@nxp.com>; Varun Sethi <V.Sethi@nxp.com>; linux-arm-
> kernel@lists.infradead.org
> Subject: Re: [ARMv8] kernel entry point
> 
> Hi Pankaj,
> 
> On Fri, May 10, 2019 at 01:24:55PM +0000, Pankaj Bansal wrote:
> > + Ard,
> > Hi Ard,
> >
> > Can you please check below mail? We are not able to boot linux loading
> > Image at 16MB offset (0x81000000) from DDR start address (0x80000000)
> > I have tested with both u-boot as well as atf.
> >
> > This issue is occurring with latest kernel (5.1) Image.  If I revert
> > kernel code to commit a7f8de168ace ("arm64: allow kernel Image to be
> > loaded anywhere in physical memory "), then this issue doesn't occur.
> 
> That commit allows the 2MiB base to be arbitrary, but the text_offset must still
> be taken into account. That's all documented in:
> 
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel
> .org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Ftree%
> 2FDocumentation%2Farm64%2Fbooting.txt%3Fh%3Dv5.1%23n125&amp;data=
> 02%7C01%7Cpankaj.bansal%40nxp.com%7C045f77d8202040db896108d6d54d1
> 5f2%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636930924443311
> 148&amp;sdata=nOHlA67bfSc21hS0kTnHGJ%2BqxSa2KvAGnRPq7%2FEQgmg%3
> D&amp;reserved=0
> 
> .. where we say:
> 
> | The Image must be placed text_offset bytes from a 2MB aligned base
> | address anywhere in usable system RAM and called there. The region
> | between the 2 MB aligned base address and the start of the image has
> | no special significance to the kernel, and may be used for other purposes.
> | At least image_size bytes from the start of the image must be free for
> | use by the kernel.
> 
> ... and where text_offset is defined in the Image header:
> 
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel
> .org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Ftree%
> 2FDocumentation%2Farm64%2Fbooting.txt%3Fh%3Dv5.1%23n73&amp;data=0
> 2%7C01%7Cpankaj.bansal%40nxp.com%7C045f77d8202040db896108d6d54d15
> f2%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6369309244433111
> 48&amp;sdata=Zw2JQ176V6cFXz%2BFcS1uJuYkCZUISjHI%2Bb3HNnkf30k%3D&a
> mp;reserved=0
> 
> On a contemporary defconfig kernel, text_offset is 0x80000, so
> 0x81000000 is not a valid address to load the kernel at.
> 
> I suspect that things will work if you load your kernel at 0x81080000.

Thank you for this tip. It worked.

> 
> I would strongly recommend you use a bootloader that parses the kernel Image
> header, and respects text_offset automatically.

I am using u-boot. I don't know if uboot takes into account text_offset in kernel Image header.
I don't think it's there, otherwise uboot would have given an error to respect the load address requirements.
I will ask uboot maintainer if such checks (load address = 2MB aligned + text_offset) can be added in uboot.
Thanks again for your help.

> 
> Thanks,
> Mark.
> 
> >
> > Do you know why the support of "loading kernel Image anywhere in
> > memory" has been removed in latest kernel ?
> >
> > Regards,
> > Pankaj Bansal
> >
> > > -----Original Message-----
> > > From: Pankaj Bansal
> > > Sent: Tuesday, 7 May, 2019 04:03 PM
> > > To: 'Catalin Marinas' <catalin.marinas@arm.com>; 'Will Deacon'
> > > <will.deacon@arm.com>
> > > Cc: 'linux-arm-kernel@lists.infradead.org' <linux-arm-
> > > kernel@lists.infradead.org>; Varun Sethi <V.Sethi@nxp.com>
> > > Subject: [ARMv8] kernel entry point
> > >
> > > Hi Catalin/Will et. Al,
> > >
> > > I am s/w engineer from NXP India Pvt. Ltd.
> > > I am facing an issue while booting linux on our ARMv8 based platform.
> > > In our platform DDR address starts from 0x80000000.
> > > If I load kernel image @ address 0x80080000 and then try to boot
> > > linux image from this address, then linux is booting fine.
> > > BUT if I load kernel image @ address 0x81000000 and then try to boot
> > > linux image from this address, then linux is not booting.
> > > I have tried to boot linux using u-boot as well as arm trusted firmware.
> > > Linux is not booting with either of these if the linux load address is
> 0x81000000.
> > >
> > > I get no kernel logs like "[    0.000000] Booting Linux on physical CPU 0x0"
> > >
> > > The linux version that I am using is 4.14.53 Can you please help me
> > > in debugging this issue?
> > >
> > > Regards,
> > > Pankaj Bansal
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists
> > .infradead.org%2Fmailman%2Flistinfo%2Flinux-arm-
> kernel&amp;data=02%7C0
> >
> 1%7Cpankaj.bansal%40nxp.com%7C045f77d8202040db896108d6d54d15f2%7C
> 686ea
> >
> 1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636930924443311148&amp;sda
> ta=Ykm
> > rBwDOYYLdrOtWFDeBxY2on3xwBP%2F8O1seKm9aiio%3D&amp;reserved=0

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Re: [ARMv8] kernel entry point

[Mark Rutland]

On Fri, May 10, 2019 at 02:36:37PM +0000, Pankaj Bansal wrote:
> Hi Mark,
> 
> > -----Original Message-----
> > From: Mark Rutland <mark.rutland@arm.com>
> > Sent: Friday, 10 May, 2019 07:11 PM
> > To: Pankaj Bansal <pankaj.bansal@nxp.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>; Will Deacon
> > <will.deacon@arm.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>; Wasim
> > Khan <wasim.khan@nxp.com>; Varun Sethi <V.Sethi@nxp.com>; linux-arm-
> > kernel@lists.infradead.org
> > Subject: Re: [ARMv8] kernel entry point

> > I would strongly recommend you use a bootloader that parses the
> > kernel Image header, and respects text_offset automatically.
> 
> I am using u-boot. I don't know if uboot takes into account
> text_offset in kernel Image header.  I don't think it's there,
> otherwise uboot would have given an error to respect the load address
> requirements.

I believe that u-boot's "booti" (boot Image) command respects
text_offset.

Thanks,
Mark.

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