linux-kernel - Re: [PATCH] arm64: head: set TEXT

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Message-ID: <aOPLv_-f5sNGtG4e@willie-the-truck>
Date: Mon, 6 Oct 2025 15:01:35 +0100
From: Will Deacon <will@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	David Heidelberg <david@...t.cz>,
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, ardb@...nel.org,
	mark.rutland@....com
Subject: Re: [PATCH] arm64: head: set TEXT_OFFSET to the historical value

[+Ard and Mark]

On Mon, Oct 06, 2025 at 01:21:04AM +0300, Dmitry Baryshkov wrote:
> From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> 
> Historically arm64 kernel contained (almost fixed) value of 0x8000 at

0x8000 or 0x80000?

> the TEXT_OFFSET. The commit cfa7ede20f13 ("arm64: set TEXT_OFFSET to 0x0
> in preparation for removing it entirely") and then commit 120dc60d0bdb
> ("arm64: get rid of TEXT_OFFSET") replaced this field with 0.

Given that we made the initial change over five years ago, I'm struggling
to see why we should start caring about old broken bootloaders _now_.

In fact, I'm far more concerned about changing this to a non-zero value
and having more recent bootloaders misbehave.

> This caused no problems so far, because nobody seemed to be playing with
> the extremely picky Qualcomm bootloader as used on some of Google Pixel
> phones. Current attempting to boot the Linux kernel on those devices
> will fail to load on those phones with the following message:
> 
> KernelDecompress failed: Invalid Parameter Kernel TextOffset does not match
> Error calling BootPrepareAsync Invalid Parameter
> 
> Since the kernel ignores the field, set it to the expected value of
> 0x8000, unbreaking boot of upstream kernels on Qualcomm devices.

(same typo)

> Note: I purposedly didn't add Fixes tags, since those commits didn't
> break any of devices that were supported at that time.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> ---
>  arch/arm64/kernel/head.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index ca04b338cb0d173f6d9f5bcee52f6d3d06552599..05e874977de376835625f52bfdda78305dca28b5 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -60,7 +60,7 @@
>  	 */
>  	efi_signature_nop			// special NOP to identity as PE/COFF executable
>  	b	primary_entry			// branch to kernel start, magic
> -	.quad	0				// Image load offset from start of RAM, little-endian
> +	.quad	0x80000				// Image load offset from start of RAM, little-endian
>  	le64sym	_kernel_size_le			// Effective size of kernel image, little-endian
>  	le64sym	_kernel_flags_le		// Informative flags, little-endian
>  	.quad	0				// reserved

Could you wrap the kernel Image in your own header to workaround the
issue?

Will