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SubjectRe: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel compilation error
On Thu, Oct 22, 2020 at 01:57:37AM +0300, Dmitry Osipenko wrote:
> The vfp_kmode_exception() function now is unreachable using relative
> branching in THUMB2 kernel configuration, resulting in a "relocation
> truncated to fit: R_ARM_THM_JUMP19 against symbol `vfp_kmode_exception'"
> linker error. Let's use long jump in order to fix the issue.

Eek. Is this with gcc or clang?

>
> Fixes: eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input sections")

Are you sure it wasn't 512dd2eebe55 ("arm/build: Add missing sections") ?
That commit may have implicitly moved the location of .vfp11_veneer,
though I thought I had chosen the correct position.

> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> arch/arm/vfp/vfphw.S | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
> index 4fcff9f59947..6e2b29f0c48d 100644
> --- a/arch/arm/vfp/vfphw.S
> +++ b/arch/arm/vfp/vfphw.S
> @@ -82,7 +82,8 @@ ENTRY(vfp_support_entry)
> ldr r3, [sp, #S_PSR] @ Neither lazy restore nor FP exceptions
> and r3, r3, #MODE_MASK @ are supported in kernel mode
> teq r3, #USR_MODE
> - bne vfp_kmode_exception @ Returns through lr
> + ldr r1, =vfp_kmode_exception
> + bxne r1 @ Returns through lr
>
> VFPFMRX r1, FPEXC @ Is the VFP enabled?
> DBGSTR1 "fpexc %08x", r1

This seems like a workaround though? I suspect the vfp11_veneer needs
moving?

--
Kees Cook

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