On Thu, Oct 22, 2020 at 07:34:38PM +0300, Dmitry Osipenko wrote: > 22.10.2020 19:23, Russell King - ARM Linux admin пишет: > > On Thu, Oct 22, 2020 at 06:20:40PM +0200, Ard Biesheuvel wrote: > >> On Thu, 22 Oct 2020 at 18:11, Russell King - ARM Linux admin > >> <li...@armlinux.org.uk> wrote: > >>> > >>> On Thu, Oct 22, 2020 at 06:06:32PM +0200, Ard Biesheuvel wrote: > >>>> On Thu, 22 Oct 2020 at 17:57, Dmitry Osipenko <dig...@gmail.com> wrote: > >>>>> > >>>>> 22.10.2020 10:06, Ard Biesheuvel пишет: > >>>>>> On Thu, 22 Oct 2020 at 05:30, Kees Cook <keesc...@chromium.org> wrote: > >>>>>>> > >>>>>>> On Thu, Oct 22, 2020 at 03:00:06AM +0300, Dmitry Osipenko wrote: > >>>>>>>> 22.10.2020 02:40, Kees Cook пишет: > >>>>>>>>> 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? > >>>>>>>> > >>>>>>>> GCC 9.3.0 > >>>>>>>> > >>>>>>>>>> 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. > >>>>>>>> > >>>>>>>> I re-checked that the fixes tag is correct. > >>>>>>>> > >>>>>>>>>> Signed-off-by: Dmitry Osipenko <dig...@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? > >>>>>>>>> > >>>>>>>> > >>>>>>>> I don't know where it needs to be moved. Please feel free to make a > >>>>>>>> patch if you have a better idea, I'll be glad to test it. > >>>>>>> > >>>>>>> I might have just been distracted by the common "vfp" prefix. It's > >>>>>>> possible that the text section shuffling just ended up being very > >>>>>>> large, > >>>>>>> so probably this patch is right then! > >>>>>>> > >>>>>> > >>>>>> I already sent a fix for this issue: > >>>>>> > >>>>>> https://www.armlinux.org.uk/developer/patches/viewpatch.php?id=9018/1 > >>>>>> > >>>>> > >>>>> The offending commit contains stable tag, so I assume that fixes tag is > >>>>> mandatory. Yours patch misses the fixes tag. > >>>> > >>>> Russell, mind adding that? Or would you like me to update the patch in > >>>> the patch system? > >>> > >>> Rather than adding the IT, I'm suggesting that we solve it a different > >>> way - ensuring that the two bits of code are co-located. There's no > >>> reason for them to be separated, and the assembly code entry point is > >>> already called indirectly. > >>> > >>> The problem is the assembly ends up in the .text section which ends up > >>> at the start of the binary, but depending on the compiler, functions > >>> in .c files end up in their own sections. It would be good if, as > >>> Dmitry has shown that it is indeed possible, to have them co-located. > >> > >> Why is that better? I provided a minimal fix which has zero impact on > >> ARM builds, and minimal impact on Thumb2 builds, given that it retains > >> the exact same semantics as before, but using a different opcode. > > > > I think you just described the reason there. Why should we force > > everything to use a different opcode when a short jump _should_ > > suffice? > > > > Your patch may be a single line, but it has a slightly greater > > impact than the alternative two line solution. > > > > But the two line change isn't portable to stable kernels as-is, isn't it?
Why not? -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!