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Message-ID: <YD6f2WqmYdJiNyQX@ls3530>
Date: Tue, 2 Mar 2021 21:28:09 +0100
From: Helge Deller <deller@....de>
To: Helge Deller <deller@....de>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>,
Arnd Bergmann <arnd@...nel.org>, linux-parisc@...r.kernel.org,
James Bottomley <James.Bottomley@...senpartnership.com>,
kbuild-all@...ts.01.org, LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Kees Cook <keescook@...omium.org>,
kernel test robot <lkp@...el.com>,
John David Anglin <dave.anglin@...l.net>
Subject: Re: hppa64-linux-ld: kernel/sched/core.o(.init.text+0x90): cannot
reach printk
* Helge Deller <deller@....de>:
> On 3/2/21 7:07 PM, Nick Desaulniers wrote:
> > + Arnd
> >
> > On Tue, Mar 2, 2021 at 10:03 AM Helge Deller <deller@....de> wrote:
> > >
> > > On 3/2/21 6:29 PM, Nick Desaulniers wrote:
> > > > + pa-risc folks
> > >
> > > Thanks for looking into this, Nick!
> > >
> > > > On Tue, Mar 2, 2021 at 2:59 AM kernel test robot <lkp@...el.com> wrote:
> > > > >
> > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > > > head: 7a7fd0de4a9804299793e564a555a49c1fc924cb
> > > > > commit: eff8728fe69880d3f7983bec3fb6cea4c306261f vmlinux.lds.h: Add PGO and AutoFDO input sections
> > > >
> > > > This commit added sections explicitly to the kernel's linker script.
> > >
> > > Yes, but even when reverting this patch it does not prevent
> > > the linking problems.
> > >
> > >
> > > > > date: 6 months ago
> > > > > config: parisc-randconfig-s031-20210228 (attached as .config)
> > > >
> > > > ^ randconfig (always find something curious)
> > >
> > > Yes :-)
> > >
> > >
> > > > > compiler: hppa64-linux-gcc (GCC) 9.3.0
> > > > > reproduce:
> > > > > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > > > > chmod +x ~/bin/make.cross
> > > > > # apt-get install sparse
> > > > > # sparse version: v0.6.3-241-geaceeafa-dirty
> > > > > # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eff8728fe69880d3f7983bec3fb6cea4c306261f
> > > > > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > > > > git fetch --no-tags linus master
> > > > > git checkout eff8728fe69880d3f7983bec3fb6cea4c306261f
> > > > > # save the attached .config to linux build tree
> > > > > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=parisc
> > > > >
> > > > > If you fix the issue, kindly add following tag as appropriate
> > > > > Reported-by: kernel test robot <lkp@...el.com>
> > > > >
> > > > > All errors (new ones prefixed by >>):
> > > > >
> > > > > hppa64-linux-ld: init/main.o(.init.text+0x294): cannot reach printk
> > > > > init/main.o: in function `do_early_param':
> > > > > (.init.text+0x294): relocation truncated to fit: R_PARISC_PCREL22F against symbol `printk' defined in .text.unlikely section in kernel/printk/printk.o
> > > >
> > > > ^ so we can't encode a jump to printk from do_early_param.
> > >
> > > Right.
> > >
> > > > If the linker is warning that printk is in the .text.unlikely
> > > > section, I'm curious why printk is marked cold?
> > >
> > > printk is always marked cold, see include/linux/printk.h:
> > > asmlinkage __printf(1, 2) __cold
> > > int printk(const char *fmt, ...);
> > >
> > > > Likely the randconfig produces a large TEXT_MAIN;
> > >
> > > Yes.
> > >
> > > > I'm guessing that .init.text is on one side of TEXT_MAIN, and
> > > > .text.unlikely is on the other. Though there are many different
> > > > instances below.
> > > Yes. But even the large TEXT_MAIN by itself can become a problem.
> > >
> > > > I'm more familiar with ARM; it's common for the linker to insert
> > > > trampolines/thunks to bridge jumps too large to encode in a given
> > > > instruction. I don't know if BFD has arch agnostic machinery for
> > > > that, but might be seeing if there's anything reuseable there.
> > >
> > > Dave mentioned in another mail, that long branch stub support is
> > > still missing in the 64-bit parisc linker.
> > >
> > > My question still remains:
> > > Is there any possibility to detect that we build/configure a
> > > 0-day kernel? If so, auto-enabling CONFIG_MLONGCALLS kernel option
> > > would solve it (temporarily).
> >
> > Arnd, is this kind of case what CONFIG_COMPILE_TEST is usually used for?
>
> Yes, I think that's the right knob!
> CONFIG_COMPILE_TEST is enabled on all parisc configs for which 0-day
> reported issues.
> I've wired it up in Kconfig and it now works around the issue.
I've committed the patch below to the parisc for-next tree, which allows
to monitor if this fixes the linkage problems...
Helge
From: Helge Deller <deller@....de>
Date: Tue, 2 Mar 2021 21:07:07 +0100
Subject: [PATCH] parisc: Enable -mlong-calls gcc option with
CONFIG_COMPILE_TEST
The kernel test robot reported multiple linkage problems like this:
hppa64-linux-ld: init/main.o(.init.text+0x56c): cannot reach printk
init/main.o: in function `unknown_bootoption':
(.init.text+0x56c): relocation truncated to fit: R_PARISC_PCREL22F against
symbol `printk' defined in .text.unlikely section in kernel/printk/printk.o
There are two ways to solve it:
a) Enable the -mlong-call compiler option (CONFIG_MLONGCALLS),
b) Add long branch stub support in 64-bit linker.
While b) is the long-term solution, this patch works around the issue by
automatically enabling the CONFIG_MLONGCALLS option when
CONFIG_COMPILE_TEST is set, which indicates that a non-production kernel
(e.g. 0-day kernel) is built.
Signed-off-by: Helge Deller <deller@....de>
Reported-by: kernel test robot <lkp@...el.com>
Fixes: 00e35f2b0e8a ("parisc: Enable -mlong-calls gcc option by default when !CONFIG_MODULES")
Cc: stable@...r.kernel.org # v5.6+
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 4e53ac46e857..afc3b8d03572 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -203,9 +203,12 @@ config PREFETCH
def_bool y
depends on PA8X00 || PA7200
+config PARISC_HUGE_KERNEL
+ def_bool y if !MODULES || UBSAN || FTRACE || COMPILE_TEST
+
config MLONGCALLS
- def_bool y if !MODULES || UBSAN || FTRACE
- bool "Enable the -mlong-calls compiler option for big kernels" if MODULES && !UBSAN && !FTRACE
+ def_bool y if PARISC_HUGE_KERNEL
+ bool "Enable the -mlong-calls compiler option for big kernels" if !PARISC_HUGE_KERNEL
depends on PA8X00
help
If you configure the kernel to include many drivers built-in instead
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