linux-kernel - Re: [PATCH v4 02/63] vmlinux.lds: Unify TEXT_MAIN, DATA

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Message-ID: <aWAouZSH0Zw39Qt3@google.com>
Date: Thu, 8 Jan 2026 21:59:21 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Will Deacon <will@...nel.org>
Cc: Ard Biesheuvel <ardb@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org, Song Liu <song@...nel.org>,
	laokz <laokz@...mail.com>, Jiri Kosina <jikos@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Weinan Liu <wnliu@...gle.com>,
	Fazla Mehrab <a.mehrab@...edance.com>,
	Chen Zhongjin <chenzhongjin@...wei.com>,
	Puranjay Mohan <puranjay@...nel.org>,
	Dylan Hatch <dylanbhatch@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Sami Tolvanen <samitolvanen@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v4 02/63] vmlinux.lds: Unify TEXT_MAIN, DATA_MAIN, and
 related macros

On Tue, Jan 06, 2026 at 10:46:33PM +0000, Will Deacon wrote:
> On Sat, Dec 20, 2025 at 04:25:50PM +0000, Carlos Llamas wrote:
> > On Wed, Sep 17, 2025 at 09:03:10AM -0700, Josh Poimboeuf wrote:
> > > TEXT_MAIN, DATA_MAIN and friends are defined differently depending on
> > > whether certain config options enable -ffunction-sections and/or
> > > -fdata-sections.
> > > 
> > > There's no technical reason for that beyond voodoo coding.  Keeping the
> > > separate implementations adds unnecessary complexity, fragments the
> > > logic, and increases the risk of subtle bugs.
> > > 
> > > Unify the macros by using the same input section patterns across all
> > > configs.
> > > 
> > > This is a prerequisite for the upcoming livepatch klp-build tooling
> > > which will manually enable -ffunction-sections and -fdata-sections via
> > > KCFLAGS.
> > > 
> > > Cc: Heiko Carstens <hca@...ux.ibm.com>
> > > Cc: Vasily Gorbik <gor@...ux.ibm.com>
> > > Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
> > > Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> > > ---
> > >  include/asm-generic/vmlinux.lds.h | 40 ++++++++++---------------------
> > >  scripts/module.lds.S              | 12 ++++------
> > >  2 files changed, 17 insertions(+), 35 deletions(-)
> 
> [...]
> 
> > I'm seeing some KP when trying to load modules after this change. I
> > believe there is some sort of incompatibility with the SCS (Shadow Call
> > Stack) code in arm64? The panic is always on __pi_scs_handle_fde_frame:
> > 
> >   init: Loading module [...]/drivers/net/wireless/virtual/mac80211_hwsim.ko
> >   Unable to handle kernel paging request at virtual address ffffffe6468f0ffc
> >   [...]
> 
> nit: please don't trim the useful stuff when reporting a crash!
> 
> >   pc : __pi_scs_handle_fde_frame+0xd8/0x15c
> >   lr : __pi_$x+0x74/0x138
> >   sp : ffffffc08005bb10
> >   x29: ffffffc08005bb10 x28: ffffffc081873010 x27: 0000000000000000
> >   x26: 0000000000000007 x25: 0000000000000000 x24: 0000000000000000
> >   x23: 0000000000000001 x22: ffffffe649794fa0 x21: ffffffe6469190b4
> >   x20: 000000000000182c x19: 0000000000000001 x18: ffffffc080053000
> >   x17: 000000000000002d x16: ffffffe6469190c5 x15: ffffffe6468f1000
> >   x14: 000000000000003e x13: ffffffe6469190c6 x12: 00000000d50323bf
> >   x11: 00000000d503233f x10: ffffffe649119cb8 x9 : ffffffe6468f1000
> >   x8 : 0000000000000100 x7 : 00656d6172665f68 x6 : 0000000000000001
> >   x5 : 6372610000000000 x4 : 0000008000000000 x3 : 0000000000000000
> >   x2 : ffffffe647e528f4 x1 : 0000000000000001 x0 : 0000000000000004
> >   Call trace:
> >    __pi_scs_handle_fde_frame+0xd8/0x15c (P)
> >    module_finalize+0xfc/0x164
> >    post_relocation+0xbc/0xd8
> >    load_module+0xfd4/0x11a8
> >    __arm64_sys_finit_module+0x23c/0x328
> >    invoke_syscall+0x58/0xe4
> >    el0_svc_common+0x80/0xdc
> >    do_el0_svc+0x1c/0x28
> >    el0_svc+0x54/0x1c4
> >    el0t_64_sync_handler+0x68/0xdc
> >    el0t_64_sync+0x1c4/0x1c8
> >   Code: 54fffd4c 1400001f 3707ff63 aa0903ef (b85fcdf0)
> 
> Hmm, looks like a translation fault from the load buried here:
> 
> 	u32 insn = le32_to_cpup((void *)loc);
> 
> in scs_patch_loc(), called from the 'DW_CFA_negate_ra_state' case in
> scs_handle_fde_frame(). So presumably 'loc' is bogus.
> 
> Since you replied to this patch, does reverting it fix the problem for
> you?

Yes, but it is only coincidental. The real issue seems to be with our
toolchain. I'll start looking there instead. Sorry for the noise.

--
Carlos Llamas