From: Michael Cree <mcree@orcon.net.nz>
To: Magnus Lindholm <linmag7@gmail.com>
Cc: Matt Turner <mattst88@gmail.com>,
linux-alpha@vger.kernel.org, richard.henderson@linaro.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/24] alpha: select ARCH_HAS_UBSAN
Date: Sun, 6 Sep 2026 13:49:59 +1200 [thread overview]
Message-ID: <apzGx5Q19wEh0SwP@creeky> (raw)
In-Reply-To: <CA+=Fv5Sg1KjAZZ3X=Yh62hUr=5qeRg_ZVq=A_C4bBovde1MeoA@mail.gmail.com>
Hi Magnus,
On Sat, Sep 05, 2026 at 01:15:18AM +0200, Magnus Lindholm wrote:
> On Fri, Sep 4, 2026 at 10:31 PM Michael Cree <mcree@orcon.net.nz> wrote:
> > On Wed, Sep 02, 2026 at 12:34:50AM +0200, Magnus Lindholm wrote:
> > > On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
> > > >
> > > > GCC's undefined behavior sanitizer has no architecture-specific runtime
> > > > requirements. Enable it for Alpha to allow UBSAN instrumentation of the
> > > > kernel.
> > > >
> > > I tested this patch on top of my rebased Alpha GENERIC_ENTRY patch on an
> > > AlphaServer ES40. The kernel built and booted successfully with
> > > CONFIG_UBSAN=y, and the UBSAN instrumentation is active.
> >
> > So have I, on an XP1000 and ES45.
> >
> > > CONFIG_UBSAN_ALIGNMENT did expose a misaligned struct bucket_table
> > > allocation in lib/rhashtable.c. This appears to be a generic rhashtable
> > > allocation-alignment issue rather than an Alpha UBSAN problem.
> >
> > But in my case the kernel vomited copious misaligned access reports,
> >
> > Interestingly "kernel unaligned acc" in /proc/cpuinfo remained at
> > zero, which really makes me wonder whether these reports are all
> > false-positives.
> >
> Good question, had to dig deeper here,
>
> Not false positives - real UB, but harmless, and I tracked down why.
Thanks for taking time to find the explanation. So, technical UB
but no consequence for operation.
Cheers,
Michael.
next prev parent reply other threads:[~2026-09-06 2:17 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-01 15:50 [PATCH 00/24] alpha: catch up on architecture Kconfig options Matt Turner
2026-09-01 15:50 ` [PATCH 01/24] alpha: fix arch_irqs_disabled_flags() to treat any raised IPL as disabled Matt Turner
2026-09-01 23:20 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 02/24] alpha: enter hardirq context before looking up the irq descriptor Matt Turner
2026-09-03 22:07 ` Magnus Lindholm
2026-09-05 2:43 ` Matt Turner
2026-09-05 8:28 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 03/24] alpha: select ARCH_HAS_UBSAN Matt Turner
2026-09-01 22:34 ` Magnus Lindholm
2026-09-04 20:31 ` Michael Cree
2026-09-04 23:15 ` Magnus Lindholm
2026-09-06 1:49 ` Michael Cree [this message]
2026-09-01 15:50 ` [PATCH 04/24] alpha: select ARCH_HAS_GCOV_PROFILE_ALL Matt Turner
2026-09-03 22:35 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 05/24] alpha: select HAVE_DEBUG_KMEMLEAK Matt Turner
2026-09-02 6:01 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 06/24] alpha: select EDAC_SUPPORT Matt Turner
2026-09-01 23:17 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 07/24] alpha: select ARCH_SUPPORTS_ATOMIC_RMW Matt Turner
2026-09-02 6:17 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 08/24] alpha: select ARCH_HAS_FAST_MULTIPLIER Matt Turner
2026-09-02 7:49 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 09/24] alpha: select ARCH_SUPPORTS_INT128 Matt Turner
2026-09-02 8:50 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 10/24] alpha: select HAVE_ARCH_COMPILER_H Matt Turner
2026-09-02 9:11 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 11/24] alpha: select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE Matt Turner
2026-09-02 9:25 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 12/24] alpha: add HAVE_ARCH_THREAD_STRUCT_WHITELIST support Matt Turner
2026-09-02 9:35 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 13/24] alpha: add ARCH_HAS_PTE_SPECIAL support Matt Turner
2026-09-02 9:42 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 14/24] alpha: add ARCH_SUPPORTS_PAGE_TABLE_CHECK support Matt Turner
2026-09-01 22:45 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 15/24] alpha: select ARCH_HAS_DEBUG_VM_PGTABLE Matt Turner
2026-09-03 22:52 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 16/24] alpha: select HAVE_GUP_FAST Matt Turner
2026-09-02 21:09 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 17/24] alpha: select ARCH_USE_MEMTEST Matt Turner
2026-09-02 21:56 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 18/24] alpha: select SYSCTL_EXCEPTION_TRACE Matt Turner
2026-09-02 22:02 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 19/24] alpha: discard .eh_frame and the relocation sections Matt Turner
2026-09-03 5:18 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 20/24] alpha: select ARCH_WANT_LD_ORPHAN_WARN Matt Turner
2026-09-03 5:34 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 21/24] alpha: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM Matt Turner
2026-09-03 5:42 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 22/24] alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support Matt Turner
2026-09-03 21:01 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 23/24] alpha: select SPARSE_IRQ Matt Turner
2026-09-03 21:26 ` Magnus Lindholm
2026-09-01 15:50 ` [PATCH 24/24] alpha: add TRACE_IRQFLAGS_SUPPORT Matt Turner
2026-09-03 22:58 ` Magnus Lindholm
2026-09-02 18:53 ` [PATCH 00/24] alpha: catch up on architecture Kconfig options Magnus Lindholm
2026-09-02 18:57 ` Matt Turner
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