From: Nathan Chancellor <nathan@kernel.org>
To: "Thomas Weißschuh" <thomas.weissschuh@linutronix.de>
Cc: Paul Walmsley <pjw@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Conor Dooley <conor.dooley@microchip.com>,
Wende Tan <twd2.me@gmail.com>,
Palmer Dabbelt <palmer@rivosinc.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
Nam Cao <namcao@linutronix.de>, kernel test robot <lkp@intel.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/2] riscv: vdso: Do not use LTO for the vDSO
Date: Mon, 6 Jul 2026 14:01:58 -0700 [thread overview]
Message-ID: <20260706210158.GA73349@ax162> (raw)
In-Reply-To: <20260701-riscv-vdso-lto-v1-1-89db0cd82077@linutronix.de>
On Wed, Jul 01, 2026 at 11:21:22AM +0200, Thomas Weißschuh wrote:
> With LTO enabled the compiler assumes that the vDSO functions are not
> used and optimizes them away completely. Currently this happens to
> __vdso_clock_getres(), __vdso_clock_gettime(), __vdso_getrandom(),
> __vdso_gettimeofday() and __vdso_riscv_hwprobe().
>
> Disable LTO for the vDSO, as these functions are hand-optimized anyways.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202606301855.WvkSC4kD-lkp@intel.com/
While this change seems correct, is this really the fix for that report?
It seems like that error happens in clang but I would expect this sort
of issue to only appear once LTO has run through ld.lld?
> Fixes: 021d23428bdb ("RISC-V: build: Allow LTO to be selected")
> Cc: stable@vger.kernel.org
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---
> arch/riscv/kernel/vdso/Makefile | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index a842dc034571..43ee881f6c6f 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -69,9 +69,9 @@ CPPFLAGS_$(vdso_lds) += -DHAS_VGETTIMEOFDAY
> endif
>
> # Disable -pg to prevent insert call site
> -CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
> -CFLAGS_REMOVE_getrandom.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
> -CFLAGS_REMOVE_hwprobe.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
> +CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_LTO)
> +CFLAGS_REMOVE_getrandom.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_LTO)
> +CFLAGS_REMOVE_hwprobe.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_LTO)
>
> # Force dependency
> $(obj)/$(vdso_o): $(obj)/$(vdso_so)
>
> --
> 2.55.0
>
--
Cheers,
Nathan
WARNING: multiple messages have this Message-ID (diff)
From: Nathan Chancellor <nathan@kernel.org>
To: "Thomas Weißschuh" <thomas.weissschuh@linutronix.de>
Cc: Paul Walmsley <pjw@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Conor Dooley <conor.dooley@microchip.com>,
Wende Tan <twd2.me@gmail.com>,
Palmer Dabbelt <palmer@rivosinc.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
Nam Cao <namcao@linutronix.de>, kernel test robot <lkp@intel.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/2] riscv: vdso: Do not use LTO for the vDSO
Date: Mon, 6 Jul 2026 14:01:58 -0700 [thread overview]
Message-ID: <20260706210158.GA73349@ax162> (raw)
In-Reply-To: <20260701-riscv-vdso-lto-v1-1-89db0cd82077@linutronix.de>
On Wed, Jul 01, 2026 at 11:21:22AM +0200, Thomas Weißschuh wrote:
> With LTO enabled the compiler assumes that the vDSO functions are not
> used and optimizes them away completely. Currently this happens to
> __vdso_clock_getres(), __vdso_clock_gettime(), __vdso_getrandom(),
> __vdso_gettimeofday() and __vdso_riscv_hwprobe().
>
> Disable LTO for the vDSO, as these functions are hand-optimized anyways.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202606301855.WvkSC4kD-lkp@intel.com/
While this change seems correct, is this really the fix for that report?
It seems like that error happens in clang but I would expect this sort
of issue to only appear once LTO has run through ld.lld?
> Fixes: 021d23428bdb ("RISC-V: build: Allow LTO to be selected")
> Cc: stable@vger.kernel.org
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---
> arch/riscv/kernel/vdso/Makefile | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index a842dc034571..43ee881f6c6f 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -69,9 +69,9 @@ CPPFLAGS_$(vdso_lds) += -DHAS_VGETTIMEOFDAY
> endif
>
> # Disable -pg to prevent insert call site
> -CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
> -CFLAGS_REMOVE_getrandom.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
> -CFLAGS_REMOVE_hwprobe.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
> +CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_LTO)
> +CFLAGS_REMOVE_getrandom.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_LTO)
> +CFLAGS_REMOVE_hwprobe.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_LTO)
>
> # Force dependency
> $(obj)/$(vdso_o): $(obj)/$(vdso_so)
>
> --
> 2.55.0
>
--
Cheers,
Nathan
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2026-07-06 21:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 9:21 [PATCH 0/2] riscv: vdso: Do not use LTO for the vDSO Thomas Weißschuh
2026-07-01 9:21 ` Thomas Weißschuh
2026-07-01 9:21 ` [PATCH 1/2] " Thomas Weißschuh
2026-07-01 9:21 ` Thomas Weißschuh
2026-07-06 21:01 ` Nathan Chancellor [this message]
2026-07-06 21:01 ` Nathan Chancellor
2026-07-07 6:10 ` Thomas Weißschuh
2026-07-07 6:10 ` Thomas Weißschuh
2026-07-01 9:21 ` [PATCH 2/2] riscv: vdso: Simplify cflags remove logic Thomas Weißschuh
2026-07-01 9:21 ` Thomas Weißschuh
2026-07-02 9:38 ` [PATCH 0/2] riscv: vdso: Do not use LTO for the vDSO Nam Cao
2026-07-02 9:38 ` Nam Cao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260706210158.GA73349@ax162 \
--to=nathan@kernel.org \
--cc=alex@ghiti.fr \
--cc=aou@eecs.berkeley.edu \
--cc=conor.dooley@microchip.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=lkp@intel.com \
--cc=namcao@linutronix.de \
--cc=palmer@dabbelt.com \
--cc=palmer@rivosinc.com \
--cc=pjw@kernel.org \
--cc=stable@vger.kernel.org \
--cc=thomas.weissschuh@linutronix.de \
--cc=twd2.me@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.