From: Nathan Chancellor <nathan@kernel.org>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH] KVM: arm64: Don't use cbz/adr with external symbols
Date: Sat, 6 Mar 2021 21:35:45 -0700 [thread overview]
Message-ID: <20210307043545.pyxy22z3rktgof4m@archlinux-ax161> (raw)
In-Reply-To: <20210305202124.3768527-1-samitolvanen@google.com>
On Fri, Mar 05, 2021 at 12:21:24PM -0800, Sami Tolvanen wrote:
> allmodconfig + CONFIG_LTO_CLANG_THIN=y fails to build due to following
> linker errors:
>
> ld.lld: error: irqbypass.c:(function __guest_enter: .text+0x21CC):
> relocation R_AARCH64_CONDBR19 out of range: 2031220 is not in
> [-1048576, 1048575]; references hyp_panic
> >>> defined in vmlinux.o
>
> ld.lld: error: irqbypass.c:(function __guest_enter: .text+0x21E0):
> relocation R_AARCH64_ADR_PREL_LO21 out of range: 2031200 is not in
> [-1048576, 1048575]; references hyp_panic
> >>> defined in vmlinux.o
>
> This is because with LTO, the compiler ends up placing hyp_panic()
> more than 1MB away from __guest_enter(). Use an unconditional branch
> and adr_l instead to fix the issue.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1317
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Suggested-by: Marc Zyngier <maz@kernel.org>
> Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
I booted an kernel with this patch in it on my Raspberry Pi 4 and booted
a kernel under KVM without any issues.
Tested-by: Nathan Chancellor <nathan@kernel.org>
> ---
> arch/arm64/kvm/hyp/entry.S | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index b0afad7a99c6..c62265951467 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -85,8 +85,10 @@ SYM_INNER_LABEL(__guest_exit_panic, SYM_L_GLOBAL)
>
> // If the hyp context is loaded, go straight to hyp_panic
> get_loaded_vcpu x0, x1
> - cbz x0, hyp_panic
> + cbnz x0, 1f
> + b hyp_panic
>
> +1:
> // The hyp context is saved so make sure it is restored to allow
> // hyp_panic to run at hyp and, subsequently, panic to run in the host.
> // This makes use of __guest_exit to avoid duplication but sets the
> @@ -94,7 +96,7 @@ SYM_INNER_LABEL(__guest_exit_panic, SYM_L_GLOBAL)
> // current state is saved to the guest context but it will only be
> // accurate if the guest had been completely restored.
> adr_this_cpu x0, kvm_hyp_ctxt, x1
> - adr x1, hyp_panic
> + adr_l x1, hyp_panic
> str x1, [x0, #CPU_XREG_OFFSET(30)]
>
> get_vcpu_ptr x1, x0
>
> base-commit: 280d542f6ffac0e6d65dc267f92191d509b13b64
> --
> 2.30.1.766.gb4fecdf3b7-goog
>
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-03-07 4:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 20:21 [PATCH] KVM: arm64: Don't use cbz/adr with external symbols Sami Tolvanen
2021-03-05 20:22 ` Kees Cook
2021-03-07 4:35 ` Nathan Chancellor [this message]
2021-03-08 14:38 ` Will Deacon
2021-03-09 8:49 ` Marc Zyngier
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=20210307043545.pyxy22z3rktgof4m@archlinux-ax161 \
--to=nathan@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=james.morse@arm.com \
--cc=keescook@chromium.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maz@kernel.org \
--cc=ndesaulniers@google.com \
--cc=samitolvanen@google.com \
--cc=will@kernel.org \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).