linux-kernel - Re: [PATCH v3 12/13] riscv: Initialize thread pointer before calling C functions

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Message-ID: <CAJF2gTQEHv1dVzv=JNCYSzD8oh6UxYOFRTdBOp-FFeeeOhSJrQ@mail.gmail.com>
Date:   Mon, 20 Dec 2021 17:11:05 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Alexandre Ghiti <alexandre.ghiti@...onical.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Zong Li <zong.li@...ive.com>, Anup Patel <anup@...infault.org>,
        Atish Patra <Atish.Patra@...osinc.com>,
        Christoph Hellwig <hch@....de>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Guo Ren <guoren@...ux.alibaba.com>,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        panqinglin2020@...as.ac.cn,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kasan-dev@...glegroups.com, linux-efi@...r.kernel.org,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v3 12/13] riscv: Initialize thread pointer before calling
 C functions

On Tue, Dec 7, 2021 at 11:55 AM Alexandre Ghiti
<alexandre.ghiti@...onical.com> wrote:
>
> Because of the stack canary feature that reads from the current task
> structure the stack canary value, the thread pointer register "tp" must
> be set before calling any C function from head.S: by chance, setup_vm
Shall we disable -fstack-protector for setup_vm() with __attribute__?
Actually, we've already init tp later.

> and all the functions that it calls does not seem to be part of the
> functions where the canary check is done, but in the following commits,
> some functions will.
>
> Fixes: f2c9699f65557a31 ("riscv: Add STACKPROTECTOR supported")
> Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>
> ---
>  arch/riscv/kernel/head.S | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index c3c0ed559770..86f7ee3d210d 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -302,6 +302,7 @@ clear_bss_done:
>         REG_S a0, (a2)
>
>         /* Initialize page tables and relocate to virtual addresses */
> +       la tp, init_task
>         la sp, init_thread_union + THREAD_SIZE
>         XIP_FIXUP_OFFSET sp
>  #ifdef CONFIG_BUILTIN_DTB
> --
> 2.32.0
>


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/