linux-kernel - Re: [PATCH V5 15/21] riscv: compat: Add hw capability check for elf

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Date:   Wed, 2 Feb 2022 10:02:12 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Guo Ren <guoren@...nel.org>, Palmer Dabbelt <palmer@...belt.com>,
        Arnd Bergmann <arnd@...db.de>,
        Anup Patel <anup@...infault.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        liush <liush@...winnertech.com>, Wei Fu <wefu@...hat.com>,
        Drew Fustini <drew@...gleboard.org>,
        Wang Junqiang <wangjunqiang@...as.ac.cn>,
        Christoph Hellwig <hch@....de>
Cc:     linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-csky@...r.kernel.org,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V5 15/21] riscv: compat: Add hw capability check for elf

On Tue, Feb 1, 2022 at 11:07 PM <guoren@...nel.org> wrote:
>
> From: Guo Ren <guoren@...ux.alibaba.com>
>
> Detect hardware COMPAT (32bit U-mode) capability in rv64. If not
> support COMPAT mode in hw, compat_elf_check_arch would return
> false by compat_binfmt_elf.c
>
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Christoph Hellwig <hch@....de>
> ---
>  arch/riscv/include/asm/elf.h |  3 ++-
>  arch/riscv/kernel/process.c  | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
> index aee40040917b..3a4293dc7229 100644
> --- a/arch/riscv/include/asm/elf.h
> +++ b/arch/riscv/include/asm/elf.h
> @@ -40,7 +40,8 @@
>   * elf64_hdr e_machine's offset are different. The checker is
>   * a little bit simple compare to other architectures.
>   */
> -#define compat_elf_check_arch(x) ((x)->e_machine == EM_RISCV)
> +extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
> +#define compat_elf_check_arch  compat_elf_check_arch
>
>  #define CORE_DUMP_USE_REGSET
>  #define ELF_EXEC_PAGESIZE      (PAGE_SIZE)
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index 1a666ad299b4..758847cba391 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -83,6 +83,38 @@ void show_regs(struct pt_regs *regs)
>                 dump_backtrace(regs, NULL, KERN_DEFAULT);
>  }
>
> +#ifdef CONFIG_COMPAT
> +static bool compat_mode_support __read_mostly;
> +
> +bool compat_elf_check_arch(Elf32_Ehdr *hdr)
> +{
> +       if (compat_mode_support && (hdr->e_machine == EM_RISCV))
> +               return true;
> +       else
> +               return false;
> +}
> +
> +static int compat_mode_detect(void)
Forgot __init, here

> +{
> +       unsigned long tmp = csr_read(CSR_STATUS);
> +
> +       csr_write(CSR_STATUS, (tmp & ~SR_UXL) | SR_UXL_32);
> +
> +       if ((csr_read(CSR_STATUS) & SR_UXL) != SR_UXL_32) {
> +               pr_info("riscv: 32bit compat mode detect failed\n");
> +               compat_mode_support = false;
> +       } else {
> +               compat_mode_support = true;
> +               pr_info("riscv: 32bit compat mode detected\n");
> +       }
> +
> +       csr_write(CSR_STATUS, tmp);
> +
> +       return 0;
> +}
> +arch_initcall(compat_mode_detect);
> +#endif
> +
>  void start_thread(struct pt_regs *regs, unsigned long pc,
>         unsigned long sp)
>  {
> --
> 2.25.1
>


-- 
Best Regards
 Guo Ren

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