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

Guo Ren
2022-02-02T02:02:32Z

On Tue, Feb 1, 2022 at 11:07 PM <guoren@kernel.org> wrote:
>
> From: Guo Ren <guoren@linux.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@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Christoph Hellwig <hch@lst.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/