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

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