[RFC v2 1/2] riscv: allow resume after exception

[Xiang W]

setjmp can be called in set_resume.

Regards,
Xiang W

Heinrich Schuchardt <heinrich.schuchardt at canonical.com> 于2023年10月29日周日 16:56写道：
>
> If CSRs like seed are readable by S-mode, may not be determinable by
> S-mode. For safe driver probing allow to resume via a longjmp after an
> exception.
>
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> ---
> v2:
>         new patch
> ---
>  arch/riscv/lib/interrupts.c | 13 +++++++++++++
>  include/interrupt.h         | 22 ++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
>  create mode 100644 include/interrupt.h
>
> diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c
> index 02dbcfd423..a26ccc721f 100644
> --- a/arch/riscv/lib/interrupts.c
> +++ b/arch/riscv/lib/interrupts.c
> @@ -12,6 +12,7 @@
>  #include <linux/compat.h>
>  #include <efi_loader.h>
>  #include <hang.h>
> +#include <interrupt.h>
>  #include <irq_func.h>
>  #include <asm/global_data.h>
>  #include <asm/ptrace.h>
> @@ -21,6 +22,13 @@
>
>  DECLARE_GLOBAL_DATA_PTR;
>
> +static struct resume_data *resume;
> +
> +void set_resume(struct resume_data *data)
> +{
> +       resume = data;
> +}
> +
>  static void show_efi_loaded_images(uintptr_t epc)
>  {
>         efi_print_image_infos((void *)epc);
> @@ -105,6 +113,11 @@ static void _exit_trap(ulong code, ulong epc, ulong tval, struct pt_regs *regs)
>                 "Store/AMO page fault",
>         };
>
> +       if (resume) {
> +               resume->code = code;
> +               longjmp(resume->jump, 1);
> +       }
> +
>         if (code < ARRAY_SIZE(exception_code))
>                 printf("Unhandled exception: %s\n", exception_code[code]);
>         else
> diff --git a/include/interrupt.h b/include/interrupt.h
> new file mode 100644
> index 0000000000..1baa60bcf2
> --- /dev/null
> +++ b/include/interrupt.h
> @@ -0,0 +1,22 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +#include <asm/setjmp.h>
> +
> +/**
> + * struct resume_data - data for resume after interrupt
> + */
> +struct resume_data {
> +       /** @jump: longjmp buffer */
> +       jmp_buf jump;
> +       /** @code: exception code */
> +       ulong code;
> +};
> +
> +/**
> + * set_resume() - set longjmp buffer for resuming after interrupt
> + *
> + * When resuming the exception code will be returned in @data->code.
> + *
> + * @data:      pointer to structure with longjmp address
> + */
> +void set_resume(struct resume_data *data);
> --
> 2.40.1
>