Re: [PATCH v7 3/6] xen/riscv: introduce decode_cause() stuff

[Alistair Francis <alistair23@xxxxxxxxx>]

On Thu, Aug 3, 2023 at 8:05 AM Oleksii Kurochko
<oleksii.kurochko@xxxxxxxxx> wrote:
>
> The patch introduces stuff needed to decode a reason of an
> exception.
>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> ---
> Changes in V7:
>  - Nothing changed. Only rebase.
> ---
> Changes in V6:
>  - Remove usage of LINK_TO_LOAD() due to the MMU being enabled first.
>  - Change early_printk() to printk()
> ---
> Changes in V5:
>   - Remove <xen/error.h> from riscv/traps/c as nothing would require
>     inclusion.
>   - decode_reserved_interrupt_cause(), decode_interrupt_cause(), 
> decode_cause, do_unexpected_trap()
>     were made as static they are expected to be used only in traps.c
>   - use LINK_TO_LOAD() for addresses which can be linker time relative.
> ---
> Changes in V4:
>   - fix string in decode_reserved_interrupt_cause()
> ---
> Changes in V3:
>   - Nothing changed
> ---
> Changes in V2:
>   - Make decode_trap_cause() more optimization friendly.
>   - Merge the pathc which introduces do_unexpected_trap() to the current one.
> ---
>  xen/arch/riscv/traps.c | 84 +++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 83 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/riscv/traps.c b/xen/arch/riscv/traps.c
> index ccd3593f5a..ea1012e83e 100644
> --- a/xen/arch/riscv/traps.c
> +++ b/xen/arch/riscv/traps.c
> @@ -4,10 +4,92 @@
>   *
>   * RISC-V Trap handlers
>   */
> +
> +#include <xen/lib.h>
> +
> +#include <asm/csr.h>
> +#include <asm/early_printk.h>
>  #include <asm/processor.h>
>  #include <asm/traps.h>
>
> -void do_trap(struct cpu_user_regs *cpu_regs)
> +static const char *decode_trap_cause(unsigned long cause)
> +{
> +    static const char *const trap_causes[] = {
> +        [CAUSE_MISALIGNED_FETCH] = "Instruction Address Misaligned",
> +        [CAUSE_FETCH_ACCESS] = "Instruction Access Fault",
> +        [CAUSE_ILLEGAL_INSTRUCTION] = "Illegal Instruction",
> +        [CAUSE_BREAKPOINT] = "Breakpoint",
> +        [CAUSE_MISALIGNED_LOAD] = "Load Address Misaligned",
> +        [CAUSE_LOAD_ACCESS] = "Load Access Fault",
> +        [CAUSE_MISALIGNED_STORE] = "Store/AMO Address Misaligned",
> +        [CAUSE_STORE_ACCESS] = "Store/AMO Access Fault",
> +        [CAUSE_USER_ECALL] = "Environment Call from U-Mode",
> +        [CAUSE_SUPERVISOR_ECALL] = "Environment Call from S-Mode",
> +        [CAUSE_MACHINE_ECALL] = "Environment Call from M-Mode",
> +        [CAUSE_FETCH_PAGE_FAULT] = "Instruction Page Fault",
> +        [CAUSE_LOAD_PAGE_FAULT] = "Load Page Fault",
> +        [CAUSE_STORE_PAGE_FAULT] = "Store/AMO Page Fault",
> +        [CAUSE_FETCH_GUEST_PAGE_FAULT] = "Instruction Guest Page Fault",
> +        [CAUSE_LOAD_GUEST_PAGE_FAULT] = "Load Guest Page Fault",
> +        [CAUSE_VIRTUAL_INST_FAULT] = "Virtualized Instruction Fault",
> +        [CAUSE_STORE_GUEST_PAGE_FAULT] = "Guest Store/AMO Page Fault",
> +    };
> +
> +    if ( cause < ARRAY_SIZE(trap_causes) && trap_causes[cause] )
> +        return trap_causes[cause];
> +    return "UNKNOWN";
> +}
> +
> +static const char *decode_reserved_interrupt_cause(unsigned long irq_cause)
> +{
> +    switch ( irq_cause )
> +    {
> +    case IRQ_M_SOFT:
> +        return "M-mode Software Interrupt";
> +    case IRQ_M_TIMER:
> +        return "M-mode TIMER Interrupt";

TIMER doesn't need to be all caps, otherwise:

Acked-by: Alistair Francis <alistair.francis@xxxxxxx>

Alistair

> +    case IRQ_M_EXT:
> +        return "M-mode External Interrupt";
> +    default:
> +        return "UNKNOWN IRQ type";
> +    }
> +}
> +
> +static const char *decode_interrupt_cause(unsigned long cause)
> +{
> +    unsigned long irq_cause = cause & ~CAUSE_IRQ_FLAG;
> +
> +    switch ( irq_cause )
> +    {
> +    case IRQ_S_SOFT:
> +        return "Supervisor Software Interrupt";
> +    case IRQ_S_TIMER:
> +        return "Supervisor Timer Interrupt";
> +    case IRQ_S_EXT:
> +        return "Supervisor External Interrupt";
> +    default:
> +        return decode_reserved_interrupt_cause(irq_cause);
> +    }
> +}
> +
> +static const char *decode_cause(unsigned long cause)
> +{
> +    if ( cause & CAUSE_IRQ_FLAG )
> +        return decode_interrupt_cause(cause);
> +
> +    return decode_trap_cause(cause);
> +}
> +
> +static void do_unexpected_trap(const struct cpu_user_regs *regs)
>  {
> +    unsigned long cause = csr_read(CSR_SCAUSE);
> +
> +    printk("Unhandled exception: %s\n", decode_cause(cause));
> +
>      die();
>  }
> +
> +void do_trap(struct cpu_user_regs *cpu_regs)
> +{
> +    do_unexpected_trap(cpu_regs);
> +}
> --
> 2.41.0
>
>