[PATCH RFC v2 1/3] riscv: add support for hardware breakpoints/watchpoints

[Conor Dooley]

On Sun, Dec 04, 2022 at 12:55:33AM +0300, Sergey Matyukevich wrote:
> From: Sergey Matyukevich <sergey.matyukevich at syntacore.com>
> 
> RISC-V backend for hw-breakpoint framework is built on top of SBI Debug
> Trigger extension. Architecture specific hooks are implemented as kernel
> wrappers around ecalls to SBI functions. This patch implements only a
> minimal set of hooks required to support user-space debug via ptrace.
> 
> Signed-off-by: Sergey Matyukevich <sergey.matyukevich at syntacore.com>
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 2a0ef738695e..ef41d60a5ed3 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -31,6 +31,9 @@ enum sbi_ext_id {
>  	SBI_EXT_SRST = 0x53525354,
>  	SBI_EXT_PMU = 0x504D55,
>  
> +	/* Experimental: Debug Trigger Extension */
> +	SBI_EXT_DBTR = 0x44425452,
> +
>  	/* Experimentals extensions must lie within this range */
>  	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
>  	SBI_EXT_EXPERIMENTAL_END = 0x08FFFFFF,

This is an RFC for something I know nothing about, so was just scrolling
mindlessly... This caught my eye as odd - There's an explicit comment
about the range for experimental stuff but you've not used it? I guess
there must be some reason for that?

Confused,
Conor.

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