linux-kernel - Re: [PATCH 4/6] riscv: Add CFI error handling

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Message-ID: <20230630-utopia-drizzle-df8c14558696@spud>
Date:   Fri, 30 Jun 2023 20:03:20 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-riscv@...ts.infradead.org, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] riscv: Add CFI error handling

Hey Sami,

On Thu, Jun 29, 2023 at 11:42:49PM +0000, Sami Tolvanen wrote:

> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index b54a830eb5c6..20a40927175e 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -44,6 +44,7 @@ config RISCV
>  	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
>  	select ARCH_SUPPORTS_HUGETLBFS if MMU
>  	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> +	select ARCH_USES_CFI_TRAPS if CFI_CLANG

Could you please add new entries in alphanumerical order?

>  	select ARCH_USE_MEMTEST
>  	select ARCH_USE_QUEUED_RWLOCKS
>  	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU

> diff --git a/arch/riscv/include/asm/insn.h b/arch/riscv/include/asm/insn.h
> index 8d5c84f2d5ef..45bc485fcf3f 100644
> --- a/arch/riscv/include/asm/insn.h
> +++ b/arch/riscv/include/asm/insn.h
> @@ -63,6 +63,7 @@
>  #define RVG_RS1_OPOFF		15
>  #define RVG_RS2_OPOFF		20
>  #define RVG_RD_OPOFF		7
> +#define RVG_RS1_MASK		GENMASK(4, 0)
>  #define RVG_RD_MASK		GENMASK(4, 0)
>  
>  /* The bit field of immediate value in RVC J instruction */
> @@ -129,6 +130,7 @@
>  #define RVC_C2_RS1_OPOFF	7
>  #define RVC_C2_RS2_OPOFF	2
>  #define RVC_C2_RD_OPOFF		7
> +#define RVC_C2_RS1_MASK		GENMASK(4, 0)
>  
>  /* parts of opcode for RVG*/
>  #define RVG_OPCODE_FENCE	0x0f
> @@ -258,6 +260,10 @@ static __always_inline bool riscv_insn_is_branch(u32 code)
>  #define RV_X(X, s, mask)  (((X) >> (s)) & (mask))
>  #define RVC_X(X, s, mask) RV_X(X, s, mask)
>  
> +#define RV_EXTRACT_RS1_REG(x) \
> +	({typeof(x) x_ = (x); \
> +	(RV_X(x_, RVG_RS1_OPOFF, RVG_RS1_MASK)); })
> +
>  #define RV_EXTRACT_RD_REG(x) \
>  	({typeof(x) x_ = (x); \
>  	(RV_X(x_, RVG_RD_OPOFF, RVG_RD_MASK)); })
> @@ -285,6 +291,10 @@ static __always_inline bool riscv_insn_is_branch(u32 code)
>  	(RV_X(x_, RV_B_IMM_11_OPOFF, RV_B_IMM_11_MASK) << RV_B_IMM_11_OFF) | \
>  	(RV_IMM_SIGN(x_) << RV_B_IMM_SIGN_OFF); })
>  
> +#define RVC_EXTRACT_C2_RS1_REG(x) \
> +	({typeof(x) x_ = (x); \
> +	(RV_X(x_, RVC_C2_RS1_OPOFF, RVC_C2_RS1_MASK)); })
> +
>  #define RVC_EXTRACT_JTYPE_IMM(x) \
>  	({typeof(x) x_ = (x); \
>  	(RVC_X(x_, RVC_J_IMM_3_1_OPOFF, RVC_J_IMM_3_1_MASK) << RVC_J_IMM_3_1_OFF) | \

I was surprised that we didn't have these bits before, had to go
looking. Think the optprobes series had handrolled copies of these,
which is probably the source of my surprise.

Reviewed-by: Conor Dooley <conor.dooley@...rochip.com> # ISA bits

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