Re: [PATCH v9 1/2] riscv: Move nop definition to insn-def.h

[Andrew Jones <ajones@ventanamicro.com>]

On Tue, Mar 18, 2025 at 05:38:45PM -0700, Charlie Jenkins wrote:
> We have duplicated the definition of the nop instruction in ftrace.h and
> in jump_label.c. Move this definition into the generic file insn-def.h
> so that they can share the definition with each other and with future
> files.
> 
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> ---
>  arch/riscv/include/asm/ftrace.h   | 1 -
>  arch/riscv/include/asm/insn-def.h | 2 ++
>  arch/riscv/kernel/ftrace.c        | 6 +++---
>  arch/riscv/kernel/jump_label.c    | 4 ++--
>  4 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
> index c4721ce44ca474654b37b3d51bc0a63d46bc1eff..b7f361a50f6445d02a0d88eef5547ee27c1fb52e 100644
> --- a/arch/riscv/include/asm/ftrace.h
> +++ b/arch/riscv/include/asm/ftrace.h
> @@ -79,7 +79,6 @@ struct dyn_arch_ftrace {
>  #define AUIPC_RA		(0x00000097)
>  #define JALR_T0			(0x000282e7)
>  #define AUIPC_T0		(0x00000297)
> -#define NOP4			(0x00000013)
>  
>  #define to_jalr_t0(offset)						\
>  	(((offset & JALR_OFFSET_MASK) << JALR_SHIFT) | JALR_T0)
> diff --git a/arch/riscv/include/asm/insn-def.h b/arch/riscv/include/asm/insn-def.h
> index 9a913010cdd93cdfdd93f467e7880e20cce0dd2b..0a1fc5134f29da190554c59f8cee3b5374c9aa2d 100644
> --- a/arch/riscv/include/asm/insn-def.h
> +++ b/arch/riscv/include/asm/insn-def.h
> @@ -200,4 +200,6 @@
>  #define ZAWRS_WRS_NTO	".4byte 0x00d00073"
>  #define ZAWRS_WRS_STO	".4byte 0x01d00073"
>  
> +#define RISCV_INSN_NOP4	0x00000013U

This should be _AC(0x00000013, U), but since this is the first of its kind
(all other defines are of the form ".4byte ..." -- either explicitly, like
the ones above, or through the INSN_* macros), then it feels like it
either doesn't belong here at all or that we should provide it and a
".4byte ..." version.

Thanks,
drew

> +
>  #endif /* __ASM_INSN_DEF_H */
> diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
> index 3524db5e4fa014a4594465f849d898a030bfb7b8..674dcdfae7a149c339f1e791adb450535f22991b 100644
> --- a/arch/riscv/kernel/ftrace.c
> +++ b/arch/riscv/kernel/ftrace.c
> @@ -36,7 +36,7 @@ static int ftrace_check_current_call(unsigned long hook_pos,
>  				     unsigned int *expected)
>  {
>  	unsigned int replaced[2];
> -	unsigned int nops[2] = {NOP4, NOP4};
> +	unsigned int nops[2] = {RISCV_INSN_NOP4, RISCV_INSN_NOP4};
>  
>  	/* we expect nops at the hook position */
>  	if (!expected)
> @@ -68,7 +68,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
>  				bool enable, bool ra)
>  {
>  	unsigned int call[2];
> -	unsigned int nops[2] = {NOP4, NOP4};
> +	unsigned int nops[2] = {RISCV_INSN_NOP4, RISCV_INSN_NOP4};
>  
>  	if (ra)
>  		make_call_ra(hook_pos, target, call);
> @@ -97,7 +97,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
>  int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
>  		    unsigned long addr)
>  {
> -	unsigned int nops[2] = {NOP4, NOP4};
> +	unsigned int nops[2] = {RISCV_INSN_NOP4, RISCV_INSN_NOP4};
>  
>  	if (patch_insn_write((void *)rec->ip, nops, MCOUNT_INSN_SIZE))
>  		return -EPERM;
> diff --git a/arch/riscv/kernel/jump_label.c b/arch/riscv/kernel/jump_label.c
> index 654ed159c830b3d5e34ac58bf367107066eb73a1..b4c1a6a3fbd28533552036194f27ed206bea305d 100644
> --- a/arch/riscv/kernel/jump_label.c
> +++ b/arch/riscv/kernel/jump_label.c
> @@ -11,8 +11,8 @@
>  #include <asm/bug.h>
>  #include <asm/cacheflush.h>
>  #include <asm/text-patching.h>
> +#include <asm/insn-def.h>
>  
> -#define RISCV_INSN_NOP 0x00000013U
>  #define RISCV_INSN_JAL 0x0000006fU
>  
>  bool arch_jump_label_transform_queue(struct jump_entry *entry,
> @@ -33,7 +33,7 @@ bool arch_jump_label_transform_queue(struct jump_entry *entry,
>  			(((u32)offset & GENMASK(10,  1)) << (21 -  1)) |
>  			(((u32)offset & GENMASK(20, 20)) << (31 - 20));
>  	} else {
> -		insn = RISCV_INSN_NOP;
> +		insn = RISCV_INSN_NOP4;
>  	}
>  
>  	if (early_boot_irqs_disabled) {
> 
> -- 
> 2.43.0
> 
> 
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