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

From: Charlie Jenkins <charlie@rivosinc.com>
To: Andrew Jones <ajones@ventanamicro.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Ben Dooks <ben.dooks@codethink.co.uk>,
	Pasha Bouzarjomehri <pasha@rivosinc.com>,
	Emil Renner Berthing <emil.renner.berthing@canonical.com>,
	Alexandre Ghiti <alexghiti@rivosinc.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	Jason Baron <jbaron@akamai.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org
Subject: Re: [PATCH v9 1/2] riscv: Move nop definition to insn-def.h
Date: Wed, 19 Mar 2025 10:24:42 -0700	[thread overview]
Message-ID: <Z9r92tCdsjoJTQ88@ghost> (raw)
In-Reply-To: <20250319-3bf29b05bf02bfdaa32b261c@orel>

On Wed, Mar 19, 2025 at 04:27:39PM +0100, Andrew Jones wrote:
> 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.

Sure, I don't have a strong opinion about this. I was debating adding
the .4byte version also but decided against it because it isn't being
used yet, I will add it.

- Charlie

> 
> 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
> > 
> > 
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv

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