[PATCH v2] riscv: jump_label: mark arguments as const to satisfy asm constraints

[PATCH v2] riscv: jump_label: mark arguments as const to satisfy asm constraints

[Jisheng Zhang]

Samuel reported that the static branch usage in cpu_relax() breaks
building with CONFIG_CC_OPTIMIZE_FOR_SIZE:

In file included from <command-line>:
./arch/riscv/include/asm/jump_label.h: In function 'cpu_relax':
././include/linux/compiler_types.h:285:33: warning: 'asm' operand 0
probably does not match constraints
  285 | #define asm_volatile_goto(x...) asm goto(x)
      |                                 ^~~
./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
'asm_volatile_goto'
   41 |         asm_volatile_goto(
      |         ^~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:285:33: error: impossible constraint
in 'asm'
  285 | #define asm_volatile_goto(x...) asm goto(x)
      |                                 ^~~
./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
'asm_volatile_goto'
   41 |         asm_volatile_goto(
      |         ^~~~~~~~~~~~~~~~~
make[1]: *** [scripts/Makefile.build:249:
arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
make: *** [arch/riscv/Makefile:128: vdso_prepare] Error 2

Maybe "-Os" prevents GCC from detecting that the key/branch arguments
can be treated as constants and used as immediate operands. Inspired
by x86's commit 864b435514b2("x86/jump_label: Mark arguments as const to
satisfy asm constraints"), and as pointed out by Steven: "The "i"
constraint needs to be a constant.", let's do similar modifications to
riscv.

Tested by CC_OPTIMIZE_FOR_SIZE + gcc and CC_OPTIMIZE_FOR_SIZE + clang.

Link: https://lore.kernel.org/linux-riscv/20220922060958.44203-1-samuel@sholland.org/
Link: https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/
Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
Reported-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---

since v1:
 - add Reported-by, Reviewed-by, Fixes and Link tag

 arch/riscv/include/asm/jump_label.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
index 38af2ec7b9bf..6d58bbb5da46 100644
--- a/arch/riscv/include/asm/jump_label.h
+++ b/arch/riscv/include/asm/jump_label.h
@@ -14,8 +14,8 @@
 
 #define JUMP_LABEL_NOP_SIZE 4
 
-static __always_inline bool arch_static_branch(struct static_key *key,
-					       bool branch)
+static __always_inline bool arch_static_branch(struct static_key * const key,
+					       const bool branch)
 {
 	asm_volatile_goto(
 		"	.option push				\n\t"
@@ -35,8 +35,8 @@ static __always_inline bool arch_static_branch(struct static_key *key,
 	return true;
 }
 
-static __always_inline bool arch_static_branch_jump(struct static_key *key,
-						    bool branch)
+static __always_inline bool arch_static_branch_jump(struct static_key * const key,
+						    const bool branch)
 {
 	asm_volatile_goto(
 		"	.option push				\n\t"
-- 
2.37.2


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Re: [PATCH v2] riscv: jump_label: mark arguments as const to satisfy asm constraints

[Heiko Stuebner]

Am Samstag, 8. Oktober 2022, 16:54:37 CEST schrieb Jisheng Zhang:
> Samuel reported that the static branch usage in cpu_relax() breaks
> building with CONFIG_CC_OPTIMIZE_FOR_SIZE:
> 
> In file included from <command-line>:
> ./arch/riscv/include/asm/jump_label.h: In function 'cpu_relax':
> ././include/linux/compiler_types.h:285:33: warning: 'asm' operand 0
> probably does not match constraints
>   285 | #define asm_volatile_goto(x...) asm goto(x)
>       |                                 ^~~
> ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> 'asm_volatile_goto'
>    41 |         asm_volatile_goto(
>       |         ^~~~~~~~~~~~~~~~~
> ././include/linux/compiler_types.h:285:33: error: impossible constraint
> in 'asm'
>   285 | #define asm_volatile_goto(x...) asm goto(x)
>       |                                 ^~~
> ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> 'asm_volatile_goto'
>    41 |         asm_volatile_goto(
>       |         ^~~~~~~~~~~~~~~~~
> make[1]: *** [scripts/Makefile.build:249:
> arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
> make: *** [arch/riscv/Makefile:128: vdso_prepare] Error 2
> 
> Maybe "-Os" prevents GCC from detecting that the key/branch arguments
> can be treated as constants and used as immediate operands. Inspired
> by x86's commit 864b435514b2("x86/jump_label: Mark arguments as const to
> satisfy asm constraints"), and as pointed out by Steven: "The "i"
> constraint needs to be a constant.", let's do similar modifications to
> riscv.
> 
> Tested by CC_OPTIMIZE_FOR_SIZE + gcc and CC_OPTIMIZE_FOR_SIZE + clang.
> 
> Link: https://lore.kernel.org/linux-riscv/20220922060958.44203-1-samuel@sholland.org/
> Link: https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/
> Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
> Reported-by: Samuel Holland <samuel@sholland.org>
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

I ran into the same build-issue when enabling CC_OPTIMIZE_FOR_SIZE
and this patch fixes it, so

Tested-by: Heiko Stuebner <heiko@sntech.de>





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Re: [PATCH v2] riscv: jump_label: mark arguments as const to satisfy asm constraints

[Conor Dooley]

Hey Jisheng,
LKP reported an error that seems to only have gone to myself & Samuel,
but the branch it's complaining about is your v1:
https://lore.kernel.org/lkml/202210122123.Cc4FPShJ-lkp@intel.com/

Any idea what the story is here?

Thanks,
Conor.

On Sat, Oct 08, 2022 at 10:54:37PM +0800, Jisheng Zhang wrote:
> Samuel reported that the static branch usage in cpu_relax() breaks
> building with CONFIG_CC_OPTIMIZE_FOR_SIZE:
> 
> In file included from <command-line>:
> ./arch/riscv/include/asm/jump_label.h: In function 'cpu_relax':
> ././include/linux/compiler_types.h:285:33: warning: 'asm' operand 0
> probably does not match constraints
>   285 | #define asm_volatile_goto(x...) asm goto(x)
>       |                                 ^~~
> ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> 'asm_volatile_goto'
>    41 |         asm_volatile_goto(
>       |         ^~~~~~~~~~~~~~~~~
> ././include/linux/compiler_types.h:285:33: error: impossible constraint
> in 'asm'
>   285 | #define asm_volatile_goto(x...) asm goto(x)
>       |                                 ^~~
> ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> 'asm_volatile_goto'
>    41 |         asm_volatile_goto(
>       |         ^~~~~~~~~~~~~~~~~
> make[1]: *** [scripts/Makefile.build:249:
> arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
> make: *** [arch/riscv/Makefile:128: vdso_prepare] Error 2
> 
> Maybe "-Os" prevents GCC from detecting that the key/branch arguments
> can be treated as constants and used as immediate operands. Inspired
> by x86's commit 864b435514b2("x86/jump_label: Mark arguments as const to
> satisfy asm constraints"), and as pointed out by Steven: "The "i"
> constraint needs to be a constant.", let's do similar modifications to
> riscv.
> 
> Tested by CC_OPTIMIZE_FOR_SIZE + gcc and CC_OPTIMIZE_FOR_SIZE + clang.
> 
> Link: https://lore.kernel.org/linux-riscv/20220922060958.44203-1-samuel@sholland.org/
> Link: https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/
> Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
> Reported-by: Samuel Holland <samuel@sholland.org>
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
> 
> since v1:
>  - add Reported-by, Reviewed-by, Fixes and Link tag
> 
>  arch/riscv/include/asm/jump_label.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
> index 38af2ec7b9bf..6d58bbb5da46 100644
> --- a/arch/riscv/include/asm/jump_label.h
> +++ b/arch/riscv/include/asm/jump_label.h
> @@ -14,8 +14,8 @@
>  
>  #define JUMP_LABEL_NOP_SIZE 4
>  
> -static __always_inline bool arch_static_branch(struct static_key *key,
> -					       bool branch)
> +static __always_inline bool arch_static_branch(struct static_key * const key,
> +					       const bool branch)
>  {
>  	asm_volatile_goto(
>  		"	.option push				\n\t"
> @@ -35,8 +35,8 @@ static __always_inline bool arch_static_branch(struct static_key *key,
>  	return true;
>  }
>  
> -static __always_inline bool arch_static_branch_jump(struct static_key *key,
> -						    bool branch)
> +static __always_inline bool arch_static_branch_jump(struct static_key * const key,
> +						    const bool branch)
>  {
>  	asm_volatile_goto(
>  		"	.option push				\n\t"
> -- 
> 2.37.2
> 

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Re: [PATCH v2] riscv: jump_label: mark arguments as const to satisfy asm constraints

[Jisheng Zhang]

On Wed, Oct 12, 2022 at 02:28:16PM +0100, Conor Dooley wrote:
> Hey Jisheng,

Hi Conor,

> LKP reported an error that seems to only have gone to myself & Samuel,
> but the branch it's complaining about is your v1:
> https://lore.kernel.org/lkml/202210122123.Cc4FPShJ-lkp@intel.com/
> 
> Any idea what the story is here?

I tried the config in the link, I can reproduce the build error w/
and w/o the my patch. So I think the root cause of the build error
is a different story. I have a fix in local repo, will send it out
soon.

Thanks

> 
> Thanks,
> Conor.
> 
> On Sat, Oct 08, 2022 at 10:54:37PM +0800, Jisheng Zhang wrote:
> > Samuel reported that the static branch usage in cpu_relax() breaks
> > building with CONFIG_CC_OPTIMIZE_FOR_SIZE:
> > 
> > In file included from <command-line>:
> > ./arch/riscv/include/asm/jump_label.h: In function 'cpu_relax':
> > ././include/linux/compiler_types.h:285:33: warning: 'asm' operand 0
> > probably does not match constraints
> >   285 | #define asm_volatile_goto(x...) asm goto(x)
> >       |                                 ^~~
> > ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> > 'asm_volatile_goto'
> >    41 |         asm_volatile_goto(
> >       |         ^~~~~~~~~~~~~~~~~
> > ././include/linux/compiler_types.h:285:33: error: impossible constraint
> > in 'asm'
> >   285 | #define asm_volatile_goto(x...) asm goto(x)
> >       |                                 ^~~
> > ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> > 'asm_volatile_goto'
> >    41 |         asm_volatile_goto(
> >       |         ^~~~~~~~~~~~~~~~~
> > make[1]: *** [scripts/Makefile.build:249:
> > arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
> > make: *** [arch/riscv/Makefile:128: vdso_prepare] Error 2
> > 
> > Maybe "-Os" prevents GCC from detecting that the key/branch arguments
> > can be treated as constants and used as immediate operands. Inspired
> > by x86's commit 864b435514b2("x86/jump_label: Mark arguments as const to
> > satisfy asm constraints"), and as pointed out by Steven: "The "i"
> > constraint needs to be a constant.", let's do similar modifications to
> > riscv.
> > 
> > Tested by CC_OPTIMIZE_FOR_SIZE + gcc and CC_OPTIMIZE_FOR_SIZE + clang.
> > 
> > Link: https://lore.kernel.org/linux-riscv/20220922060958.44203-1-samuel@sholland.org/
> > Link: https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/
> > Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
> > Reported-by: Samuel Holland <samuel@sholland.org>
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> > ---
> > 
> > since v1:
> >  - add Reported-by, Reviewed-by, Fixes and Link tag
> > 
> >  arch/riscv/include/asm/jump_label.h | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
> > index 38af2ec7b9bf..6d58bbb5da46 100644
> > --- a/arch/riscv/include/asm/jump_label.h
> > +++ b/arch/riscv/include/asm/jump_label.h
> > @@ -14,8 +14,8 @@
> >  
> >  #define JUMP_LABEL_NOP_SIZE 4
> >  
> > -static __always_inline bool arch_static_branch(struct static_key *key,
> > -					       bool branch)
> > +static __always_inline bool arch_static_branch(struct static_key * const key,
> > +					       const bool branch)
> >  {
> >  	asm_volatile_goto(
> >  		"	.option push				\n\t"
> > @@ -35,8 +35,8 @@ static __always_inline bool arch_static_branch(struct static_key *key,
> >  	return true;
> >  }
> >  
> > -static __always_inline bool arch_static_branch_jump(struct static_key *key,
> > -						    bool branch)
> > +static __always_inline bool arch_static_branch_jump(struct static_key * const key,
> > +						    const bool branch)
> >  {
> >  	asm_volatile_goto(
> >  		"	.option push				\n\t"
> > -- 
> > 2.37.2
> > 

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Re: [PATCH v2] riscv: jump_label: mark arguments as const to satisfy asm constraints

[Palmer Dabbelt]

On Sat, 8 Oct 2022 22:54:37 +0800, Jisheng Zhang wrote:
> Samuel reported that the static branch usage in cpu_relax() breaks
> building with CONFIG_CC_OPTIMIZE_FOR_SIZE:
> 
> In file included from <command-line>:
> ./arch/riscv/include/asm/jump_label.h: In function 'cpu_relax':
> ././include/linux/compiler_types.h:285:33: warning: 'asm' operand 0
> probably does not match constraints
>   285 | #define asm_volatile_goto(x...) asm goto(x)
>       |                                 ^~~
> ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> 'asm_volatile_goto'
>    41 |         asm_volatile_goto(
>       |         ^~~~~~~~~~~~~~~~~
> ././include/linux/compiler_types.h:285:33: error: impossible constraint
> in 'asm'
>   285 | #define asm_volatile_goto(x...) asm goto(x)
>       |                                 ^~~
> ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro
> 'asm_volatile_goto'
>    41 |         asm_volatile_goto(
>       |         ^~~~~~~~~~~~~~~~~
> make[1]: *** [scripts/Makefile.build:249:
> arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
> make: *** [arch/riscv/Makefile:128: vdso_prepare] Error 2
> 
> [...]

Applied, thanks!

[1/1] riscv: jump_label: mark arguments as const to satisfy asm constraints
      commit: 89fd4a1df829187d4d35f6a520cc531de622e6f0

Best regards,
-- 
Palmer Dabbelt <palmer@rivosinc.com>

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