[PATCH] x86/speculation: Remove the extra ifdef around CALL_NOSPEC

[PATCH] x86/speculation: Remove the extra ifdef around CALL_NOSPEC

[Pawan Gupta]

Commit 010c4a461c1d ("x86/speculation: Simplify and make CALL_NOSPEC
consistent") added an ifdef CONFIG_MITIGATION_RETPOLINE around the
CALL_NOSPEC definition. This is not required as this code is already under
a larger ifdef.

Remove the extra ifdef, no functional change.

vmlinux size remains same before and after this change.

CONFIG_MITIGATION_RETPOLINE=y:
    text	   data	    bss	    dec		hex	filename
25434752	7342290	2301212	35078254	217406e	vmlinux.before
25434752	7342290	2301212	35078254	217406e	vmlinux.after

 # CONFIG_MITIGATION_RETPOLINE is not set:
    text	   data	    bss	    dec		hex	filename
22943094	6214994	1550152	30708240	1d49210	vmlinux.before
22943094	6214994	1550152	30708240	1d49210	vmlinux.after

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index aee26bb8230f861dda7a4a568159d4cf77df45f6..c4816719150dce9f5ecc676cdcf38356fc96d166 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -434,12 +434,8 @@ static inline void call_depth_return_thunk(void) {}
  * Inline asm uses the %V modifier which is only in newer GCC
  * which is ensured when CONFIG_MITIGATION_RETPOLINE is defined.
  */
-#ifdef CONFIG_MITIGATION_RETPOLINE
 #define CALL_NOSPEC	__CS_PREFIX("%V[thunk_target]")	\
 			"call __x86_indirect_thunk_%V[thunk_target]\n"
-#else
-#define CALL_NOSPEC	"call *%[thunk_target]\n"
-#endif
 
 # define THUNK_TARGET(addr) [thunk_target] "r" (addr)
 

---
base-commit: 4701f33a10702d5fc577c32434eb62adde0a1ae1
change-id: 20250320-call-nospec-extra-ifdef-64b4942e7597

Best regards,
-- 
Thanks,
Pawan

Re: [PATCH] x86/speculation: Remove the extra ifdef around CALL_NOSPEC

[Josh Poimboeuf]

On Thu, Mar 20, 2025 at 11:13:15AM -0700, Pawan Gupta wrote:
> Commit 010c4a461c1d ("x86/speculation: Simplify and make CALL_NOSPEC
> consistent") added an ifdef CONFIG_MITIGATION_RETPOLINE around the
> CALL_NOSPEC definition. This is not required as this code is already under
> a larger ifdef.
> 
> Remove the extra ifdef, no functional change.
> 
> vmlinux size remains same before and after this change.
> 
> CONFIG_MITIGATION_RETPOLINE=y:
>     text	   data	    bss	    dec		hex	filename
> 25434752	7342290	2301212	35078254	217406e	vmlinux.before
> 25434752	7342290	2301212	35078254	217406e	vmlinux.after
> 
>  # CONFIG_MITIGATION_RETPOLINE is not set:
>     text	   data	    bss	    dec		hex	filename
> 22943094	6214994	1550152	30708240	1d49210	vmlinux.before
> 22943094	6214994	1550152	30708240	1d49210	vmlinux.after
> 
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>

-- 
Josh

Re: [PATCH] x86/speculation: Remove the extra ifdef around CALL_NOSPEC

[Pawan Gupta]

On Fri, Mar 21, 2025 at 12:15:59AM -0700, Josh Poimboeuf wrote:
> On Thu, Mar 20, 2025 at 11:13:15AM -0700, Pawan Gupta wrote:
> > Commit 010c4a461c1d ("x86/speculation: Simplify and make CALL_NOSPEC
> > consistent") added an ifdef CONFIG_MITIGATION_RETPOLINE around the
> > CALL_NOSPEC definition. This is not required as this code is already under
> > a larger ifdef.
> > 
> > Remove the extra ifdef, no functional change.
> > 
> > vmlinux size remains same before and after this change.
> > 
> > CONFIG_MITIGATION_RETPOLINE=y:
> >     text	   data	    bss	    dec		hex	filename
> > 25434752	7342290	2301212	35078254	217406e	vmlinux.before
> > 25434752	7342290	2301212	35078254	217406e	vmlinux.after
> > 
> >  # CONFIG_MITIGATION_RETPOLINE is not set:
> >     text	   data	    bss	    dec		hex	filename
> > 22943094	6214994	1550152	30708240	1d49210	vmlinux.before
> > 22943094	6214994	1550152	30708240	1d49210	vmlinux.after
> > 
> > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
> 
> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>

Thanks!

[tip: x86/urgent] x86/speculation: Remove the extra #ifdef around CALL_NOSPEC

[tip-bot2 for Pawan Gupta]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     c8c81458863ab686cda4fe1e603fccaae0f12460
Gitweb:        https://git.kernel.org/tip/c8c81458863ab686cda4fe1e603fccaae0f12460
Author:        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
AuthorDate:    Thu, 20 Mar 2025 11:13:15 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 22 Mar 2025 08:41:47 +01:00

x86/speculation: Remove the extra #ifdef around CALL_NOSPEC

Commit:

  010c4a461c1d ("x86/speculation: Simplify and make CALL_NOSPEC consistent")

added an #ifdef CONFIG_MITIGATION_RETPOLINE around the CALL_NOSPEC definition.
This is not required as this code is already under a larger #ifdef.

Remove the extra #ifdef, no functional change.

vmlinux size remains same before and after this change:

 CONFIG_MITIGATION_RETPOLINE=y:
      text       data        bss         dec        hex    filename
  25434752    7342290    2301212    35078254    217406e    vmlinux.before
  25434752    7342290    2301212    35078254    217406e    vmlinux.after

 # CONFIG_MITIGATION_RETPOLINE is not set:
      text       data        bss         dec        hex    filename
  22943094    6214994    1550152    30708240    1d49210    vmlinux.before
  22943094    6214994    1550152    30708240    1d49210    vmlinux.after

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20250320-call-nospec-extra-ifdef-v1-1-d9b084d24820@linux.intel.com
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 804b66a..29ea8fb 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -435,12 +435,8 @@ static inline void call_depth_return_thunk(void) {}
  * Inline asm uses the %V modifier which is only in newer GCC
  * which is ensured when CONFIG_MITIGATION_RETPOLINE is defined.
  */
-#ifdef CONFIG_MITIGATION_RETPOLINE
 #define CALL_NOSPEC	__CS_PREFIX("%V[thunk_target]")	\
 			"call __x86_indirect_thunk_%V[thunk_target]\n"
-#else
-#define CALL_NOSPEC	"call *%[thunk_target]\n"
-#endif
 
 # define THUNK_TARGET(addr) [thunk_target] "r" (addr)