linux-kernel - [tip: x86/percpu] x86/callthunks: Fix and unify call thunks assembly snippets

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Message-ID: <170137899220.398.1284129355490971042.tip-bot2@tip-bot2>
Date:   Thu, 30 Nov 2023 21:16:32 -0000
From:   "tip-bot2 for Uros Bizjak" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Uros Bizjak <ubizjak@...il.com>, Ingo Molnar <mingo@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/percpu] x86/callthunks: Fix and unify call thunks assembly snippets

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

Commit-ID:     2adeed985a42ff3334e6898c8c0827e7626c1336
Gitweb:        https://git.kernel.org/tip/2adeed985a42ff3334e6898c8c0827e7626c1336
Author:        Uros Bizjak <ubizjak@...il.com>
AuthorDate:    Sun, 05 Nov 2023 22:34:37 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 30 Nov 2023 20:06:17 +01:00

x86/callthunks: Fix and unify call thunks assembly snippets

Currently thunk debug macros explicitly define %gs: segment register
prefix for their percpu variables. This is not compatible with
!CONFIG_SMP, which requires non-prefixed percpu variables.

Fix call thunks debug macros to use PER_CPU_VAR macro from percpu.h
to conditionally use %gs: segment register prefix, depending on
CONFIG_SMP.

Finally, unify ASM_ prefixed assembly macros with their non-prefixed
variants. With support of %rip-relative relocations in place, call
thunk templates allow %rip-relative addressing, so unified assembly
snippet can be used everywhere.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20231105213731.1878100-4-ubizjak@gmail.com
---
 arch/x86/include/asm/nospec-branch.h | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c55cc24..65fbf6b 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -59,13 +59,13 @@
 
 #ifdef CONFIG_CALL_THUNKS_DEBUG
 # define CALL_THUNKS_DEBUG_INC_CALLS				\
-	incq	%gs:__x86_call_count;
+	incq	PER_CPU_VAR(__x86_call_count);
 # define CALL_THUNKS_DEBUG_INC_RETS				\
-	incq	%gs:__x86_ret_count;
+	incq	PER_CPU_VAR(__x86_ret_count);
 # define CALL_THUNKS_DEBUG_INC_STUFFS				\
-	incq	%gs:__x86_stuffs_count;
+	incq	PER_CPU_VAR(__x86_stuffs_count);
 # define CALL_THUNKS_DEBUG_INC_CTXSW				\
-	incq	%gs:__x86_ctxsw_count;
+	incq	PER_CPU_VAR(__x86_ctxsw_count);
 #else
 # define CALL_THUNKS_DEBUG_INC_CALLS
 # define CALL_THUNKS_DEBUG_INC_RETS
@@ -80,9 +80,6 @@
 #define CREDIT_CALL_DEPTH					\
 	movq	$-1, PER_CPU_VAR(pcpu_hot + X86_call_depth);
 
-#define ASM_CREDIT_CALL_DEPTH					\
-	movq	$-1, PER_CPU_VAR(pcpu_hot + X86_call_depth);
-
 #define RESET_CALL_DEPTH					\
 	xor	%eax, %eax;					\
 	bts	$63, %rax;					\
@@ -95,20 +92,14 @@
 	CALL_THUNKS_DEBUG_INC_CALLS
 
 #define INCREMENT_CALL_DEPTH					\
-	sarq	$5, %gs:pcpu_hot + X86_call_depth;		\
-	CALL_THUNKS_DEBUG_INC_CALLS
-
-#define ASM_INCREMENT_CALL_DEPTH				\
 	sarq	$5, PER_CPU_VAR(pcpu_hot + X86_call_depth);	\
 	CALL_THUNKS_DEBUG_INC_CALLS
 
 #else
 #define CREDIT_CALL_DEPTH
-#define ASM_CREDIT_CALL_DEPTH
 #define RESET_CALL_DEPTH
-#define INCREMENT_CALL_DEPTH
-#define ASM_INCREMENT_CALL_DEPTH
 #define RESET_CALL_DEPTH_FROM_CALL
+#define INCREMENT_CALL_DEPTH
 #endif
 
 /*
@@ -158,7 +149,7 @@
 	jnz	771b;					\
 	/* barrier for jnz misprediction */		\
 	lfence;						\
-	ASM_CREDIT_CALL_DEPTH				\
+	CREDIT_CALL_DEPTH				\
 	CALL_THUNKS_DEBUG_INC_CTXSW
 #else
 /*
@@ -325,7 +316,7 @@
 .macro CALL_DEPTH_ACCOUNT
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 	ALTERNATIVE "",							\
-		    __stringify(ASM_INCREMENT_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		    __stringify(INCREMENT_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
 #endif
 .endm