linux-kernel - [PATCH] runtime constants: move list of constants to vmlinux.lds.h

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Message-Id: <20240730-runtime-constants-refactor-v1-1-90c2c884c3f8@google.com>
Date: Tue, 30 Jul 2024 22:15:16 +0200
From: Jann Horn <jannh@...gle.com>
To: Arnd Bergmann <arnd@...db.de>, 
 Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>, Heiko Carstens <hca@...ux.ibm.com>, 
 Vasily Gorbik <gor@...ux.ibm.com>, 
 Alexander Gordeev <agordeev@...ux.ibm.com>, 
 Christian Borntraeger <borntraeger@...ux.ibm.com>, 
 Sven Schnelle <svens@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>, 
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
 "H. Peter Anvin" <hpa@...or.com>, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org, 
 linux-arch@...r.kernel.org, Jann Horn <jannh@...gle.com>
Subject: [PATCH] runtime constants: move list of constants to vmlinux.lds.h

Refactor the list of constant variables into a macro.
This should make it easier to add more constants in the future.

Signed-off-by: Jann Horn <jannh@...gle.com>
---
I'm not sure whose tree this has to go through - I guess Arnd's?
---
 arch/arm64/kernel/vmlinux.lds.S   | 3 +--
 arch/s390/kernel/vmlinux.lds.S    | 3 +--
 arch/x86/kernel/vmlinux.lds.S     | 3 +--
 include/asm-generic/vmlinux.lds.h | 4 ++++
 4 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 55a8e310ea12..58d89d997d05 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -261,14 +261,13 @@ SECTIONS
 		*(.init.altinstructions .init.bss)	/* from the EFI stub */
 	}
 	.exit.data : {
 		EXIT_DATA
 	}
 
-	RUNTIME_CONST(shift, d_hash_shift)
-	RUNTIME_CONST(ptr, dentry_hashtable)
+	RUNTIME_CONST_VARIABLES
 
 	PERCPU_SECTION(L1_CACHE_BYTES)
 	HYPERVISOR_PERCPU_SECTION
 
 	HYPERVISOR_RELOC_SECTION
 
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 975c654cf5a5..3e8ebf1d64c5 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -187,14 +187,13 @@ SECTIONS
 	_eamode31 = .;
 
 	/* early.c uses stsi, which requires page aligned data. */
 	. = ALIGN(PAGE_SIZE);
 	INIT_DATA_SECTION(0x100)
 
-	RUNTIME_CONST(shift, d_hash_shift)
-	RUNTIME_CONST(ptr, dentry_hashtable)
+	RUNTIME_CONST_VARIABLES
 
 	PERCPU_SECTION(0x100)
 
 	. = ALIGN(PAGE_SIZE);
 	__init_end = .;		/* freed after init ends here */
 
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 6e73403e874f..6726be89b7a6 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -354,14 +354,13 @@ SECTIONS
 	}
 
 #if !defined(CONFIG_X86_64) || !defined(CONFIG_SMP)
 	PERCPU_SECTION(INTERNODE_CACHE_BYTES)
 #endif
 
-	RUNTIME_CONST(shift, d_hash_shift)
-	RUNTIME_CONST(ptr, dentry_hashtable)
+	RUNTIME_CONST_VARIABLES
 
 	. = ALIGN(PAGE_SIZE);
 
 	/* freed after init ends here */
 	.init.end : AT(ADDR(.init.end) - LOAD_OFFSET) {
 		__init_end = .;
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index ad6afc5c4918..54986eac2f73 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -916,12 +916,16 @@
 #define RUNTIME_CONST(t,x)						\
 	. = ALIGN(8);							\
 	RUNTIME_NAME(t,x) : AT(ADDR(RUNTIME_NAME(t,x)) - LOAD_OFFSET) {	\
 		*(RUNTIME_NAME(t,x));					\
 	}
 
+#define RUNTIME_CONST_VARIABLES						\
+		RUNTIME_CONST(shift, d_hash_shift)			\
+		RUNTIME_CONST(ptr, dentry_hashtable)
+
 /* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */
 #define KUNIT_TABLE()							\
 		. = ALIGN(8);						\
 		BOUNDED_SECTION_POST_LABEL(.kunit_test_suites, __kunit_suites, _start, _end)
 
 /* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */

---
base-commit: 94ede2a3e9135764736221c080ac7c0ad993dc2d
change-id: 20240730-runtime-constants-refactor-309f966d4100
-- 
Jann Horn <jannh@...gle.com>