linux-kernel - [PATCH 1/9] Macros to override naming of percpu symbols and sections

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Message-Id: <20200722164424.42225-2-dbrazdil@google.com>
Date:   Wed, 22 Jul 2020 17:44:16 +0100
From:   David Brazdil <dbrazdil@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>, Arnd Bergmann <arnd@...db.de>
Cc:     James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, linux-arch@...r.kernel.org,
        kernel-team@...gle.com, David Brazdil <dbrazdil@...gle.com>
Subject: [PATCH 1/9] Macros to override naming of percpu symbols and sections

Modify generic linker script macros to generate section/symbol names for
percpu area using overridable macros. No functional changes.

This will allow arm64 linker script to define a second KVM-specific percpu
data section using the generic PERCPU_SECTION macro.

Signed-off-by: David Brazdil <dbrazdil@...gle.com>
---
 include/asm-generic/vmlinux.lds.h | 40 +++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index db600ef218d7..1bfc002ecfce 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -892,6 +892,20 @@
 #define INIT_RAM_FS
 #endif
 
+/*
+ * Macros to override the naming of percpu symbols and sections.
+ * Used by arm64 linker script to define a separate percpu area for KVM.
+ */
+#define PERCPU_SECTION_BASE_NAME .data..percpu
+
+#ifndef PERCPU_SECTION_NAME
+#define PERCPU_SECTION_NAME(suffix) PERCPU_SECTION_BASE_NAME ## suffix
+#endif
+
+#ifndef PERCPU_SYMBOL_NAME
+#define PERCPU_SYMBOL_NAME(name) name
+#endif
+
 /*
  * Memory encryption operates on a page basis. Since we need to clear
  * the memory encryption mask for this section, it needs to be aligned
@@ -903,7 +917,7 @@
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 #define PERCPU_DECRYPTED_SECTION					\
 	. = ALIGN(PAGE_SIZE);						\
-	*(.data..percpu..decrypted)					\
+	*(PERCPU_SECTION_NAME(..decrypted))				\
 	. = ALIGN(PAGE_SIZE);
 #else
 #define PERCPU_DECRYPTED_SECTION
@@ -947,17 +961,17 @@
  * sharing between subsections for different purposes.
  */
 #define PERCPU_INPUT(cacheline)						\
-	__per_cpu_start = .;						\
-	*(.data..percpu..first)						\
+	PERCPU_SYMBOL_NAME(__per_cpu_start) = .;			\
+	*(PERCPU_SECTION_NAME(..first))					\
 	. = ALIGN(PAGE_SIZE);						\
-	*(.data..percpu..page_aligned)					\
+	*(PERCPU_SECTION_NAME(..page_aligned))				\
 	. = ALIGN(cacheline);						\
-	*(.data..percpu..read_mostly)					\
+	*(PERCPU_SECTION_NAME(..read_mostly))				\
 	. = ALIGN(cacheline);						\
-	*(.data..percpu)						\
-	*(.data..percpu..shared_aligned)				\
+	*(PERCPU_SECTION_NAME())					\
+	*(PERCPU_SECTION_NAME(..shared_aligned))			\
 	PERCPU_DECRYPTED_SECTION					\
-	__per_cpu_end = .;
+	PERCPU_SYMBOL_NAME(__per_cpu_end) = .;
 
 /**
  * PERCPU_VADDR - define output section for percpu area
@@ -984,11 +998,11 @@
  * address, use PERCPU_SECTION.
  */
 #define PERCPU_VADDR(cacheline, vaddr, phdr)				\
-	__per_cpu_load = .;						\
-	.data..percpu vaddr : AT(__per_cpu_load - LOAD_OFFSET) {	\
+	PERCPU_SYMBOL_NAME(__per_cpu_load) = .;				\
+	PERCPU_SECTION_NAME() vaddr : AT(PERCPU_SYMBOL_NAME(__per_cpu_load) - LOAD_OFFSET) { \
 		PERCPU_INPUT(cacheline)					\
 	} phdr								\
-	. = __per_cpu_load + SIZEOF(.data..percpu);
+	. = PERCPU_SYMBOL_NAME(__per_cpu_load) + SIZEOF(PERCPU_SECTION_NAME());
 
 /**
  * PERCPU_SECTION - define output section for percpu area, simple version
@@ -1004,8 +1018,8 @@
  */
 #define PERCPU_SECTION(cacheline)					\
 	. = ALIGN(PAGE_SIZE);						\
-	.data..percpu	: AT(ADDR(.data..percpu) - LOAD_OFFSET) {	\
-		__per_cpu_load = .;					\
+	PERCPU_SECTION_NAME() : AT(ADDR(PERCPU_SECTION_NAME()) - LOAD_OFFSET) { \
+		PERCPU_SYMBOL_NAME(__per_cpu_load) = .;			\
 		PERCPU_INPUT(cacheline)					\
 	}
 
-- 
2.27.0