[PATCH v1 8/9] powerpc/vdso: Remove __kernel_datapage_offset and simplify __get_datapage()

[Christophe Leroy]

The VDSO datapage and the text pages are always located immediately
next to each other, so it can be hardcoded without an indirection
through __kernel_datapage_offset

Before:
clock-getres-realtime-coarse:    vdso: 714 nsec/call
clock-gettime-realtime-coarse:    vdso: 792 nsec/call
clock-gettime-realtime:    vdso: 1243 nsec/call

After:
clock-getres-realtime-coarse:    vdso: 699 nsec/call
clock-gettime-realtime-coarse:    vdso: 784 nsec/call
clock-gettime-realtime:    vdso: 1231 nsec/call

Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
---
 arch/powerpc/include/asm/vdso_datapage.h |  8 +++--
 arch/powerpc/kernel/vdso.c               | 37 ------------------------
 arch/powerpc/kernel/vdso32/datapage.S    |  3 --
 arch/powerpc/kernel/vdso32/vdso32.lds.S  |  7 ++---
 arch/powerpc/kernel/vdso64/datapage.S    |  3 --
 arch/powerpc/kernel/vdso64/vdso64.lds.S  |  7 ++---
 6 files changed, 9 insertions(+), 56 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
index c4d320504d26..2bc415f7714c 100644
--- a/arch/powerpc/include/asm/vdso_datapage.h
+++ b/arch/powerpc/include/asm/vdso_datapage.h
@@ -104,10 +104,12 @@ extern struct vdso_arch_data *vdso_data;
 
 .macro get_datapage ptr, tmp
 	bcl	20, 31, .+4
+999:
 	mflr	\ptr
-	addi	\ptr, \ptr, (__kernel_datapage_offset - (.-4))@l
-	lwz	\tmp, 0(\ptr)
-	add	\ptr, \tmp, \ptr
+#if CONFIG_PPC_PAGE_SHIFT > 14
+	addis	\ptr, \ptr, (_vdso_datapage - 999b)@ha
+#endif
+	addi	\ptr, \ptr, (_vdso_datapage - 999b)@l
 .endm
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 1d72c4b7672f..e2568d9ecdff 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -500,40 +500,6 @@ static __init void vdso_setup_trampolines(struct lib32_elfinfo *v32,
 	vdso32_rt_sigtramp = find_function32(v32, "__kernel_sigtramp_rt32");
 }
 
-static __init int vdso_fixup_datapage(struct lib32_elfinfo *v32,
-				       struct lib64_elfinfo *v64)
-{
-#ifdef CONFIG_VDSO32
-	Elf32_Sym *sym32;
-#endif
-#ifdef CONFIG_PPC64
-	Elf64_Sym *sym64;
-
-       	sym64 = find_symbol64(v64, "__kernel_datapage_offset");
-	if (sym64 == NULL) {
-		printk(KERN_ERR "vDSO64: Can't find symbol "
-		       "__kernel_datapage_offset !\n");
-		return -1;
-	}
-	*((int *)(vdso64_kbase + sym64->st_value - VDSO64_LBASE)) =
-		(sym64->st_value - VDSO64_LBASE) - PAGE_SIZE;
-#endif /* CONFIG_PPC64 */
-
-#ifdef CONFIG_VDSO32
-	sym32 = find_symbol32(v32, "__kernel_datapage_offset");
-	if (sym32 == NULL) {
-		printk(KERN_ERR "vDSO32: Can't find symbol "
-		       "__kernel_datapage_offset !\n");
-		return -1;
-	}
-	*((int *)(vdso32_kbase + (sym32->st_value - VDSO32_LBASE))) =
-		(sym32->st_value - VDSO32_LBASE) - PAGE_SIZE;
-#endif
-
-	return 0;
-}
-
-
 static __init int vdso_fixup_features(struct lib32_elfinfo *v32,
 				      struct lib64_elfinfo *v64)
 {
@@ -634,9 +600,6 @@ static __init int vdso_setup(void)
 	if (vdso_do_find_sections(&v32, &v64))
 		return -1;
 
-	if (vdso_fixup_datapage(&v32, &v64))
-		return -1;
-
 	if (vdso_fixup_features(&v32, &v64))
 		return -1;
 
diff --git a/arch/powerpc/kernel/vdso32/datapage.S b/arch/powerpc/kernel/vdso32/datapage.S
index 217bb630f8f9..5513a4f8253e 100644
--- a/arch/powerpc/kernel/vdso32/datapage.S
+++ b/arch/powerpc/kernel/vdso32/datapage.S
@@ -13,9 +13,6 @@
 #include <asm/vdso_datapage.h>
 
 	.text
-	.global	__kernel_datapage_offset;
-__kernel_datapage_offset:
-	.long	0
 
 /*
  * void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 582c5b046cc9..25be27b47a9f 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -4,6 +4,7 @@
  * library
  */
 #include <asm/vdso.h>
+#include <asm/page.h>
 
 #ifdef __LITTLE_ENDIAN__
 OUTPUT_FORMAT("elf32-powerpcle", "elf32-powerpcle", "elf32-powerpcle")
@@ -15,6 +16,7 @@ ENTRY(_start)
 
 SECTIONS
 {
+	PROVIDE(_vdso_datapage = . - PAGE_SIZE);
 	. = VDSO32_LBASE + SIZEOF_HEADERS;
 
 	.hash          	: { *(.hash) }			:text
@@ -139,11 +141,6 @@ VERSION
 {
 	VDSO_VERSION_STRING {
 	global:
-		/*
-		 * Has to be there for the kernel to find
-		 */
-		__kernel_datapage_offset;
-
 		__kernel_get_syscall_map;
 #ifndef CONFIG_PPC_BOOK3S_601
 		__kernel_gettimeofday;
diff --git a/arch/powerpc/kernel/vdso64/datapage.S b/arch/powerpc/kernel/vdso64/datapage.S
index 067247d3efb9..03bb72c440dc 100644
--- a/arch/powerpc/kernel/vdso64/datapage.S
+++ b/arch/powerpc/kernel/vdso64/datapage.S
@@ -13,9 +13,6 @@
 #include <asm/vdso_datapage.h>
 
 	.text
-.global	__kernel_datapage_offset;
-__kernel_datapage_offset:
-	.long	0
 
 /*
  * void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S
index 4e3a8d4ee614..aaa5acf6d1b9 100644
--- a/arch/powerpc/kernel/vdso64/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S
@@ -4,6 +4,7 @@
  * library
  */
 #include <asm/vdso.h>
+#include <asm/page.h>
 
 #ifdef __LITTLE_ENDIAN__
 OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
@@ -15,6 +16,7 @@ ENTRY(_start)
 
 SECTIONS
 {
+	PROVIDE(_vdso_datapage = . - PAGE_SIZE);
 	. = VDSO64_LBASE + SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text
@@ -139,11 +141,6 @@ VERSION
 {
 	VDSO_VERSION_STRING {
 	global:
-		/*
-		 * Has to be there for the kernel to find
-		 */
-		__kernel_datapage_offset;
-
 		__kernel_get_syscall_map;
 		__kernel_gettimeofday;
 		__kernel_clock_gettime;
-- 
2.25.0