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From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH v7 2/7] powerpc/vdso: Remove __kernel_datapage_offset and
 simplify __get_datapage()
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, nathanl@linux.ibm.com
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com,
        luto@kernel.org
Date:   Mon, 20 Apr 2020 16:56:29 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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

In order to ease things, move the data page in front like other
arches, that way there is no need to know the size of the library
to locate the data page.

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@c-s.fr>
---
v7:
- Moved the removal of the tmp param of __get_datapage()
in a subsequent patch
- Included the addition of the offset param to __get_datapage()
in the further preparatory patch
---
 arch/powerpc/include/asm/vdso_datapage.h |  8 ++--
 arch/powerpc/kernel/vdso.c               | 53 ++++--------------------
 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, 16 insertions(+), 65 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
index b9ef6cf50ea5..11886467dfdf 100644
--- a/arch/powerpc/include/asm/vdso_datapage.h
+++ b/arch/powerpc/include/asm/vdso_datapage.h
@@ -118,10 +118,12 @@ extern struct vdso_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 f38f26e844b6..d33fa22ddbed 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -190,7 +190,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	 * install_special_mapping or the perf counter mmap tracking code
 	 * will fail to recognise it as a vDSO (since arch_vma_name fails).
 	 */
-	current->mm->context.vdso_base = vdso_base;
+	current->mm->context.vdso_base = vdso_base + PAGE_SIZE;
 
 	/*
 	 * our vma flags don't have VM_WRITE so by default, the process isn't
@@ -482,42 +482,6 @@ 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)) =
-		(vdso64_pages << PAGE_SHIFT) -
-		(sym64->st_value - VDSO64_LBASE);
-#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))) =
-		(vdso32_pages << PAGE_SHIFT) -
-		(sym32->st_value - VDSO32_LBASE);
-#endif
-
-	return 0;
-}
-
-
 static __init int vdso_fixup_features(struct lib32_elfinfo *v32,
 				      struct lib64_elfinfo *v64)
 {
@@ -618,9 +582,6 @@ 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;
 
@@ -761,26 +722,26 @@ static int __init vdso_init(void)
 	vdso32_pagelist = kcalloc(vdso32_pages + 2, sizeof(struct page *),
 				  GFP_KERNEL);
 	BUG_ON(vdso32_pagelist == NULL);
+	vdso32_pagelist[0] = virt_to_page(vdso_data);
 	for (i = 0; i < vdso32_pages; i++) {
 		struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 		get_page(pg);
-		vdso32_pagelist[i] = pg;
+		vdso32_pagelist[i + 1] = pg;
 	}
-	vdso32_pagelist[i++] = virt_to_page(vdso_data);
-	vdso32_pagelist[i] = NULL;
+	vdso32_pagelist[i + 1] = NULL;
 #endif
 
 #ifdef CONFIG_PPC64
 	vdso64_pagelist = kcalloc(vdso64_pages + 2, sizeof(struct page *),
 				  GFP_KERNEL);
 	BUG_ON(vdso64_pagelist == NULL);
+	vdso64_pagelist[0] = virt_to_page(vdso_data);
 	for (i = 0; i < vdso64_pages; i++) {
 		struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 		get_page(pg);
-		vdso64_pagelist[i] = pg;
+		vdso64_pagelist[i + 1] = pg;
 	}
-	vdso64_pagelist[i++] = virt_to_page(vdso_data);
-	vdso64_pagelist[i] = NULL;
+	vdso64_pagelist[i + 1] = NULL;
 #endif /* CONFIG_PPC64 */
 
 	get_page(virt_to_page(vdso_data));
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 5206c2eb2a1d..6cf729612268 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
@@ -138,11 +140,6 @@ 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 256fb9720298..f58c7e2e9cbd 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
@@ -138,11 +140,6 @@ 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