linux-kernel - [PATCH v1 7/9] powerpc/vdso: Move vdso datapage up front

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Message-Id: <4c0893ca6848386eb764a016b2783f368b7d6740.1598363608.git.christophe.leroy@csgroup.eu>
Date:   Tue, 25 Aug 2020 13:54:05 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 7/9] powerpc/vdso: Move vdso datapage up front

Move the vdso datapage in front of the VDSO area,
before vdso test.

This will allow to remove the __kernel_datapage_offset symbol
and simplify __get_datapage() in the following patch.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/mmu_context.h |  4 +++-
 arch/powerpc/kernel/vdso.c             | 22 ++++++++++------------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 7f3658a97384..be18ad12bb54 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -262,7 +262,9 @@ extern void arch_exit_mmap(struct mm_struct *mm);
 static inline void arch_unmap(struct mm_struct *mm,
 			      unsigned long start, unsigned long end)
 {
-	if (start <= mm->context.vdso_base && mm->context.vdso_base < end)
+	unsigned long vdso_base = mm->context.vdso_base - PAGE_SIZE;
+
+	if (start <= vdso_base && vdso_base < end)
 		mm->context.vdso_base = 0;
 }
 
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index b9270923452e..1d72c4b7672f 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -124,7 +124,7 @@ static int vdso_mremap(unsigned long vdso_pages,
 	if (new_size != vdso_size)
 		return -EINVAL;
 
-	current->mm->context.vdso_base = (unsigned long)new_vma->vm_start;
+	current->mm->context.vdso_base = (unsigned long)new_vma->vm_start + PAGE_SIZE;
 
 	return 0;
 }
@@ -217,7 +217,7 @@ 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
@@ -516,8 +516,7 @@ static __init int vdso_fixup_datapage(struct lib32_elfinfo *v32,
 		return -1;
 	}
 	*((int *)(vdso64_kbase + sym64->st_value - VDSO64_LBASE)) =
-		(vdso64_pages << PAGE_SHIFT) -
-		(sym64->st_value - VDSO64_LBASE);
+		(sym64->st_value - VDSO64_LBASE) - PAGE_SIZE;
 #endif /* CONFIG_PPC64 */
 
 #ifdef CONFIG_VDSO32
@@ -528,8 +527,7 @@ static __init int vdso_fixup_datapage(struct lib32_elfinfo *v32,
 		return -1;
 	}
 	*((int *)(vdso32_kbase + (sym32->st_value - VDSO32_LBASE))) =
-		(vdso32_pages << PAGE_SHIFT) -
-		(sym32->st_value - VDSO32_LBASE);
+		(sym32->st_value - VDSO32_LBASE) - PAGE_SIZE;
 #endif
 
 	return 0;
@@ -771,10 +769,10 @@ static int __init vdso_init(void)
 		if (!pagelist)
 			goto alloc_failed;
 
-		for (i = 0; i < vdso32_pages; i++)
-			pagelist[i] = virt_to_page(vdso32_kbase + i * PAGE_SIZE);
+		pagelist[0] = virt_to_page(vdso_data);
 
-		pagelist[i++] = virt_to_page(vdso_data);
+		for (i = 0; i < vdso32_pages; i++)
+			pagelist[i + 1] = virt_to_page(vdso32_kbase + i * PAGE_SIZE);
 
 		vdso32_spec.pages = pagelist;
 	}
@@ -784,10 +782,10 @@ static int __init vdso_init(void)
 		if (!pagelist)
 			goto alloc_failed;
 
-		for (i = 0; i < vdso64_pages; i++)
-			pagelist[i] = virt_to_page(vdso64_kbase + i * PAGE_SIZE);
+		pagelist[0] = virt_to_page(vdso_data);
 
-		pagelist[i++] = virt_to_page(vdso_data);
+		for (i = 0; i < vdso64_pages; i++)
+			pagelist[i + 1] = virt_to_page(vdso64_kbase + i * PAGE_SIZE);
 
 		vdso64_spec.pages = pagelist;
 	}
-- 
2.25.0