linux-kernel - [PATCHv3 2/6] x86/vdso: replace calculate_addr in map

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Date:   Fri, 26 Aug 2016 20:13:13 +0300
From:   Dmitry Safonov <dsafonov@...tuozzo.com>
To:     <linux-kernel@...r.kernel.org>
CC:     <0x7f454c46@...il.com>, <luto@...nel.org>, <oleg@...hat.com>,
        <tglx@...utronix.de>, <hpa@...or.com>, <mingo@...hat.com>,
        <linux-mm@...ck.org>, <x86@...nel.org>, <gorcunov@...nvz.org>,
        <xemul@...tuozzo.com>, Dmitry Safonov <dsafonov@...tuozzo.com>
Subject: [PATCHv3 2/6] x86/vdso: replace calculate_addr in map_vdso() with addr

That will allow to specify address where to map vDSO blob.
For the randomized vDSO mappings introduce map_vdso_randomized()
which will simplify calls to map_vdso.

Cc: Andy Lutomirski <luto@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: linux-mm@...ck.org
Cc: x86@...nel.org
Cc: Cyrill Gorcunov <gorcunov@...nvz.org>
Cc: Pavel Emelyanov <xemul@...tuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@...tuozzo.com>
---
 arch/x86/entry/vdso/vma.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 3bab6ba3ffc5..5bcb25a9e573 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -176,11 +176,16 @@ static int vvar_fault(const struct vm_special_mapping *sm,
 	return VM_FAULT_SIGBUS;
 }
 
-static int map_vdso(const struct vdso_image *image, bool calculate_addr)
+/*
+ * Add vdso and vvar mappings to current process.
+ * @image          - blob to map
+ * @addr           - request a specific address (zero to map at free addr)
+ */
+static int map_vdso(const struct vdso_image *image, unsigned long addr)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
-	unsigned long addr, text_start;
+	unsigned long text_start;
 	int ret = 0;
 
 	static const struct vm_special_mapping vdso_mapping = {
@@ -193,13 +198,6 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
 		.fault = vvar_fault,
 	};
 
-	if (calculate_addr) {
-		addr = vdso_addr(current->mm->start_stack,
-				 image->size - image->sym_vvar_start);
-	} else {
-		addr = 0;
-	}
-
 	if (down_write_killable(&mm->mmap_sem))
 		return -EINTR;
 
@@ -251,13 +249,20 @@ up_fail:
 	return ret;
 }
 
+static int map_vdso_randomized(const struct vdso_image *image)
+{
+	unsigned long addr = vdso_addr(current->mm->start_stack,
+				 image->size - image->sym_vvar_start);
+	return map_vdso(image, addr);
+}
+
 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 static int load_vdso32(void)
 {
 	if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
 		return 0;
 
-	return map_vdso(&vdso_image_32, false);
+	return map_vdso(&vdso_image_32, 0);
 }
 #endif
 
@@ -267,7 +272,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	if (!vdso64_enabled)
 		return 0;
 
-	return map_vdso(&vdso_image_64, true);
+	return map_vdso_randomized(&vdso_image_64);
 }
 
 #ifdef CONFIG_COMPAT
@@ -278,8 +283,7 @@ int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 	if (test_thread_flag(TIF_X32)) {
 		if (!vdso64_enabled)
 			return 0;
-
-		return map_vdso(&vdso_image_x32, true);
+		return map_vdso_randomized(&vdso_image_x32);
 	}
 #endif
 #ifdef CONFIG_IA32_EMULATION
-- 
2.9.0