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[PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum

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  [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-01 15:20 +0200
    Re: [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum Cyrill Gorcunov <gorcunov@gmail.com> - 2016-06-03 12:00 +0200
      Re: [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-03 12:40 +0200

#1411209 — [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum

Make in-kernel API to map vDSO blobs on x86.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
 arch/x86/entry/vdso/vma.c   | 70 +++++++++++++++++++++++++--------------------
 arch/x86/include/asm/vdso.h |  4 +++
 2 files changed, 43 insertions(+), 31 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 387028e6755d..4017b60eed33 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -176,11 +176,18 @@ 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)
+ * @calculate_addr - turn on aslr (@addr will be ignored)
+ */
+static int map_vdso(const struct vdso_image *image,
+		unsigned long addr, bool calculate_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 = {
@@ -193,12 +200,9 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
 		.fault = vvar_fault,
 	};
 
-	if (calculate_addr) {
+	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;
@@ -249,48 +253,52 @@ up_fail:
 	return ret;
 }
 
-#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
-static int load_vdso32(void)
+int do_map_vdso(vdso_type type, unsigned long addr, bool randomize_addr)
 {
-	if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
-		return 0;
-
-	return map_vdso(&vdso_image_32, false);
-}
+	switch (type) {
+#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
+	case VDSO_32:
+		if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
+			return 0;
+		/* vDSO aslr turned off for i386 vDSO */
+		return map_vdso(&vdso_image_32, addr, false);
+#endif
+#ifdef CONFIG_X86_64
+	case VDSO_64:
+		if (!vdso64_enabled)
+			return 0;
+		return map_vdso(&vdso_image_64, addr, randomize_addr);
+#endif
+#ifdef CONFIG_X86_X32_ABI
+	case VDSO_X32:
+		if (!vdso64_enabled)
+			return 0;
+		return map_vdso(&vdso_image_x32, addr, randomize_addr);
 #endif
+	default:
+		return -EINVAL;
+	}
+}
 
 #ifdef CONFIG_X86_64
 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 do_map_vdso(VDSO_64, 0, true);
 }
 
 #ifdef CONFIG_COMPAT
 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 				       int uses_interp)
 {
-#ifdef CONFIG_X86_X32_ABI
-	if (test_thread_flag(TIF_X32)) {
-		if (!vdso64_enabled)
-			return 0;
-
-		return map_vdso(&vdso_image_x32, true);
-	}
-#endif
-#ifdef CONFIG_IA32_EMULATION
-	return load_vdso32();
-#else
-	return 0;
-#endif
+	if (test_thread_flag(TIF_X32))
+		return do_map_vdso(VDSO_X32, 0, true);
+	return do_map_vdso(VDSO_32, 0, false);
 }
 #endif
 #else
 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
-	return load_vdso32();
+	return do_map_vdso(VDSO_32, 0, false);
 }
 #endif
 
diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index 43dc55be524e..2be137897842 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -41,6 +41,10 @@ extern const struct vdso_image vdso_image_32;
 
 extern void __init init_vdso_image(const struct vdso_image *image);
 
+typedef enum { VDSO_32, VDSO_64, VDSO_X32 } vdso_type;
+
+extern int do_map_vdso(vdso_type type, unsigned long addr, bool randomize_addr);
+
 #endif /* __ASSEMBLER__ */
 
 #endif /* _ASM_X86_VDSO_H */
-- 
2.8.2

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#1412982

On Wed, Jun 01, 2016 at 04:11:33PM +0300, Dmitry Safonov wrote:
> Make in-kernel API to map vDSO blobs on x86.
> 
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>

Hi! Sorry for delay in reply. Dima, here is a moment I somehow missing:
when do_map_vdso is called it is implied that old vdso is unmapped already,
or both can be present in the system?

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#1413035

On 06/03/2016 12:50 PM, Cyrill Gorcunov wrote:
> On Wed, Jun 01, 2016 at 04:11:33PM +0300, Dmitry Safonov wrote:
>> Make in-kernel API to map vDSO blobs on x86.
>>
>> Cc: Andy Lutomirski <luto@kernel.org>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
>
> Hi! Sorry for delay in reply. Dima, here is a moment I somehow missing:
> when do_map_vdso is called it is implied that old vdso is unmapped already,
> or both can be present in the system?
>

Both can be present. There are some limitations: if first vDSO was
32-bit, syscalls through it wouldn't work, only on the last mapped.
It's because of mm->context.vdso pointer, which for 32-bit vDSO
should point on it. (and this code make it point to a new mapped vDSO)

On RFC I did patch that unmaps previous vDSO, but I have though
it's better to simplify this code and drop unmapping.

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