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