2016-10-27 14:32:24

by Dmitry Safonov

[permalink] [raw]
Subject: [PATCH 0/2] x86/vdso: small fixups for map_vdso

The first one is a fixup for arch_prctl constants uapi visability,
the second is code simplification.

Dmitry Safonov (2):
x86/prctl/uapi: remove ifdef for CHECKPOINT_RESTORE
x86/vdso: set vdso pointer only after success

arch/x86/entry/vdso/vma.c | 10 +++-------
arch/x86/include/uapi/asm/prctl.h | 8 +++-----
2 files changed, 6 insertions(+), 12 deletions(-)

--
2.10.1


2016-10-27 14:32:15

by Dmitry Safonov

[permalink] [raw]
Subject: [PATCH 2/2] x86/vdso: set vdso pointer only after success

Those pointers were initialized before call to _install_special_mapping
after the commit f7b6eb3fa072 ("x86: Set context.vdso before installing
the mapping"). This is not required anymore as special mappings have
their vma name and don't use arch_vma_name() after commit a62c34bd2a8a
("x86, mm: Improve _install_special_mapping and fix x86 vdso naming").
So, this way to init looks less entangled.
I even belive, we can remove null initializers:
- on failure load_elf_binary() will not start a new thread;
- arch_prctl will have the same pointers as before syscall.

Cc: [email protected]
Cc: Cyrill Gorcunov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: [email protected]
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Dmitry Safonov <[email protected]>
---
arch/x86/entry/vdso/vma.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 23c881caabd1..e739002427ed 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -161,8 +161,6 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
}

text_start = addr - image->sym_vvar_start;
- current->mm->context.vdso = (void __user *)text_start;
- current->mm->context.vdso_image = image;

/*
* MAYWRITE to allow gdb to COW and set breakpoints
@@ -189,14 +187,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
do_munmap(mm, text_start, image->size);
+ } else {
+ current->mm->context.vdso = (void __user *)text_start;
+ current->mm->context.vdso_image = image;
}

up_fail:
- if (ret) {
- current->mm->context.vdso = NULL;
- current->mm->context.vdso_image = NULL;
- }
-
up_write(&mm->mmap_sem);
return ret;
}
--
2.10.1

2016-10-27 17:51:00

by Dmitry Safonov

[permalink] [raw]
Subject: [PATCH 1/2] x86/prctl/uapi: remove ifdef for CHECKPOINT_RESTORE

As userspace knows nothing about kernel config, this ifdefs
will make prctl constants invisible to userspace.
Let it be clean'n'simple: remove ifdefs.
If kernel has CONFIG_CHECKPOINT_RESTORE disabled, sys_prctl()
will return -EINVAL for those prctls.

Fixes: 2eefd8789698 ("x86/arch_prctl/vdso: Add ARCH_MAP_VDSO_*")
Cc: [email protected]
Cc: Cyrill Gorcunov <[email protected]>
Cc: Paul Bolle <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: [email protected]
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Reported-by: Paul Bolle <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
---
arch/x86/include/uapi/asm/prctl.h | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index ae135de547f5..835aa51c7f6e 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -6,10 +6,8 @@
#define ARCH_GET_FS 0x1003
#define ARCH_GET_GS 0x1004

-#ifdef CONFIG_CHECKPOINT_RESTORE
-# define ARCH_MAP_VDSO_X32 0x2001
-# define ARCH_MAP_VDSO_32 0x2002
-# define ARCH_MAP_VDSO_64 0x2003
-#endif
+#define ARCH_MAP_VDSO_X32 0x2001
+#define ARCH_MAP_VDSO_32 0x2002
+#define ARCH_MAP_VDSO_64 0x2003

#endif /* _ASM_X86_PRCTL_H */
--
2.10.1

2016-10-27 22:26:18

by Andy Lutomirski

[permalink] [raw]
Subject: Re: [PATCH 2/2] x86/vdso: set vdso pointer only after success

On Thu, Oct 27, 2016 at 7:15 AM, Dmitry Safonov <[email protected]> wrote:
> Those pointers were initialized before call to _install_special_mapping
> after the commit f7b6eb3fa072 ("x86: Set context.vdso before installing
> the mapping"). This is not required anymore as special mappings have
> their vma name and don't use arch_vma_name() after commit a62c34bd2a8a
> ("x86, mm: Improve _install_special_mapping and fix x86 vdso naming").
> So, this way to init looks less entangled.
> I even belive, we can remove null initializers:
> - on failure load_elf_binary() will not start a new thread;
> - arch_prctl will have the same pointers as before syscall.

Acked-by: Andy Lutomirski <[email protected]>

Subject: [tip:x86/asm] x86/prctl/uapi: Remove #ifdef for CHECKPOINT_RESTORE

Commit-ID: a01aa6c9f40fe03c82032e7f8b3bcf1e6c93ac0e
Gitweb: http://git.kernel.org/tip/a01aa6c9f40fe03c82032e7f8b3bcf1e6c93ac0e
Author: Dmitry Safonov <[email protected]>
AuthorDate: Thu, 27 Oct 2016 17:15:15 +0300
Committer: Ingo Molnar <[email protected]>
CommitDate: Fri, 28 Oct 2016 08:15:55 +0200

x86/prctl/uapi: Remove #ifdef for CHECKPOINT_RESTORE

As userspace knows nothing about kernel config, thus #ifdefs
around ABI prctl constants makes them invisible to userspace.

Let it be clean'n'simple: remove #ifdefs.

If kernel has CONFIG_CHECKPOINT_RESTORE disabled, sys_prctl()
will return -EINVAL for those prctls.

Reported-by: Paul Bolle <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
Cc: [email protected]
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Fixes: 2eefd8789698 ("x86/arch_prctl/vdso: Add ARCH_MAP_VDSO_*")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/include/uapi/asm/prctl.h | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index ae135de..835aa51 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -6,10 +6,8 @@
#define ARCH_GET_FS 0x1003
#define ARCH_GET_GS 0x1004

-#ifdef CONFIG_CHECKPOINT_RESTORE
-# define ARCH_MAP_VDSO_X32 0x2001
-# define ARCH_MAP_VDSO_32 0x2002
-# define ARCH_MAP_VDSO_64 0x2003
-#endif
+#define ARCH_MAP_VDSO_X32 0x2001
+#define ARCH_MAP_VDSO_32 0x2002
+#define ARCH_MAP_VDSO_64 0x2003

#endif /* _ASM_X86_PRCTL_H */

Subject: [tip:x86/asm] x86/vdso: Set vDSO pointer only after success

Commit-ID: 67dece7d4c5841e84a3c795e79bf0dcd5be54f55
Gitweb: http://git.kernel.org/tip/67dece7d4c5841e84a3c795e79bf0dcd5be54f55
Author: Dmitry Safonov <[email protected]>
AuthorDate: Thu, 27 Oct 2016 17:15:16 +0300
Committer: Ingo Molnar <[email protected]>
CommitDate: Fri, 28 Oct 2016 08:15:55 +0200

x86/vdso: Set vDSO pointer only after success

Those pointers were initialized before call to _install_special_mapping()
after the commit:

f7b6eb3fa072 ("x86: Set context.vdso before installing the mapping")

This is not required anymore as special mappings have their vma name and
don't use arch_vma_name() after commit:

a62c34bd2a8a ("x86, mm: Improve _install_special_mapping and fix x86 vdso naming")

So, this way to init looks less entangled.

I even belive that we can remove NULL initializers:

- on failure load_elf_binary() will not start a new thread;
- arch_prctl will have the same pointers as before syscall.

Signed-off-by: Dmitry Safonov <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
Cc: [email protected]
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/entry/vdso/vma.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 23c881c..e739002 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -161,8 +161,6 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
}

text_start = addr - image->sym_vvar_start;
- current->mm->context.vdso = (void __user *)text_start;
- current->mm->context.vdso_image = image;

/*
* MAYWRITE to allow gdb to COW and set breakpoints
@@ -189,14 +187,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
do_munmap(mm, text_start, image->size);
+ } else {
+ current->mm->context.vdso = (void __user *)text_start;
+ current->mm->context.vdso_image = image;
}

up_fail:
- if (ret) {
- current->mm->context.vdso = NULL;
- current->mm->context.vdso_image = NULL;
- }
-
up_write(&mm->mmap_sem);
return ret;
}