[PATCHv5 0/6] x86: 32-bit compatible C/R on x86_64

[PATCHv5 0/6] x86: 32-bit compatible C/R on x86_64

[Dmitry Safonov]

Changes from v4:
- check both vm_ops and vm_private_data to avoid (unlikely) confusion
  with some other vma in map_vdso_once (as Andy noticed) - which would
  lead to unable to use this API in that unlikely-case
  (vm_private_data may be uninitialized and be the same as vvar_mapping
  or vdso_mapping pointer) - so I introduced one-liner helper
  vma_is_special_mapping().

Changes from v3:
- proper ifdefs around vdso_image_32
- missed Reviewed-by tag

Changes from v2:
- reworked map_vdso() part with Andy suggestions
- int arch_prctl(ARCH_MAP_VDSO_*, addr) now returns size of mapped
  vdso blob on success, which is handy for the following blob parsing
  in userspace
- disallowed two vDSO blobs mappings: as Andy noted,
  __insert_special_mapping may not get all accounting right, which
  may lead to abuse this API from userspace. Return -EEXIST if process
  has mapped vdso blob - this will ensure that caller knows what it does.

The following changes are available since v1:
- killed PR_REG_SIZE macro as Oleg suggested
- cleared SA_IA32_ABI|SA_X32_ABI from oact->sa.sa_flags in do_sigaction()
  as noticed by Oleg
- moved SA_IA32_ABI|SA_X32_ABI from uapi header as those flags shouldn't
  be exposed to user-space

I also reworked CRIU's patches to work with this patches set, rather than
on first RFC that swapped TIF_IA32 with arch_prctl. By now it yet fails
~10% of 32-bit tests of CRIU's test suite called ZDTM.
The CRIU branch for this can be viewed on [6] and v3 patches to add
this functionality have been sent to maillist [7].

The patches set is based on [3] and while it's not yet applied -- it
may make kbuild test robot unhappy.

Description from v1 [5]:

This patches set is an attempt to add checkpoint/restore
for 32-bit tasks in compatibility mode on x86_64 hosts.

Restore in CRIU starts from one root restoring process, which
reads info for all threads being restored from images files.
This information is used further to find out which processes
share some resources. Later shared resources are restored only
by one process and all other inherit them.
After that it calls clone() and new threads restore their
properties in parallel. Those threads inherit all parent's
mappings and fetch properties from those mappings
(and do clone themself, if they have children/subthreads). [1]
Then starts restorer blob's play, it's PIE binary, which
unmaps all unneeded for restoring VMAs, maps new VMAs and
finalize restoring with sigreturn syscall. [2]

To restore of 32-bit task we need three things to do in running
x86_64 restorer blob:
a) set code selector to __USER32_CS (to run 32-bit code);
b) remap vdso blob from 64-bit to 32-bit
   This is primary needed because restore may happen on a different
   kernel, which has different vDSO image than we had on dump.
c) if 32-bit vDSO differ to dumped image, move it on free place
   and add jump trampolines to that place.
d) switch TIF_IA32 flag, so kernel would know that it deals with
   compatible 32-bit application.

>From all this:
a) setting CS may be done from userspace, no patches needed;
b) patches 1-3 add ability to map different vDSO blobs on x86 kernel;
c) for remapping/moving 32-bit vDSO blob patches have been send earlier
   and seems to be accepted [3]
d) and for swapping TIF_IA32 flag discussion with Andy ended in conclusion
   that it's better to remove this flag completely.
   Patches 4-6 deletes usage of TIF_IA32 from ptrace, signal and coredump
   code. This is rework/resend of RFC [4]

[1] https://criu.org/Checkpoint/Restore#Restore
[2] https://criu.org/Restorer_context
[3] https://lkml.org/lkml/2016/6/28/489
[4] https://lkml.org/lkml/2016/4/25/650
[5] https://lkml.org/lkml/2016/6/1/425
[6] https://github.com/0x7f454c46/criu/tree/compat-4
[7] https://lists.openvz.org/pipermail/criu/2016-June/029788.html

Dmitry Safonov (6):
  x86/vdso: unmap vdso blob on vvar mapping failure
  x86/vdso: replace calculate_addr in map_vdso() with addr
  x86/arch_prctl/vdso: add ARCH_MAP_VDSO_*
  x86/coredump: use pr_reg size, rather that TIF_IA32 flag
  x86/ptrace: down with test_thread_flag(TIF_IA32)
  x86/signal: add SA_{X32,IA32}_ABI sa_flags

 arch/x86/entry/vdso/vma.c         | 81 +++++++++++++++++++++++++++------------
 arch/x86/ia32/ia32_signal.c       |  2 +-
 arch/x86/include/asm/compat.h     |  8 ++--
 arch/x86/include/asm/fpu/signal.h |  6 +++
 arch/x86/include/asm/signal.h     |  4 ++
 arch/x86/include/asm/vdso.h       |  2 +
 arch/x86/include/uapi/asm/prctl.h |  6 +++
 arch/x86/kernel/process_64.c      | 25 ++++++++++++
 arch/x86/kernel/ptrace.c          |  2 +-
 arch/x86/kernel/signal.c          | 20 +++++-----
 arch/x86/kernel/signal_compat.c   | 34 ++++++++++++++--
 fs/binfmt_elf.c                   | 23 ++++-------
 kernel/signal.c                   |  7 ++++
 13 files changed, 162 insertions(+), 58 deletions(-)

-- 
2.9.0

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[PATCHv5 1/6] x86/vdso: unmap vdso blob on vvar mapping failure

[Dmitry Safonov]

If remapping of vDSO blob failed on vvar mapping,
we need to unmap previously mapped vDSO blob.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mm@kvack.org
Cc: x86@kernel.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/vdso/vma.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index f840766659a8..3bab6ba3ffc5 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -238,12 +238,14 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
 
 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
-		goto up_fail;
+		do_munmap(mm, text_start, image->size);
 	}
 
 up_fail:
-	if (ret)
+	if (ret) {
 		current->mm->context.vdso = NULL;
+		current->mm->context.vdso_image = NULL;
+	}
 
 	up_write(&mm->mmap_sem);
 	return ret;
-- 
2.9.0

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[PATCHv5 2/6] x86/vdso: replace calculate_addr in map_vdso() with addr

[Dmitry Safonov]

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@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mm@kvack.org
Cc: x86@kernel.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
---
 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

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[PATCHv5 3/6] x86/arch_prctl/vdso: add ARCH_MAP_VDSO_*

[Dmitry Safonov]

Add API to change vdso blob type with arch_prctl.
As this is usefull only by needs of CRIU, expose
this interface under CONFIG_CHECKPOINT_RESTORE.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mm@kvack.org
Cc: x86@kernel.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
 arch/x86/entry/vdso/vma.c         | 45 ++++++++++++++++++++++++++++++---------
 arch/x86/include/asm/vdso.h       |  2 ++
 arch/x86/include/uapi/asm/prctl.h |  6 ++++++
 arch/x86/kernel/process_64.c      | 25 ++++++++++++++++++++++
 include/linux/mm.h                |  2 ++
 mm/mmap.c                         |  8 +++++++
 6 files changed, 78 insertions(+), 10 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 5bcb25a9e573..4459e73e234d 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -176,6 +176,16 @@ static int vvar_fault(const struct vm_special_mapping *sm,
 	return VM_FAULT_SIGBUS;
 }
 
+static const struct vm_special_mapping vdso_mapping = {
+	.name = "[vdso]",
+	.fault = vdso_fault,
+	.mremap = vdso_mremap,
+};
+static const struct vm_special_mapping vvar_mapping = {
+	.name = "[vvar]",
+	.fault = vvar_fault,
+};
+
 /*
  * Add vdso and vvar mappings to current process.
  * @image          - blob to map
@@ -188,16 +198,6 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
 	unsigned long text_start;
 	int ret = 0;
 
-	static const struct vm_special_mapping vdso_mapping = {
-		.name = "[vdso]",
-		.fault = vdso_fault,
-		.mremap = vdso_mremap,
-	};
-	static const struct vm_special_mapping vvar_mapping = {
-		.name = "[vvar]",
-		.fault = vvar_fault,
-	};
-
 	if (down_write_killable(&mm->mmap_sem))
 		return -EINTR;
 
@@ -256,6 +256,31 @@ static int map_vdso_randomized(const struct vdso_image *image)
 	return map_vdso(image, addr);
 }
 
+int map_vdso_once(const struct vdso_image *image, unsigned long addr)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+
+	down_write(&mm->mmap_sem);
+	/*
+	 * Check if we have already mapped vdso blob - fail to prevent
+	 * abusing from userspace install_speciall_mapping, which may
+	 * not do accounting and rlimit right.
+	 * We could search vma near context.vdso, but it's a slowpath,
+	 * so let's explicitely check all VMAs to be completely sure.
+	 */
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		if (vma_is_special_mapping(vma, &vdso_mapping) ||
+				vma_is_special_mapping(vma, &vvar_mapping)) {
+			up_write(&mm->mmap_sem);
+			return -EEXIST;
+		}
+	}
+	up_write(&mm->mmap_sem);
+
+	return map_vdso(image, addr);
+}
+
 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 static int load_vdso32(void)
 {
diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index 43dc55be524e..2444189cbe28 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -41,6 +41,8 @@ extern const struct vdso_image vdso_image_32;
 
 extern void __init init_vdso_image(const struct vdso_image *image);
 
+extern int map_vdso_once(const struct vdso_image *image, unsigned long addr);
+
 #endif /* __ASSEMBLER__ */
 
 #endif /* _ASM_X86_VDSO_H */
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index 3ac5032fae09..ae135de547f5 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -6,4 +6,10 @@
 #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
+
 #endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 63236d8f84bf..f240a465920b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -49,6 +49,7 @@
 #include <asm/debugreg.h>
 #include <asm/switch_to.h>
 #include <asm/xen/hypervisor.h>
+#include <asm/vdso.h>
 
 asmlinkage extern void ret_from_fork(void);
 
@@ -524,6 +525,17 @@ void set_personality_ia32(bool x32)
 }
 EXPORT_SYMBOL_GPL(set_personality_ia32);
 
+static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr)
+{
+	int ret;
+
+	ret = map_vdso_once(image, addr);
+	if (ret)
+		return ret;
+
+	return (long)image->size;
+}
+
 long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 {
 	int ret = 0;
@@ -577,6 +589,19 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 		break;
 	}
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
+#ifdef CONFIG_X86_X32
+	case ARCH_MAP_VDSO_X32:
+		return prctl_map_vdso(&vdso_image_x32, addr);
+#endif
+#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
+	case ARCH_MAP_VDSO_32:
+		return prctl_map_vdso(&vdso_image_32, addr);
+#endif
+	case ARCH_MAP_VDSO_64:
+		return prctl_map_vdso(&vdso_image_64, addr);
+#endif
+
 	default:
 		ret = -EINVAL;
 		break;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ef815b9cd426..5f14534f0c90 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2019,6 +2019,8 @@ extern struct file *get_task_exe_file(struct task_struct *task);
 extern bool may_expand_vm(struct mm_struct *, vm_flags_t, unsigned long npages);
 extern void vm_stat_account(struct mm_struct *, vm_flags_t, long npages);
 
+extern bool vma_is_special_mapping(const struct vm_area_struct *vma,
+				   const struct vm_special_mapping *sm);
 extern struct vm_area_struct *_install_special_mapping(struct mm_struct *mm,
 				   unsigned long addr, unsigned long len,
 				   unsigned long flags,
diff --git a/mm/mmap.c b/mm/mmap.c
index ca9d91bca0d6..6373ebd358c0 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3063,6 +3063,14 @@ out:
 	return ERR_PTR(ret);
 }
 
+bool vma_is_special_mapping(const struct vm_area_struct *vma,
+	const struct vm_special_mapping *sm)
+{
+	return vma->vm_private_data == sm &&
+		(vma->vm_ops == &special_mapping_vmops ||
+		 vma->vm_ops == &legacy_special_mapping_vmops);
+}
+
 /*
  * Called with mm->mmap_sem held for writing.
  * Insert a new vma covering the given region, with the given flags.
-- 
2.9.0

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[PATCHv5 4/6] x86/coredump: use pr_reg size, rather that TIF_IA32 flag

[Dmitry Safonov]

Killed PR_REG_SIZE and PR_REG_PTR macro as we can get regset size
from regset view.
I wish I could also kill PRSTATUS_SIZE nicely.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mm@kvack.org
Cc: x86@kernel.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
 arch/x86/include/asm/compat.h |  8 ++++----
 fs/binfmt_elf.c               | 23 ++++++++---------------
 2 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index a18806165fe4..03d269bed941 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -275,10 +275,10 @@ struct compat_shmid64_ds {
 #ifdef CONFIG_X86_X32_ABI
 typedef struct user_regs_struct compat_elf_gregset_t;
 
-#define PR_REG_SIZE(S) (test_thread_flag(TIF_IA32) ? 68 : 216)
-#define PRSTATUS_SIZE(S) (test_thread_flag(TIF_IA32) ? 144 : 296)
-#define SET_PR_FPVALID(S,V) \
-  do { *(int *) (((void *) &((S)->pr_reg)) + PR_REG_SIZE(0)) = (V); } \
+/* Full regset -- prstatus on x32, otherwise on ia32 */
+#define PRSTATUS_SIZE(S, R) (R != sizeof(S.pr_reg) ? 144 : 296)
+#define SET_PR_FPVALID(S, V, R) \
+  do { *(int *) (((void *) &((S)->pr_reg)) + R) = (V); } \
   while (0)
 
 #define COMPAT_USE_64BIT_TIME \
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index e5495f37c6ed..2472af2798c7 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1624,20 +1624,12 @@ static void do_thread_regset_writeback(struct task_struct *task,
 		regset->writeback(task, regset, 1);
 }
 
-#ifndef PR_REG_SIZE
-#define PR_REG_SIZE(S) sizeof(S)
-#endif
-
 #ifndef PRSTATUS_SIZE
-#define PRSTATUS_SIZE(S) sizeof(S)
-#endif
-
-#ifndef PR_REG_PTR
-#define PR_REG_PTR(S) (&((S)->pr_reg))
+#define PRSTATUS_SIZE(S, R) sizeof(S)
 #endif
 
 #ifndef SET_PR_FPVALID
-#define SET_PR_FPVALID(S, V) ((S)->pr_fpvalid = (V))
+#define SET_PR_FPVALID(S, V, R) ((S)->pr_fpvalid = (V))
 #endif
 
 static int fill_thread_core_info(struct elf_thread_core_info *t,
@@ -1645,6 +1637,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 				 long signr, size_t *total)
 {
 	unsigned int i;
+	unsigned int regset_size = view->regsets[0].n * view->regsets[0].size;
 
 	/*
 	 * NT_PRSTATUS is the one special case, because the regset data
@@ -1653,12 +1646,11 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 	 * We assume that regset 0 is NT_PRSTATUS.
 	 */
 	fill_prstatus(&t->prstatus, t->task, signr);
-	(void) view->regsets[0].get(t->task, &view->regsets[0],
-				    0, PR_REG_SIZE(t->prstatus.pr_reg),
-				    PR_REG_PTR(&t->prstatus), NULL);
+	(void) view->regsets[0].get(t->task, &view->regsets[0], 0, regset_size,
+				    &t->prstatus.pr_reg, NULL);
 
 	fill_note(&t->notes[0], "CORE", NT_PRSTATUS,
-		  PRSTATUS_SIZE(t->prstatus), &t->prstatus);
+		  PRSTATUS_SIZE(t->prstatus, regset_size), &t->prstatus);
 	*total += notesize(&t->notes[0]);
 
 	do_thread_regset_writeback(t->task, &view->regsets[0]);
@@ -1688,7 +1680,8 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 						  regset->core_note_type,
 						  size, data);
 				else {
-					SET_PR_FPVALID(&t->prstatus, 1);
+					SET_PR_FPVALID(&t->prstatus,
+							1, regset_size);
 					fill_note(&t->notes[i], "CORE",
 						  NT_PRFPREG, size, data);
 				}
-- 
2.9.0

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[PATCHv5 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32)

[Dmitry Safonov]

As the task isn't executing at the moment of {GET,SET}REGS,
return regset that corresponds to code selector, rather than
value of TIF_IA32 flag.
I.e. if we ptrace i386 elf binary that has just changed it's
code selector to __USER_CS, than GET_REGS will return
full x86_64 register set.

Note, that this will work only if application has changed it's CS.
If the application does 32-bit syscall with __USER_CS, ptrace
will still return 64-bit register set. Which might be still confusing
for tools that expect TS_COMPACT to be exposed [1, 2].

So this this change should make PTRACE_GETREGSET more reliable and
this will be another step to drop TIF_{IA32,X32} flags.

[1]: https://sourceforge.net/p/strace/mailman/message/30471411/
[2]: https://lkml.org/lkml/2012/1/18/320

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mm@kvack.org
Cc: x86@kernel.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
 arch/x86/kernel/ptrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index f79576a541ff..ad0bab8fc594 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1358,7 +1358,7 @@ void update_regset_xstate_info(unsigned int size, u64 xstate_mask)
 const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 {
 #ifdef CONFIG_IA32_EMULATION
-	if (test_tsk_thread_flag(task, TIF_IA32))
+	if (!user_64bit_mode(task_pt_regs(task)))
 #endif
 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 		return &user_x86_32_view;
-- 
2.9.0

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[PATCHv5 6/6] x86/signal: add SA_{X32,IA32}_ABI sa_flags

[Dmitry Safonov]

Introduce new flags that defines which ABI to use on creating sigframe.
Those flags kernel will set according to sigaction syscall ABI,
which set handler for the signal being delivered.

So that will drop the dependency on TIF_IA32/TIF_X32 flags on signal deliver.
Those flags will be used only under CONFIG_COMPAT.

Similar way ARM uses sa_flags to differ in which mode deliver signal
for 26-bit applications (look at SA_THIRYTWO).

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mm@kvack.org
Cc: x86@kernel.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/ia32/ia32_signal.c       |  2 +-
 arch/x86/include/asm/fpu/signal.h |  6 ++++++
 arch/x86/include/asm/signal.h     |  4 ++++
 arch/x86/kernel/signal.c          | 20 +++++++++++---------
 arch/x86/kernel/signal_compat.c   | 34 +++++++++++++++++++++++++++++++---
 kernel/signal.c                   |  7 +++++++
 6 files changed, 60 insertions(+), 13 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 2f29f4e407c3..cb13c0564ea7 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -378,7 +378,7 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
 		put_user_ex(*((u64 *)&code), (u64 __user *)frame->retcode);
 	} put_user_catch(err);
 
-	err |= copy_siginfo_to_user32(&frame->info, &ksig->info);
+	err |= __copy_siginfo_to_user32(&frame->info, &ksig->info, false);
 	err |= ia32_setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 				     regs, set->sig[0]);
 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
diff --git a/arch/x86/include/asm/fpu/signal.h b/arch/x86/include/asm/fpu/signal.h
index 0e970d00dfcd..20a1fbf7fe4e 100644
--- a/arch/x86/include/asm/fpu/signal.h
+++ b/arch/x86/include/asm/fpu/signal.h
@@ -19,6 +19,12 @@ int ia32_setup_frame(int sig, struct ksignal *ksig,
 # define ia32_setup_rt_frame	__setup_rt_frame
 #endif
 
+#ifdef CONFIG_COMPAT
+int __copy_siginfo_to_user32(compat_siginfo_t __user *to,
+		const siginfo_t *from, bool x32_ABI);
+#endif
+
+
 extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
 			      struct task_struct *tsk);
 extern void convert_to_fxsr(struct task_struct *tsk,
diff --git a/arch/x86/include/asm/signal.h b/arch/x86/include/asm/signal.h
index dd1e7d6387ab..8af22be0fe61 100644
--- a/arch/x86/include/asm/signal.h
+++ b/arch/x86/include/asm/signal.h
@@ -23,6 +23,10 @@ typedef struct {
 	unsigned long sig[_NSIG_WORDS];
 } sigset_t;
 
+/* non-uapi in-kernel SA_FLAGS for those indicates ABI for a signal frame */
+#define SA_IA32_ABI	0x02000000u
+#define SA_X32_ABI	0x01000000u
+
 #ifndef CONFIG_COMPAT
 typedef sigset_t compat_sigset_t;
 #endif
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 04cb3212db2d..b1a5d252d482 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -42,6 +42,7 @@
 #include <asm/syscalls.h>
 
 #include <asm/sigframe.h>
+#include <asm/signal.h>
 
 #define COPY(x)			do {			\
 	get_user_ex(regs->x, &sc->x);			\
@@ -547,7 +548,7 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
 		return -EFAULT;
 
 	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
-		if (copy_siginfo_to_user32(&frame->info, &ksig->info))
+		if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
 			return -EFAULT;
 	}
 
@@ -660,20 +661,21 @@ badframe:
 	return 0;
 }
 
-static inline int is_ia32_compat_frame(void)
+static inline int is_ia32_compat_frame(struct ksignal *ksig)
 {
 	return IS_ENABLED(CONFIG_IA32_EMULATION) &&
-	       test_thread_flag(TIF_IA32);
+		ksig->ka.sa.sa_flags & SA_IA32_ABI;
 }
 
-static inline int is_ia32_frame(void)
+static inline int is_ia32_frame(struct ksignal *ksig)
 {
-	return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame();
+	return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 }
 
-static inline int is_x32_frame(void)
+static inline int is_x32_frame(struct ksignal *ksig)
 {
-	return IS_ENABLED(CONFIG_X86_X32_ABI) && test_thread_flag(TIF_X32);
+	return IS_ENABLED(CONFIG_X86_X32_ABI) &&
+		ksig->ka.sa.sa_flags & SA_X32_ABI;
 }
 
 static int
@@ -684,12 +686,12 @@ setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 	compat_sigset_t *cset = (compat_sigset_t *) set;
 
 	/* Set up the stack frame */
-	if (is_ia32_frame()) {
+	if (is_ia32_frame(ksig)) {
 		if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 			return ia32_setup_rt_frame(usig, ksig, cset, regs);
 		else
 			return ia32_setup_frame(usig, ksig, cset, regs);
-	} else if (is_x32_frame()) {
+	} else if (is_x32_frame(ksig)) {
 		return x32_setup_rt_frame(ksig, cset, regs);
 	} else {
 		return __setup_rt_frame(ksig->sig, ksig, set, regs);
diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
index b44564bf86a8..40df33753bae 100644
--- a/arch/x86/kernel/signal_compat.c
+++ b/arch/x86/kernel/signal_compat.c
@@ -1,5 +1,6 @@
 #include <linux/compat.h>
 #include <linux/uaccess.h>
+#include <linux/ptrace.h>
 
 /*
  * The compat_siginfo_t structure and handing code is very easy
@@ -92,10 +93,31 @@ static inline void signal_compat_build_tests(void)
 	/* any new si_fields should be added here */
 }
 
-int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
+void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
+{
+	/* Don't leak in-kernel non-uapi flags to user-space */
+	if (oact)
+		oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
+
+	if (!act)
+		return;
+
+	/* Don't let flags to be set from userspace */
+	act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
+
+	if (user_64bit_mode(current_pt_regs()))
+		return;
+
+	if (in_ia32_syscall())
+		act->sa.sa_flags |= SA_IA32_ABI;
+	if (in_x32_syscall())
+		act->sa.sa_flags |= SA_X32_ABI;
+}
+
+int __copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from,
+		bool x32_ABI)
 {
 	int err = 0;
-	bool ia32 = test_thread_flag(TIF_IA32);
 
 	signal_compat_build_tests();
 
@@ -146,7 +168,7 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
 				put_user_ex(from->si_arch, &to->si_arch);
 				break;
 			case __SI_CHLD >> 16:
-				if (ia32) {
+				if (!x32_ABI) {
 					put_user_ex(from->si_utime, &to->si_utime);
 					put_user_ex(from->si_stime, &to->si_stime);
 				} else {
@@ -180,6 +202,12 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
 	return err;
 }
 
+/* from syscall's path, where we know the ABI */
+int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
+{
+	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
+}
+
 int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
 {
 	int err = 0;
diff --git a/kernel/signal.c b/kernel/signal.c
index af21afc00d08..75761acc77cf 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3044,6 +3044,11 @@ void kernel_sigaction(int sig, __sighandler_t action)
 }
 EXPORT_SYMBOL(kernel_sigaction);
 
+void __weak sigaction_compat_abi(struct k_sigaction *act,
+		struct k_sigaction *oact)
+{
+}
+
 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 {
 	struct task_struct *p = current, *t;
@@ -3059,6 +3064,8 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 	if (oact)
 		*oact = *k;
 
+	sigaction_compat_abi(act, oact);
+
 	if (act) {
 		sigdelsetmask(&act->sa.sa_mask,
 			      sigmask(SIGKILL) | sigmask(SIGSTOP));
-- 
2.9.0

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Re: [PATCHv5 3/6] x86/arch_prctl/vdso: add ARCH_MAP_VDSO_*

[Andy Lutomirski]

On Mon, Sep 5, 2016 at 6:33 AM, Dmitry Safonov <dsafonov@virtuozzo.com> wrote:
> Add API to change vdso blob type with arch_prctl.
> As this is usefull only by needs of CRIU, expose
> this interface under CONFIG_CHECKPOINT_RESTORE.

Acked-by: Andy Lutomirski <luto@kernel.org>

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Re: [PATCHv5 0/6] x86: 32-bit compatible C/R on x86_64

[Dmitry Safonov]

On 09/05/2016 04:33 PM, Dmitry Safonov wrote:
> Changes from v4:
> - check both vm_ops and vm_private_data to avoid (unlikely) confusion
>   with some other vma in map_vdso_once (as Andy noticed) - which would
>   lead to unable to use this API in that unlikely-case
>   (vm_private_data may be uninitialized and be the same as vvar_mapping
>   or vdso_mapping pointer) - so I introduced one-liner helper
>   vma_is_special_mapping().
>
> Changes from v3:
> - proper ifdefs around vdso_image_32
> - missed Reviewed-by tag

Ping?
It looks like, all acks are there and there are no objections.

-- 
              Dmitry

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