Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 vdso updates from Ingo Molnar:
 "The main changes in this cycle centered around adding support for
  32-bit compatible C/R of the vDSO on 64-bit kernels, by Dmitry
  Safonov"

* 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vdso: Use CONFIG_X86_X32_ABI to enable vdso prctl
  x86/vdso: Only define map_vdso_randomized() if CONFIG_X86_64
  x86/vdso: Only define prctl_map_vdso() if CONFIG_CHECKPOINT_RESTORE
  x86/signal: Add SA_{X32,IA32}_ABI sa_flags
  x86/ptrace: Down with test_thread_flag(TIF_IA32)
  x86/coredump: Use pr_reg size, rather that TIF_IA32 flag
  x86/arch_prctl/vdso: Add ARCH_MAP_VDSO_*
  x86/vdso: Replace calculate_addr in map_vdso() with addr
  x86/vdso: Unmap vdso blob on vvar mapping failure

15 files changed, 220 insertions, 106 deletions

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index f840766659a8..23c881caabd1 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -37,54 +37,6 @@ void __init init_vdso_image(const struct vdso_image *image)
 
 struct linux_binprm;
 
-/*
- * Put the vdso above the (randomized) stack with another randomized
- * offset.  This way there is no hole in the middle of address space.
- * To save memory make sure it is still in the same PTE as the stack
- * top.  This doesn't give that many random bits.
- *
- * Note that this algorithm is imperfect: the distribution of the vdso
- * start address within a PMD is biased toward the end.
- *
- * Only used for the 64-bit and x32 vdsos.
- */
-static unsigned long vdso_addr(unsigned long start, unsigned len)
-{
-#ifdef CONFIG_X86_32
-        return 0;
-#else
-        unsigned long addr, end;
-        unsigned offset;
-
-        /*
-         * Round up the start address.  It can start out unaligned as a result
-         * of stack start randomization.
-         */
-        start = PAGE_ALIGN(start);
-
-        /* Round the lowest possible end address up to a PMD boundary. */
-        end = (start + len + PMD_SIZE - 1) & PMD_MASK;
-        if (end >= TASK_SIZE_MAX)
-                end = TASK_SIZE_MAX;
-        end -= len;
-
-        if (end > start) {
-                offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
-                addr = start + (offset << PAGE_SHIFT);
-        } else {
-                addr = start;
-        }
-
-        /*
-         * Forcibly align the final address in case we have a hardware
-         * issue that requires alignment for performance reasons.
-         */
-        addr = align_vdso_addr(addr);
-
-        return addr;
-#endif
-}
-
 static int vdso_fault(const struct vm_special_mapping *sm,
                       struct vm_area_struct *vma, struct vm_fault *vmf)
 {
@@ -176,30 +128,28 @@ 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)
+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
+ * @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 = {
-                .name = "[vdso]",
-                .fault = vdso_fault,
-                .mremap = vdso_mremap,
-        };
-        static const struct vm_special_mapping vvar_mapping = {
-                .name = "[vvar]",
-                .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;
 
@@ -238,24 +188,104 @@ 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;
 }
 
+#ifdef CONFIG_X86_64
+/*
+ * Put the vdso above the (randomized) stack with another randomized
+ * offset.  This way there is no hole in the middle of address space.
+ * To save memory make sure it is still in the same PTE as the stack
+ * top.  This doesn't give that many random bits.
+ *
+ * Note that this algorithm is imperfect: the distribution of the vdso
+ * start address within a PMD is biased toward the end.
+ *
+ * Only used for the 64-bit and x32 vdsos.
+ */
+static unsigned long vdso_addr(unsigned long start, unsigned len)
+{
+        unsigned long addr, end;
+        unsigned offset;
+
+        /*
+         * Round up the start address.  It can start out unaligned as a result
+         * of stack start randomization.
+         */
+        start = PAGE_ALIGN(start);
+
+        /* Round the lowest possible end address up to a PMD boundary. */
+        end = (start + len + PMD_SIZE - 1) & PMD_MASK;
+        if (end >= TASK_SIZE_MAX)
+                end = TASK_SIZE_MAX;
+        end -= len;
+
+        if (end > start) {
+                offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
+                addr = start + (offset << PAGE_SHIFT);
+        } else {
+                addr = start;
+        }
+
+        /*
+         * Forcibly align the final address in case we have a hardware
+         * issue that requires alignment for performance reasons.
+         */
+        addr = align_vdso_addr(addr);
+
+        return addr;
+}
+
+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);
+}
+#endif
+
+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)
 {
         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
 
@@ -265,7 +295,7 @@ 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
@@ -276,8 +306,7 @@ 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
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/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/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/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 de9acaf2d371..ee944bd2310d 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>
 
 __visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
 
@@ -523,6 +524,19 @@ void set_personality_ia32(bool x32)
 }
 EXPORT_SYMBOL_GPL(set_personality_ia32);
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
+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;
+}
+#endif
+
 long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 {
         int ret = 0;
@@ -576,6 +590,19 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
                 break;
         }
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
+# ifdef CONFIG_X86_X32_ABI
+        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/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index ce94c38cf4d6..0e63c0267f99 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1358,7 +1358,7 @@ void __init 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;
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index da20ecb5397a..763af1d0de64 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/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);
                                 }
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/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));
diff --git a/mm/mmap.c b/mm/mmap.c
index 69cad562cd00..7a0707a48047 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3068,6 +3068,14 @@ 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.