[RFC v16][PATCH 01/43] c/r: extend arch_setup_additional_pages()

[Oren Laadan <orenl@cs.columbia.edu>]

From: Alexey Dobriyan <adobriyan@gmail.com>

Add "start" argument, to request to map vDSO to a specific place,
and fail the operation if not.

This is useful for restart(2) to ensure that memory layout is restore
exactly as needed.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
---
 arch/powerpc/include/asm/elf.h     |    1 +
 arch/powerpc/kernel/vdso.c         |   11 ++++++++++-
 arch/s390/include/asm/elf.h        |    2 +-
 arch/s390/kernel/vdso.c            |   13 ++++++++++++-
 arch/sh/include/asm/elf.h          |    1 +
 arch/sh/kernel/vsyscall/vsyscall.c |    2 +-
 arch/x86/include/asm/elf.h         |    3 ++-
 arch/x86/vdso/vdso32-setup.c       |    9 +++++++--
 arch/x86/vdso/vma.c                |    9 +++++++--
 fs/binfmt_elf.c                    |    2 +-
 10 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index d6b4a12..3946e01 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -271,6 +271,7 @@ extern int ucache_bsize;
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
+				       unsigned long start,
 				       int uses_interp);
 #define VDSO_AUX_ENT(a,b) NEW_AUX_ENT(a,b);
 
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index ad06d5c..48beff6 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -184,7 +184,8 @@ static void dump_vdso_pages(struct vm_area_struct * vma)
  * This is called from binfmt_elf, we create the special vma for the
  * vDSO and insert it into the mm struct tree
  */
-int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+int arch_setup_additional_pages(struct linux_binprm *bprm,
+				unsigned long start, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	struct page **vdso_pagelist;
@@ -211,6 +212,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	vdso_base = VDSO32_MBASE;
 #endif
 
+	/* in case restart(2) mandates a specific location */
+	if (start)
+		vdso_base = start;
+
 	current->mm->context.vdso_base = 0;
 
 	/* vDSO has a problem and was disabled, just don't "enable" it for the
@@ -234,6 +239,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		goto fail_mmapsem;
 	}
 
+	/* for restart(2), double check that we got we asked for */
+	if (start && vdso_base != start)
+		goto fail_mmapsem;
+
 	/*
 	 * our vma flags don't have VM_WRITE so by default, the process isn't
 	 * allowed to write those pages.
diff --git a/arch/s390/include/asm/elf.h b/arch/s390/include/asm/elf.h
index 74d0bbb..54235bc 100644
--- a/arch/s390/include/asm/elf.h
+++ b/arch/s390/include/asm/elf.h
@@ -205,6 +205,6 @@ do {									    \
 struct linux_binprm;
 
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
-int arch_setup_additional_pages(struct linux_binprm *, int);
+int arch_setup_additional_pages(struct linux_binprm *, unsigned long, int);
 
 #endif
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index 89b2e7f..bab43b3 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -182,7 +182,8 @@ static void vdso_init_cr5(void)
  * This is called from binfmt_elf, we create the special vma for the
  * vDSO and insert it into the mm struct tree
  */
-int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+int arch_setup_additional_pages(struct linux_binprm *bprm,
+				unsigned long start, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	struct page **vdso_pagelist;
@@ -213,6 +214,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	vdso_pages = vdso32_pages;
 #endif
 
+	/* in case restart(2) mandates a specific location */
+	if (start)
+		vdso_base = start;
+
 	/*
 	 * vDSO has a problem and was disabled, just don't "enable" it for
 	 * the process
@@ -235,6 +240,12 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		goto out_up;
 	}
 
+	/* for restart(2), double check that we got we asked for */
+	if (start && vdso_base != start) {
+		rc = -EINVAL;
+		goto out_up;
+	}
+
 	/*
 	 * our vma flags don't have VM_WRITE so by default, the process
 	 * isn't allowed to write those pages.
diff --git a/arch/sh/include/asm/elf.h b/arch/sh/include/asm/elf.h
index ccb1d93..6c27b1f 100644
--- a/arch/sh/include/asm/elf.h
+++ b/arch/sh/include/asm/elf.h
@@ -202,6 +202,7 @@ do {									\
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
+				       unsigned long start,
 				       int uses_interp);
 
 extern unsigned int vdso_enabled;
diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c
index 3f7e415..64c70e5 100644
--- a/arch/sh/kernel/vsyscall/vsyscall.c
+++ b/arch/sh/kernel/vsyscall/vsyscall.c
@@ -59,7 +59,7 @@ int __init vsyscall_init(void)
 }
 
 /* Setup a VMA at program startup for the vsyscall page */
-int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+int arch_setup_additional_pages(struct linux_binprm *bprm, unsigned long start, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long addr;
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 83c1bc8..a4398c8 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -336,9 +336,10 @@ struct linux_binprm;
 
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
+				       unsigned long start,
 				       int uses_interp);
 
-extern int syscall32_setup_pages(struct linux_binprm *, int exstack);
+extern int syscall32_setup_pages(struct linux_binprm *, unsigned long start, int exstack);
 #define compat_arch_setup_additional_pages	syscall32_setup_pages
 
 extern unsigned long arch_randomize_brk(struct mm_struct *mm);
diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c
index 1241f11..9c72a23 100644
--- a/arch/x86/vdso/vdso32-setup.c
+++ b/arch/x86/vdso/vdso32-setup.c
@@ -310,7 +310,8 @@ int __init sysenter_setup(void)
 }
 
 /* Setup a VMA at program startup for the vsyscall page */
-int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+int arch_setup_additional_pages(struct linux_binprm *bprm,
+				unsigned long start, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long addr;
@@ -331,13 +332,17 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	if (compat)
 		addr = VDSO_HIGH_BASE;
 	else {
-		addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
+		addr = get_unmapped_area(NULL, start, PAGE_SIZE, 0, 0);
 		if (IS_ERR_VALUE(addr)) {
 			ret = addr;
 			goto up_fail;
 		}
 	}
 
+	/* for restart(2), double check that we got we asked for */
+	if (start && addr != start)
+		goto up_fail;
+
 	if (compat_uses_vma || !compat) {
 		/*
 		 * MAYWRITE to allow gdb to COW and set breakpoints
diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
index 7133cdf..81fce6d 100644
--- a/arch/x86/vdso/vma.c
+++ b/arch/x86/vdso/vma.c
@@ -98,7 +98,8 @@ static unsigned long vdso_addr(unsigned long start, unsigned len)
 
 /* Setup a VMA at program startup for the vsyscall page.
    Not called for compat tasks */
-int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+int arch_setup_additional_pages(struct linux_binprm *bprm,
+				unsigned long start, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long addr;
@@ -108,13 +109,17 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		return 0;
 
 	down_write(&mm->mmap_sem);
-	addr = vdso_addr(mm->start_stack, vdso_size);
+	addr = start ? : vdso_addr(mm->start_stack, vdso_size);
 	addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0);
 	if (IS_ERR_VALUE(addr)) {
 		ret = addr;
 		goto up_fail;
 	}
 
+	/* for restart(2), double check that we got we asked for */
+	if (start && addr != start)
+		goto up_fail;
+
 	ret = install_special_mapping(mm, addr, vdso_size,
 				      VM_READ|VM_EXEC|
 				      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 40381df..aa9a802 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -945,7 +945,7 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 	set_binfmt(&elf_format);
 
 #ifdef ARCH_HAS_SETUP_ADDITIONAL_PAGES
-	retval = arch_setup_additional_pages(bprm, !!elf_interpreter);
+	retval = arch_setup_additional_pages(bprm, 0, !!elf_interpreter);
 	if (retval < 0) {
 		send_sig(SIGKILL, current, 0);
 		goto out;
-- 
1.6.0.4

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